CN106703842A - Calculation method of permeability coefficient of shield tunnel lining structure - Google Patents

Abstract

The calculation method of the permeability coefficient of the lining structure of the shield tunnel, the steps are implemented: (1) Determine the geometric characteristics of the tunnel; (2) Determine the permeability coefficient k _s of the strata around the tunnel; (2) Determine the amount of water seepage in the tunnel: groundwater seeps into the tunnel from the tunnel joint , and collect through the water collection well, measure the groundwater seepage volume V _l collected by the water collection well; (3) determine the tunnel surface area S and water collection time t in the water collection section of the tunnel; (4) calculate the unit time unit of the tunnel (5) Calculate the water head height H _R at the interface between the tunnel and the soil layer; (6) Calculate the average permeability coefficient k _l of the tunnel _. Based on the basic characteristics of shield tunnel leakage water, the present invention establishes an average permeability coefficient determination method that can consider the penetration characteristics of shield tunnel joints, and can obtain the average permeability coefficient of shield tunnel according to the calculation, and more accurately analyze the impact of tunnel leakage water on The surrounding environment and the force and deformation of the shield tunnel.

Description

Calculation Method of Permeability Coefficient of Lining Structure of Shield Tunnel

technical field

The invention relates to the field of tunnel structure parameter calculation, in particular to a method for determining the average permeability coefficient of a shield tunnel lining structure.

Background technique

Shield tunnels are assembled from segments, and the joints between segments are called joints. Water seepage is one of the main problems of operating tunnels, and joints are the main part of shield tunnel water seepage, and the water seepage of concrete segments is less than that of joints. However, in the practice of design and construction, in order not to make the calculation too complicated, the tunnel lining is usually simplified as a mean ring, and the permeability coefficient of the lining is considered to be equal, which is called the average permeability coefficient of the lining. Therefore, it is of great significance to accurately determine the average permeability coefficient of tunnel lining to obtain correct calculation results. At present, there are mainly the following methods for determining the average permeability coefficient of lining:

(1) Ignore the joint method

In some designs, the influence of the lining joint on the tunnel is ignored, and the tunnel is considered to be a homogeneous ring composed of concrete segments, and the concrete is regarded as an impermeable material, so groundwater will not seep into the tunnel from the lining. This method is inconsistent with the actual situation, and the tunnel is subjected to a large external water pressure, so the calculation results are also somewhat different from the actual situation.

(2) Empirical method

In engineering practice, the permeability coefficient of the formation around the tunnel can be obtained from the previous exploration results. The empirical method is to calculate the average permeability coefficient of the lining by artificially setting the ratio of the average permeability coefficient of the lining to the permeability coefficient of the formation around the tunnel when the permeability coefficient of the formation around the tunnel is known. However, since this ratio is determined artificially based on experience, it is highly subjective, and it is difficult to obtain a relatively correct average permeability coefficient of the lining, and the calculation results are also somewhat different from the actual situation.

(3) Numerical method

In the numerical simulation software, the tunnel lining is simulated as a homogeneous ring, and a set of average permeability coefficients is artificially determined, which are sequentially assigned to the homogeneous ring for numerical calculation. If the calculated seepage is not much different from the actual seepage, the current value is artificially the average permeability coefficient of the lining. This method can determine a numerical solution that is not much different from the real value of the average permeability coefficient of the lining, but the process is complicated, and empirical support is needed to estimate the range of the permeability coefficient, and it is not easy to find the optimal solution.

The existing calculation methods mainly have the following two problems: 1. Relying on empirical support, it is necessary to roughly judge the range of the average permeability coefficient value of the lining before calculation, and there are certain errors between the calculation results and the actual situation. 2. It is highly subjective, and the parameters need to be set manually, and the parameters will change with the difference between the structure of the joint and the hydrogeological conditions of the stratum around the tunnel, which is not conducive to software calculation and cannot be used for commercial software development. At present, the determination of the average permeability coefficient of lining is mainly based on empirical methods, and the water permeability of concrete segments and joints is directly ignored in some designs. The average permeability coefficient of the lining obtained by these two methods has a certain error from its true value, which will have a certain impact on the calculation of the internal force and deformation of the tunnel in the design stage, and the durability and settlement of the tunnel in the operation stage. Therefore, it is of great significance to correctly determine the average permeability coefficient of the lining to guide the rational design and construction.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for calculating the average permeability coefficient of the shield tunnel lining structure, and calculate the value of the average permeability coefficient of the lining more accurately.

The present invention adopts following technical scheme:

A method for calculating the average permeability coefficient of a shield tunnel lining structure is characterized in that it is implemented according to the following steps:

(1) Measure the total volume V _l of groundwater infiltrated into the tunnel in this section by using the existing water collection well;

(2) Calculating the amount of leakage Q _l per unit area of the tunnel per unit time: first calculate the outer surface area S of the tunnel in the water-collecting section and the water-collecting time t, and divide V _l by the product of S and t to obtain the unit of tunnel time Area leakage Q _l ;

(3) Calculate the amount of leakage per unit area Q _s of the tunnel per unit time; since the seepage water in the soil is completely infiltrated into the tunnel by the tunnel joint, Q _s is equal to Q _l ;

(4) Determine the basic geometric parameters of the tunnel: determine the outer diameter R of the tunnel, the inner diameter r ₀ , and the distance h from the ground surface to the center of the tunnel;

(5) Determine the permeability coefficient k _s of the formation around the tunnel;

(6) Calculate the water head height H _R at the interface between the tunnel and the formation; calculate the interface between the tunnel and the formation according to the outer diameter R of the tunnel, the inner diameter r ₀ , the distance h from the ground surface to the center of the tunnel, and the permeability coefficient k _s of the formation around the tunnel head height H _R ;

(7) Calculate the average permeability coefficient _{k l} of the tunnel _lining ; calculate the average permeability coefficient k _l . where k _l is calculated by combining the following two equations:

In order to establish a more accurate calculation method for the average permeability coefficient of the lining, the present invention obtains the seepage flow rate of the tunnel by setting a water collection well, and theoretically deduces the average permeability coefficient of the lining according to the basic geometric parameters of the tunnel and the permeability coefficient of the formation around the tunnel. Compared with other calculation methods of lining average permeability coefficient, the calculation formula has the following characteristics:

(1) The average permeability coefficient of the lining is completely calculated by mathematical formulas, and all the parameters used for calculation are objective and do not depend on empirical judgment, avoiding the subjective influence in the calculation process;

(2) The calculation program is fixed, the parameters are less and better obtained, the calculation formulas are less, and the calculation amount is small, which can be used for the secondary development of commercial software;

(3) The average lining permeability coefficient calculated by this method is more accurate, which is of positive significance for the correct calculation of tunnel internal force and deformation and accurate prediction of tunnel damage during operation;

Description of drawings

Fig. 1 is a flowchart of the present invention.

Fig. 2 Schematic diagram of the parameters involved in the calculation process.

Figure 3 is a schematic diagram of the calculation example.

Figure 4 is a schematic diagram of the axonometric view of the staggered assembly of tunnel segments.

Figure 5 is a schematic diagram of the tunnel water collection well.

detailed description

Referring to Figure 1, the implementation steps are as follows:

(1) start;

(2) Utilize the existing water collection well to measure the total volume V _l of groundwater infiltrated into the tunnel in this section;

(3) Calculation of the leakage _Ql per unit area of the tunnel per unit time: first calculate the outer surface area S of the tunnel in the water-collecting section and the water-collecting time t, and divide _Vl by the product of S and t to obtain the unit of tunnel time Area leakage Q _l ;

(4) Calculate the amount of leakage per unit area Q _s of the tunnel per unit time; since the seepage water in the soil is completely infiltrated into the tunnel by the tunnel joint, Q _s is equal to Q _l ;

(5) Determine the basic geometric parameters of the tunnel: determine the outer diameter R of the tunnel, the inner diameter r ₀ , and the distance h from the ground surface to the center of the tunnel;

(6) Determine the permeability coefficient k _s of the formation around the tunnel;

(7) Calculate the water head height H _R at the interface between the tunnel and the formation; calculate the interface between the tunnel and the formation according to the outer diameter R of the tunnel, the inner diameter r ₀ , the distance h from the ground surface to the center of the tunnel, and the permeability coefficient k _s of the formation around the tunnel head height H _R ;

(8) Calculate the average permeability coefficient _{k l} of the tunnel _lining ; calculate the average permeability coefficient k _l .

where k _l is calculated by combining the following two equations:

Based on the seepage theory, the present invention establishes a mathematical model for calculating the average permeability coefficient of the lining, and calculates the average permeability coefficient of the lining according to the geometric parameters of the tunnel and the permeability coefficient of the formation around the tunnel. Compared with the current mainstream empirical method, the result is more accurate and subject to subjectivity It has little influence, does not depend on empirical judgment, has simple parameters and a small amount of calculation, and can be used for secondary development of commercial software. It has positive significance for obtaining correct calculation results in the design and construction process.

Further describe the present invention by example below

The center of a shield tunnel is 15m away from the surface, the outer diameter and inner diameter are 6.3m and 6m respectively, and the tunnel is surrounded by soft soil stratum, its permeability coefficient is k _s =3×10 ^-9 m/s, Young's modulus of elasticity E =10MPa, Poisson's ratio ν=0.3, the groundwater table is located on the surface. The water seepage quantity Q _l per unit area and unit time in the leakage section obtained from the measurement is 9.3×10 ^-9 m/s.

All the water in the tunnel comes from seepage in the soil, so Q _s =Q _l =9.3×10 ^-9 m/s.

So by the formula The water head at the interface between the tunnel and the soil can be calculated as:

Then by the formula The average permeability coefficient of the lining can be calculated as:

.

Claims (1)

1. the determination method of the average infiltration coefficient of a kind of shield tunnel lining structure, it is characterized in that implementing as follows：

(1) sump for utilizing collects the underground water cumulative volume V for measuring and tunnel being penetrated into the section_l；

(2) tunnel unit interval unit area leakage Q is calculated_l：The external surface area S and collection in the section tunnel that catchments are calculated first Water time t, uses V_lDivided by the product of S and t, tunnel unit interval unit area leakage Q is just obtained_l；

(3) tunnel unit interval unit area leakage Q is calculated_s；Because the percolating water in the soil body all penetrates into tunnel by tunnel joint In road, therefore Q_sEqual to Q_l；

(4) tunnel basic geometric parameters are determined：Determine tunnel external diameter R, internal diameter r₀, earth's surface to tunnel center apart from h；

(5) osmotic coefficient k of tunnel surrounding formation is determined_s；

(6) the head height H in tunnel and stratum interface is calculated_R；According to tunnel external diameter R, internal diameter r₀, earth's surface to tunnel center Apart from h, and tunnel surrounding formation osmotic coefficient k_s, calculate the head height H in tunnel and stratum interface_R；

(7) the average osmotic coefficient k of tunnel-liner is calculated_l；According to tunnel external diameter R, internal diameter r₀, earth's surface to tunnel center apart from h, And the head height H of tunnel and stratum interface_R, calculate the average osmotic coefficient k of tunnel-liner_l。

Wherein k_lCalculated by the following two equations of simultaneous：

。