A soil sample compaction method

Abstract

The present application proposes a soil sample compaction method, comprising: establishing a correspondence between the dry density and compressive stress of a soil layer through a filling test, and determining a compressive stress level sequence corresponding to the dry density of the soil layer at a target dry density; filling soil layers in layers in a 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 of the target dry density in the test model box, and arranging a soil pressure detection component in the composite soil body; after compaction of part of the soil layer of the composite soil body is completed, performing positioning drilling to form a borehole cavity, and pressing a simulated pile body with a pre-installed strain detection component into the borehole cavity; through stress transfer during the compaction of the composite soil body, causing radial deformation of the borehole cavity, so as to achieve close coupling between the composite soil body and the pile periphery interface of the simulated pile body; and solving the problems of low efficiency and poor uniformity in adjusting the dry density of the soil body, easy damage to the detection equipment during the pile formation process, and insufficient compaction of the soil around and between the piles.

Description

Technical Field

[0001] The present application relates to the technical field of foundation simulation tests, and in particular to a soil sample compaction method. Background Art

[0002] As the core technical means of evaluating the bearing capacity of foundations, foundation load testing is based on the technical principle of implementing graded loading in a simulated foundation environment, while simultaneously monitoring the deformation response and stress transfer laws of the foundation soil, so as to scientifically determine the stability of the foundation and the safe bearing threshold. This test is of decisive significance to the entire construction cycle of a building project. Its test data directly supports the rational selection of foundation design parameters and is a key technical link in ensuring the safety and durability of buildings. Especially in major infrastructure projects such as dams, high-rise buildings, and bridges, accurately obtaining the bearing capacity parameters under the geological conditions of the foundation can effectively avoid the risks of structural cracking, tilting, and even collapse caused by uneven foundation settlement and insufficient bearing capacity, thereby fundamentally reducing safety hazards and maintenance costs throughout the life cycle of the project.

[0003] When conducting foundation load tests in a laboratory environment, a scaled foundation model must be constructed using a standardized simulation test apparatus. This apparatus, with a model box as its core carrier, accurately simulates the geological profile of the target site by layering soil layers with varying physical and mechanical parameters. The specific implementation process is as follows: First, each soil layer is compacted. By controlling parameters such as compaction work, layer thickness, and number of compaction passes, the soil density (such as void ratio and dry density) is brought close to the in-situ test indicators of the actual foundation. Next, mechanical drilling equipment is used to drill holes at predetermined locations. Model piles are then driven into the soil layer according to the designed parameters through static pressure or vibration, simulating the pile installation process and pile-soil interaction in actual projects. Once the stress state of the model pile and the surrounding soil stabilizes, a loading system applies graded loads to the pile top or foundation surface. Key data, such as settlement displacement, pile strain, and soil stress, are simultaneously collected to evaluate the bearing capacity and deformation behavior of the simulated foundation under different load conditions. The boundary conditions must be strictly controlled throughout the entire test process to ensure that the stress and strain characteristics of the simulated foundation are comparable to the mechanical behavior of the in-situ foundation, providing a reliable technical basis for engineering design.

[0004] Existing foundation simulation methods have significant technical limitations, primarily in two key areas: controlling the dry density of the foundation soil layer and the pile modeling process. Controlling the dry density of the foundation soil layer faces a technical bottleneck: the lack of standardized procedures. Current engineering practices lack reproducible operational specifications for quantitatively controlling the dry density of the soil layer, often relying on trial-and-error adjustments. Specifically, multiple sampling tests and compaction parameter adjustments are required to bring the simulated foundation dry density close to the target working condition. This process results in low efficiency and significantly increased costs. In terms of pile-driving technology for pile foundation model tests, traditional methods are mainly divided into two categories: embedded and squeezed. Both have technical bottlenecks: embedded pile driving is limited by the narrow working space around the pile, making it difficult to effectively compact the soil around the pile, resulting in insufficient interface tightness between the pile and the soil, and weakening the mechanism for transferring pile stress to the surrounding soil, which directly affects the true simulation of the load transfer law in the test; squeezed pile driving, due to the dynamic effect of the extrusion force and friction between the pile and the soil during the pile pressing process, may cause mechanical damage to the pre-buried strain detection elements, resulting in distortion or even interruption of test data collection, and interfering with the accurate evaluation of the mechanical response of the pile foundation. Summary of the Invention

[0005] The present application provides a soil sample compaction method to solve the problems of low efficiency and insufficient uniformity in adjusting the dry density of the foundation during load testing, as well as the technical problems of the existing pile-pressing method that easily damages the testing equipment and the insufficient compactness of the soil around and between the piles of the simulated pile body. The technical solution is as follows:

[0006] The present invention provides a soil sample densification method, comprising:

[0007] The corresponding relationship between soil dry density and compressive stress is established through filling tests, and the compressive stress level sequence corresponding to the dry density of the soil layer at the target dry density is determined;

[0008] Filling soil layers in a test model box in layers, applying corresponding compressive stresses to the soil layers based on the compressive stress hierarchy sequence to adjust the dry density, thereby forming a composite soil mass with a target dry density in the test model box, and arranging earth pressure detection components in the composite soil mass;

[0009] After compaction of a portion of the composite soil layer is completed, 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;

[0010] Through the stress transfer during the compaction process of the composite soil, the borehole cavity is radially deformed to achieve close coupling between the composite soil and the pile periphery of the simulated pile.

[0011] In one embodiment, 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 on the soil layer, F n is the reading of the force sensor when compacting the nth soil layer, 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.

[0012] In one embodiment, a method for establishing a corresponding relationship between dry density and compressive stress of a soil layer through a filling test and determining a compressive stress level sequence corresponding to the dry density of the soil layer at a target dry density includes:

[0013] A reaction frame and a test cylinder are set up in the test device, a soil sample is filled in the test cylinder, and compressive stress is applied to the soil sample through the 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 sample in the test cylinder is detected;

[0014] Adjust the compressive stress applied by the loading system, repeatedly fill the test cylinder with soil samples and compact the soil samples with the loading system, and detect the dry density of the soil samples in the test cylinder. Then, establish a relationship curve between compressive stress and dry density, determine the compressive stress required to achieve the target dry density, and obtain a compressive stress level sequence by dividing the compressive stress required for the target dry density into grades.

[0015] The loading system includes a pressure-bearing component, a jack, and a force sensor stacked on the soil in sequence, and the jack is connected to the force transmission rod of the reaction frame through the force sensor;

[0016] 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.

[0017] In one embodiment, the method of filling soil layers in a test model box in layers, applying corresponding compressive stresses to the soil layers based on a 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 further includes:

[0018] In the test device, the test cylinder is replaced with a test model box, and soil layers are laid in the test model box from bottom to top to form a composite soil body. The composite soil body includes at least a first soil layer, a second soil layer, and a third soil layer. The following steps are performed:

[0019] A first soil layer is laid in the test model box and initially leveled. A pressure-bearing component is placed on the first soil layer. The pressure-bearing component is then pressed together with a jack to apply a first compressive stress to the first soil layer to adjust the dry density of the first soil layer. The reading on the force sensor when the jack applies the first compressive stress is obtained by a calculation formula as F1.

[0020] A second soil layer is laid above the first soil layer in the test model box, and preliminary leveling is performed on the second soil layer. A pressure-bearing component is placed on the second soil layer, and then a second compressive stress is applied to the second soil layer by pressing the pressure-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. The calculation formula shows that when the jack applies the second compressive stress, the reading on the force sensor is F2;

[0021] A third soil layer is laid above the second soil layer in the test model box, and preliminary leveling is performed on the third soil layer. A 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 a jack to adjust the dry density of the third soil layer and further increase the dry density of the first and second soil layers. The calculation formula shows that when the jack applies the third compressive stress, the reading on the force sensor is F3.

[0022] In one embodiment, the method of filling soil layers in a test model box in layers, applying corresponding compressive stresses to the soil layers based on a 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 further includes:

[0023] Earth pressure detection components are buried above the first soil layer to the third soil layer respectively, and the cables of the earth pressure detection components are led out along the inner wall of the test model box and connected to the static strain acquisition system.

[0024] In one embodiment, after compaction of a portion of the composite soil layer, positioning drilling is performed to form a borehole cavity, a simulated pile body pre-installed with a strain detection component is pressed into the borehole cavity, and a method for 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 includes:

[0025] Before filling the third soil layer, a drilling template with guide holes is used to determine the pile position coordinates on the soil layer above the first soil layer;

[0026] Use an auger to drill according to the pile position coordinates to form a borehole with a diameter that matches the simulated pile body;

[0027] A strain detection component is arranged on the peripheral surface of the simulated pile body, and is insulated and packaged before being pressed into the drilled hole;

[0028] 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 around the simulated pile to form a composite soil body tightly coupled with the simulated pile body.

[0029] In one embodiment, the third compressive stress>the second compressive stress≥the first compressive stress;

[0030] Among them, the reading of the force sensor is F2 / F1=F3 / F2=1.08~1.16; or,

[0031] The force sensor reading is F1=F2=F3 / (1.2~1.3).

[0032] In one embodiment, the method of arranging a strain detection component on the outer surface of the simulated pile body, insulating and encapsulating the component, and then pressing the component into the drilled hole further includes:

[0033] A mounting area is determined on the peripheral surface of the simulated pile body, and the mounting area is polished to form a rough surface;

[0034] Bonding each strain detection component to the corresponding mounting area;

[0035] After the adhesive layer on the back of each strain detection component is cured, test whether each strain detection component can work normally;

[0036] After confirming that each strain detection component can work normally, use insulating tape to wrap each strain detection component.

[0037] In one embodiment, the method of filling soil layers in a test model box in layers, applying corresponding compressive stresses to the soil layers based on a 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 further includes:

[0038] The inner wall of the test model box is covered with a vaseline coating, and a plastic film is laid on the vaseline coating;

[0039] Mark the inner wall of the test model box with size scales to determine the thickness of the soil layer before and after compaction in the test model box.

[0040] In one embodiment, it also includes: detecting the test device to eliminate the circuit breakage: using a multimeter to detect each soil pressure detection component, each strain detection component and the force sensor, and then electrically connecting each soil pressure detection component, each strain detection component and the force sensor to the static strain acquisition system after the detection.

[0041] Compared with the existing technology, the soil sample compaction method provided by the present invention has significant technical advantages and practical value: through filling tests, a quantitative correspondence between soil dry density and 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 trial and error in the traditional method is transformed into a data-driven parametric control, avoiding the repetitive operation of multiple sampling and detection, significantly improving the efficiency of dry density control, saving time and cost, and reducing the error in the uniformity of soil dry density through controllable compressive stress loading. In the process of composite soil compaction, a simulated pile body with pre-installed strain detection components is incorporated. The radial deformation of the soil around the borehole cavity caused by the transmission of graded compressive stress is used to achieve close coupling of the pile interface, thereby improving the compaction of the soil around and between the piles, avoiding the blind spot of pile compaction around the pile in buried pile driving, and eliminating the serious mechanical damage to the detection equipment caused by squeezed pile driving. The damage to the strain detection components during the pile driving process is reduced and reliable data collection is provided for subsequent load tests. After adopting this method, the compression modulus, shear strength and other mechanical parameters of the simulated foundation are closer to the industry standards than those of the prototype foundation, providing a more reliable technical solution for foundation load testing. It solves the core problems of low efficiency, insufficient uniformity of the density of the simulated soil layer, and improvement of the compaction degree of the soil around and between piles in the traditional method, and can provide a scientific and reliable test basis for the design and safety assessment of the foundation of construction projects.

[0042] The above summary is for illustrative purposes 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 accompanying drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the multiple drawings represent 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 this application and should not be construed as limiting the scope of this application.

[0044] Figure 1 This is a schematic diagram of the structure of arranging soil layers in a test device using a soil sample compaction method according to an embodiment of the present application;

[0045] Figure 2 A schematic diagram of a curve showing the relationship between compressive stress and dry density obtained by conducting a filling test using a soil sample compaction method proposed in an embodiment of the present application.

[0046] Reference numerals:

[0047] 1. Test model box; 2. Reaction frame; 3. Jack; 4. Force sensor; 5. Pressure-bearing component; 6. Simulated pile; 7. Strain detection component; 8. Soil pressure detection component;

[0048] 51. Pressure cover plate; 52. Foam board;

[0049] 101, first soil layer; 102, second soil layer; 103, third soil layer. DETAILED DESCRIPTION

[0050] Hereinafter, only certain exemplary embodiments are briefly described. As will be appreciated by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the present application. Therefore, the drawings and description are to be regarded as illustrative in nature and not restrictive.

[0051] Reference Figure 1 and Figure 2 As shown, a soil sample densification method is proposed in the embodiment of the present application, and the soil sample densification method can be performed according to the following steps:

[0052] The corresponding relationship between soil dry density and compressive stress is established through filling tests, and the compressive stress level sequence corresponding to the dry density of the soil layer at the target dry density is determined;

[0053] Filling soil layers in the test model box 1 in layers, 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 1, and arranging the soil pressure detection component 8 in the composite soil body;

[0054] After compaction of a portion of the composite soil layer is completed, positioning drilling is performed to form a borehole cavity, and the simulated pile body 6 pre-installed with the strain detection component 7 is pressed into the borehole cavity;

[0055] The stress transfer during the compaction of the composite soil mass causes radial deformation of the borehole cavity, thereby achieving close coupling between the composite soil mass and the pile periphery interface of the simulated pile body 6 .

[0056] Among them, the soil pressure stress parameters satisfy σ n =(F n +G) / A, where: σ n is the compressive stress value applied to the nth soil layer, and its unit of measurement is kPa, F n is the reading of force sensor 4 when compacting the nth soil layer, its unit of measurement is kN, G is the total deadweight of the loading system in the test device, its unit of measurement is kN, and A is the bearing area of the soil layer in the test model box 1, its unit of measurement is m².

[0057] Specifically, in the technical solution adopted in this application, in the filling test, according to the formula σ n =(F n +G) / A calculates the correspondence between the dry density of the soil and the compressive stress, thereby determining the compressive stress level sequence required for the soil to form the target dry density; it should be explained that the compressive stress level sequence is the compressive stress required for obtaining the target dry density by compacting the soil layer sample in the filling test, and the compressive stress of each soil layer is determined according to the compressive stress required for the target dry density to obtain the parameters of the compressive stress level sequence. In the test model box 1, the compressive stress applied to the uppermost soil layer is the compressive stress required for the target dry density, and the compressive stresses applied to the remaining soil layers are all less than the compressive stress required for the target dry density, so that each soil layer in the composite soil can be closer to the target dry density, and the target dry density is closer to the dry density of the actual foundation soil layer compared with the existing artificial compaction process. In the step of filling the soil layers in layers in the test model box 1, the foundation soil layer and the capping soil layer as well as several test soil layers located between the foundation soil layer and the capping soil layer can be filled in the test model box 1. The test soil layer is used to press into the simulated pile body 6 after positioning drilling. During the compaction of the capping soil layer, stress can be transferred to the test soil layer, so that the soil around the pile in the drilled cavity in the test soil layer is deformed 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 the present application, compared with the existing technology of artificially compacting soil layers, the dry density of the composite soil is made closer to the dry density of the actual soil by calculating the graded compressive stress, that is, the target dry density; and in the process of graded compaction of the soil layers of the composite soil, a simulated pile body 6 is pressed into the soil layer, and the pile surrounding soil of the test soil layer is tightly fitted with the simulated pile body 6 through the step of compacting the capping soil layer, so that in the process of positioning the drilling hole, a drilling cavity larger than the diameter of the simulated pile body 6 can be used to avoid damage during the process of pressing the simulated pile body 6, and the pile surrounding soil formed by the drilling hole is ensured to be tightly fitted with the simulated pile body 6 through the step of compacting the capping soil layer, so that the simulated foundation environment is closer to the actual foundation environment, thereby significantly improving the reliability and accuracy of the foundation load test.

[0058] Further, refer to Figure 2 As shown, in some embodiments, a method for establishing a correspondence between the dry density of a soil layer and the compressive stress through a filling test and determining a compressive stress level sequence corresponding to the dry density of the soil layer at a target dry density includes:

[0059] A reaction frame 2 and a test cylinder are set in the test device, a soil sample is filled in the test cylinder, and compressive stress is applied to the soil sample through the loading system on the reaction frame 2; the reading of the force sensor 4 in the loading system is recorded, and the dry density of the soil sample in the test cylinder is detected;

[0060] Adjust the compressive stress applied by the loading system, repeatedly fill the test cylinder with soil samples and compact the soil samples with the loading system, and detect the dry density of the soil samples in the test cylinder. Then, establish a relationship curve between compressive stress and dry density, determine the compressive stress required to achieve the target dry density, and obtain a compressive stress level sequence by dividing the compressive stress required for the target dry density into grades.

[0061] The loading system includes a pressure-bearing component 5, a jack 3, and a force sensor 4 stacked on the soil in sequence. The jack 3 is abutted against the force transmission rod of the reaction frame 2 through the force sensor 4.

[0062] The deadweight compensation value of the loading system is G=G1+G2+G3, where G1 is the weight of the force sensor 4, G2 is the weight of the jack 3, and G3 is the weight of the pressure-bearing component 5.

[0063] Specifically, in the technical solution adopted in the present application, the test device may include a reaction frame 2, a test cylinder that can replace the test model box 1, and a loading system composed of a pressure-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 the test model box 1, so as to facilitate repeated tests. Specifically, the soil layer sample is filled in the test cylinder, and the pressure-bearing component 5 is placed on the soil layer sample in the test cylinder. One end of the jack 3 is pressed against the pressure-bearing component 5, and the other end is pressed against the force transmission rod on the reaction frame 2 through the force sensor 4. The soil layer sample filled in the test cylinder is compacted by the jack 3; after recording the reading of the force sensor 4 and the dry density of the soil layer sample, a relationship curve can be established based on the compressive stress and the dry density, 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 component 5 can be a foam plate 52 of not less than 3 cm and a pressure-bearing cover plate 51. The foam plate 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 a steel plate. In the filling test, the pressure-bearing cover plate 51 needs to be adapted to the test cylinder; when the test model box 1 is filled with composite soil, the pressure-bearing cover plate 51 needs to be adapted to the test model box 1. With the cooperation of the pressure-bearing cover plate 51 and the foam plate 52, the compressive stress applied by the jack 3 can be evenly transferred to the soil layer in the test cylinder or the test model box 1. Since the foam template can be flexibly deformed during the extrusion process, the pressure on the soil layer is kept consistent during the compaction process, so as to ensure that the uniformity of the dry density of the soil layer is improved during the compaction process.

[0064] In one embodiment, compressive stress is applied to the soil sample by the jack 3. The compressive stress applied by the jack 3 in each filling test can be 16 kPa, 32 kPa, 48 kPa, 64 kPa, and 80 kPa, respectively, and the compaction time is 10 minutes. It should be noted that the compressive stress applied by the jack 3 to the soil sample and the compaction time need to be adjusted according to actual conditions and are not limited to the specifications proposed in this embodiment. It is sufficient to be able to obtain a curve showing the relationship between compressive stress and soil sample dry density.

[0065] Furthermore, in some embodiments, the method of filling soil layers in the test model box 1 in layers, 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 1, and arranging the earth pressure detection component 8 in the composite soil body further includes:

[0066] In the test device, the test cylinder is replaced with a test model box 1, and soil layers are laid in the test model box 1 in layers from bottom to top to form a composite soil body. The composite soil body includes at least: a first soil layer 101, a second soil layer 102, and a third soil layer 103. The following steps are performed:

[0067] A first soil layer 101 is laid in the test model box 1 and initially leveled. A pressure-bearing component 5 is placed on the first soil layer 101. The pressure-bearing component 5 is then pressed by the jack 3 to apply a first compressive stress to the first soil layer 101 to adjust the dry density of the first soil layer 101. The calculation formula shows that when the jack 3 applies the first compressive stress, the reading on the force sensor 4 is F1.

[0068] A second soil layer 102 is laid above the first soil layer 101 in the test model box 1, and preliminary leveling is performed on the second soil layer 102. A pressure-bearing component 5 is placed on the second soil layer 102, and the pressure-bearing component 5 is pressed by the jack 3 to apply a second compressive stress to the second soil layer 102 to adjust the dry density of the second soil layer 102 and further increase the dry density of the first soil layer 101. The calculation formula shows that when the jack 3 applies the second compressive stress, the reading on the force sensor 4 is F2;

[0069] A third soil layer 103 is laid above the second soil layer 102 in the test model box 1, and preliminary leveling is performed on the third soil layer 103. A pressure-bearing component 5 is placed on the third soil layer 103. The pressure-bearing component 5 is pressed by the jack 3 to apply a third compressive stress to the third soil layer 103 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. The calculation formula shows that when the jack 3 applies the third compressive stress, the reading on the force sensor 4 is F3.

[0070] Specifically, in the technical solution adopted in the present application, the thickness of the first soil layer 101 before compaction can be 30~40cm. The initial leveling can be performed by scraping the upper surface of the first soil layer 101 with a scraper, and the leveling degree can be detected by a spirit level. Subsequently, a foam board 52 and a pressure cover plate 51 are laid on the first soil layer 101, so that the jack 3 applies a first compressive stress σ1 on the pressure cover plate 51, and the reading of the force sensor 4 is F1. After the compaction operation is completed, a first soil layer 101 with a specific dry density is obtained. The first soil layer 101 is further leveled using a spirit level and a scraper, and the thickness of the first soil layer 101 is controlled to be about 20cm. Finally, the upper surface of the first soil layer 101 is scraped to ensure the adhesion between the soil layers during the compaction process. The second and third soil layers 102 and 103 are constructed using the same filling method as the first soil layer 101. The differences are that a second compressive stress σ2 is applied to the second soil layer 102, and the reading of force sensor 4 is F2. A third compressive stress σ3 is applied to the third soil layer 103, and the reading of force sensor 4 is F3. In this embodiment, the third compressive stress σ3 is the compressive stress required for the aforementioned soil layers to reach the target dry density. To achieve a composite soil mass approaching the target dry density required for the test by applying graded compressive stresses to each soil layer, the reading of force sensor 4 can be increased by a factor of 1.08 to 1.16, depending on the layer, until the third compressive stress σ3 applied to the third soil layer 103 is reached, thereby achieving a more balanced dry density for the composite soil mass. In some embodiments, when the soil layers in the composite soil body need to have different dry densities, the readings of the force sensors 4 corresponding to each compressive stress can be set to the same compressive stress applied to the first soil layer 101 and the second soil layer 102, and the reading of the third soil layer 103 can be 1.2 to 1.3 times the compressive stress reading of the base soil layer, so that there is a difference in dry density between 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 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 compressive stress and dry density, so as to obtain a composite soil body that is closer to the actual dry density after loosening the soil in the compaction test model box 1.

[0071] Furthermore, in some embodiments, the method of filling soil layers in the test model box 1 in layers, 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 1, and arranging the earth pressure detection component 8 in the composite soil body further includes:

[0072] Earth pressure detection components 8 are buried above the first to third soil layers 101 to 103 respectively, 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.

[0073] Specifically, in the technical solution adopted in this application, two calibrated soil pressure detection components 8 are placed at preset positions on the surface of the first soil layer 101, specifically with the sensing surface of the soil pressure detection component 8 facing upward, and then the cable of the soil 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. Each soil pressure detection component 8 buried in the first soil layer 101 is connected to the static strain acquisition system, and the circuit is inspected and tested. After the inspection is correct, the second soil layer 102 is filled and compacted in the test model box 1. The two calibrated soil pressure detection components 8 are placed at preset positions on the surface of the second soil layer 102, specifically with the sensing surface of the soil pressure detection component 8 facing upward, and then the cable of the soil 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 soil pressure detection component 8 buried in the second soil layer 102 to the static strain acquisition system, and inspect and test the circuit. After the inspection is correct, fill and compact the third soil layer 103 in the test model box 1. Place the two calibrated soil pressure detection components 8 at the preset position on the surface of the third soil layer 103, specifically with the sensing surface of the soil pressure detection component 8 facing upward. Then, lead the cable of the soil pressure detection component 8 along the surface of the third soil layer 103 to the inner wall of the test model box 1, then lead it upward from the inner wall of the test model box 1 and fix it with transparent tape. Connect each soil pressure detection component 8 buried in the third soil layer 103 to the static strain acquisition system, and inspect and test the circuit. After the inspection is correct, complete the step of filling the composite soil in the test model box 1.

[0074] Furthermore, in some embodiments, after compaction of a portion of the composite soil layer, positioning drilling is performed to form a borehole cavity, and a simulated pile body 6 pre-installed with a strain detection component 7 is pressed into the borehole cavity. The method of causing radial deformation of the borehole cavity through stress transmission during the compaction of the composite soil to achieve tight coupling between the composite soil and the simulated pile body 6 at the pile periphery includes:

[0075] Before filling the third soil layer 103, a drilling template with guide positioning holes is used to determine the pile position coordinates on the soil layer above the first soil layer 101;

[0076] Drilling is performed using a spiral drill according to the pile position coordinates to form a borehole having a diameter that matches the simulated pile body 6;

[0077] A strain detection component 7 is arranged on the peripheral surface of the simulated pile body 6 and is insulated and packaged before being pressed into the drilled hole;

[0078] The compaction step of the third soil layer 103 generates lateral stress in the soil layer above the first soil layer 101 , thereby causing radial deformation of the soil around the simulated pile 6 to form a composite soil body tightly coupled with the simulated pile 6 .

[0079] Furthermore, in some embodiments, the third compressive stress>the second compressive stress≥the first compressive stress;

[0080] The reading of the force sensor 4 is F2 / F1=F3 / F2=1.08-1.16; or the reading of the force sensor 4 is F1=F2=F3 / (1.2-1.3).

[0081] Specifically, in the technical solution adopted in this application, the first soil layer 101 is the foundation 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 foundation soil layer is the cushion layer in the composite soil body, the test soil layer is mainly used to accommodate the simulated pile body 6, and when drilling on the test soil layer, it is necessary not to enter the foundation soil layer, while 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 the number of test soil layers being one layer. Between the first soil layer 101 and the third soil layer 103, a fourth soil layer, a fifth soil layer, a sixth soil layer, etc. can also be built, all of which are test soil layers and are located above the second soil layer 102. Therefore, by adding a test soil layer, the layout density of the soil pressure detection components 8 in the composite soil body can be adjusted. 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 repeated. It should be noted that the additional soil layer and the second soil layer 102 can be adjusted to the same dry density or different dry densities. The compressive stress applied to the additional soil layer is greater than or equal to the second compressive stress σ2 and less than the third compressive stress σ3. When the compressive stress is applied to the fourth soil layer, the fifth soil layer, and the sixth soil layer, the readings of the force sensor 4 can be obtained by the above formula, namely: F4, F5, F6. When the jack 3 presses the pressure-bearing component 5 to apply the corresponding compressive stress to each soil layer, the formula that the force sensor 4 reading should satisfy is F2 / F1= F4 / F2=F5 / F4=F6 / F5=……F n / F n-1 =F3 / F n =1.08~1.16, where n is a positive integer and n≠3; or, the reading of the force sensor 4 should satisfy the formula F1=F2=F4=F5=F6=……F n= F3 / (1.2-1.3), where n is a positive integer and n ≠ 3. After determining the third compressive stress σ3 and the force sensor reading F3 when applying the third compressive stress σ3 through the filling test, the aforementioned compressive stress hierarchy sequence is calculated using the formula that the force sensor 4 reading should satisfy. It should be noted that in this embodiment, the third compressive stress σ3 is the compressive stress required to adjust the soil layer to the target dry density during the filling test.

[0082] Furthermore, in some embodiments, the method of arranging a strain detection component 7 on the outer surface of the simulated pile body 6 and then pressing the simulated pile body 6 into the drilled hole after insulation packaging further includes:

[0083] A mounting area is determined on the pile peripheral surface of the simulated pile body 6, and the mounting area is polished to form a rough surface;

[0084] Bonding each strain detection component 7 to the corresponding mounting area;

[0085] After the adhesive layer on the back of each strain detection component 7 is cured, each strain detection component 7 is tested to see if it can work normally;

[0086] After confirming that each strain detection component 7 can work normally, each strain detection component 7 is wrapped with insulating tape.

[0087] Specifically, in the technical solution adopted in this application, a simulated pile body 6 is selected for testing, and a grinding wheel 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 on the polished area to remove grease and residues on the surface of the mounting area. The central axis is marked on the surface of the simulated pile body 6, and the mounting reference line is calibrated along the axis according to the spacing required by the test plan. 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 performed. Anti-static tweezers are used to fine-tune the position. The sealing film is covered and rolled to eliminate bubbles in the glue layer. After standing until initial solidification, the sealing film is removed and the integrity of the bonding surface is checked. Then, use a multimeter to check the circuit conductivity and insulation resistance. Finally, wrap the strain gauge 7 with insulating tape using a spiral wrapping method to protect the strain gauge 7 and its terminals. After packaging, retest the circuit conductivity to confirm that there is no construction damage. Qualified piles are labeled and stored in a constant temperature test warehouse for future use. It is recommended that the constant temperature of the test warehouse be adjusted to 20±1°C.

[0088] Furthermore, in some embodiments, the method of filling soil layers in the test model box 1 in layers, 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 1, and arranging the earth pressure detection component 8 in the composite soil body further includes:

[0089] The inner wall of the test model box 1 is covered with a vaseline coating, and a plastic film is laid on the vaseline coating;

[0090] Size scales are marked 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 .

[0091] Specifically, in the technical solution adopted in the present application, the vaseline coating can be applied to the inner wall of the test model box 1 before the composite soil is filled in the test model box 1. This can effectively reduce the amount of soil adhering to the inner wall of the test model box 1 when the composite soil is removed from the test model box 1, thereby improving the efficiency of removing the soil from the test model box 1. Furthermore, a plastic film is applied 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 preventing soil from adhering to the inner wall of the test model box 1 can be achieved, thereby saving the need for manual cleaning of the test model box 1 when the soil sample is removed from the test model box 1.

[0092] Furthermore, in some embodiments, it also includes: detecting the test device to eliminate the circuit breaker situation: 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 the static strain acquisition system after the detection.

[0093] Specifically, in the technical solution adopted in this application, the static strain acquisition system is an instrument for electrically measuring non-electrical quantities such as structural loads and material deformation in a non-destructive manner. 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. This type of instrument can be used to measure mine pressure, material deformation, and the stress and strain of engineering structures. Multimeters, also known as multiplexers, multimeters, three-way meters, and multi-function meters, are indispensable measuring instruments in power electronics and other fields, generally used to measure voltage, current, and resistance. Multimeters are categorized by display type as analog multimeters and digital multimeters. They are multifunctional, multi-range measuring instruments. Generally, multimeters can measure DC current, DC voltage, AC current, AC voltage, resistance, and audio level. Some can also measure AC current, capacitance, inductance, and some semiconductor parameters. The static strain acquisition system and multimeter in this embodiment do not represent improvements and are state-of-the-art, so their structure and usage will not be described in detail.

[0094] This application also proposes a method for foundation load testing, which is implemented after completing the above-mentioned soil sample compaction method, and is specifically carried out in the following steps:

[0095] After the filling of the composite soil is completed, the model box is covered with a film and left to stand for 7 days to allow the composite soil and the test components required for the test to stabilize.

[0096] Determine the position of the mattress layer using the positioning line and tape measure, then place the mattress frame, and then lay the mattress material. After leveling, press it slightly, then scrape the surface and check it with a spirit level. Use an ink cartridge to draw lines to determine the position of the pressure plate.

[0097] Place the jack 3, force sensor 4, and force transmission column on the pressure plate in the order shown, aligning their centers vertically and aligning them with the force points on the reaction frame 2. Install the displacement gauges. For this test, the displacement gauges should be symmetrically arranged on the pressure plate, centered at the midpoint of the pressure plate's edge. Install a square steel pipe on top of the model box to secure the displacement gauges and ensure accurate data.

[0098] The force sensor 4 and all displacement meters, strain detection components 7, soil pressure detection components 8, and force sensor 4 are electrically connected to the static strain acquisition system, and the circuits are inspected and tested to ensure that the data acquisition system can maintain normal operation during operation.

[0099] After assembly is complete, pre-compression is required, static loading is carried out for two days, and the data of the force sensor 4, displacement meter, earth pressure detection component 8 and strain detection component 7 are recorded. After the data is stable, the next step of loading is carried out.

[0100] The test was conducted using step-by-step loading, with an estimated maximum load of 900 kPa. The specific method was as follows: a total load of 900 kPa was applied in eight stages, starting from 0 kN and increasing by 112.5 kPa at each stage. The settlement of the pressure plate was recorded before each load application and again after the load application was completed. The settlement was then recorded every 10 minutes, 20 minutes, 30 minutes, 45 minutes, and 60 minutes. Thereafter, the settlement was measured and recorded every 30 minutes, and the test data was collected and saved. Load maintenance was required throughout the entire loading process using hydraulic jack 3. When the load pressure at the same stage dropped by 1%, the pressurization system was pressurized to supplement the load to meet the constant pressure requirement. When the settlement within 1 hour was less than 0.1 mm, loading of the next stage began. When the cumulative settlement of the pressure plate reaches 28.8 mm, or the settlement increases dramatically, soil is squeezed out, or a noticeable bulge appears around the pressure plate, or the ultimate load is not reached and the maximum loading pressure is greater than 900 kPa, loading is stopped. This concludes the first set of tests.

[0101] After the first set of tests, the fill in the model box needs to be cleaned.

[0102] New composite soil is refilled into the model box and the next set of tests is carried out in a similar manner.

[0103] The simulation device used in the foundation load test method includes: a base made of reinforced concrete, a reaction frame 2 installed on the base, and a test model box 1 placed on the base. After the composite soil is filled in the test model box 1 using a soil sample compaction method in the above embodiment, the load test is carried out according to the above steps. It should be noted that the simulation device used is existing technology, so it will not be repeated.

[0104] In the description of this specification, the reference terms "one embodiment," "some embodiments," "example," "specific example," or "some examples" mean that the specific features, structures, materials, or characteristics described in conjunction 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 may be combined in any appropriate manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification, as well as features of different embodiments or examples, unless they are mutually inconsistent.

[0105] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0106] Any process or method description in a flow chart or otherwise described herein can be understood to represent a module, segment or portion of code comprising one or more executable instructions for implementing the steps of a specific logical function or process. The scope of the preferred embodiments of the present application includes additional implementations in which the functions may be performed in a different order than shown or discussed, including in a substantially simultaneous manner or in a reverse order depending on the functions involved.

[0107] The logic and / or steps represented in the flowchart or otherwise described herein may be considered, for example, as a sequenced list of executable instructions for implementing the logical functions, and may be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a system including a processor, or other system that can fetch and execute instructions from an instruction execution system, apparatus, or device).

[0108] It should be understood that various parts of the present application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. All or part of the steps of the above embodiment method can be completed by instructing the relevant hardware through a program, which 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 embodiment.

[0109] In addition, the functional units in the various embodiments of the present application may be integrated into a single processing module, or each unit may exist physically separately, or two or more units may be integrated into a single module. The aforementioned integrated modules may be implemented in the form of hardware or in the form of software functional modules. If the aforementioned integrated modules are implemented in the form of software functional modules and sold or used as independent products, they may also be stored in a computer-readable storage medium. The storage medium may be a read-only memory, a magnetic disk, or an optical disk, etc.

[0110] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any person skilled in the art can easily conceive of various modifications or substitutions within the technical scope disclosed in this application, and such modifications or substitutions should be included within the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A soil sample compaction method, characterized in that: include: The corresponding relationship between the dry density of the soil layer and the compressive stress is established through a filling test, specifically including: setting a reaction frame and a test cylinder in a test device, filling a soil layer sample in the test cylinder, and applying compressive stress to the soil layer sample through a loading system on the reaction frame; recording the reading of a force sensor in the loading system, and detecting the dry density of the soil layer sample in the test cylinder; adjusting the compressive stress applied by the loading system, filling the soil layer sample and compacting the soil layer sample with the loading system in the test cylinder multiple times, and detecting the dry density of the soil layer sample in the test cylinder, establishing a relationship curve between compressive stress and dry density, determining the compressive stress required to achieve the target dry density, and obtaining a compressive stress level sequence by grading and splitting the compressive stress required for the target dry density; Filling soil layers in a test model box in layers to form a composite soil body, the composite soil body including at least a first soil layer, a second soil layer, and a third soil layer from bottom to top; applying corresponding compressive stresses to each soil layer based on the compressive stress hierarchy sequence: applying a first compressive stress to the first soil layer, applying a second compressive stress to the second soil layer, and applying a third compressive stress to the third soil layer, wherein the third compressive stress>the second compressive stress≥the first compressive stress, so as to adjust the dry density of each soil layer and form a composite soil body with a target dry density, and disposing an earth pressure detection component above each soil layer, and because the third compressive stress>the second compressive stress≥the first compressive stress, the reading of the force sensor is F2 / F1=F3 / F2=1.08-1.16; alternatively, the reading of the force sensor is F1=F2=F3 / (1.2-1.3); Before filling the third soil layer, a drilling template with guide positioning holes is used to determine the pile position coordinates on the soil layer above the first soil layer; an auger is used to drill according to the pile position coordinates to form a borehole with a diameter that matches the simulated pile body; a strain detection component is arranged on the pile circumference of the simulated pile body, insulated and encapsulated, and then pressed into the borehole, wherein the diameter of the borehole is larger than the diameter of the simulated pile body; 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 around the simulated pile body to form the composite soil body tightly coupled with the simulated pile body.

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 loading system includes a pressure-bearing component, a jack, and the force sensor stacked sequentially on the soil, wherein 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 further includes: filling soil layers in layers in a test model box to form a composite soil body, wherein the composite soil body includes at least a first soil layer, a second soil layer, and a third soil layer from bottom to top; applying corresponding compressive stresses to each soil layer based on the compressive stress hierarchy sequence: applying a first compressive stress to the first soil layer, applying a second compressive stress to the second soil layer, and applying a third compressive stress to the third soil layer, wherein the third compressive stress>the second compressive stress≥the first compressive stress, so as to adjust the dry density of each soil layer and form a composite soil body with a target dry density; and arranging an earth pressure detection component above each soil layer. In the test device, the test cylinder is replaced with the test model box, and soil layers arranged in layers from bottom to top are laid in the test model box to form the composite soil body, specifically according to the following steps: A first soil layer is laid in the test model box, and preliminary leveling is performed on the first soil layer. The pressure-bearing component is placed on the first soil layer, and then a first compressive stress is applied to the first soil layer by pressing the pressure-bearing component with the jack to adjust the dry density of the first soil layer. When the jack applies the first compressive stress, the reading on the force sensor is obtained as F1 through a calculation formula; A second soil layer is laid above the first soil layer in the test model box, and preliminary leveling is performed on the second soil layer. The pressure-bearing component is placed on the second soil layer, and the pressure-bearing component is pressed by the jack to apply a second compressive stress to the second soil layer to adjust the dry density of the second soil layer and further increase the dry density of the first soil layer. 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 when the jack applies the third compressive stress through a calculation formula.

5. A soil sample compaction method according to claim 4, characterized in that: The method further includes: filling soil layers in layers in a test model box to form a composite soil body, wherein the composite soil body includes at least a first soil layer, a second soil layer, and a third soil layer from bottom to top; applying corresponding compressive stresses to each soil layer based on the compressive stress hierarchy sequence: applying a first compressive stress to the first soil layer, applying a second compressive stress to the second soil layer, and applying a third compressive stress to the third soil layer, wherein the third compressive stress>the second compressive stress≥the first compressive stress, so as to adjust the dry density of each soil layer and form a composite soil body with a target dry density; and arranging an earth pressure detection component above each soil layer. 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 1, characterized in that: The method of arranging a strain detection component on the outer surface of the simulated pile body and pressing the component into the drill hole after performing insulation packaging further includes: Determining a mounting area on the peripheral surface of the simulated pile body, and grinding the mounting area to form a rough surface; Adhere 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 detection components can operate normally, each of the strain detection components is wrapped with insulating tape.

7. A soil sample compaction method according to claim 6, characterized in that: The method further includes: filling soil layers in layers in a test model box to form a composite soil body, wherein the composite soil body includes at least a first soil layer, a second soil layer, and a third soil layer from bottom to top; applying corresponding compressive stresses to each soil layer based on the compressive stress hierarchy sequence: applying a first compressive stress to the first soil layer, applying a second compressive stress to the second soil layer, and applying a third compressive stress to the third soil layer, wherein the third compressive stress>the second compressive stress≥the first compressive stress, so as to adjust the dry density of each soil layer and form a composite soil body with a target dry density; and arranging an earth pressure detection component above each soil layer. 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.

8. A soil sample compaction method according to claim 6 or 7, characterized in that: Also includes: Inspect the test device to eliminate the circuit breakage: use a multimeter to inspect each of the soil pressure detection components, each of the strain detection components and the force sensor, and then electrically connect each of the soil pressure detection components, each of the strain detection components and the force sensor to the static strain acquisition system after the inspection.

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