Soil sample compacting method

Abstract

The invention provides a soil sample compacting method which comprises the following steps: establishing a corresponding relationship between dry density and pressure stress of a soil layer through a filling test, and determining a pressure stress level sequence corresponding to the dry density of the soil layer under a target dry density; filling a soil layer in the test model box in a layered manner, respectively applying corresponding pressure stress to the soil layer based on the pressure stress hierarchical sequence to adjust the dry density so as to form a composite soil body with a target dry density in the test model box, and arranging a soil pressure detection part in the composite soil body; after a part of the soil layer of the composite soil body is compacted, positioning drilling is carried out to form a drilling cavity, and the simulation pile body of the pre-installed strain detection component is pressed into the drilling cavity; through stress transfer in the compaction process of the composite soil body, the drilling cavity generates radial deformation so as to realize tight coupling of the composite soil body and the pile periphery interface of the simulation pile body; the problems that when the dry density of the soil body is adjusted, efficiency is low, uniformity is poor, detection equipment is prone to damage in the pile forming process, and the compaction degree of soil around the piles and between the piles is insufficient are solved.

Description

Technical Field

[0001] This application relates to the technical field of foundation simulation tests, and particularly to a method for compacting soil samples. Background Art

[0002] As the core technical means for evaluating the bearing capacity of foundations, the technical principle of the foundation load test is to conduct staged loading in a simulated foundation environment, synchronously monitor the deformation response and stress transfer law of foundation soil, so as to scientifically determine the stability and safe bearing threshold of the foundation. This test is of decisive significance for the whole life cycle construction of building projects. Its test data directly supports the reasonable selection of foundation design parameters and is the key technical link to ensure the safety and durability of buildings. Especially in major infrastructure projects such as sluice dams, high-rise buildings, and bridges, accurately obtaining the bearing capacity parameters under the geological conditions of the foundation can effectively avoid risks such as structural cracking, tilting, and even collapse caused by uneven foundation settlement and insufficient bearing capacity, and fundamentally reduce the potential safety hazards and maintenance costs in the whole life cycle of the project.

[0003] When conducting a foundation load test in a laboratory environment, it is necessary to rely on a standardized simulation test device to construct a scaled foundation model. This device takes the model box as the core carrier and precisely simulates the geological profile of the target site by laying different soil layers with different physical and mechanical parameters in layers. The specific implementation process is as follows: First, compact each soil layer, and by controlling parameters such as compaction work, layer thickness, and compaction passes, make the soil layer density (such as void ratio, dry density) approach the in-situ test indexes of the actual foundation; then, use mechanical drilling equipment to form holes at the predetermined positions, and press the model piles into the soil layer according to the design parameters by static pressure or vibration, etc., to simulate the pile forming process and the pile-soil interaction state in actual projects; after the stress state of the model piles and the surrounding soil is stable, apply staged loads to the pile top or the foundation surface through the loading system, and synchronously collect key data such as settlement displacement, pile body strain, and soil stress, so as to evaluate the bearing performance and deformation law of the simulated foundation under different load conditions. The whole test process needs to strictly control the boundary conditions to ensure that the stress and strain characteristics of the simulated foundation are comparable to the mechanical behavior of the in-situ foundation, and provide a reliable technical basis for engineering design.

[0004] Existing simulated foundation methods have obvious limitations in technical implementation, mainly reflected in two key aspects: the regulation of dry density of foundation soil layers and the pile-forming process of pile foundation models. Among them, in terms of the regulation of dry density of foundation soil layers, there is a technical bottleneck in the lack of standardized processes. In current engineering practices, the quantitative regulation of soil layer dry density lacks reproducible operation specifications and often relies on repeated trial-and-error adjustments. Specifically, it is only through multiple sampling detections and compaction parameter corrections that the dry density index of the simulated foundation can approach the target working conditions. This process leads to low work efficiency and a significant increase in costs. In terms of the pile-forming process of pile foundation model tests, traditional methods are mainly divided into two categories: embedded and jacked-in. Both have technical bottlenecks: The embedded pile-forming method is limited by the narrow working space around the pile, making it difficult to effectively compact the soil around the pile, resulting in insufficient tightness of the interface between the pile and the soil, and weakening the stress transfer mechanism from the pile body to the surrounding soil, directly affecting the true simulation of the load transfer law in the test; The jacked-in pile-forming method may cause mechanical damage to the pre-embedded strain detection components due to the dynamic action of the extrusion force and friction force between the pile and the soil during the pile jacking process, resulting in distortion or even interruption of test data collection and interfering with the accurate assessment of the mechanical response of the pile foundation. Summary of the Invention

[0005] In an embodiment of the present application, a method for compacting soil samples is provided to solve the problems of low efficiency and insufficient uniformity in adjusting the dry density of the foundation during the load test, as well as the technical problems that the existing pile jacking methods are prone to damage the detection equipment and the tightness between the soil around the simulated pile body and between the piles is insufficient. The technical solution is as follows: An embodiment of the present application provides a method for compacting soil samples, including: Establish the corresponding relationship between the dry density of the soil layer and the compaction stress through a filling test, and determine the compaction stress level sequence corresponding to the dry density of the soil layer at the target dry density; Layer by layer fill the soil layer in the test model box, and apply the corresponding compaction stress to the soil layer based on the compaction stress level sequence to adjust the dry density, so as to form a composite soil body with the target dry density in the test model box, and arrange soil pressure detection components in the composite soil body; After partial compaction of some soil layers in the composite soil body, implement positioning drilling to form a drilling cavity, and press the simulated pile body pre-installed with strain detection components into the drilling cavity; Through the stress transfer during the compaction process of the composite soil body, make the drilling cavity generate radial deformation to achieve the tight coupling of the pile circumference interface between the composite soil body and the simulated pile body.

[0006] In one embodiment, the calculation formula for applying the compaction stress on the surface of each soil layer is σ n =(F n +G) / A, where: σ n is the compaction stress value applied on the soil layer, F nWhen compacting the nth layer of soil, the reading of the force sensor is F, G is the total self-weight of the loading system in the test device, and A is the bearing area of the soil in the test model box.

[0007] In one embodiment, in the method for establishing the correspondence between the dry density and the compaction stress of the soil layer through the filling test and determining the compaction stress level sequence corresponding to the dry density at the target dry density of the soil layer, it includes: Set up a reaction frame and a test cylinder in the test device. Fill the soil layer sample in the test cylinder, and apply compaction stress to the soil layer sample through the loading system on the reaction frame; record the reading of the force sensor in the loading system, and detect the dry density of the soil layer sample in the test cylinder; Adjust the compaction stress applied by the loading system. Fill the soil layer sample and compact the soil layer sample by the loading system multiple times in the test cylinder, and detect the dry density of the soil layer sample in the test cylinder. Then establish the relationship curve between the compaction stress and the dry density, determine the compaction stress required to reach the target dry density, and obtain the compaction stress level sequence by grading and splitting the compaction stress required for the target dry density; Among them, the loading system includes a bearing component, a jack, and a force sensor that are sequentially stacked on the soil. The jack abuts against the force transfer rod of the reaction frame through the force sensor; The self-weight compensation value of the loading system is G = G 1 +G 2 +G 3 , where G 1 is the weight of the force sensor, G 2 is the weight of the jack, and G 3 is the weight of the bearing component.

[0008] In one embodiment, when filling the soil layer in layers in the test model box, applying the corresponding compaction stress to the soil layer based on the compaction stress level sequence to adjust the dry density, so as to form a composite soil body with the target dry density in the test model box, and the method for arranging the soil pressure detection components in the composite soil body further includes: Replace the test cylinder with a test model box in the test device, and form a composite soil body in the test model box by laying soil layers arranged in layers from bottom to top. The composite soil body at least includes: the first soil layer, the second soil layer, and the third soil layer. The following steps are carried out: Lay the first soil layer in the test model box, and conduct preliminary leveling on the first soil layer. Place the bearing component on the first soil layer, and then apply the first compaction stress to the first soil layer by pressing the bearing component with the jack to adjust the dry density of the first soil layer. Through the calculation formula, when the jack applies the first compaction stress, the reading on the force sensor is F 1 ; Lay the second soil layer above the first soil layer in the test model box, and conduct preliminary leveling on the second soil layer. Place the bearing component on the second soil layer, and then apply the second compressive stress to the second soil layer by pressing the bearing component with a jack to adjust the dry density of the second soil layer and further increase the dry density of the first soil layer. According to the calculation formula, when the jack applies the second compressive stress, the reading on the force sensor is F 2 ; Lay the third soil layer above the second soil layer in the test model box, and conduct preliminary leveling on the third soil layer. Place the bearing component on the third soil layer, and apply the third compressive stress to the third soil layer by pressing the bearing component with a jack to adjust the dry density of the third soil layer and further increase the dry density of the first soil layer and the second soil layer. According to the calculation formula, when the jack applies the third compressive stress, the reading on the force sensor is F 3 。

[0009] In one embodiment, when filling the soil layer in layers in the test model box and applying corresponding compressive stresses to the soil layer based on the compressive stress level sequence to adjust the dry density, so as to form a composite soil body with a target dry density in the test model box, the method of arranging the earth pressure detection component in the composite soil body further includes: Embed the earth pressure detection components above the first soil layer to the third soil layer respectively, and lead out the cables of the earth pressure detection components along the inner wall of the test model box and connect them to the static strain acquisition system.

[0010] In one embodiment, in the method of forming a drilling cavity by positioning drilling after partial compaction of some soil layers of the composite soil body and pressing the simulated pile body pre-installed with strain detection components into the drilling cavity, and realizing the close coupling of the pile circumference interface between the composite soil body and the simulated pile body through the stress transfer during the compaction process of the composite soil body, it includes: Before filling the third soil layer, use a drilling template with a guiding positioning hole to determine the pile position coordinates on the soil layer above the first soil; Use a spiral drill to drill according to the pile position coordinates to form a drill hole with a diameter adapted to the simulated pile body; Strain detection components are arranged on the circumferential surface of the simulated pile body, and after insulation packaging, they are pressed into the drill hole; Through the compaction step of the third soil layer, lateral stress is generated in the soil layer above the first soil layer, so that the soil within the pile circumference range of the simulated pile body generates radial deformation to form a composite soil body that is closely coupled with the simulated pile body.

[0011] In one embodiment, the third compressive stress > the second compressive stress ≥ the first compressive stress; wherein, the reading of the force sensor is F 2 / F 1 =F3 / F 2 = 1.08 to 1.16; alternatively, The reading of the force sensor is F 1 = F 2 = F 3 / (1.2 to 1.3).

[0012] In one embodiment, in the method of arranging strain detection components on the outer surface of the simulated pile body and then press-fitting them into the borehole after insulation encapsulation, it further includes: Determine the mounting area on the pile body surface of the simulated pile body, and polish the mounting area to form a rough surface; Bond each strain detection component to the corresponding mounting area; After the adhesive layer on the back of each strain detection component is cured, check whether each strain detection component can work properly; After determining that each strain detection component can work properly, wrap each strain detection component with insulating tape.

[0013] In one embodiment, in the method of laying soil layers in a test model box, applying corresponding compaction stresses to the soil layers based on the compaction stress level sequence to adjust the dry density, so as to form a composite soil body with a target dry density in the test model box, and arranging earth pressure detection components in the composite soil body, it further includes: Cover the inner wall of the test model box with a vaseline coating, and then lay a plastic film on the vaseline coating; Mark the size scale on the inner wall of the test model box to determine the thickness of the soil layer before and after compaction in the test model box.

[0014] In one embodiment, it further includes: detecting the test device to eliminate open circuit situations: using a multimeter to detect each earth pressure detection component, each strain detection component, and the force sensor, and then electrically connecting each earth pressure detection component, each strain detection component, and the force sensor to a static strain acquisition system.

[0015] Compared with the prior art, a soil sample compaction method provided by the present invention has significant technical advantages and practical value: By conducting filling tests, a quantitative correspondence relationship between the dry density of the soil and the compressive stress is established, and the compressive stress level sequence corresponding to the target dry density is accurately determined. The "adjustment and detection" mode that relies on repeated trial and error in the traditional method is transformed into data-driven parametric control, avoiding the repetitive operations of multiple sampling detections, significantly improving the dry density regulation efficiency, saving time costs, and at the same time reducing the error of the dry density uniformity of the soil layer through controllable compressive stress loading. During the compaction process of the composite soil, a simulated pile body pre-installed with strain detection components is incorporated. By utilizing the radial deformation of the soil around the borehole cavity caused by the hierarchical transfer of compressive stress, close coupling of the pile circumference interface is achieved, thereby improving the compaction degree of the soil around and between the piles, avoiding the compaction blind area around the piles in the case of embedded pile formation, and also preventing serious mechanical damage to the detection equipment caused by the jacked-in pile formation. It reduces the damage to the strain detection components during the pile pressing process and provides reliable data acquisition for subsequent load tests. After adopting this method, the mechanical parameters such as the compression modulus and shear strength of the simulated foundation are more in line with the industry standard with the prototype foundation, providing a more reliable technical solution for the foundation load test, solving the core problems of low efficiency, insufficient compaction density uniformity of the simulated soil layer, and improving the compaction degree between the soil around and between the piles in the traditional method, and being able to provide a scientific and reliable test basis for the foundation design and safety assessment of building projects.

[0016] The above summary is for the purpose of the specification only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features of the present application will be readily apparent by reference to the drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In the drawings, unless otherwise specified, the same reference numerals throughout the several views refer to the same or similar components or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings only depict some embodiments disclosed in the present application and should not be regarded as limiting the scope of the present application.

[0018] Figure 1 It is a schematic structural diagram of arranging a soil layer in a test device by adopting a soil sample compaction method in an embodiment of the present application; Figure 2 It is a schematic curve diagram of the relationship between the compressive stress and the dry density obtained by conducting a filling test with a soil sample compaction method proposed in an embodiment of the present application.

[0019] Reference Numerals: 1. Test model box; 2. Reaction frame; 3. Jack; 4. Force sensor; 5. Bearing component; 6. Simulated pile body; 7. Strain detection component; 8. Earth pressure detection component; 51. Pressure-bearing cover plate; 52. Foam board; 101. First soil layer; 102. Second soil layer; 103. Third soil layer. Detailed implementation manners

[0020] In the following text, only some exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present application. Therefore, the drawings and the description are considered to be exemplary in nature rather than restrictive.

[0021] Referring to Figure 1 and Figure 2 As shown, in the embodiments of the present application, a method for compacting soil samples is proposed, and this method for compacting soil samples can be carried out according to the following steps: Establish the corresponding relationship between the dry density of the soil layer and the compressive stress through the filling test, and determine the compressive stress level sequence corresponding to the dry density of the soil layer at the target dry density; Layer by layer fill the soil layer in the test model box 1, and apply the corresponding compressive stress to the soil layer respectively based on the compressive stress level sequence to adjust the dry density, so as to form a composite soil body with the target dry density in the test model box 1, and arrange the soil pressure detection component 8 in the composite soil body; After the compaction of some soil layers in the composite soil body is completed, carry out positioning drilling to form a drilling cavity, and press the simulated pile body 6 pre-installed with the strain detection component 7 into the drilling cavity; Through the stress transfer during the compaction process of the composite soil body, make the drilling cavity generate radial deformation, so as to realize the close coupling of the pile circumference interface between the composite soil body and the simulated pile body 6.

[0022] Among them, the soil pressure stress parameter satisfies σ n = (F n + G) / A, where: σ n is the value of the compressive stress applied on the nth soil layer, and its measurement unit is kPa, F n is the reading of the force sensor 4 when compacting the nth soil layer, and its measurement unit is kN, G is the total self-weight of the loading system in the test device, and its measurement unit is kN, A is the bearing area of the soil layer in the test model box 1, and its measurement unit is m².

[0023] Specifically, in the technical solution adopted in the present application, in the filling test, according to the formula σ n = (F nCalculate the corresponding relationship between the dry density of the soil mass and the compressive stress by (+G) / A, so as to determine the sequence of compressive stress levels required for the soil mass to form the target dry density; it should be noted that this sequence of compressive stress levels is the compressive stress required for the compacted soil layer specimen to obtain the target dry density in the filling test. Determine the compressive stress of each soil layer according to the compressive stress required for the target dry density to obtain the parameters of the compressive stress level sequence. The compressive stress applied to the topmost soil layer in the test model box 1 is the compressive stress required for the target dry density, while the compressive stress applied to the remaining soil layers is less than the compressive stress required for the target dry density, so that each soil layer in the composite soil mass can be closer to the target dry density. The target dry density is closer to the dry density of the actual foundation soil layer than the existing artificial compaction process. In the step of filling the soil layer in the test model box 1 layer by layer, the basic soil layer, the capping soil layer and several test soil layers located between the basic soil layer and the capping soil layer can be filled in the test model box 1. After positioning and drilling the test soil layer, it is used to press into the simulated pile body 6. During the compaction process of the capping soil layer, stress can be transmitted to the test soil layer, so that the soil around the pile in the drilled cavity of the test soil layer deforms along the radial direction of the simulated pile body 6, thereby tightly coupling the test soil layer and the simulated pile body 6. In a soil sample compaction method proposed in this application, compared with the existing technology of manually ramming the soil layer, by calculating the graded compressive stress, the dry density of the composite soil mass is closer to the dry density of the actual soil mass, that is: the target dry density; and during the process of grading and compacting the soil layer of the composite soil mass, the simulated pile body 6 is pressed in, and through the step of compacting the capping soil layer, the soil around the pile of the test soil layer is tightly attached to the simulated pile body 6. Therefore, during the process of positioning and drilling, a drilling cavity larger than the diameter of the simulated pile body 6 can be used to avoid damage during the process of pressing in the simulated pile body 6, and through the step of compacting the capping soil layer, it is ensured that the soil around the pile formed by drilling is tightly attached to the simulated pile body 6, so that the simulated foundation environment is more similar to the actual foundation environment, thereby significantly improving the reliability and accuracy of the foundation load test.

[0024] Further, referring to Figure 2 As shown, in some embodiments, in the method of establishing the corresponding relationship between the dry density of the soil layer and the compressive stress through the filling test and determining the sequence of compressive stress levels corresponding to the dry density of the soil layer under the target dry density, it includes: Set up a reaction frame 2 and a test cylinder in the test device. Fill the soil layer specimen in the test cylinder, and apply compressive stress to the soil layer specimen through the loading system on the reaction frame 2; record the readings of the force sensor 4 in the loading system, and detect the dry density of the soil layer specimen in the test cylinder; Adjust the compressive stress applied by the loading system. Fill the soil layer specimen in the test cylinder and compact the soil layer specimen with the loading system multiple times. After detecting the dry density of the soil layer specimen in the test cylinder, establish the relationship curve between the compressive stress and the dry density, determine the compressive stress required to reach the target dry density, and obtain the compressive stress level sequence by grading and splitting the compressive stress required for the target dry density; Among them, the loading system includes a bearing component 5, a jack 3, and a force sensor 4 that are sequentially stacked on the soil body. The jack 3 abuts against the force transfer rod of the reaction frame 2 through the force sensor 4; The self-weight compensation value of the loading system is G = G 1 + G 2 + G 3 , where G 1 is the weight of the force sensor 4, G 2 is the weight of the jack 3, and G 3 is the weight of the bearing component 5.

[0025] Specifically, in the technical solution adopted in this application, the test device may include a reaction frame 2, a test cylinder for the replaceable test model box 1, and a loading system composed of a bearing component 5, a jack 3, and a force sensor 4. It should be noted that in this embodiment, the test model box 1 can also be used for filling tests. The purpose of using the test cylinder is that the size of the test cylinder is smaller than that of the test model box 1, which is convenient for repeated tests. Specifically, fill the soil layer specimen in the test cylinder, place the bearing component 5 on the soil layer specimen in the test cylinder, one end of the jack 3 abuts against the bearing component 5, and the other end abuts against the force transfer rod on the reaction frame 2 through the force sensor 4, and compact the soil layer specimen filled in the test cylinder through the jack 3; after recording the reading of the force sensor 4 and the dry density of the soil layer specimen, the relationship curve between the compressive stress and the dry density can be established, and then the compressive stress σ required for the soil layer to reach the target dry density can be determined n , obtain the compressive stress level sequence according to the compressive stress required for the target dry density, for example: σ n-2 , σ n-1 , σ n , or σ n-1 , σ n-1 , σ n。In this embodiment, the pressure-bearing member 5 can be a foam board 52 with a thickness of not less than 3 cm and a pressure-bearing cover plate 51. The foam board 52 is arranged between the pressure-bearing cover plate 51 and the soil layer, and the pressure-bearing cover plate 51 can be made of steel plate. During the filling test, the pressure-bearing cover plate 51 needs to be adapted to the test cylinder; when filling the composite soil in the test model box 1, the pressure-bearing cover plate 51 needs to be adapted to the test model box 1. The pressure stress applied by the jack 3 can be evenly transmitted to the soil layer in the test cylinder or the test model box 1 under the cooperation of the pressure-bearing cover plate 51 and the foam board 52. Since the foam template can deform flexibly during extrusion, the pressure borne by the soil layer is kept consistent during the compaction process, so as to ensure the uniformity of the dry density of the soil layer during compaction.

[0026] In one embodiment, a pressure stress is applied to the soil sample by the jack 3. The pressure stress applied by the jack 3 in each group of filling tests can be 16 kPa, 32 kPa, 48 kPa, 64 kPa, and 80 kPa respectively, and the pressing time lasts for 10 minutes. It should be noted that the pressure stress applied by the jack 3 to the soil sample and the compaction time need to be adjusted according to the actual situation, and are not limited to the specifications proposed in this embodiment. As long as the relationship curve between the pressure stress and the dry density of the soil sample can be obtained.

[0027] Furthermore, in some embodiments, when filling the soil layer in layers in the test model box 1, applying corresponding pressure stresses to the soil layer based on the pressure stress level sequence to adjust the dry density, so as to form a composite soil body with a target dry density in the test model box 1, and the method of arranging the soil pressure detection component 8 in the composite soil body further includes: Replace the test cylinder with the test model box 1 in the test device, and form a composite soil body by laying soil layers arranged in layers from bottom to top in the test model box 1. The composite soil body at least includes: a first soil layer 101, a second soil layer 102, and a third soil layer 103. The following steps are carried out: Lay the first soil layer 101 in the test model box 1, and perform preliminary leveling on the first soil layer 101. Place the pressure-bearing member 5 on the first soil layer 101, and then press the pressure-bearing member 5 through the jack 3 to apply a first pressure stress to the first soil layer 101 to adjust the dry density of the first soil layer 101. According to the calculation formula, when the jack 3 applies the first pressure stress, the reading on the force sensor 4 is F 1 ; Lay the second soil layer 102 above the first soil layer 101 in the test model box 1, and perform preliminary leveling on the second soil layer 102. Place the pressure-bearing component 5 on the second soil layer 102, and then apply a second compressive stress to the second soil layer 102 by pressing the pressure-bearing component 5 with the jack 3 to adjust the dry density of the second soil layer 102 and further increase the dry density of the first soil layer 101. According to the calculation formula, when the jack 3 applies the second compressive stress, the reading on the force sensor 4 is F 2 ; Lay the third soil layer 103 above the second soil layer 102 in the test model box 1, and perform preliminary leveling on the third soil layer 103. Place the pressure-bearing component 5 on the third soil layer 103, and apply a third compressive stress to the third soil layer 103 by pressing the pressure-bearing component 5 with the jack 3 to adjust the dry density of the third soil layer 103 and further increase the dry density of the first soil layer 101 and the second soil layer 102. According to the calculation formula, when the jack 3 applies the third compressive stress, the reading on the force sensor 4 is F 3 。

[0028] Specifically, in the technical solution adopted in this application, the thickness of the first soil layer 101 before compaction can be 30 - 40 cm. The preliminary leveling can be carried out by scraping the upper surface of the first soil layer 101 with a scraper and detecting the flatness with a spirit level. Subsequently, lay the foam board 52 and the pressure-bearing cover plate 51 on the first soil layer 101, so that the jack 3 applies the first compressive stress σ on the pressure-bearing cover plate 51 1 , and the reading of the force sensor 4 is F 1 . After completing the compaction operation, obtain the first soil layer 101 with a specific dry density. Use the spirit level and the scraper to further level the first soil layer 101 again, and control the thickness of the first soil layer 101 to about 20 cm. Finally, perform a scraping treatment on the upper surface of the first soil layer 101 to ensure the adhesion between soil layers during the compaction process. The second soil layer 102 and the third soil layer 103 adopt the same filling method as the first soil layer 101. The difference is that a second compressive stress σ is applied on the second soil layer 102 2 , and the reading of the force sensor 4 is F 2 ; A third compressive stress σ is applied on the third soil layer 103 3 , and the reading of the force sensor 4 is F 3 . In this embodiment, the third compressive stress σ 3 is the compressive stress required for the above soil layers to reach the target dry density. In order to obtain a composite soil body that approaches the target dry density required by the test by applying graded compressive stresses on each soil layer, the readings of the stress sensor 4 can be set to increase by 1.08 - 1.16 times according to the level until reaching the third compressive stress σ applied on the third soil layer 103 3, so that the dry density of the composite soil body as a whole can be more balanced. In some embodiments, when different dry densities are required for the soil layers in the composite soil body, the readings of the force sensors 4 corresponding to each compressive stress can also be set to the same compressive stress applied to the first soil layer 101 and the second soil layer 102, while the reading of the third soil layer 103 is 1.2 to 1.3 times the compressive stress reading of the base soil layer, so that there are differences in the dry densities of the capping soil layer, the base soil layer and the test soil layer, which can also meet the requirements of some specific tests. In short, the dry density of the composite soil body can simulate the actual situation of the dry density of the soil body as needed, and the compressive stress level sequence can be purposefully matched according to the established relationship curve between the compressive stress and the dry density, so as to obtain a composite soil body closer to the actual dry density after loosening the soil in the compaction test model box 1.

[0029] Further, in some embodiments, when the soil layers are filled in layers in the test model box 1 and the corresponding compressive stresses are applied to the soil layers based on the compressive stress level sequence to adjust the dry density, so as to form a composite soil body with a target dry density in the test model box 1, the method of arranging the earth pressure detection component 8 in the composite soil body further includes: The earth pressure detection components 8 are respectively buried above the first soil layer 101 to the third soil layer 103, and the cables of the earth pressure detection components 8 are led out along the inner wall of the test model box 1 and connected to the static strain acquisition system.

[0030] Specifically, in the technical solution adopted in this application, two calibrated earth pressure detection components 8 are placed at preset positions on the surface of the first soil layer 101. Specifically, the sensing surface of the earth pressure detection component 8 is facing upward, and then the cable of the earth pressure detection component 8 is led along the surface of the first soil layer 101 to the inner wall of the test model box 1, and then led upward from the inner wall of the test model box 1 and fixed with transparent tape. Connect each earth pressure detection component 8 buried in the first soil layer 101 to the static strain acquisition system, check and test the circuit. After the detection is correct, fill and compact the second soil layer 102 in the test model box 1. Place two calibrated earth pressure detection components 8 at preset positions on the surface of the second soil layer 102. Specifically, the sensing surface of the earth pressure detection component 8 is facing upward, and then the cable of the earth pressure detection component 8 is led along the surface of the second soil layer 102 to the inner wall of the test model box 1, and then led upward from the inner wall of the test model box 1 and fixed with transparent tape. Connect each earth pressure detection component 8 buried in the second soil layer 102 to the static strain acquisition system, check and test the circuit. After the detection is correct, fill and compact the third soil layer 103 in the test model box 1. Place two calibrated earth pressure detection components 8 at preset positions on the surface of the third soil layer 103. Specifically, the sensing surface of the earth pressure detection component 8 is facing upward, and then the cable of the earth pressure detection component 8 is led along the surface of the third soil layer 103 to the inner wall of the test model box 1, and then led upward from the inner wall of the test model box 1 and fixed with transparent tape. Connect each earth pressure detection component 8 buried in the third soil layer 103 to the static strain acquisition system, check and test the circuit. After the detection is correct, the step of filling the composite soil body in the test model box 1 is completed.

[0031] Further, in some embodiments, in the method of forming a drilling cavity by positioning drilling after some soil layers of the composite soil body are compacted and pressing the simulated pile body 6 pre-installed with the strain detection component 7 into the drilling cavity, and in the method of making the drilling cavity generate radial deformation through the stress transfer during the compaction process of the composite soil body to achieve the close coupling of the pile circumference interface between the composite soil body and the simulated pile body 6, it includes: Before filling the third soil layer 103, use a drilling template with a guiding positioning hole to determine the pile position coordinates on the soil layer above the first soil. Use a spiral drill to drill according to the pile position coordinates to form a drill hole with a diameter adapted to the simulated pile body 6. The strain detection component 7 is arranged on the circumferential surface of the simulated pile body 6, and after being insulated and encapsulated, it is pressed into the drill hole. Through the compaction step of the third soil layer 103, the soil layer above the first soil layer 101 generates lateral stress, so that the soil body within the pile circumference range of the simulated pile body 6 generates radial deformation to form a composite soil body closely coupled with the simulated pile body 6.

[0032] Further, in some embodiments, the third compressive stress > the second compressive stress ≥ the first compressive stress; wherein, the reading of the force sensor 4 is F 2 / F 1 =F 3 / F 2 = 1.08 to 1.16; alternatively, the reading of the force sensor 4 is F 1 =F 2 =F 3 / (1.2 to 1.3).

[0033] Specifically, in the technical solution adopted in this application, the first soil layer 101 is the base soil layer, the third soil layer 103 is the capping soil layer, and the second soil layer 102 is the test soil layer. It can be explained that the base soil layer is the cushion in the composite soil mass. The test soil layer is mainly used to accommodate the simulated pile body 6. When drilling holes in the test soil layer, it is required not to enter the base soil layer, and the capping soil layer is used to cover the simulated pile body 6 and further compact the test soil layer. It should be noted that in this embodiment, it is not limited to only one layer of test soil layer. A fourth soil layer, a fifth soil layer, a sixth soil layer... etc. can also be filled between the first soil layer 101 and the third soil layer 103, all of which are test soil layers and are located above the second soil layer 102. Thus, by adding test soil layers, the layout density of the soil pressure detection component 8 in the composite soil mass can be adjusted. And in this embodiment, the compaction method of the added test soil layer is the same as that of the second soil layer 102, so it will not be elaborated here. It should be noted that the added soil layer and the second soil layer 102 can be adjusted to the same dry density or different dry densities, and the compressive stress applied to the added soil layer is greater than or equal to the second compressive stress σ 2 , and less than the third compressive stress σ 3 That's all. When applying compressive stress to the fourth soil layer, the fifth soil layer, and the sixth soil layer, the reading of the force sensor 4 can be obtained through the above formula, that is: F 4 , F 5 , F 6 . And when the jack 3 jacks the pressure-bearing component 5 to apply corresponding compressive stress to each soil layer, the formula that the reading of the force sensor 4 should satisfy is F 2 / F 1 = F 4 / F 2 =F 5 / F 4 =F 6 / F 5 =……F n / F n-1 =F 3 / F n = 1.08 to 1.16, where n is a positive integer and n≠3; alternatively, the formula that the reading of the force sensor 4 should satisfy is F 1 =F2 =F 4 =F 5 =F 6 =……F n =F 3 / (1.2~1.3), where n is a positive integer and n≠3. The third compressive stress σ is determined by filling test 3 And apply the third compressive stress σ 3 The reading of the force sensor is F 3 After that, the above compressive stress level sequence is obtained by calculating the formula that the reading of the force sensor 4 should satisfy. It should be explained that, in this embodiment, the third compressive stress σ 3 To determine the compressive stress required to adjust the soil layer to the target dry density in the filling test.

[0034] Furthermore, in some embodiments, a strain detection component 7 is arranged on the outer surface of the simulated pile body 6, and the strain detection component 7 is pressed into the borehole after being insulated and packaged, and the method further includes: A mounting area is determined on the surface of the simulated pile body 6, and the mounting area is polished to form a rough surface; Bonding each strain detection component 7 to the corresponding mounting area; After the adhesive layer on the back of each strain detection component 7 is cured, each strain detection component 7 is tested to see whether it can work normally; After ensuring that each strain sensing component 7 can work normally, each strain sensing component 7 is wrapped with insulating tape.

[0035] Specifically, in the technical solution adopted in this application, a simulated pile body 6 is selected for testing, and a grinding machine is used to grind the predetermined strain detection component 7 mounting area until the surface presents a rough texture. Subsequently, a non-woven fabric soaked in alcohol is used to perform a secondary cleaning of the polished area to remove grease and residues on the surface of the mounting area, and the central axis is marked on the surface of the simulated pile body 6. The mounting reference line is calibrated along the axis according to the spacing required by the test plan, and the marked surface is finally cleaned with alcohol, and naturally dried until there is no volatile residue. Glue is applied to the mounting area of ​​the calibrated intersection to form a moisture-proof protective layer. 502 glue can be used. After the strain detection component 7 is accurately aligned, bonding is implemented. Anti-static tweezers are used to fine-tune the position, and the sealing film is covered and rolled to eliminate bubbles in the glue layer. After standing until initial solidification, the sealing film is removed to check the integrity of the bonding surface. Then use a multimeter to test the circuit conductivity and insulation resistance value, and finally use the spiral winding method to wrap the strain detection component 7 with insulating tape to protect the strain detection component 7 and the wiring terminals of the strain detection component 7. After packaging, retest the circuit conductivity to confirm that there is no construction damage. After the qualified pile is marked with a number, it is stored in the constant temperature test warehouse for standby. It is recommended to adjust the temperature of the constant temperature test warehouse to 20±1℃.

[0036] Further, in some embodiments, in the method of layering and filling soil layers in the test model box 1, applying corresponding compressive stresses to the soil layers respectively based on the compressive stress level sequence to adjust the dry density, so as to form a composite soil body with a target dry density in the test model box 1, and arranging soil pressure detection components 8 in the composite soil body, the method further includes: Cover the inner wall of the test model box 1 with a vaseline coating, and then lay a plastic film on the vaseline coating; Mark dimension scales on the inner wall of the test model box 1 to determine the thickness of the soil layer before and after compaction in the test model box 1.

[0037] Specifically, in the technical solution adopted in the present application, before filling the composite soil body in the test model box 1, the vaseline coating can be applied to the inner wall of the test model box 1, so as to effectively reduce the soil adhered to the inner wall of the test model box 1 when removing the composite soil body from the test model box 1, thereby improving the efficiency of removing the soil from the test model box 1. By attaching a plastic film to the inner wall of the test model box 1, with the cooperation of the vaseline coating and the plastic film, the technical effect of almost completely avoiding the adhesion of the soil to the inner wall of the test model box 1 can be achieved, and the operation requirement of manually cleaning the test model box 1 can be saved when removing the soil sample from the test model box 1.

[0038] Further, in some embodiments, it further includes: detecting the test device to eliminate open - circuit conditions: using a multimeter to detect each soil pressure detection component 8, each strain detection component 7, and the force sensor 4, and then electrically connecting each soil pressure detection component 8, each strain detection component 7, and the force sensor 4 to a static strain acquisition system after detection.

[0039] Specifically, in the technical solution adopted in the present application, the static strain acquisition system is an instrument for electrically measuring non - electrical quantities such as the load of a structure and the deformation of materials under non - destructive conditions. Its basic structure consists of a measuring bridge, an AC amplifier, a phase - sensitive detector, a balance indicator, an oscillator, a power supply, and a conversion box, etc. Such instruments can be used to measure mine pressure, material deformation, and the stress and strain of engineering structural components; while a multimeter, also known as a multiplexer, multi - meter, three - use meter, or general - purpose meter, etc., is an indispensable measuring instrument in departments such as power electronics. Generally, it is mainly used to measure voltage, current, and resistance. Multimeters are divided into pointer multimeters and digital multimeters according to the display method. It is a multi - functional and multi - range measuring instrument. Generally, a multimeter can measure DC current, DC voltage, AC current, AC voltage, resistance, and audio level, etc. Some can also measure AC current, capacitance, inductance, and some parameters of semiconductors, etc. The static strain acquisition system and the multimeter in this embodiment have not been improved and belong to the prior art, so their structures and usage methods will not be elaborated further.

[0040] In this application, a method for foundation load test is also proposed, which is implemented after the above-mentioned method for compacting soil samples. The specific steps are as follows: After the filling of the composite soil body is completed, cover the model box with a film and let it stand for 7 days to make the composite soil body and the detection components required for the test tend to be stable.

[0041] Determine the position of the cushion layer through the positioning line and tape measure, then place the outer frame of the cushion layer, and then lay the cushion layer material. After leveling, slightly compact it and then scrape it flat on the surface and detect it with a spirit level. Use an ink box to draw a line to determine the position of the loading plate.

[0042] Place the jack 3, force sensor 4 and load transfer column on the loading plate in sequence upward, so that their centers are vertically aligned, and align with the stress points on the reaction frame 2; install displacement gauges. In the test, displacement gauges need to be symmetrically arranged on the loading plate, and the displacement gauges are located at the midpoints of the sides of the loading plate. Erect square steel pipes on the top of the model box to fix the displacement gauges, so as to ensure the accuracy of the displacement gauge data.

[0043] Electrically connect the force sensor 4 and all displacement gauges, strain detection components 7, earth pressure detection components 8, and force sensor 4 to the static strain acquisition system, and check and test the circuit to ensure that the data acquisition system can operate normally during the working process.

[0044] After the assembly is completed, preloading needs to be carried out, with a static load for two days, and record the data of the force sensor 4, displacement gauges, earth pressure detection components 8 and strain detection components 7. After the data is stable, the next step of loading is carried out.

[0045] The test is carried out by gradually loading, and the estimated maximum loading amount reaches 900 kPa. The specific method: the total load is 900 kPa, and it is loaded in 8 levels, starting from 0 kN, increasing by 112.5 kPa for each level. Before applying the load each time, record the settlement amount of the loading plate once. After applying the load, record the settlement amount of the loading plate again, and then read and record it once every 10 min, 20 min, 30 min, 45 min, 60 min, and then measure and read it once every 30 min, and record the readings, collect and save the test data. During the whole loading process using the hydraulic jack 3, load maintenance needs to be carried out. When the settlement under the same level of load reaches 1%, the pressurization system pressurizes and supplements the load to meet the constant pressure requirement. When the settlement amount within 1 h is less than 0.1 mm, start loading the next level. When the cumulative settlement amount of the loading plate reaches 28.8 mm, or the settlement increases sharply, the soil is extruded or obvious bulges appear around the loading plate, or the ultimate load cannot be reached, and the maximum loading pressure has been greater than 900 kPa, the loading is stopped. The first group of tests is over.

[0046] After the first group of tests is over, it is necessary to clean the filling soil in the model box.

[0047] Refill the new composite soil mass in the model box and conduct the next set of tests in a similar manner.

[0048] The simulation device adopted by the method of the foundation load test includes: a pedestal made of reinforced concrete, a reaction frame 2 installed on the pedestal, and a test model box 1 placed on the pedestal. After the composite soil mass is filled in the test model box 1 by adopting one of the soil sample compaction methods in the above embodiments, the load test is carried out according to the above steps. It should be noted that the adopted simulation device is a prior art and will not be elaborated here.

[0049] In the description of this specification, the descriptions with reference to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0050] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" can explicitly or implicitly include at least one of the features. In the description of the present application, "a plurality of" means two or more unless otherwise specifically defined.

[0051] Any process or method description represented in the flowchart or described in other ways herein can be understood as representing a module, segment or part of code including one or more executable instructions for implementing a specific logical function or process. And the scope of the preferred embodiments of the present application includes additional implementations, where the functions can be executed in a substantially simultaneous manner or in a reverse order according to the involved functions, rather than in the order shown or discussed.

[0052] The logic and / or steps represented in the flowchart or described in other ways herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by an instruction execution system, apparatus or device (such as a computer-based system, a system including a processor, or other systems that can fetch instructions from the instruction execution system, apparatus or device and execute the instructions), or in combination with these instruction execution systems, apparatus or devices.

[0053] It should be understood that each part of the present application can be implemented by hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. All or part of the steps of the above-described method embodiments can be completed by a program instructing relevant hardware. The program can be stored in a computer-readable storage medium. When the program is executed, it includes one or a combination of the steps of the method embodiments.

[0054] In addition, in each embodiment of the present application, the functional units can be integrated into one processing module, or each unit can exist physically alone, or two or more units can be integrated into one module. The above integrated module can be implemented in the form of hardware or in the form of a software functional module. If the above integrated module is implemented in the form of a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium. The storage medium can be a read-only memory, a magnetic disk, an optical disk, or the like.

[0055] The above is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present application can easily think of various changes or substitutions, and these should all be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A soil sample compaction method, characterized in that: include: The corresponding relationship between soil dry density and compressive stress is established through filling test, and the compressive stress level sequence corresponding to the dry density of the soil layer under the target dry density is determined; Filling soil layers in layers in the test model box, applying corresponding compressive stresses to the soil layers based on the compressive stress level sequence to adjust the dry density, thereby forming a composite soil body with a target dry density in the test model box, and arranging an earth pressure detection component in the composite soil body; After the soil layer of the composite soil body is partially compacted, positioning drilling is performed to form a borehole cavity, and a simulated pile body pre-installed with a strain detection component is pressed into the borehole cavity; The stress transfer during the compaction of the composite soil mass causes the borehole cavity to produce radial deformation, so as to achieve close coupling between the composite soil mass and the pile periphery interface of the simulated pile mass.

2. A soil sample compaction method according to claim 1, characterized in that: The calculation formula for applying compressive stress on the surface of each soil layer is σ n =(F n +G) / A, where: σ n is the compressive stress value applied to the nth layer of soil, F n is the reading of the force sensor when compacting the nth layer of soil, G is the total deadweight of the loading system in the test device, and A is the bearing area of ​​the soil in the test model box.

3. A soil sample compaction method according to claim 2, characterized in that: The method of establishing the corresponding relationship between the dry density of the soil layer and the compressive stress through the filling test and determining the compressive stress level sequence corresponding to the dry density of the soil layer at the target dry density includes: A reaction frame and a test cylinder are arranged in the test device, a soil layer sample is filled in the test cylinder, and compressive stress is applied to the soil layer sample through a loading system on the reaction frame; the reading of the force sensor in the loading system is recorded, and the dry density of the soil layer sample in the test cylinder is detected; The compressive stress applied by the loading system is adjusted to fill the soil layer sample in the test cylinder for multiple times and the loading system compacts the soil layer sample, and after the dry density of the soil layer sample in the test cylinder is detected, a relationship curve between the compressive stress and the dry density is established to determine the compressive stress required to achieve the target dry density, and the compressive stress required for the target dry density is graded and split to obtain the compressive stress level sequence; Wherein, the loading system comprises a pressure-bearing component, a jack and the force sensor which are sequentially stacked on the soil body, and the jack abuts against the force transmission rod of the reaction frame through the force sensor; The deadweight compensation value of the loading system is G=G1+G2+G3, where G1 is the weight of the force sensor, G2 is the weight of the jack, and G3 is the weight of the pressure-bearing component.

4. A soil sample compaction method according to claim 3, characterized in that: The method of filling soil layers in layers in the test model box, applying corresponding compressive stresses to the soil layers based on the compressive stress level sequence to adjust the dry density, thereby forming a composite soil body with a target dry density in the test model box, and arranging an earth pressure detection component in the composite soil body also includes: The test cylinder is replaced with the test model box in the test device, and the composite soil body is formed by laying soil layers arranged in layers from bottom to top in the test model box, wherein the composite soil body comprises at least a first soil layer, a second soil layer and a third soil layer, and the following steps are performed: Laying a first soil layer in the test model box, and performing preliminary leveling on the first soil layer, placing the pressure-bearing component on the first soil layer, and then applying a first compressive stress to the first soil layer by pressing the pressure-bearing component with the jack to adjust the dry density of the first soil layer, and obtaining a reading on the force sensor when the jack applies the first compressive stress through a calculation formula as F1; A second soil layer located above the first soil layer is laid in the test model box, and the second soil layer is preliminarily leveled, the pressure-bearing component is placed on the second soil layer, and the second compressive stress is applied to the second soil layer by pressing the pressure-bearing component with the jack to adjust the dry density of the second soil layer and further increase the dry density of the first soil layer, and the reading on the force sensor when the jack applies the second compressive stress is obtained by a calculation formula as F2; A third soil layer located above the second soil layer is laid in the test model box, and preliminary leveling is performed on the third soil layer. The pressure-bearing component is placed on the third soil layer, and a third compressive stress is applied to the third soil layer by pressing the pressure-bearing component with the jack to adjust the dry density of the third soil layer and further increase the dry densities of the first soil layer and the second soil layer. The reading on the force sensor is obtained as F3 through a calculation formula when the jack applies the third compressive stress.

5. A soil sample compaction method according to claim 4, characterized in that: The method of filling soil layers in layers in the test model box, applying corresponding compressive stresses to the soil layers based on the compressive stress level sequence to adjust the dry density, thereby forming a composite soil body with a target dry density in the test model box, and arranging an earth pressure detection component in the composite soil body also includes: The soil pressure detection components are buried above the first soil layer to the third soil layer respectively, and the cables of the soil pressure detection components are led out along the inner wall of the test model box and connected to the static strain acquisition system.

6. A soil sample compaction method according to claim 4, characterized in that: The method of performing positioning drilling to form a borehole cavity after compaction of part of the soil layer of the composite soil body is completed, pressing a simulated pile body pre-installed with a strain detection component into the borehole cavity, and the method of causing radial deformation of the borehole cavity through stress transmission during the compaction of the composite soil body to achieve tight coupling between the composite soil body and the pile periphery interface of the simulated pile body include: Before filling the third soil layer, using a drilling template with guide positioning holes to determine the pile position coordinates on the soil layer above the first soil layer; Using a spiral drill to drill according to the pile position coordinates to form a borehole with a diameter matching the simulated pile body; A strain detection component is arranged on the pile peripheral surface of the simulated pile body, and is pressed into the drill hole after being insulated and packaged; The compaction step of the third soil layer generates lateral stress in the soil layer above the first soil layer, thereby causing radial deformation of the soil within the circumference of the simulated pile body to form the composite soil body tightly coupled with the simulated pile body.

7. A soil sample compaction method according to claim 4, characterized in that: The third compressive stress> the second compressive stress ≥ the first compressive stress; Wherein, the reading of the force sensor is F2 / F1=F3 / F2 =1.08~1.16; or, The reading of the force sensor is F1=F2=F3 / (1.2~1.3).

8. A soil sample compaction method according to claim 6, characterized in that: The method of arranging a strain detection component on the outer surface of the simulated pile body and pressing it into the borehole after insulating and packaging it also includes: Determining a mounting area on the surface of the simulated pile body, and grinding the mounting area to form a rough surface; Bonding each of the strain detection components to the corresponding mounting area; After the adhesive layer on the back of each strain detection component is cured, detecting whether each strain detection component can work normally; After determining that each of the strain sensing components can work normally, each of the strain sensing components is wrapped with insulating tape.

9. A soil sample compaction method according to claim 8, characterized in that: The method of filling soil layers in layers in the test model box, applying corresponding compressive stresses to the soil layers based on the compressive stress level sequence to adjust the dry density, thereby forming a composite soil body with a target dry density in the test model box, and arranging an earth pressure detection component in the composite soil body also includes: Covering the inner wall of the test model box with a vaseline coating, and then laying a plastic film on the vaseline coating; Size scales are marked on the inner wall of the test model box to determine the thickness of the soil layer before and after compaction in the test model box.

10. A soil sample compaction method according to claim 8 or 9, characterized in that: Also includes: The test device is inspected to eliminate the circuit breakage: each soil pressure detection component, each strain detection component and the force sensor are inspected using a multimeter, and then each soil pressure detection component, each strain detection component and the force sensor are electrically connected to the static strain acquisition system after the inspection.

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