JP2009133164A - Penetration test method - Google Patents

Abstract

【Task】
Providing an intrusion test method that makes it possible to distinguish between diluvium, alluvium, and humus.
[Solution]
The present invention applies a load W to a penetrating rod 4 formed by attaching a screw point 4b to the tip of a rod-shaped rod 4a, penetrates the ground while rotating it, and acts on the screw point 4b at the time of penetration. in penetration test method for detecting a torque T, and detects the rotation number .DELTA.n _ht of penetration rod 4 between incremental .delta.s _t and penetration rod 4 penetration amount of penetration rod 4 is the penetration volume penetration, these and the load W The energy δE associated with the penetration of the penetration rod 4 is obtained from the rotational load torque T, and the formation is evaluated based on the energy δE. In addition, energy δE can be determined by _{δE = π · T · δn ht} + W · δs t.
[Selection] Figure 1

Description

  The present invention relates to a penetration test method for collecting test data by penetrating a penetrating rod having a penetrating body attached to the tip thereof, and evaluating a formation in a test ground based on the test data.

Conventionally, as a means for knowing the degree of firmness and tightness of the ground, the geological structure of the ground, that is, the soil quality from the ground surface to a certain depth has been investigated. Such soil surveys are generally conducted using a standard penetration test method based on a boring survey. One of the methods used to determine soil quality in the previous stage or in a relatively shallow part is the Swedish sounding test method (hereinafter referred to as “sound quality test”). SWS test). This SWS test measures the hardness of the ground by measuring its resistance when the screw point attached to the rod penetrates the ground. As shown in Non-Patent Document 1 (JIS A 1221, Geotechnical Society), the intrusion method is a load stage in which so-called self-intrusion is performed with only a load by applying a load in six stages up to a maximum of 1 KN with a built-in weight, and the maximum load. Even in 1KN, when the rod does not penetrate, the rod or screw point is rotated under the load, and so-called rotational penetration is performed. The measurement items corresponding to the penetration resistance are the load (W _sw ) when the screw point penetrates a predetermined depth (each 25 cm penetration) at the load stage, and the half revolution of the screw point converted per penetration amount at the rotation stage. (N _sw ). This half rotation number is the number of rotations obtained by counting one rotation of the screw point (or rod) as two.

Japanese Industrial Standard A1221 Swedish Sounding Test Method

In general, the formation of the strata is broadly divided into the Hongu Formation and the Alluvium Formation. In general, the diluvium is hard and the alluvium is classified as a soft formation, but in the SWS test, it is very often difficult to clearly distinguish them. The decisive reason is that the SWS test obtains the load W _sw and the half rotation speed N _sw as data, and is not a test for obtaining soil quality at each depth. Also, unlike sandy and gravel layers, which are often very hard and tight, the Hiroki and alluvium are often composed of clays with different water content ratios, which is a major factor for rod penetration conditions in the SWS test. It is also mentioned that there is no difference. In addition, the moisture content said here is ratio of the mass of the soil particle which comprises the soil of unit volume, and the mass of water.

Fig. 6 shows the SWS test results at the test site A (Kizaki, Urawa Ward, Saitama City, Saitama Prefecture) and the test site B (Kishimachi, Urawa Ward, Saitama City, Saitama Prefecture). Is also written. FIG. 6A shows the result of the test site A composed of the Kanto loam layer, which is the Hongu layer, and FIG. 6B shows the result of the test site B composed of the alluvium layer. In all cases, the W _sw is about 1 KN, and it is impossible to judge whether it is a diluvium layer or an alluvium layer by looking only at the SWS test result. In general, Honghong is a stratum where almost no subsidence occurs, so there is no need to perform ground reinforcement work when building a house on that land. However, when it is difficult to distinguish as described above, pile construction and ground improvement work are often performed as an alluvial layer for safety reasons, and construction periods, labor, and costs that are not necessary are generated. ing. In addition to alluvium, there may be humus layers with a particularly high water content. Looking at the columnar diagram of FIG. 6 (b), there is a humus layer at the top of the alluvium, but no difference is seen in the SWS test. This humus layer is a relatively new stratum, similar to the alluvium, formed by the accumulation and deposition of plant-derived organic soil such as humus, peat, peat, etc. To do. Since this humus soil layer contains a lot of fiber, it has a characteristic of being strong against compression and shearing (having strength) due to these bonds. For this reason, as described above, in the SWS test, data that cannot be distinguished from the diluvium and alluvium appear. On the other hand, the humus soil layer has a very high moisture content of 200 to 400%, and has a characteristic that it is much softer than the diluvium and alluvium in terms of hardness. In other words, when the same mass is placed on the upper part, the humus soil layer is most easily deformed. Therefore, the ground where the humus soil layer exists easily causes land subsidence. With the SWS test alone, it is difficult to distinguish the most vigilant humus layer, which may cause problems such as the lack of ground reinforcement due to the evaluation of alluvium and diluvium. It was.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an intrusion test method capable of discriminating between diluvium, alluvium, and humus.

In order to achieve the above object, the present invention applies a load W to a penetrating rod formed by attaching a penetrating body to the tip of a rod-shaped rod, and penetrates it into the ground while rotating it, and acts on the penetrating body at the time of this penetrating. in penetration test method for detecting a rotational load torque T, penetrating amount of incremental .delta.s _t and penetration rod penetration rod detects the rotation number .DELTA.n _ht penetration rod during the penetration amount penetration, these and the load W The energy δE associated with the penetration of the penetration rod is obtained from the rotational load torque T, and the formation is evaluated based on the energy δE.

In the above method, the load W is changed, and the increment δst _t of the penetration amount of the penetration rod at each load W, the number of rotations δn _ht of the penetration rod therebetween, and the rotational load torque T are detected. It is desirable to obtain an energy δE associated with the penetration of the penetration rod under each load W and evaluate the formation based on the energy δE. The energy δE is
It is desirable to obtain by Further, it is desirable that the number of rotations δn _ht of the penetrating rod is a half-rotation number obtained by counting one rotation of the penetrating rod as two. Furthermore, it is desirable to evaluate the formation based on a graph in which the energy δE is plotted corresponding to the penetration depth of the penetration rod.

In the present invention, a load W is applied to a penetrating rod formed by attaching a penetrating body to the tip of a rod-shaped rod, and the rotating rod is penetrated into the ground while rotating it. A rotational load torque T acting on the penetrating body at the time of this penetrating is obtained. in penetration test method for detecting the penetration amount of incremental .delta.s _t and penetration rod penetration rod detects the rotation number .DELTA.n _ht penetration rod during the penetration amount penetration, these and the load W, the rotational load torque T and With the maximum diameter D of the penetrating rod,
Seeking plastic potential coefficient c _p, it is also characterized by evaluating the formation based on the plastic potential coefficient c _p.

In the method for evaluating the formation by the plastic potential coefficient c _p, changing the load W, and incremental .delta.s _t penetration amount of penetration rod in each load W, a rotational number .DELTA.n _ht therebetween penetration rod, the rotational load detecting the torque T, determine the plastic potential coefficient c _p under the load W from these, it is desirable to evaluate the formation based on the plastic potential coefficient c _p. Further, it is desirable that the number of rotations δn _ht of the penetrating rod is a half-rotation number obtained by counting one rotation of the penetrating rod as two. Further, it is more desirable to evaluate the formation based on the plot of plastic potential coefficient c _p in correspondence with penetration depth of the penetration rod.

In the present invention, a load and rotation are added to the penetrating rod to penetrate into the ground, and the formation is evaluated by the energy δE at the time of penetration caused by this load and the rotational load torque at the time of rotation. For this reason, it is possible to evaluate the strength and hardness of each layer comprehensively and evaluate them. It is possible to determine the diluvium, alluvium, and humus soil layers that are composed of viscous soil, which was difficult to distinguish in the SWS test. There are advantages such as being able to discriminate. The present invention is to penetrate into the ground by adding a rotation load penetration rod detects a rotation number and penetration amount of penetration rod, determine the plastic potential coefficient c _p from these, the plastic potential coefficient c _The formation is evaluated by _p . This plastic potential coefficient can also be used to comprehensively quantify the strength and hardness of each layer, so that it is possible to distinguish between diluvium and alluvium or diluvium and humus.

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.
In FIG. 1 to FIG. 4, reference numeral 1 denotes an automatic penetration testing machine, which has a lifting platform 3 that can be lifted and lowered along a standing column 2. The lift 3 includes a penetrating rod 4 connected to the tip of a rod-like rod 4a and a tip connected to the tip, a chuck unit 5 capable of holding the penetrating rod 4 integrally, and the chuck unit 5 A chuck motor 6 that rotates, a sprocket 7 that meshes with a chain member 2 a that extends in the longitudinal direction of the support column 2, a lift motor 8 that rotates the sprocket 7, and the sprocket 7 is rotated. Brake means 9 for braking and weights 3a for adjusting the mass are provided. When the total mass of the mass of these equipments and the mass of the lifting platform 3 is loaded on the penetrating rod 4, a load of 1 KN at maximum is applied to the penetrating rod 4. The chuck motor 6, lift motor 8 and brake means 9 are driven and controlled by a control unit 10.

  The chuck unit 5 is rotatably disposed on the lifting platform 3. Sprockets 11 and 12 are integrally fixed to the lower part of the chuck unit 5 and the output shaft 6a of the chuck motor 6, respectively, and both are connected by winding an annular chain 13 around them. A proximity sensor (not shown) is provided at a position facing the teeth of the sprocket 11 on the chuck unit 5 side to detect ON and OFF of the passage of the teeth when the sprocket 11 rotates. The signal of the proximity sensor is acquired by the control unit 10, and the control unit 10 is configured to determine the half rotation number of the penetrating rod 4 from this signal.

  The sprocket 7 is connected to the elevating motor 8 via the one-way clutch 14 and the brake means 9, and the one-way clutch 14 moves up and down to rotate the sprocket 7 in the direction to raise the elevator 3. When the motor 8 is driven, this is transmitted to the sprocket 7. Driving the lifting motor 8 that rotates the sprocket 7 in the reverse direction (hereinafter referred to as reverse driving) causes the one-way clutch 14 to run idle. For this reason, when the lifting / lowering motor 8 is reversely driven while the screw point 4b is in contact with the ground, the penetrating rod 4 (rod 4a or screw point 4b) is loaded with a load such as the lifting platform 3 or the like. This load can be freely changed from 0 N to a maximum load of 1 KN by changing the force with which the brake means 9 brakes the sprocket 7. The brake means 9 is preferably a powder brake or a powder clutch.

  In the automatic penetration testing machine 1, the penetration test is started from the position where the screw point 4b at the tip of the penetration rod 4 is in contact with the ground surface. Up to this position, the manual operation button provided in the control unit 10 is pushed to reversely drive the lifting motor 8 to lower the lifting platform 3. When a test start signal is given by pressing the start button from this position, the control unit 10 automatically starts penetrating control of the penetrating rod 4 into the ground. That is, the control unit 10 receives the test start signal and reversely drives the lifting motor 8 and rotates the chuck motor 6. Thereby, the load by the mass of the lifting platform 3 etc. is applied to the penetration rod 4, and it penetrates in the ground, rotating these.

  During the test, the control unit 10 controls the brake means 9 to increase the load applied to the penetrating rod 4 in the order of the minimum load 50N to 150N, 250N, 500N, 750N, 1000N (1KN). Then, the rotational load torque applied to the penetrating rod 4 under each load, the half rotation number of the penetrating rod 4 and the increment of the penetrating amount of the penetrating rod 4 are obtained and stored. This is performed for each unit section, with a section where the penetration rod 4 penetrates 25 cm as a unit section. Here, since the rotational load torque acting on the penetrating rod 4 is proportional to the current value applied to the chuck motor 6, the rotational load torque is obtained from the load current value of the chuck motor 6 in this example. Further, the increment of the penetration amount of the penetration rod 4 is calculated by calculating the number of rotations of the sprocket 7 from the signal of the rotary encoder 15 that detects the rotation of the sprocket 7, and multiplying this by the penetration amount per one revolution of the sprocket. Can do. Further, the control unit 10 calculates and stores the penetration depth of the screw point 4b by integrating the increments of the penetration amount, and calculates the penetration speed of the screw point 4b from the penetration amount per unit time. The control unit 10 repeats the above process to penetrate the screw point 4b to a predetermined depth (for example, a depth of 10 m in the ground). During the penetration test, the rod 4a of the penetration rod 4 is extended by screwing an extension rod (not shown) to the upper threaded portion 4c as necessary.

The energy δE at the time of penetration by each load W and the rotational load torque T applied to the screw point 4b is:
It can be expressed as. Here .DELTA.n _ht semi rpm under each load (half the rotation speed of the incremental), .delta.s _t is the incremental penetration amount under each load. The value on the right side of the same number 1 indicates the energy at the time of penetration due to the load on the left, and the energy at the time of penetration due to rotation addition on the right. That is, the energy δE is represented by the sum of the penetration energy due to the load and the penetration energy due to the rotation.

FIG. 5 shows the results of a uniaxial compression test conducted for all soils of alluvium and humus. As can be seen from this result, the alluvium with a low moisture content and a large amount of soil components compared to the humus layer is tight in terms of hardness, but as shown in FIG. Cause fatigue failure at an early stage. On the other hand, the humus soil layer with a high water content ratio and a large amount of organic matter is soft in terms of hardness in a so-called water-containing sponge state, but as shown in FIG. Fatigue failure is less likely to occur, and it can withstand the same stresses as the diluvium and alluvium. This is considered to be because the fibers and the like contained in the humus soil layer are combined to ensure strength. Also, by analogy with this, in the diluvium, which has a lower water content than the alluvium, fatigue failure occurs at an earlier stage, but the fatigue limit is considered to be equivalent to the alluvium because it is the same cohesive soil. In this way, it is clear that the humus layer, alluvium layer, and humus layer are different in hardness but the fatigue limit is the same or rather, the humus layer tends to be higher and the difference in strength is small. For this reason, in the SWS test in which the maximum load is about 1 KN, there is no difference in the W _sw value. Moreover, since all the strata are cohesive soil, they are vulnerable to excavation by rotation. The humus soil layer also has a high water content ratio and is very soft as a ground layer. Therefore, the above-described fiber bonding and the like are easily deconstructed by applying rotational torque. For this reason, there is almost no difference in the _Nsw value of the SWS test in each layer. However, the difference in the hardness of each layer appears in the rotational load torque T. The rotational load torque T is high when the moisture content is low and the soil component is large as in the case of diluvium, and the rotational load torque T is low when the moisture and organic matter are increased with respect to the soil component as in the humus soil layer. Moreover, such a difference becomes conspicuous due to the synergistic effect of the load and rotation by rotating the penetrating rod 4 while changing the applied load W instead of simply rotating the penetrating rod 4. Therefore, if the energy δE at the time of intrusion is expressed as the sum of the intrusion energies caused by the load and the rotational load torque as shown in Equation 1, it is possible to clearly discriminate the diluvium, alluvium and humus soil layers. .

Regarding the test site A composed of the diluvium in Fig. 6 (a) and the test site B composed of the alluvium and the humus soil layer in Fig. 6 (b), as described above, there is almost no difference in the SWS test results. I can't. In contrast, FIGS. 7 and 8 by the penetration test method of the present invention in the same experimental site, acquired rotational load torque T of each load is W, the increment .delta.s _t semi rotational speed .DELTA.n _ht and penetration amount as test data, It is the graph which calculated | required energy (delta) E under each load W based on these based on these, and plotted the typical value per unit area (penetration amount 25cm) corresponding to the penetration depth of the screw point 4b. FIG. 7 shows the test site A of the Hongu layer and FIG. 8 shows the test site B of the alluvium layer and the humus layer. A thick broken line drawn in each figure is an approximate straight line of energy δE. Here, the representative value per unit section is plotted in order to clarify the fluctuation of the energy δE. Usually, a plurality of energies δE are obtained while the unit section penetrating rod 4 penetrates, and when all of them are plotted, the mode shown in FIG. 9 is obtained. Incidentally, this FIG. 9 shows the data obtained by the penetration test in the ground different from the test site A and the test site B. Even when all energies δE are plotted as shown in FIG. 9, changes in δE can be identified. However, it is easier to identify changes in δE when these representative values are determined based on a certain standard. Is obtained. As the representative value, an average value, a maximum value, a minimum value, or the like of the energy δE for each unit section is preferable. Note that the penetration depth-energy δE graphs as shown in FIGS. 7 and 8 are displayed and output on the liquid crystal panel 10a of the control unit 10 or printed out by the printer 10b so as to be visible to the operator. The

  When FIG. 7 and FIG. 8 are compared, it can be seen that the energy δE is large in the diluvium, small in the alluvium, and greatly varied in the humus soil layer. From this, it is possible to discriminate the diluvium, alluvium, and humus layer from the change in energy δE with respect to the penetration depth.

To determine the diluvial and alluvial or diluvial and humus layer, besides by energy &Dgr; E, by using the obtained test data, the plastic potential coefficient c _p at each depth by the following equation (2) calculated, or depending on the size of the c _p.
In Equation 2, D indicates the maximum diameter of the penetration rod 4, that is, the maximum diameter of the screw point 4b, and N _sw indicates the number of half revolutions (δn _ht / δs _t ) per meter of penetration.

Conducting a standard penetration test and conducting the penetration test according to the above method of the present invention on the actual ground whose geology and soil properties are known in advance, obtaining the test data, substituting this into Equation 2, and calculating the plastic potential coefficient c _p Table 1 shows the obtained results.

Plastic potential coefficient c _p is to yield surface obtained by processing the test data in the mathematical model known as macro elements, which indicate the slope of a straight line intersecting at right angles through the coordinate origin, in Table 1 As shown, different values are shown for each formation and soil type. Graph representative values were plotted to correspond to the penetration depth in the unit section of the plastic potential coefficient c _p is 10 and 11. Figure 10 shows the changes to the penetration depth of the plastic potential coefficient c _p of the test locations A of diluvial represented by FIG. 6 (a), the 11, alluvium and humus layer shown in FIG. 6 (b) It shows the changes to the penetration depth of the plastic potential coefficient c _p of test plots B. Thick broken line drawn in the figures is an approximate straight line of the plastic potential coefficient c _p. According to these FIGS. 10 and 11, it can be seen that the magnitude of the plastic potential coefficient c _p is distinctly different in diluvial and alluvial or diluvial and humus layer. Therefore, to calculate the plastic potential c _p in the control unit 10, which by outputting as a table or graph to correspond to penetration depth, is possible to determine diluvial and alluvial or diluvial and humus layer It becomes possible.

  The above macro element is also called a plasticity analogy model, and it uses the same framework (analogue) as the constitutive law that gives the relationship between soil stress and strain, and describes a mathematical model that describes the relationship between the load and displacement of a structure. That is. The load applied to the structure includes a vertical load, a moment, a horizontal load, etc., but the load at the time of destruction of the structure changes depending on the combination of other loads. In the microelement, the magnitude of such a combined load is described as a yield surface, and the displacement increment corresponding to each of these loads is described using a plastic potential function. The test that penetrates the penetrating rod into the ground by applying load and rotation, such as the Swedish sounding test and the penetration test introduced in this example, applies the rotational load torque in the rotation stage in addition to the vertical load in the load stage. Since this is a load test, it can be said that this is one of the problems of combined loads to which microelements can be applied.

Therefore, a microelement for such penetration test is constructed as follows. First, the energy δE by the load W at the load stage and the rotational load torque T at the rotation stage applied to the screw point is as shown in Equation 1. When Formula 1 is normalized using the product of the self-sinking load _Wp and the maximum diameter D of the screw point,
It becomes. Here, T _n is a normalized torque, and W _n is a normalized load. Also, the number 3 results in the application of plastic potential to be described later, T _n and .DELTA.n _ht and W _n and .delta.s t _{/ D} is determined to have a coaxiality respectively.
From the experimental results to be described later, it has been confirmed that the yield curved surface by the rotational load torque T and the load W obtained by the penetration test can be expressed by an elliptical curve centered at the origin. Therefore, the shape of the yield surface with yield surface coefficients c _y,
It expresses. When this equation 4 is expressed using equation 3,
If this is arranged, the yield surface can be expressed in another form as follows.
Assuming that the plastic potential function also exhibits an elliptic curve similar to the yield surface,
It can be expressed. Here c _p is the plastic potential coefficient, which is associated flow rule is satisfied when equal to said c _y. Differentiating Eq. 7 by W _n and further obtaining the direction orthogonal to the plastic potential function,
It becomes. Here defining the _{N sw} D multiplied by the screw point maximum diameter D to the half rotational speed _{N sw} per 1m penetration amount and the normalization _{N sw.} The above equation 2 is obtained from this equation 8.

  FIG. 12 to FIG. 14 show the analysis results of experiments conducted on clay soil samples. The experiment was carried out with an experimental artificial strata made of clay. The experimental artificial stratum is Fujinomori Clay C, in which sand and gravel are spread as a drainage layer at the bottom of a circular earth basin B with a diameter of 28 cm and a height of 50 cm as shown in FIG. In order to increase the water permeability of this clay C, it is deaerated using a vacuum pump for 24 hours, and then it is obtained by carrying out consolidation by loading about 20 kPa stepwise from the upper part and reducing the lower part to -100 kPa. It was.

  As shown in FIG. 15, the experimental device includes a rod 20, a weight 21, a weight loading device 22 with a bearing, a screw point 23, and a torque meter 24. Here, the screw point 23 is made of silver clay so as to be 1/5 of the actual size, and has a shape in which a square weight is twisted once to the right and has a maximum diameter of 6.7 mm and a long length. The length is 40 mm.

In the experiment method, first, the screw point 23 and the weight loading device 22 are attached to the tip of the rod 20, and the rod 20 is fixed so as to penetrate vertically. Next, the initial weight 21 is loaded, and the amount of penetration at that time is measured after self-sink (penetration only by load) stops. On the other hand, if the self-sink does not settle even when the maximum load is loaded, the torque gauge 24 is used for rotational penetration. The screw point 23 penetrates to a depth of 25 cm while obtaining a self-sinking load or rotational load torque every 5 cm by this method. When the screw point 23 penetrates to a depth of 25 cm, the test is repeated in a similar manner withdrawing once and changing the maximum load. This is performed by changing the maximum load in five stages of 40N, 80N, 120N, 160N, and 200N, for example, so that a self-sinking load at the same depth (every 5 cm) or a rotational load torque with different loads can be obtained. FIG. 12 is a plot of these (πT / D) ² and W ² relationships for each depth. The slope in FIG. 12 is the yield surface coefficient c _y , and the X-axis intercept is the self-sink load W _p . FIG. 13 plots the relationship between πT / W _p D and W / W _p by substituting the self-sink load W _p , maximum load W, and rotational load torque T at each depth obtained in this way into Equation 4. , the solid line in the figure indicates a theoretical value calculated by substituting the yield surface coefficients c _y number 4. Comparing the theoretical value with the experimental value, although there was some variation, the existence of an elliptical yield surface like the theoretical value was confirmed. FIG. 14 is a graph showing the relationship between normalized N _sw in Equation 8 and πT / WD using the load W and the rotational load torque T obtained for the clay ground.

  FIG. 16 shows an experiment using experimental soil layers prepared for each soil sample of Kanto loam, medium-density sand, and dense sand in the same manner as the above-mentioned clay ground. It is the figure plotted on the same scale together with the thing. Thereby, it turns out that a yield surface shows a different shape in each soil. In this way, it is also possible to determine the soil quality by comparing the yield surface obtained for each soil with the yield surface obtained in the test on the actual ground (hereinafter referred to as the actual ground). Is possible. It should be noted that the yield surface is not limited to an ellipse, and is considered to have various shapes depending on the soil quality. For this reason, it is preferable to prepare as many types of yield curved surfaces for each soil as the soil determination criteria by experiments with various soil samples or actual measurements on the actual ground.

FIG. 17 shows the relationship between normalized N _sw in Equation 8 obtained from the experimental results of Kanto loam, medium-density sand, and dense sand, and πT / WD together with those of clay ground on the same scale. is there. Tilt also different for each soil type in this relationship, that is, from to exhibit plastic potential coefficient c _p, it is also possible to use this chart as a reference for soil determination. In actual ground, easy person plotting c _p corresponding to the depth as described above to determine the change in the strata and soil. Further, Table 2 following, the above experiment clay obtained from the results, Kanto loam, it summarizes Chumitsusuna, the yield surface coefficients for dense sand c _y and the plastic potential coefficient c _p. It can be seen that these values also differ depending on the soil quality. Therefore, to get the rotational load torque T and the load W by penetrometer in a real ground, them from using Equation 4 to Equation 8 each coefficient c _y, seek c _p, reference obtained in these experiments in advance It is possible to determine the soil quality by comparing with the value.

In the penetration test in the actual ground, when the penetration rod 4 penetrates into the ground, the length of the rod 4a is increased, and thus the resistance of the soil acting on the rod 4a is increased. Therefore, when the analysis based on the plasticity analogy model described above is applied to an actual penetration test, it is necessary to consider the influence of the peripheral friction acting on the rod 4a. FIG. 18 shows a conceptual diagram of the peripheral friction acting on the penetrating rod 4. The vertical circumferential friction acting on the rod 4a is W _f , the horizontal circumferential friction is T _f , the true load applied to the screw point 4b is W, and the true rotational load torque is T. In this case, the load W _a and the rotational load torque T _a (the load actually applied to the penetrating rod 4 and the detected rotational load torque) in consideration of the peripheral surface friction are expressed by Equations 9 and 10.
Assuming that the resultant velocity direction and the resultant shear stress direction are equal, Equations 11 and 12 are obtained.
Here, .DELTA.n _ht is a half rotational speed increment, .delta.s _t is penetration of increments, r is the rod diameter, tau Expediently shear stress, tau _theta Horizontal shear stress, tau _z is vertical shear stress .
On the other hand, if the friction caused by rotation and self-sinking penetration is T _f and W _f , respectively, Equation 13 is obtained.
From this number 13,
From Equations 12 and 13,
It becomes. Here, F is the resultant force of circumferential friction due to load and torque. From Equation 8, Equation 9, and Equation 14,
From Equations 10 and 16,
And solving this number 17 for N _sw D,
It becomes. By this equation 18, normalized N _sw in consideration of the peripheral surface friction of the rod 4a can be obtained. When the normalized N _sw is used as a reference for determining soil quality, it is preferable to use the normalized N _sw considering the circumferential friction. Also, when obtaining the above-mentioned yield surface, it is better to use the load W and the rotational load torque T acting on the screw point 4b. In this case, the scheme indicated by the JP 2001-228068, it is possible to obtain the vertical direction of the peripheral surface frictional W _f acting on the load W and a rod 4a according to the screw point 4b. Thereby substituting the number 14 a vertical skin friction W _f obtained determined the horizontal peripheral surface frictional torque T _f which acts on the rod 4a and further, the horizontal peripheral surface frictional torque T _f, actual measured rotational load and Tokuru T _a can be determined rotational load torque T applied to the screw point 4b by substituting the equation 9. In this way, the load W and the rotational load torque T acting on the screw point 4b excluding the load and torque due to the circumferential friction acting on the rod 4a are obtained, and by using these, a more accurate yield surface is obtained. Can be sought.

Load and rotational load torque was obtained as the test data in the penetration test according to the automatic penetration tester 1 is equivalent to the load W _a and the rotational load torque T _a in the number 9, number 10 precisely. Therefore, in order to evaluate more accurately formations, the control unit 10, is loaded on the obtained load W _a exclude the effect of skin friction and a rotation load torque T _a ,, screw point 4b It is preferable to obtain the load W and the rotational load torque T.

In the above description, the load applied to the penetrating rod 4 is changed stepwise to obtain the rotational load torque under each load every time the screw point 4b penetrates a unit section of 25 cm. In addition, the rotational load torque for different loads at each predetermined depth may be acquired by the following method. That is, while penetrating the rod at a predetermined depth (for example, 25 cm), the penetrating rod 4 is penetrated into the ground by appropriately performing self-sinking and rotating penetration according to a normal Swedish sounding test method. Each time the screw point 4b penetrates to a predetermined depth, the load is once set to 0 (zero), and from this point, the load is 50N, 150N, 250N, 500N, 750N, 1KN (however, the self-sinking penetration occurs while penetrating the predetermined depth). In the case where the self-sinking penetration occurs, the load is increased) and the penetration rod 4 is rotated for each load to obtain rotational load torque and other data. Even from this by the obtained test data determined energy δE and plastic potential coefficient c _p, it is possible to determine the formation.

It is a perspective view of the automatic penetration testing machine which enforces the penetration testing method concerning the present invention. It is an expanded side view of the automatic penetration testing machine which enforces the penetration testing method concerning the present invention. It is an expanded sectional view concerning the AA line of FIG. It is a principal part expanded partial notch sectional view of the automatic penetration test machine which implements the penetration test method which concerns on this invention. (A) is an alluvium soil, (b) is a graph which shows the uniaxial compression test result of humus soil. (A) is a comparative test drawing of the SWS test results in the test site A of the Hongu layer and (b) in the test site B of the alluvium layer and the humus layer. It is a graph of penetration energy (delta) E with respect to the penetration depth in the test site A of a basin. It is a graph of penetration energy (delta) E with respect to the penetration depth in the test site B of an alluvium and a humus soil layer. It is a graph for explanation of penetration energy δE with respect to penetration depth. It is a graph of the plastic potential coefficient c _p for penetration depth in the experimental area A of diluvial. It is a graph of the plastic potential coefficient c _p for penetration depth in the experimental area B of alluvium and humus layer. It is a graph for the description of the experimental data regarding a macro element. It is a graph for the description of the experimental data regarding a macro element. It is a graph for the description of the experimental data regarding a macro element. It is a schematic explanatory drawing of the experimental apparatus regarding a macro element. It is a graph which shows an example of the yield surface about various soils. It is a graph which shows an example of the plastic potential coefficient about various soils. It is a conceptual diagram for the description of the circumferential friction which acts on the penetration rod penetrated into the ground.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Automatic penetration test machine 2 Support | pillar 2a Chain member 3 Lifting stand 4 Penetrating rod 4a Rod 4b Screw point 5 Chuck unit 6 Chuck motor 7 Sprocket 8 Lifting motor 9 Brake means 10 Control unit

Claims (9)

An intrusion test method for detecting a rotational load torque T acting on the penetrating body when the penetrating rod is inserted into the ground while rotating the load W by loading the penetrating rod with the penetrating body attached to the penetrating rod. In
Penetration amount of incremental .delta.s _t and penetration rod penetration rod detects the rotation number .DELTA.n _ht penetration rod during the penetration amount penetration, due to the penetration of the penetration rod from these and the load W and the rotational load torque T An intrusion test method characterized by obtaining energy δE and evaluating the formation based on energy δE. Changing the load W, and incremental .delta.s _t penetration amount of penetration rod in each load W, a rotational number .DELTA.n _ht therebetween penetration rod, and detects the rotational load torque T, from under the load W These The penetration test method according to claim 1, wherein an energy δE associated with the penetration of the penetration rod is obtained, and the formation is evaluated based on the energy δE. The energy δE is
The penetration test method according to claim 1, wherein the penetration test method is obtained by: The penetration test method according to any one of claims 1 to 3, wherein the number of rotations δn _ht of the penetration rod is a half rotation number obtained by counting one revolution of the penetration rod as two.   The penetration test method according to any one of claims 1 to 4, wherein the formation is evaluated based on a graph in which energy δE is plotted corresponding to the penetration depth of the penetration rod. An intrusion test method for detecting a rotational load torque T acting on the penetrating body when the penetrating rod is inserted into the ground while rotating the load W by loading the penetrating rod with the penetrating body attached to the penetrating rod. In
Penetration amount of incremental .delta.s _t and penetration rod penetration rod detects the rotation number .DELTA.n _ht penetration rod during the penetration amount penetration, these and the load W, the maximum diameter D of the rotational load torque T and penetration rod Using,
Plastic potential determined coefficients c _p, Penetration Test method characterized by evaluating the formation based on the plastic potential coefficient c _p by. Changing the load W, and incremental .delta.s _t penetration amount of penetration rod in each load W, a rotational number .DELTA.n _ht therebetween penetration rod, and detects the rotational load torque T, from under the load W These It is seeking plastic potential coefficient c _p, penetration test method according to claim 6, characterized in that to evaluate the formation based on the plastic potential coefficient c _p. The penetration test method according to claim 6, wherein the number of rotations δn _ht of the penetration rod is a half rotation number obtained by counting one revolution of the penetration rod as two. Penetration test method according to any one of claims 6 to 8, characterized in that to evaluate the formation based on the plot of plastic potential coefficient c _p in correspondence with penetration depth of the penetration rod.