CN213062128U - Pile foundation static load test device suitable for expansive soil - Google Patents

Abstract

The utility model discloses a pile foundation static load test device suitable for expansive soil, which comprises a pressure loading device, a model pile, an expansive soil compaction cylinder and a drain valve, wherein the outer surface of the model pile is provided with a concrete wrapping layer, and a plurality of strain sensors which are arranged at equal intervals from top to bottom are fixed on the concrete wrapping layer; the model pile is vertically inserted into the expansive soil compaction cylinder, and the bottom of the model pile is contacted with the pressure sensor; the pressure loading end of the pressure loading device is in contact with the top of the model pile to apply vertical pressure to the model pile; the drain valve is arranged at the bottom end of the expansive soil compaction cylinder; the expansive soil compaction cylinder is internally provided with stones, medium sand and expansive soil samples from bottom to top in sequence, and is provided with a horizontal sand infiltration layer and a vertical sand infiltration layer. Four horizontal sand infiltration layers are arranged at equal intervals from top to bottom, wherein three horizontal sand infiltration layers are uniformly arranged in the expansive soil sample, and one horizontal sand infiltration layer is arranged in the medium sand sample. The test period is short, the measurement result is reliable, and objective and accurate measurement of the stress index of the pile foundation can be realized.

Description

Pile foundation static load test device suitable for expansive soil

Technical Field

The utility model belongs to geotechnical test measures the field, relates to a pile foundation static load test device suitable for inflation soil.

Background

The expansive soil is a disastrous geology in engineering, and in the treatment of highway foundations, pile foundation reinforcement treatment on the expansive soil is one of effective methods, and the method and the principle can be simply summarized as that a pile body is driven into a certain depth of a non-expansive soil area at the lower part of the expansive soil foundation, and the damage to an upper pavement structure caused by the expansion of the expansive soil in water or dehydration and drying shrinkage is resisted by utilizing the strength of the pile body and the constraint action on the soil body.

Under the condition that the expansive soil expands when encountering water, the soil body can generate uplift force on the pile; the expansion soil is dehydrated and dried to shrink, and then the pile generates a pull-down force (negative frictional resistance), so that the research on the pile-soil combined action in the expansion soil is much more complicated than that of common soil, and the load transmission mechanisms of the expansion soil are not completely the same. Therefore, the research on the load transfer characteristics of the pile foundation is carried out, and the method has important engineering significance for realizing the uneven arching and settlement of the expansive soil foundation, resisting the damage to the upper pavement structure caused by the expansion of the expansive soil in water or dehydration drying shrinkage and realizing the reasonable design of the pile foundation.

In the prior art, the research means for the load transfer characteristics of the pile foundation mainly comprises a static load test, a model test and a numerical analysis. The most direct and reliable method adopts a static load test, not only can provide direct basis for researching the load transmission characteristics of the pile foundation and the design of the pile foundation, but also is a means for verifying the rationality of model test and numerical analysis. However, the technical defects mainly faced by the static load test in the prior art scheme are as follows: the existing static load test mostly adopts direct water seepage modes such as spray head water spray and the like, the water seepage is slow, the test period is long, and the test result can not objectively reflect the load transfer rule of the pile foundation in the engineering practice, so that the test result has large deviation with the engineering practice and low reliability.

Disclosure of Invention

An object of the embodiment of the utility model is to provide a pile foundation static load test device suitable for inflation soil to solve the test result of current static load test instrument and the problem that engineering actual deviation is great, test result reliability is low, and the problem of the experimental cycle length of current static load test instrument.

The embodiment of the utility model adopts the technical scheme that the pile foundation static load test device suitable for expansive soil comprises a pressure loading device, a model pile, an expansive soil compaction cylinder and a drain valve, wherein a concrete wrapping layer is uniformly arranged on the outer surface of the model pile, and a plurality of strain sensors which are arranged at equal intervals from top to bottom are fixed on the concrete wrapping layer; the model pile is vertically inserted into the expansive soil compaction cylinder, and the bottom of the model pile is contacted with a pressure sensor in the expansive soil compaction cylinder; the pressure loading end of the pressure loading device is in contact with the top of the model pile to apply vertical pressure to the model pile; the drain valve is arranged at the bottom end of the expansive soil compacting barrel;

and stones, medium sand and expansive soil samples are sequentially paved in the expansive soil compacting cylinder from bottom to top, and a horizontal sand seepage layer and a vertical sand seepage layer are arranged.

The utility model provides an advantageous effect is, has provided a pile foundation static load test device suitable for inflation soil, has following advantage:

(1) the pile foundation static load test device suitable for expansive soil of the embodiment has fully considered the sensitivity characteristic of expansive soil to water, through set up vertical sand infiltration layer and horizontal sand infiltration layer in the inside of the expansive soil compaction cylinder, compare the direct infiltration mode that adopts in traditional device and method, the utility model discloses a water injection hole and vertical sand infiltration layer mouth carry on the infiltration, moisture can ooze along vertical sand infiltration layer, horizontal sand infiltration layer evenly, guaranteed the even distribution of moisture in the expansive soil, make it more press close to the moisture distribution state in the actual engineering; when static load test under the conditions of drainage and water seepage is carried out on the basis, the expansion and contraction deformation of the expansive soil is more in accordance with the actual engineering, and the purpose of accurately simulating the interaction between the pile and the soil is realized, so that the pile foundation load transfer rule of the test result in the actual reaction engineering is more objective, the test result is closer to the actual engineering, and the problem that the test result of the existing static load test instrument is larger in deviation with the actual engineering is solved.

(2) The utility model discloses pile foundation static test device suitable for inflation soil's experimental data reliability is high. When the stress characteristics of the pile foundation are researched, the constraint of the expansive soil sample and the pile foundation is interaction, including the transverse embedding force and the vertical frictional resistance, in the prior art, numerical calculation analysis is carried out on the expansive soil sample by adopting finite element software or analytical calculation is carried out by adopting a theoretical method, the analysis results of the finite element software fail to well reflect the interaction between the expansive soil sample and the pile foundation, and although the analysis results of the numerical solution and the experimental solution tend to be consistent, the error between the numerical solution and the experimental solution is larger. The embodiment of the utility model provides a use concrete layer parcel in the model pile outside, effectively simulated the roughness on pile body surface, can add stone, middlings, inflation soil sample in proper order in the inflation soil increases a solid section of thick bamboo, set up vertical infiltration sand layer, horizontal infiltration sand layer in the inflation soil increases the inside of a solid section of thick bamboo, has restoreed the actual operating condition of the pile body in the engineering; pile foundation deformation and pile foundation atress two indexes are mainly considered in the atress characteristic research of pile body among the static load test, the utility model discloses a strain transducer can measure the pile foundation deformation index of the interface department of pile body and concrete, and model pile bottom surface is provided with pressure sensor, can be in the change situation of whole journey monitoring pile foundation atress in the test process, by pile foundation deformation and pile foundation atress between the correlation realize the direct judgement to test data accuracy and rationality to improve test data's reliability, effectively solved the problem that current static load test instrument's test result reliability is low.

(3) The utility model discloses pile foundation static test device suitable for inflation soil has effectively shortened test period. In the expansive soil pile foundation static load test, the main reason that leads to test cycle length is that moisture permeates slowly and causes in expansive soil, the utility model discloses increase a solid inside of section of thick bamboo at expansive soil and set up vertical sand infiltration layer and level and ooze the sand bed, ooze water through the water filling hole and the vertical sand infiltration layer that ooze the sand bed intercommunication with the level to utilize the high characteristic of sand osmotic coefficient to realize moisture quick, the even infiltration in expansive soil, effectively shorten test cycle, solved the problem of current static load test instrument test cycle length.

Overall, the utility model discloses pile foundation static load test device test period suitable for inflation soil is short, measuring result is reliable, can realize objectively, accurately measuring pile foundation atress index, provides the foundation for security, the rationality of research pile foundation load transmission characteristics and pile foundation design.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is the utility model discloses a pile foundation static load test device's schematic structure suitable for inflation soil.

Fig. 2 is a schematic structural view of the expansive soil compacting cylinder of the embodiment of the present invention.

Fig. 3 is a schematic structural diagram of a model pile according to an embodiment of the present invention.

In the figure, 1, a bearing plate, 2, a force transmission shaft, 3, a bearing block, 4, a model pile, 5, a horizontal sand penetration layer, 6, a vertical sand penetration layer, 7, a strain sensor, 8, a concrete wrapping layer, 9, a pressure sensor, 10, a bracket, 11, an expansive soil compaction cylinder, 12, a water injection hole, 13, a soil pressure box and 14, a drain valve are arranged.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

The existing static load test mostly adopts a direct water seepage mode, the characteristic of sensitivity of expansive soil to water cannot be fully considered, because the expansive soil has the characteristics of more clay grains and small permeability coefficient, the direct water seepage mode causes slow water seepage in the expansive soil, and the direct water seepage causes excessive non-uniformity of water in the expansive soil to generate obvious expansion and shrinkage difference, the simulation of pile-soil interaction after the expansive soil is subjected to expansion and shrinkage deformation has obvious difference with the actual engineering, and the interaction has obvious influence on the analysis of the pile foundation load transfer rule, so that the test result cannot objectively reflect the load transfer rule of the pile foundation in the actual engineering. Based on this, the embodiment of the utility model provides a pile foundation static load test device suitable for inflation soil, as shown in fig. 1, including pressure loading device, model stake 4, inflation soil increase solid section of thick bamboo 11 and drain valve 14, the surface of model stake 4 evenly is provided with a layer of concrete parcel layer 8, concrete parcel layer 8 is used for simulating the roughness on pile body surface in the actual engineering, and is fixed with a plurality of from the top down equidistant strain sensor 7 that set up on the concrete parcel layer 8 of model stake 4, strain sensor 7 is used for measuring the strain condition of model stake 4. The model pile 4 is vertically inserted into the expansive soil compaction cylinder 11, the bottom of the model pile is contacted with the pressure sensor 9 in the expansive soil compaction cylinder 11, and the pressure sensor 9 is used for measuring the vertical pressure transmitted by the model pile 4; the pressure loading end of the pressure loading device is in contact with the top of the model pile 4 to apply vertical pressure to the model pile 4; the drain valve 14 is arranged at the bottom end of the expansive soil compacting barrel 11 and used for draining water in the expansive soil in a pile foundation static load test.

The permeability of sand is big, the permeability of inflation soil is little, there is the infiltration difference between the two, can make the water that flows into horizontal sand layer 5 and vertical sand layer 6 that oozes get into the inflation soil rapidly, in addition, the moisture in the same sand layer that oozes, because the big characteristics of the permeability of sand, can make moisture be full of whole sand layer that oozes rapidly, moisture can ooze 5 advection back even infiltration in horizontal sand layer rapidly, moisture can ooze to even infiltration all around after vertical sand layer 6 downward flow rapidly, thereby reach evenly distributed's purpose, this process has simulated the seepage flow in the engineering reality.

The stone has been placed in proper order the pave from the bottom up in the section of thick bamboo 11 is increased to the inflation soil, medium sand and inflation soil sample, and be equipped with the level and ooze sand bed 5 and vertical sand bed 6 that oozes, 5 from the top down equidistant laying of horizontal sand bed 4 layers are oozed, wherein 3 layers are evenly laid in the inflation soil sample, as shown in fig. 1~2, first layer level oozes sand bed 5 and should set up the last 1/3 height within range at the inflation soil sample, second floor level oozes sand bed 5 and should set up in the middle 1/3 height within range of inflation soil sample, third layer level oozes sand bed 5 and should set up the lower 1/3 height within range at the inflation soil sample, like this level ooze the distribution that sand bed 5 can be even in the inflation soil sample, the homogeneity of infiltration has further been guaranteed. The last horizontal sand infiltration layer 5 is arranged in the medium sand sample, and a large number of tests confirm that when the horizontal sand infiltration layer 5 is arranged in such a way, the moisture distribution condition in the expansive soil sample is closest to the actual engineering, the obtained test result is more objective, and if more than 6 horizontal sand infiltration layers 5 are designed in the expansive soil sample, the test result and the actual deviation are too large, and the accuracy is not as high as that of the existing device. Vertical sand layer 6 that oozes is equipped with two-layerly and along 4 symmetric distributions of model pile, and vertical sand layer 6 that oozes top and the inflation soil increase solid sample top parallel and level in a section of thick bamboo 11, and the well sand sample bottom parallel and level in its bottom and the inflation soil increase solid section of thick bamboo 11. When guaranteeing the infiltration, can also make the inflation soil increase and have left sufficient inflation soil in the solid section of thick bamboo 11, vertical infiltration sand bed 6 sets up 2 layers is in order to realize even infiltration, and when the infiltration was followed like this, moisture can evenly infiltrate down in the vertical direction of inflation soil sample.

Horizontal sand layer 5 and vertical sand layer 6 that oozes thickness that paves is too big, leads to the sand to account for the inflation soil proportion too big, can influence the objectivity of inflation soil load test data, and the level oozes the thickness undersize that paves of sand layer 5 and vertical sand layer 6, and it is difficult to play the seepage flow effect, just does not influence inflation soil load test result for guaranteeing the even seepage flow of moisture, the embodiment of the utility model provides a set up the level and ooze sand layer 5 and vertical sand layer 6's thickness and all be less than the 1/10 of inflation soil sample thickness, and vertical sand layer 6 that oozes thickness is less than the level and oozes sand layer 5's thickness.

Be equipped with 3 water injection holes 12 on the swelling soil enrichment section of thick bamboo 11, 3 water injection holes 12 highly with be located the high one-to-one of 3 layers level infiltration sand bed 5 in the swelling soil sample, and 3 water injection holes 12 and the 3 layers level that are located the swelling soil sample infiltration sand bed 5 one-to-one intercommunication, add water in water injection hole 12 in the experiment, rivers can directly flow to level after through water injection hole 12 and infiltrate sand bed 5, utilize the permeability of level infiltration sand bed 5 to realize the evenly distributed of moisture in the swelling soil sample.

As shown in fig. 1, the pressure loading device comprises a bearing plate 1, a force transmission shaft 2, a bearing block 3 and a support 10, wherein the support 10 is covered outside an expansive soil compacting cylinder 11, the bearing block 3 is placed at the top of a model pile 4, the bottom of the force transmission shaft 2 vertically penetrates through the support 10 and then is in contact with the bearing block 3, and the top of the force transmission shaft 2 is fixedly connected with the bearing plate 1. When the pile foundation static load test device is used, the support 10 is horizontally fixed on the ground, and a stable loading platform is provided for the bearing plate 1 and the force transmission shaft 2.

As shown in fig. 1, the pressure sensor 9 is located in the soil pressure cell 13, and the soil pressure cell 13 is located at the center of the upper surface of the stone sample in the expansive soil compacting cylinder 11. The soil pressure cell 13 is a rectangular parallelepiped cell with an open top, and the bottom surface thereof is a square with a side length of 5cm and a height of 2 cm.

The model pile 4 is a cylindrical pile, the diameter of the pile is 10cm, and the height of the pile is not less than 2/3 of the height of the expansive soil compaction cylinder 11, so that the pile-soil friction effect can be fully exerted.

The bearing block 3 is a cylindrical solid iron block, the thickness of the bearing block is 5cm, the diameters of the upper surface and the lower surface of the bearing block are 10cm, and the bearing block and the central axes of the model pile 4 and the force transmission shaft 2 are in the same straight line, so that the model pile 4 is uniformly stressed by uniform loading in the test process.

The use method of the pile foundation static load test device suitable for expansive soil is carried out according to the following steps:

step S1, field sampling and preparation before test: combining the actual geological conditions of the reinforcement treatment of the expansive soil pile foundation in a certain area, sampling expansive soil, medium sand and stones on a construction site on the spot, and carrying out closed standing treatment on the expansive soil, the medium sand and the stones under the same humidity condition according to the actual humidity in the engineering, so that the water in the expansive soil, the medium sand and the stones is uniformly distributed, and the water content reaches a stable state; and checking whether the insides of the drain valve 14 and the water injection hole 12 are smooth to ensure that the insides can be normally infiltrated and drained, and cleaning the insides of the expansive soil compacting barrel 11 and the soil pressure cell 13.

Step S2, manufacturing a model pile 4: taking a PVC pipe with the diameter of 10cm and the length of 65cm, filling foam into the PVC pipe, compacting, then injecting glass cement, and after the glass cement is completely solidified, flattening the upper bottom surface and the lower bottom surface of the model pile 4 to ensure that the upper surface of the model pile 4 is subjected to vertical load under the action of the bearing block 3 and the lower surface of the model pile 4 can be tightly attached to the pressure sensor 9; meanwhile, a concrete wrapping layer 8 is uniformly wrapped on the outer surface of the model pile 4, and the roughness of a pile body in the expansive soil foundation is simulated; after the concrete wrapping layer 8 is completely solidified, the strain sensor 7 is arranged along the pile body of the model pile 4, the strain sensor 7 is used for measuring the stress change condition of the model pile 4, and the manufactured model pile 4 is shown in fig. 3.

Step S3, placing the stone sample in the expansive soil compacting cylinder 11: placing the expansive soil compaction cylinder 11 on a horizontal ground, uniformly spreading the stones processed in the step 1 on the bottom layer of the expansive soil compaction cylinder 11, wherein the spreading height of the stones is 12cm, slightly compacting by adopting manual operation, simulating the strength of the subbase layer in the expansive soil foundation, measuring and checking whether the spreading height meets the requirement or not by adopting a ruler after compacting, and the error is not greater than 0.5 cm; in the process of placing the stone sample, a layer of filter paper is padded at the interface of the drain valve 14 and the expansive soil compacting cylinder 11 to prevent the stone sample from blocking the drain valve 14.

Step S4: placing a medium sand sample of the expansive soil compaction cylinder 11: as shown in fig. 1, on the basis of step S3, the earth pressure cell 13 is placed in the center of the upper surface of the stone sample, the pressure sensor 9 is horizontally placed in the earth pressure cell 13, and the gap between the earth pressure cell 13 and the pressure sensor 9 is uniformly filled with the medium sand sample processed in step 1; placing the model pile 4 manufactured in the step S2 on the upper part of the pressure sensor 9, wherein the model pile 4 and the pressure sensor 9 are in close contact, so that the pressure sensor 9 can accurately measure the vertical load value of the pile end of the model pile 4; and then uniformly filling the medium sand sample subjected to curing treatment in the step S1 into the expansive soil compaction cylinder 11, in the filling process, laying a vertical sand infiltration layer 6 and a 1-layer horizontal sand infiltration layer 5 in the medium sand sample as shown in figures 1-2, wherein the thickness of the medium sand sample is 25cm, and adopting a ruler to measure and check whether the paving height meets the requirement, and the error is not greater than 0.5 cm.

Step S5: placing the expansive soil sample of the expansive soil compacting cylinder 11: as shown in fig. 1, on the basis of step S4, the expansive soil sample subjected to curing treatment in step S1 is uniformly filled into the expansive soil compacting barrel 11; in the filling process, as shown in fig. 1-2, a vertical sand infiltration layer 6 and a 3-layer horizontal sand infiltration layer 5 are arranged in the expansive soil sample, the height of the horizontal sand infiltration layer 5 is equal to that of the water injection hole 12, so that the uniform infiltration of water is ensured, and the surface of the expansive soil in the expansive soil compaction barrel 11 is compacted to a preset compactness by adopting a manual method. The thickness of the stone sample in the expansive soil compaction cylinder 11 cannot be higher than that of the medium sand sample, the thickness of the medium sand sample is smaller than that of the expansive soil sample, and the thickness of the expansive soil sample is not smaller than 1/2 of the height of the expansive soil compaction cylinder 11.

Step S6: adjusting test equipment: moving the expansive soil compaction cylinder 11 to the lower part of the bracket 10, and placing the bearing block 3 on the pile top surface of the model pile 4 to ensure that the central axes of the model pile 4 and the bearing block 3 are on the same straight line; adjusting the plane position of the expansive soil compaction cylinder 11 to enable the force transmission shaft 2 to act on the central position of the bearing block 3, and ensuring that the acting force of the force transmission shaft 2 can be transmitted vertically and downwards along the bearing block 3 and the model pile 4 in sequence; and finally, slowly adjusting the position of the bearing plate 1, horizontally placing the bearing plate 1 above the center of the force transmission shaft 2, and tightly contacting the lower surface of the bearing plate 1 with the upper surface of the force transmission shaft 2.

Step S7: sensor parameter adjustment: the strain sensor 7, the pressure sensor 9 are checked for normal operation and the readings are calibrated.

Step S8: the test was started: opening the drain valve 14 to simulate water seepage conditions in the expansive soil; water is injected through the water injection holes 12 and the top of the vertical sand infiltration layer 6. Sequentially applying vertical pressures of 0, 500N, 1000N and 1500N.. 4000N to the upper part of the bearing plate 1 by taking 500N as a gradient; when the displacement rate of the pile body is less than 0.01mm/h after the pressure is applied, the device is considered to reach a stable state under the condition, and the next stage of load can be applied; when the vertical pressure is 4000N and the displacement rate of the pile body is less than 0.01mm/h, the test can be stopped when the values of the strain sensor 7 and the pressure sensor 9 reach a stable state, and the test result is recorded, so that one test is completed.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.

Claims (10)

1. A pile foundation static load test device suitable for expansive soil is characterized by comprising a pressure loading device, a model pile (4), an expansive soil compaction barrel (11) and a drain valve (14), wherein a concrete wrapping layer (8) is uniformly arranged on the outer surface of the model pile (4), and a plurality of strain sensors (7) which are arranged at equal intervals from top to bottom are fixed on the concrete wrapping layer (8); the model pile (4) is vertically inserted into the expansive soil compaction cylinder (11), and the bottom of the model pile is contacted with a pressure sensor (9) in the expansive soil compaction cylinder (11); the pressure loading end of the pressure loading device is in contact with the top of the model pile (4) to apply vertical pressure to the model pile (4); the drain valve (14) is arranged at the bottom end of the expansive soil compacting barrel (11);

stones, medium sand and expansive soil samples are sequentially paved in the expansive soil compacting cylinder (11) from bottom to top, and a horizontal sand infiltration layer (5) and a vertical sand infiltration layer (6) are arranged.

2. The pile foundation static load test device suitable for the expansive soil is characterized in that the thickness of the stone sample in the expansive soil compaction cylinder (11) is smaller than or equal to that of the medium sand sample, the thickness of the medium sand sample is smaller than that of the expansive soil sample, and the thickness of the expansive soil sample is not smaller than 1/2 of the height of the expansive soil compaction cylinder (11).

3. The device for testing the static load of the pile foundation suitable for the expansive soil is characterized in that the horizontal sand infiltration layers (5) are arranged in four layers at equal intervals from top to bottom, wherein three horizontal sand infiltration layers (5) are uniformly arranged in the expansive soil sample, and one horizontal sand infiltration layer (5) is arranged in the medium sand sample.

4. The pile foundation static load test device suitable for the expansive soil is characterized in that three water injection holes (12) are formed in the expansive soil consolidation cylinder (11), the heights of the three water injection holes (12) correspond to the heights of three horizontal sand infiltration layers (5) in the expansive soil sample in a one-to-one mode, and the three water injection holes (12) are communicated with the three horizontal sand infiltration layers (5) in the expansive soil sample in a one-to-one mode.

5. The pile foundation static load test device suitable for expansive soil according to any one of claims 1 to 4, wherein the vertical sand infiltration layer (6) is provided with two layers and is symmetrically distributed along the model pile (4), the top end of the vertical sand infiltration layer (6) is flush with the top end of the expansive soil sample in the expansive soil compaction cylinder (11), and the bottom end of the vertical sand infiltration layer is flush with the bottom end of the medium sand sample in the expansive soil compaction cylinder (11).

6. The pile foundation static load test device suitable for expansive soil is characterized in that the thickness of each of the horizontal sand infiltration layer (5) and the vertical sand infiltration layer (6) is less than 1/10 of the thickness of the expansive soil sample, and the thickness of the vertical sand infiltration layer (6) is less than that of the horizontal sand infiltration layer (5).

7. The pile foundation static load test device suitable for the expansive soil is characterized in that the pressure sensor (9) is positioned in an earth pressure cell (13), the earth pressure cell (13) is positioned in the center of the upper surface of a stone sample in the expansive soil compaction cylinder (11), and the earth pressure cell (13) is a cuboid box with an open top.

8. The pile foundation static load test device suitable for the expansive soil is characterized in that the model pile (4) is a cylindrical pile, and the height of the cylindrical pile is not less than 2/3 of the height of the expansive soil reinforcing cylinder (11).

9. The pile foundation static load test device suitable for expansive soil according to any one of claims 1 to 4 or 6, wherein the pressure loading device comprises a bearing plate (1), a force transmission shaft (2), a bearing block (3) and a support (10), the support (10) is covered outside the expansive soil compacting cylinder (11), the bearing block (3) is placed at the top of the model pile (4), the bottom of the force transmission shaft (2) vertically penetrates through the support (10) and then is in contact with the bearing block (3), and the top of the force transmission shaft (2) is fixedly connected with the bearing plate (1).

10. The device for testing the static load of the pile foundation suitable for the expansive soil is characterized in that the bearing block (3) is a cylindrical solid iron block which is in the same straight line with the central axes of the model pile (4) and the force transmission shaft (2).

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