CN111908853A - Self-compacting soil, preparation method thereof and construction method for backfilling municipal cavity - Google Patents

Abstract

The invention belongs to the technical field of civil engineering, and in particular relates to a self-compacting soil, comprising: undisturbed soil, cement, water and additives, and the mass ratio of the cement to the dry soil in the undisturbed soil is 1:(3-4) , the mass ratio of the total mass of the cement and the dry soil in the undisturbed soil to the water is 1: (1.5-2.5), and the additive amount is 0.3%-1.0% of the cement mass. The self-compacting soil provided by the invention takes the undisturbed soil excavated by the municipal engineering earthwork as the main raw material in the cavity to be backfilled, and combines the raw materials such as cement, water and additives with a specific ratio, which not only rationally utilizes the raw material of the cavity to be backfilled The undisturbed soil reduces the cost of raw materials, the cost of backfilling the cavity and the cost of the project; and the self-compacting soil has good self-compacting, reasonable fluidity, good compressive strength, and good backfilling effect.

Description

Self-compacting soil and preparation method thereof and construction method for backfilling municipal cavity

technical field

The invention belongs to the technical field of civil engineering, and in particular relates to a self-compacting soil and a preparation method thereof and a construction method for backfilling a municipal cavity.

Background technique

With the rapid development of urbanization in my country, urban municipal roads, bridges, tunnels, subways and other projects are in full swing, and trench earthwork excavation projects are increasing day by day. Cavities are formed on both sides of the excavation, especially at the bottom of the pavement, which destroys the stability and compressive strength of the road pavement, causes potential safety hazards, and leads to road pavement damage. In the municipal earthwork excavation project, in order to ensure the project quality and the smooth progress of the project construction, it is necessary to backfill the cavity formed by the municipal earthwork excavation project, especially the pavement bottom cavity formed by the earthwork excavation of the pipeline trench.

At present, in my country's municipal pipeline engineering, the cavity backfill material formed by the municipal earthwork excavation project is a mixed backfill formed by cement as the main material and additionally mined plain soil, lime soil, yellow sand, stone powder or stone chips as auxiliary materials. Due to the particularity of the existing backfill materials, the backfill method generally adopts compaction or rolling methods. However, at this stage, the cavities at the bottom of the road surface during construction are rarely filled. In many cases, the road surface is directly excavated, and then the road surface is re-laid. On the one hand, the raw materials of the existing backfill materials need to be mined and transported from other places, which not only has a great impact on the environment and makes the limited natural resources face depletion, but also has high transportation costs, high engineering costs, and large resource consumption. On the other hand, the cavities formed in municipal earthwork excavation projects often have many haunch corners, such as the cavities at the bottom of the road. The haunch corners are difficult to be compacted or compacted due to the lack of sufficient working surface of the tamping machine. The filling effect of the existing backfill materials Not good, the void ratio is large. In order to facilitate filling, it is often necessary to excavate a small cavity with multiple side angles in one step, and then re-lay the filling material. The excavation cost is high and the construction time is prolonged.

SUMMARY OF THE INVENTION

The purpose of the embodiments of the present invention is to provide a method for preparing self-compacting soil, which aims to solve the problem that the cavity formed by the existing municipal earthwork excavation project often has many haunches, such as the cavity of the road bottom layer, etc., and the manufacturing cost of the backfill material for the cavity is High, backfill is difficult to compact or compact the axillary corners of the cavity, and the combination with the undisturbed soil around the cavity is not good, resulting in poor filling effect and large porosity. The small cavity is excavated in one step, and then the filling material is re-laid. The excavation cost is high, and the construction time is prolonged.

Another object of the embodiments of the present invention is to provide a self-compacting soil.

Another object of the embodiments of the present invention is to provide a construction method for backfilling municipal cavities with self-compacting soil.

In order to realize the above-mentioned purpose of the invention, the technical scheme adopted in the present invention is as follows:

A preparation method of self-compacting soil, comprising the following steps:

Obtain the undisturbed soil, and after the undisturbed soil is subjected to desilting and impurity removal treatment, the moisture content of the undisturbed soil is measured;

Obtain cement, and the mass ratio of the cement to the dry soil in the undisturbed soil is 1: (3-4);

Obtaining water, so that the ratio of the total mass of the cement and the undisturbed soil to the total mass of the water in the self-compacting soil is 1: (1.5-2.5);

Obtaining additives, the addition amount of the additives is 0.3% to 1.0% of the cement quality;

The undisturbed soil, the cement, the water and the additive are mixed and stirred according to the ratio to obtain self-compacting soil.

Preferably, the flow value of the self-compacting soil is 160 mm to 200 mm; the maximum dry density of the self-compacting soil is greater than the maximum dry density of the undisturbed soil; the unconfined compressive strength of the self-compacting soil after drying is 2MPa～8MPa.

Preferably, the undisturbed soil is soil excavated due to municipal engineering in the cavity to be backfilled, including: at least one of sand and clay; and/or;

The additive is selected from: at least one of an early-strength agent and a water-reducing agent; and/or,

The cement is selected from: ordinary Portland cement of PO32.5.

Preferably, the additive is selected from at least one of sodium sulfate, triethanolamine, and calcium chloride; and/or,

The maximum dry density of the self-compacting soil is 2 g/cm ³ to 2.2 g/cm ³ .

Preferably, the step of performing desilting and impurity removal treatment on the undisturbed soil includes: crushing the undisturbed soil and passing through a 5-10 mm sieve hole, and making the organic matter content in the undisturbed soil less than 8%; and/or,

The mixing and stirring treatment time is 2 to 5 minutes.

A self-compacting soil, comprising: undisturbed soil, cement, water and additives, the mass ratio of the cement and the dry soil in the undisturbed soil is 1:(3-4), and the cement and the undisturbed soil are in a mass ratio of 1:(3-4). The mass ratio of the total mass of the dry soil to the water is 1:(1.5-2.5), and the addition amount of the additive is 0.3%-1.0% of the cement mass.

A construction method for backfilling municipal cavity with self-compacting soil, comprising the following steps:

Prepare self-compacting soil: measure the moisture content of the undisturbed soil in the municipal cavity, and prepare the self-compacting soil according to the moisture content of the undisturbed soil;

Grouting: pouring the self-compacting soil into the municipal cavity;

Curing: Curing the municipal cavity filled with the self-compacting soil.

Preferably, before the grouting step, it further comprises: supporting a formwork, supporting the formwork at the periphery of the municipal cavity; the step of supporting the formwork comprises: the enclosing template of the formwork is 20-30 cm away from the edge of the municipal cavity , the enclosure template of the support formwork is 20-30 cm higher than the highest horizontal plane of the municipal cavity.

Preferably, before the grouting step, the method further comprises: coating the template of the support with a release agent; and/or,

The step of grouting includes: using artificial grouting and/or mechanical grouting to pour the self-compacting soil into the municipal cavity in layers, and the layers of the layered pouring include at least one layer.

Preferably, it is characterized in that the step of curing comprises: curing the municipal cavity of the poured self-compacting soil until the strength of the self-compacting soil reaches more than 75% of its permanent strength, and within the curing period The self-compacting soil is not disturbed by external loads.

In the method for preparing self-compacting soil provided by the present invention, the moisture content of the undisturbed soil in the cavity formed by the municipal earthwork excavation project to be backfilled is obtained to determine the dry soil content in the undisturbed soil; The ratio of cement, water and additives in the raw materials of compacted soil is: the mass ratio of cement and dry soil in undisturbed soil is 1: (3-4), and the total mass of cement and undisturbed soil in dry soil and the mass ratio of water is 1: (1.5～2.5), the additive amount is 0.3%～1.0% of the cement quality. Finally, the raw materials in the specific ratio are mixed and stirred to obtain self-compacting soil. On the one hand, the self-compacting soil prepared by the present invention uses the undisturbed soil excavated by municipal engineering in the cavity to be backfilled as the main raw material, which not only makes reasonable use of the undisturbed soil to be filled in the cavity, but also eliminates the need to mine sand and gravel from other places as the backfill. Raw materials, reduce the cost of raw material use, reduce the discharge of solid waste, and save the cost of spoil transportation, and the workload of mechanical equipment during construction is correspondingly reduced, which greatly reduces the cost of cavity backfilling, saves project costs, and accelerates The construction progress is controlled, the energy consumption is controlled, and it meets the development requirements of energy conservation and environmental protection in the construction industry. On the other hand, the self-compacting soil prepared by the present invention through the specific ratio of undisturbed soil, cement, water and additives has good self-compacting properties. When backfilled into the cavity, the self-compacting soil has good self-compacting properties Under the action of its own gravity, it can flow and compact to achieve the purpose of completely filling the cavity, and the backfilling effect of the cavity is good and the void ratio is low. Moreover, since the self-compacting soil of the present invention uses the undisturbed soil to be filled in the cavity as the main raw material, the self-compacting soil has good compatibility with the soil inside the cavity, and the binding effect of the self-compacting soil and the soil around the cavity is increased. .

The self-compacting soil provided by the invention takes the undisturbed soil excavated by the municipal engineering earthwork as the main raw material in the cavity to be backfilled, and combines the raw materials such as cement, water and additives with a specific ratio, which not only rationally utilizes the raw material of the cavity to be backfilled Undisturbed soil reduces the cost of using raw materials, reduces the discharge of solid waste, reduces the workload of machinery and equipment during construction, saves the cost of spoil transportation, reduces the cost of cavity backfilling and engineering costs, and speeds up the construction progress. It meets the development requirements of energy conservation and environmental protection in the construction industry; and through a specific ratio of undisturbed soil, cement, water and additives, the self-compacting soil has both good self-compacting properties and reasonable fluidity (fluidity is 160mm ~ 200mm). The cavity has good backfilling effect and good compressive strength. The unconfined compressive strength of self-compacting soil after drying is greater than 2MPa to meet the needs of municipal construction.

According to the construction method for backfilling municipal cavities with self-compacting soil provided by the present invention, the self-compacting soil is prepared according to the above preparation method by measuring the moisture content of the undisturbed soil that forms the cavity to be backfilled due to earthwork excavation projects such as municipal roads, bridges, tunnels, subways, etc. , and then the backfilling of the municipal cavity can be completed through grouting and maintenance. The construction method is simple and the operation is convenient. It not only makes reasonable use of the undisturbed soil excavated from the municipal cavity to be backfilled, but also saves the project cost and speeds up the construction progress. In addition, the self-compacting soil has good backfilling effect on municipal cavities, low porosity, and high permanent strength after curing and curing of self-compacting soil.

Description of drawings

FIG. 1 is a schematic diagram of a pavement bottom cavity provided by an embodiment of the present invention.

FIG. 2 is a diagram showing the combination of self-compacting soil and undisturbed soil after filling with self-compacting soil according to an embodiment of the present invention.

Detailed ways

In order to make the purposes, technical solutions and technical effects of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Example. In combination with the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

In the description of the present invention, it should be understood that the terms "first" and "second" are only used for description purposes, and cannot be interpreted as indicating or implying relative importance or the number of indicated technical features. Thus, a feature defined as "first" or "second" may expressly or implicitly include one or more of that feature. In the description of the present invention, "plurality" means two or more, unless otherwise expressly and specifically defined.

The weight of the relevant components mentioned in the description of the embodiment of the present invention can not only refer to the specific content of each component, but also can represent the proportional relationship between the weights of the components. It is within the scope disclosed in the description of the embodiments of the present invention that the content of the ingredients is scaled up or down. Specifically, the weight described in the description of the embodiment of the present invention may be a mass unit known in the chemical field, such as μg, mg, g, and kg.

The embodiment of the present invention provides a preparation method of self-compacting soil, comprising the following steps:

S10. Obtain undisturbed soil, and after performing desilting and impurity removal treatment on the undisturbed soil, measure the moisture content of the undisturbed soil;

S20. Obtain cement, the mass ratio of the cement to the dry soil in the undisturbed soil is 1: (3-4);

S30. Obtain water, so that the ratio of the total mass of the dry soil in the cement and the undisturbed soil to the total mass of the water in the self-compacting soil is 1: (1.5-2.5);

S40. Obtain additives, the amount of which is 0.3% to 1.0% of the cement quality;

S50. The undisturbed soil, the cement, the water and the additive are mixed and stirred according to the ratio to obtain self-compacting soil.

In the method for preparing self-compacting soil provided by the embodiment of the present invention, the moisture content of the undisturbed soil in the cavity formed by the municipal earthwork excavation project to be backfilled is obtained to determine the content of the undisturbed soil after removing the moisture contained in the undisturbed soil; then According to the moisture content of undisturbed soil, the ratio of cement, water and additives in the raw materials for preparing self-compacting soil is determined as follows: the mass ratio of cement to dry soil in undisturbed soil is 1:(3-4), and the ratio of cement to dry soil in undisturbed soil is 1:(3-4). The mass ratio of the total mass to the water is 1:(1.5-2.5), and the addition amount of the additive is 0.3%-1.0% of the cement mass. Finally, the raw materials in the specific ratio are mixed and stirred to obtain self-compacting soil. On the one hand, the self-compacting soil prepared in the embodiment of the present invention uses the undisturbed soil excavated by the municipal engineering in the cavity to be backfilled as the main raw material, which not only makes reasonable use of the undisturbed soil to be filled in the cavity, but also does not need to mine sand and gravel from other places. As a backfilling raw material, it reduces the cost of using raw materials, reduces the discharge of solid waste, and saves the cost of spoil transportation. The workload of mechanical equipment during construction is also reduced accordingly, which greatly reduces the cost of cavity backfilling and saves engineering costs. , speed up the construction progress, control energy consumption, and meet the development requirements of energy conservation and environmental protection in the construction industry. On the other hand, the self-compacting soil prepared by the undisturbed soil, cement, water and additives in specific proportions in the embodiment of the present invention has good self-compacting properties. When backfilled into the cavity, the self-compacting soil has good Self-compacting, under the action of its own gravity, it can flow and compact to achieve the purpose of completely filling the cavity, the backfilling effect of the cavity is good, and the void ratio is low. Moreover, since the self-compacting soil in the embodiment of the present invention uses the undisturbed soil to be filled in the cavity as the main raw material, the self-compacting soil has good compatibility with the soil inside the cavity, and the relationship between the self-compacting soil and the soil around the cavity is increased. Combine effect.

Specifically, the dry soil in the undisturbed soil refers to the soil after removing the moisture contained in the undisturbed soil; the flow value of the self-compacting soil is 160 mm to 200 mm; the maximum dry density of the self-compacting soil is greater than The maximum dry density of the undisturbed soil; the unconfined compressive strength of the self-compacting soil after drying is 2 MPa to 8 MPa. The self-compacting soil prepared in the embodiment of the present invention has excellent characteristics. On the one hand, the self-compacting soil prepared in the embodiment of the present invention has a suitable fluidity, and its flow value is 160 mm to 200 mm, which ensures the self-compacting property of the self-compacting soil. When the self-compacting soil is backfilled into the cavity, it can flow, diffuse and compact the entire cavity better through its own gravity, with good filling effect and low porosity. When the flow value is greater than 200mm, the water content in the self-compacting soil is too high, which not only affects the solidification time and solidification effect of the self-compacting soil, but also tends to bleed during the backfilling and solidification process of the self-compacting soil, which damages the strength of the self-compacting soil. , which affects the fill effect. When the flow value is less than 160mm, the fluidity of the self-compacting soil is poor, the compaction effect is poor, the filling of the cavity is insufficient, and voids and holes are easy to appear. On the other hand, the self-compacting soil prepared in the embodiment of the present invention has a large maximum dry density, and the maximum dry density of the self-compacting soil is greater than that of the undisturbed soil. The self-compacting soil extrudes and spreads the undisturbed soil of relatively small density, so that the self-compacting soil and the undisturbed soil around the cavity are very closely combined, and the combination effect is better, ensuring the backfilling of the cavity by the self-compacting soil. Effect. As a preferred embodiment, the maximum dry density of the self-compacting soil in the embodiment of the present invention is 2g/cm ³ -2.2g/cm ³ , which can meet the requirements of backfilling cavities in different municipal projects. On the other hand, the self-compacting soil prepared in the embodiment of the present invention has good strength, and its unconfined compressive strength after drying is 2MPa-8MPa, and the high compressive strength after drying not only ensures the roadbed after backfilling, etc. The integrity of the project ensures the quality of the restored subgrade and other projects, and the strength is much higher than the quality standard of the subgrade soil, which not only meets the acceptance standard of the subgrade soil, but also meets the strength of the backfill cavity for various subsequent municipal construction operations. requirements.

Specifically, in the above step S10, undisturbed soil is obtained, and after the undisturbed soil is subjected to desilting and impurity removal treatment, the moisture content of the undisturbed soil is measured. In the embodiment of the present invention, the soil excavated by the municipal engineering earthwork in the cavity to be backfilled is used as the main raw material, and the undisturbed soil of the cavity to be backfilled is reasonably utilized, thereby reducing the cost of using raw materials, saving the transportation cost of spoil, and reducing the engineering cost. , to speed up the construction progress. In addition, the self-compacting soil has good compatibility with the soil inside the cavity, and the binding effect of the self-compacting soil and the soil around the cavity is increased. In the embodiment of the present invention, impurities such as large stones, plastics, leaves, etc. in the undisturbed soil are removed by desilting and slag removal. Impurities in the undisturbed soil will affect the self-compacting soil as an organic whole. For example, degradable materials such as leaves will degrade in the self-compacting soil and eventually form a cavity, which will affect the stability of the self-compacting soil. In the compacted soil, there are many weak surfaces in the self-compacting soil, which affects the strength; large stones affect the fluidity of the soil and cannot completely fill the narrow voids in the cavity. Then, by measuring the moisture content in the undisturbed soil, the moisture content in the undisturbed soil can be determined, and the moisture contained in the undisturbed soil can be removed to determine the dry soil content in the undisturbed soil, which is beneficial to determine other self-compacting soils. The addition ratio of raw materials can make the amount of each raw material in the prepared self-compacting soil reasonable, so that the self-compacting soil has the best self-compacting performance and can meet the needs of cavity backfilling.

In some implementations, the undisturbed soil is sand; in another embodiment, the undisturbed soil is clay, and in other embodiments, the undisturbed soil is a mixture of sand and clay.

As a preferred embodiment, the step of desilting and removing impurities on the undisturbed soil includes: crushing the undisturbed soil and passing through a 5-10 mm sieve hole, so that the organic matter content in the undisturbed soil is less than 8%. In the embodiment of the present invention, the undisturbed soil is crushed and then sieved, so as to remove the impurity substances in the undisturbed soil and at the same time refine the particle size of the undisturbed soil. On the one hand, the undisturbed soil with small particle size has better compatibility and mixing effect with raw materials such as cement, additives and water, which further ensures the self-compacting performance of the prepared self-compacting soil. On the other hand, raw materials with small particle size are also conducive to the better spread and penetration of self-compacting soil into small gaps during the backfilling process, reducing the porosity and improving the backfilling effect. In addition, through the desilting and impurity removal treatment, the organic matter content in the undisturbed soil is less than 8%, and the low content of organic matter in the undisturbed soil further ensures the stability and longevity of the self-compacting soil, so that it will not be damaged even with the passage of time. It appears that the formation of voids due to the degradation of organic matter affects the performance of roadbed strength. In some embodiments, the undisturbed soil is sand, and the sand is crushed and passed through a 5mm sieve; in other embodiments, the undisturbed soil is clay, and the clay is crushed and passed through a 10mm sieve, and the organic matter content is less than 8%.

Specifically, in the above step S20, cement is obtained, and the mass ratio of the cement to the dry soil in the undisturbed soil is 1:(3-4). In the embodiment of the present invention, the moisture content in the undisturbed soil is determined to determine the content of the dry soil in the undisturbed soil, and then the proportion of cement required to prepare the self-compacting soil is determined according to the dry soil content as follows: the ratio of cement to the dry soil in the undisturbed soil is: The mass ratio is 1:(3-4), so that the prepared self-compacting soil has good strength, and the cavity strength filled with the self-compacting soil according to the embodiment of the present invention can meet various municipal construction requirements. If the proportion of cement in the self-compacting soil is too low, the strength of the self-compacting soil cannot meet the requirements, and cannot meet the strength requirements of municipal construction. If the cement content in the self-compacting soil is too high, on the one hand, the fluidity of the self-compacting soil will be affected, the fluidity will decrease, the self-compacting effect in the cavity will decrease, and the filling effect will decrease; On the contrary, the strength of compacted soil will gradually decrease, and the phenomenon of cracks will gradually become obvious.

Specifically, in the above step S30, water is obtained, so that the ratio of the total mass of the cement and the dry soil in the undisturbed soil to the total mass of the water in the self-compacting soil is 1: (1.5-2.5). In the embodiment of the present invention, the total mass of water required for self-compacting soil is determined by the total mass of dry soil and cement added in the raw materials, and then the amount of additional water that needs to be added can be obtained according to the measured moisture content of the undisturbed soil. On the one hand, the amount of added water provides conditions for cement hydration, and on the other hand, the prepared self-compacting soil has better fluidity and self-compacting properties, and improves the filling effect. If the water content added to the self-compacting soil is too low, the prepared self-compacting soil will have poor fluidity and poor self-compacting effect, and will not be able to fill the gaps in the backfill cavity. If the water content added to the self-compacting soil is too high, the prepared self-compacting soil will have too high water content, excessive fluidity, long solidification time, and prone to bleeding, thereby destroying the strength of the self-compacting soil and affecting the backfilling effect.

Specifically, in the above step S40, an additive is obtained, and the additive amount is 0.3% to 1.0% of the cement mass. In the embodiment of the present invention, according to the amount of cement added in the self-compacting soil, the additive amount is determined to be 0.3% to 1.0% of the cement quality, and the solidification time of the self-compacting soil is controlled by a reasonable amount of the additive to ensure that the prepared self-compacting soil is in the air. Self-compacting and backfilling effect in cavity. If the additive content in the self-compacting soil is too high, the solidification speed is too fast, and the slurry will solidify when the filling in the municipal cavity is not complete, and it is easy to form holes and the filling effect is not good; if the additive content in the self-compacting soil is too low , The solidification time of self-compacting soil is too long, which increases the maintenance and construction time. In some specific embodiments, the additive amount may be 0.3%, 0.5%, 0.7%, 0.9%, 1% of the cement quality.

As a preferred embodiment, the additive is selected from at least one of early strength agent and water reducing agent. The additives used in the embodiments of the present invention may be added with at least one of an early-strength agent and a water-reducing agent according to specific construction requirements. Among them, the early strength agent can accelerate the hydration rate of cement in the self-compacting soil, promote the development of the early strength of the self-compacting soil, and have no significant effect on the later strength of the self-compacting soil. It has both early strength function and certain water reduction enhancement function. . The water reducing agent has a dispersing effect on the cement particles in the self-compacting soil, which can improve the workability of the cement, reduce the unit water consumption, and improve the fluidity of the self-compacting soil. In the embodiment of the present invention, the solidification time of the self-compacting soil is effectively controlled by adding a reasonable proportion of additives such as an early-strength agent and a water-reducing agent, so as to ensure the self-compacting and backfilling effects of the prepared self-compacting soil in the cavity. In some embodiments, the solidification time of the self-compacting soil is controlled within 30 minutes to 60 minutes through additives, so as to facilitate the construction of backfilling the cavity with the self-compacting soil, and the self-compacting soil can sufficiently flow and compact the cavity in the cavity. To ensure the filling effect at the gaps such as the axillary corner of the cavity.

As a preferred embodiment, the additive is selected from at least one of sodium sulfate, triethanolamine, and calcium chloride. Among them, calcium chloride additive, on the one hand, through the action of chloride and calcium in cement, generates hydrated chloroaluminate which is insoluble in water, and accelerates the hydration of calcium in cement. On the other hand, calcium hydroxide formed by chloride and cement hydration generates calcium chlorate that is not easily soluble in water, reduces the concentration of calcium hydroxide in the liquid phase, accelerates the hydration rate of calcium, and the generated double salt increases The volume of the solid phase in the cement slurry forms an internal skeleton system, which is conducive to the formation of the cement stone structure. Therefore, calcium chloride additives can accelerate the setting and hardening of cement and improve the early strength of self-compacting soil; it can also increase the hydration heat of cement and increase the temperature of cement. By adjusting the amount of additives, self-compacting can be better controlled Soil setting time. The sodium sulfate composite early strength agent dissolves in water and acts with calcium hydroxide produced by cement hydration to generate calcium oxide and calcium sulfate. The particles of this newly formed calcium sulfate are extremely fine, and its activity is much higher than that of calcium sulfate, so it reacts with calcium to generate calcium sulfoaluminate hydrate much faster, so as to control the solidification time of self-compacting soil. . Although the triethanolamine compound early strength agent cannot change the cement hydration product, it can promote the action of calcium aluminate hydrate and gypsum to form calcium aluminum sulfate crystals, and accelerate the hydration of tricalcium silicate, which has early strength for self-compacting soil. It can adjust the solidification time of self-compacting soil with the effect of later enhancement.

The embodiment of the present invention does not specifically limit the type of cement, as long as the self-compacting soil of the embodiment of the present invention can meet the requirements of municipal construction on properties such as strength, fluidity, and maximum dry density. In some embodiments, the cement is selected from: ordinary Portland cement of PO32.5, and the PO32.5 cement selected in the embodiment of the present invention has higher 7-day strength than other cements of 32.5, which is more favorable Compared with on-site construction, the construction period is shortened, and the cement has large output, wide sources and low cost.

Specifically, in the above step S50, the undisturbed soil, the cement, the water and the additive are mixed and stirred according to the stated ratio to obtain self-compacting soil. In the embodiment of the present invention, self-compacting soil can be obtained by mixing and stirring raw materials of undisturbed soil, cement, water and additives in specific proportions. The preparation method is simple and the operation is easy. Cavity backfilling is highly feasible. The embodiment of the present invention does not specifically limit the mixing order of the raw materials of the self-compacting soil, and the self-compacting soil can be obtained by mixing according to specific construction conditions. In some embodiments, the undisturbed soil, the cement, the water and the additive are mixed and stirred according to the stated proportions at the same time to obtain self-compacting soil. In other embodiments, the water and soil in a specific proportion are mixed and stirred evenly, and then cement and additives are added for further mixing and stirring treatment to obtain self-compacting soil.

As a preferred embodiment, the mixing and stirring treatment time is 2-5 minutes. In the embodiment of the present invention, the raw materials of the self-compacting soil are stirred and mixed according to a specific ratio for 2-5 minutes, which can be used in the cavity backfilling of various municipal projects, and the preparation is simple and fast, and the practicability is high. If the cement ash in the self-compacting soil is solidified for too long, the self-compacting soil will stick too much on the wall of the equipment, which is not conducive to the treatment of the self-compacting soil, affecting the fluidity and self-compacting properties of the self-compacting soil, and is not conducive to the follow-up The self-compacting backfilling effect during the backfilling process, and at the same time long-time stirring prolongs the construction time. In the embodiment of the present invention, the specific technological means and equipment for stirring and mixing are not specifically limited, and the type of stirring equipment can be determined according to the demand for on-site self-compacting soil and the type of undisturbed soil, as long as the specific proportion of self-compacting soil can be realized The raw materials such as cement, undisturbed soil, water and additives are mixed evenly, without agglomerates, without bleeding and segregation, and a stable self-compacting soil can be formed. In some specific embodiments, the mixing and stirring time may be 2 minutes, 3 minutes, 4 minutes, or 5 minutes.

The embodiment of the present invention also provides a self-compacting soil, comprising: undisturbed soil, cement, water and additives, wherein the mass ratio of the cement to the dry soil in the undisturbed soil is 1:(3-4), and the The mass ratio of the total mass of the cement and the dry soil in the undisturbed soil to the water is 1:(1.5-2.5), and the additive amount is 0.3%-1.0% of the cement mass.

The self-compacting soil provided by the embodiment of the present invention uses the undisturbed soil excavated by the municipal engineering earthwork as the main raw material, and combines the raw materials such as cement, water, and additives with a specific ratio, which not only rationally utilizes the unfilled cavity to be backfilled The undisturbed soil of the cavity reduces the use cost of raw materials, reduces the discharge of solid waste, and reduces the workload of machinery and equipment during construction accordingly, saves the transportation cost of spoil, reduces the cost of backfilling the cavity and the cost of the project, and speeds up the construction. The progress is in line with the development requirements of energy conservation and environmental protection in the construction industry; and through a specific proportion of undisturbed soil, cement, water and additives, the self-compacting soil has both good self-compacting properties and reasonable fluidity (fluidity is 160mm ~ 200mm ) has a good backfilling effect on the cavity, and also has a good compressive strength. The unconfined compressive strength of the self-compacting soil after drying is greater than 2MPa to meet the needs of municipal construction.

The embodiment of the present invention also provides a construction method for the bottom cavity of the self-compacting municipal pavement, comprising the following steps:

S60. Prepare self-compacting soil: measure the moisture content of the undisturbed soil in the municipal cavity, and prepare the self-compacting soil according to the moisture content of the undisturbed soil;

S70. Grouting: pouring the self-compacting soil into the municipal cavity;

S80. Curing: curing the municipal cavity filled with the self-compacting soil.

The construction method for backfilling municipal cavities with self-compacting soil provided in the embodiment of the present invention is prepared by measuring the moisture content of the undisturbed soils to be backfilled cavities formed by earthwork excavation projects such as municipal roads, bridges, tunnels, subways, etc. according to the above preparation method. Compact soil, and then backfill the municipal cavity through grouting and maintenance. The construction method is simple and the operation is convenient. It not only makes reasonable use of the undisturbed soil excavated from the municipal cavity to be backfilled, but also saves the project cost and speeds up the construction. In addition, the self-compacting soil has good backfilling effect on municipal cavities, low porosity, and high permanent strength after curing and curing of self-compacting soil, which can meet the strength requirements of various municipal construction for backfilling cavities, with high use value and feasibility. high.

As a preferred embodiment, the construction method for returning the self-compacting soil to the municipal cavity provided by the embodiment of the present invention is preferably suitable for backfilling the pavement bottom cavity formed by the excavation of the pipeline trench, as shown in FIG. 1 . After using the construction method provided by the embodiment of the present invention, the cavity filling quality of the subgrade settlement area is high, the integrity of the subgrade is ensured, the quality of the restored traffic road is guaranteed, and the damage to the road surface is controlled.

Specifically, in the above step S60, self-compacting soil is prepared: the moisture content of the undisturbed soil in the municipal cavity is measured, and the self-compacting soil is prepared according to the moisture content of the undisturbed soil. The method for preparing self-compacting soil in the embodiment of the present invention is consistent with the above-mentioned preparation method of self-compacting soil and the effect of the prepared self-compacting soil, and will not be repeated again.

Specifically, in the above step S70, grouting: pouring the self-compacting soil into the municipal cavity. In the embodiment of the present invention, the prepared self-compacting soil is poured into the municipal cavity, so that the self-compacting soil flows and densifies under the action of its own gravity in the cavity, so as to achieve the purpose of completely filling the cavity, and backfill the municipal cavity. The effect is good and the void ratio is low.

In some embodiments, before the grouting step, the method further comprises: supporting the formwork, supporting the formwork at the periphery of the municipal cavity; the step of supporting the formwork comprises: the surrounding formwork of the formwork is 20 away from the edge of the municipal cavity ~30 cm, and the enclosure template of the support formwork is 20-30 cm higher than the highest horizontal plane of the municipal cavity. In the embodiment of the present invention, at a distance of 20-30 centimeters from the peripheral edge of the municipal cavity, a fence formwork that is 20-30 centimeters higher than the highest level of the municipal cavity is supported to facilitate the grouting of self-compacting soil, prevent the slurry from flowing out, and make the slurry material to better fill the cavity. Before the formwork is supported, the strength, stiffness and stability of the formwork should be calculated to ensure the safety of the formwork. After the mold support is completed, check whether there is a gap in the joint part to avoid the outflow of the slurry. The formwork, ancillary components, and supporting structures shall comply with the installation requirements of the "Technical Specification for Safety of Construction Formwork" (JGJ162-2008).

As a preferred embodiment, before the grouting step, the method further includes: coating a mold release agent on the template of the support mold to facilitate mold release.

In some embodiments, the formwork formwork adopts steel or wood formwork, the panel deformation value of the steel formwork is less than 1.5mm, and the thickness of the wooden formwork is not less than 40mm. Make sure that the deformation value of the template is small, so as to ensure the compactness of the filling. If the deformation value is large, with the deformation of the template in the subsequent solidification process, voids are likely to appear in the cavity, which affects the filling effect.

In some embodiments, since the self-compacting soil used in the embodiments of the present invention has good compactness and reasonable curing time, the mold can be removed 2 days after pouring.

In some embodiments, if the working surface is not suitable for formwork to establish a fence, a hole can be drilled, the steel sheet piles around the trench can be used to form a closed cavity around it, and the slurry can be introduced into the cavity under the road surface through the hole.

As a preferred embodiment, the step of grouting includes: using artificial grouting and/or mechanical grouting to pour the self-compacting soil into the municipal cavity in layers, and the layers of the layered pouring include at least one layer. In the embodiment of the present invention, artificial grouting and/or mechanical grouting are used to pour the self-compacting soil into the municipal cavity in layers. Multi-layer grouting, the upper grouting is completed before the initial setting of the lower grouting. When the filling thickness exceeds 0.5m or more, in order to ensure the dense filling effect of self-compacting soil, the method of layered grouting can better achieve the filling effect. In some embodiments, a grouting pump can be used for mechanical grouting, and a rapid grouting effect can be achieved by controlling the grouting pressure and speed. When the volume of the municipal cavity is relatively small, artificial grouting can be used.

Specifically, in the above-mentioned step S80, the maintenance is performed on the municipal cavity in which the self-compacting soil is poured. In the embodiment of the present invention, by curing the municipal cavity in which the self-compacting soil is poured, the filled self-compacting soil is guaranteed not to be disturbed by external loads during the curing period, and the hardened soil body is kept intact.

As a preferred embodiment, the curing step includes: curing the municipal cavity of the poured self-compacting soil until the strength of the self-compacting soil reaches more than 75% of its permanent strength, and within the curing period, the self-compacting soil The compacted soil is not disturbed by external loads, ensuring the integrity of the hardened soil.

In some embodiments, the poured self-compacting soil is cured for 7 days, and its strength reaches 75% of the permanent strength, and later construction can be carried out.

In some embodiments, when the air temperature is lower than 5°C, the construction of backfilling the municipal cavity with self-compacting soil is not suitable. During construction in the rainy season, avoid the impact of precipitation on raw materials, and construction should not be carried out when it rains.

In order to make the above-mentioned implementation details and operations of the present invention clearly understood by those skilled in the art, as well as the self-compacting soil and the preparation method and construction method of the embodiment of the present invention, the improvement performance is remarkably reflected. the above technical solution.

Example 1

A self-compacting soil backfills the pavement bottom cavity formed by the excavation of the Shajing River sewage interception project in the Maozhou River Basin in Bao'an District, Shenzhen.

①Project overview: During the implementation of the pipeline network project of the Shenzhen Maozhou River (Bao'an Area) comprehensive water environment improvement project, the geological conditions of the pipeline network laying area are complex, mainly silt soil, miscellaneous fill soil and sandy soil. This sub-project is located in the administrative district of Songgang Sub-district, Bao'an District, Shenzhen. The project mainly includes the construction of the rain and sewage pipe network in the Shapu District of Songgang Sub-district, the Hongxing District of Songgang Sub-district, the Dongfanghong District, and the area west of Songgang Avenue, Lougang Sub-district, Songgang Sub-district. Songgang Sub-district sewage pipe network connection improvement project construction, the total length of the pipe network is 173km.

During the excavation process, the stability of the soil is poor, and after the grooved foundation pit is formed, the soil at the bottom of the pit is easy to bulge, causing great damage to the roadbed on both sides of the trench, resulting in the uneven settlement of the road pavement on both sides of the foundation trench. Cracking, or even collapse, and other damage problems occur. After the foundation pit supporting steel sheet piles are removed, the silty soft soil around the foundation trench is easily deformed, and it will also damage the subgrade structure, increase the repair cost of the road in the later stage, and cause great hidden dangers to the construction safety.

②Backfill situation: The construction method of backfilling the pavement cavity with self-compacting soil is adopted. First, the undisturbed soil after excavation is crushed and passed through a 5-micron sieve to remove most organic and inorganic impurities; then, the moisture content of the undisturbed soil is measured, Determine the content of the dry soil in the undisturbed soil; then, according to the moisture content of the undisturbed soil, the addition ratio of soil, water, cement, and early-strength agent is: the mass ratio of the cement to the dry soil in the undisturbed soil is 1: (3～ 4), the mass ratio of the total mass of the dry soil to the water in the cement and undisturbed soil is 1:(1.5-2.5), and the addition amount of the early strength agent is 0.3%-1.0% of the cement mass. Then, soil, water, cement, and early strength agent are put into the mixing equipment, and the slurry after mixing is self-compacting soil. Then the self-compacting soil is poured into the cavity of the pavement floor, and the soil after curing and hardening is used as a part of the subgrade to make the subgrade complete.

3. Backfilling effect: as shown in Figure 2 of the combination of self-compacting soil and surrounding undisturbed soil after filling, the self-compacting soil in the embodiment of the present invention is very closely combined with undisturbed soil around the cavity after filling, and the void ratio is very small. It is 0.2%, and the deformation is very small after filling with self-compacting soil. The measured deformation value is only 0.2 mm, and the stability is good. After filling with self-compacting soil, the strength of the cavity reaches 2.6MPa, which enhances the stability of the subgrade structure and makes up for the void of the pavement floor caused by the loss of the base sand or soil deformation. After the construction is completed, the pavement does not crack. The strength of the subgrade meets the requirements of subsequent municipal construction operations. This construction method saves project investment, speeds up construction progress, improves project quality, provides a good solution to pipeline trench excavation, and conforms to the development idea of environmental protection and energy saving.

Example 2

A self-compacting soil backfills the bottom cavities of the pavement formed by the excavation of the comprehensive improvement project of the pond and the gorge in the Maozhou River Basin in Bao'an District, Shenzhen.

①Project overview: During the implementation of the pipeline network project of the Shenzhen Maozhou River Water Environment Comprehensive Improvement Project, the pipeline network construction is widely distributed and the geological conditions of the construction area are complex. This sub-project is located in the administrative area of Songgang Sub-district, Bao'an District, Shenzhen. The project mainly includes Yanchuan Village Area of Songgang Sub-district, Tangxiayong Industrial Area of Songgang Sub-district, Tangxiayong Sub-district of Songgang Sub-district and Hongqiaotou Area of Songgang Sub-district Rain and Sewage Diversion Pipes The construction of the network, and the construction of the reclaimed water replenishment project of the Songgang Water Purification Plant. The total length of the pipeline network is 125km. After the trenches of the pipe network are excavated, the soil around the trenches in some sections is seriously deformed, and cavities are formed in the lower part of the pavement floor, which affects the construction work. security hazard.

②Backfill situation: The construction method of backfilling the pavement cavity with self-compacting soil is adopted. First, the undisturbed soil of the spoil after excavation is crushed and passed through a 5-micron sieve to remove most of the organic and inorganic impurities; then, the content of the undisturbed soil is measured. The amount of water determines the content of the dry soil in the undisturbed soil; then, according to the moisture content of the undisturbed soil, the addition ratio of soil, water, cement, and early-strength agent is: the mass ratio of the cement and the dry soil in the undisturbed soil is 1:( 3-4), the mass ratio of the total mass of the dry soil in the cement and the undisturbed soil to the water is 1: (1.5-2.5), and the addition amount of the early-strength agent is 0.3%-1.0% of the cement mass. Then, soil, water, cement, and early strength agent are put into the mixing equipment, and the slurry after mixing is self-compacting soil. Then the self-compacting soil is poured into the cavity of the pavement floor, and the soil after curing and hardening is used as a part of the subgrade to make the subgrade complete.

③Effect evaluation: The self-compacting soil uses on-site spoil as raw material, and is mixed with cement, water and additives, so as to maximize the utilization of on-site solid waste, reduce the engineering cost and reduce the discharge of solid waste. After using this construction method, the self-compacting soil is very closely combined with the undisturbed soil around the cavity after filling. The strength of the cavity after filling reaches 3.2MPa, and the void ratio is small, only 0.3%. The filling of the pavement floor can meet the construction requirements. The strength meets the requirements of subsequent municipal construction operations and improves the bearing capacity of the pavement. The investigation of the restored pavement showed that there was no cracking of the pavement. The construction method replaces the traditional pavement breaking method, reduces the damage to the pavement caused by construction, improves the construction efficiency, saves the labor cost and material cost, and saves the construction period, ensures the progress of the project, is easy to operate, and conforms to the environmental protection and sustainable development. idea.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (10)

1. a preparation method of self-compacting soil, is characterized in that, comprises the following steps: Obtain the undisturbed soil, and after the undisturbed soil is subjected to desilting and impurity removal treatment, the moisture content of the undisturbed soil is measured; Obtain cement, and the mass ratio of the cement to the dry soil in the undisturbed soil is 1: (3-4); Obtaining water, so that the ratio of the total mass of the cement and the undisturbed soil to the total mass of the water in the self-compacting soil is 1: (1.5-2.5); Obtaining additives, the addition amount of the additives is 0.3% to 1.0% of the cement quality; The undisturbed soil, the cement, the water and the additive are mixed and stirred according to the ratio to obtain self-compacting soil. 2 . The method for preparing self-compacting soil according to claim 1 , wherein the flow value of the self-compacting soil is 160 mm to 200 mm; the maximum dry density of the self-compacting soil is greater than the maximum dry density of the undisturbed soil. 3 . Density; the unconfined compressive strength of the self-compacting soil after drying is 2 MPa to 8 MPa. 3. the preparation method of self-compacting soil as claimed in claim 1 or 2, is characterized in that, described undisturbed soil is the soil to be backfilled cavity excavated due to municipal engineering, comprising: at least one in sandy soil and clay ;and / or; The additive is selected from: at least one of an early-strength agent and a water-reducing agent; and/or, The cement is selected from: ordinary Portland cement of PO32.5. 4. the preparation method of self-compacting soil as claimed in claim 3, is characterized in that, described additive is selected from: at least one in sodium sulfate, triethanolamine, calcium chloride; And/or, The maximum dry density of the self-compacting soil is 2 g/cm ³ to 2.2 g/cm ³ . 5. The preparation method of self-compacting soil according to any one of claims 1 or 2 or 4, wherein the step of carrying out desilting and impurity-removing treatment to the undisturbed soil comprises: crushing the undisturbed soil and passing through the 5-10mm sieve holes, and make the organic matter content in the undisturbed soil less than 8%; and/or, The mixing and stirring treatment time is 2 to 5 minutes. 6. A self-compacting soil, characterized in that it comprises: undisturbed soil, cement, water and additives, wherein the mass ratio of the cement to the dry soil in the undisturbed soil is 1:(3-4), the cement The ratio of the total mass of the dry soil to the total mass of the water in the undisturbed soil is 1:(1.5-2.5), and the addition amount of the additive is 0.3%-1.0% of the cement mass. 7. a construction method of self-compacting soil backfilling municipal cavity, is characterized in that, comprises the following steps: Prepare self-compacting soil: measure the moisture content of the undisturbed soil in the municipal cavity, and prepare the self-compacting soil according to the moisture content of the undisturbed soil; Grouting: pouring the self-compacting soil into the municipal cavity; Curing: Curing the municipal cavity filled with the self-compacting soil. 8. the construction method of self-compacting soil backfilling municipal cavity as claimed in claim 7, is characterized in that, before described grouting step, also comprises: supporting formwork, supporting formwork at the periphery of described municipal cavity; Described supporting formwork The steps include: the enclosure template of the supporting formwork is 20-30 cm away from the edge of the municipal cavity, and the enclosure template of the supporting form is 20-30 cm higher than the highest horizontal surface of the municipal cavity. 9. The construction method of self-compacting soil backfilling municipal cavity as claimed in claim 8, characterized in that, before the grouting step, it also comprises: coating a film release agent on the formwork of the supporting formwork; and/or, The step of grouting includes: using artificial grouting and/or mechanical grouting to pour the self-compacting soil into the municipal cavity in layers, and the layers of the layered pouring include at least one layer. 10. The construction method for backfilling municipal cavities with self-compacting soil according to any one of claims 7 to 9, wherein the curing step comprises: curing the municipal cavities of the poured self-compacting soil Until the strength of the self-compacting soil reaches more than 75% of its permanent strength, the self-compacting soil is not disturbed by external loads during the curing period.

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