Geotechnical test device and method for simulating different construction rates and dry-wet cycle changes

Abstract

The invention discloses a geotechnical test device and method for simulating different construction rates and dry-wet cycle changes, and relates to the technical field of geotechnical tests.The geotechnical test device comprises a microcomputer processing system, a sample loading, fixing and reading device and a water injection and pumping device. The method comprises the following steps: (1) after a foundation pit is excavated to a certain depth, excavation is suspended or a lower foundation structure is constructed, the surrounding underground water level changes greatly; (2) the surrounding underground water level is greatly changed in the excavation process of foundation pits with different depths and the construction process of a lower foundation structure; (3) in the excavation process of the foundation pits with different depths and the construction process of the lower foundation structure, the construction speeds are different, and the surrounding underground water level is basically stable; (4) in the excavation process of foundation pits with different depths and the construction process of a lower foundation structure, the construction rates are different, and the surrounding underground water level changes drastically, according to the method, through sequential superposition of the change factors of the foundation pit depth, the construction rates and the underground water level, the influence mode of all the factors on foundation soil deformation is judged according to the test result.

Description

Technical Field

[0001] The invention relates to the technical field of geotechnical testing, and in particular to a geotechnical testing device and method for simulating different construction rates and dry-wet cycle changes. Background Art

[0002] In the field of foundation pit construction, accurate assessment and prediction of soil deformation is crucial to ensure the stability and safety of the project. As key factors affecting the deformation of the underlying soil layer, foundation pit depth, construction rate, and groundwater level fluctuation have always been the focus of research. However, existing technologies have obvious deficiencies in this regard.

[0003] First, in terms of conventional test methods, the current design is to calculate deformation based on the compression index provided in the survey report, and this index is usually tested under the conditions of natural moisture content, fixed loading and unloading rate, and pressurization to self-weight pressure + 100 / 200kPa; and the changes in moisture content, loading and unloading rate, and maximum test pressure have a great impact on the test results, that is, the compression index under different construction conditions is a variable value rather than a constant value. This situation has a certain impact on the deformation calculation, especially under the conditions of deep and large foundation pits, rapid excavation and backfill loading, and large changes in the surrounding groundwater level. The test results will change significantly and cannot objectively reflect the actual deformation characteristics, which poses a great risk to the safety of the project.

[0004] The second is other design test methods. In the past, research on compression tests at different loading rates focused on uniaxial compression tests on rocks, with the main purpose of studying the structural failure mechanism of rocks at different loading rates. As for dry-wet cycle compression tests, scholars mainly explored the effects of dry-wet cycles on shear and compression indicators or simulated tidal fluctuations. Although large-scale side-confined compression tests and shear test integrated machines based on dry-wet cycle conditions have been developed, these studies often only consider a single variable.

[0005] In actual construction, foundation pit depth, excavation rate and groundwater fluctuation exist simultaneously and intertwine to affect the deformation of foundation soil. For example, in urban foundation pit construction, rapid excavation may be accompanied by rapid changes in groundwater levels, and the two act together on the stability and deformation characteristics of the foundation soil. The research method that only considers a single factor cannot truly reflect the actual engineering situation, and it is difficult to accurately evaluate and predict the deformation of the foundation soil. Therefore, there is an urgent need for an experimental method that can comprehensively consider different construction conditions (single factor influence and joint influence) of multiple factors such as foundation pit depth, construction rate and dry-wet cycle changes, so as to fill the gap in existing technology and provide more scientific and accurate theoretical support for foundation pit construction. Summary of the invention

[0006] The purpose of the present invention is to provide a geotechnical test device and method for simulating different construction rates and dry-wet cycle changes, so as to solve the problems existing in the above-mentioned prior art, and to simulate the deformation characteristics of foundation soil under different construction conditions. By sequentially superimposing the factors of foundation pit depth, construction rate, and groundwater level change (water content change), the influence mode of each factor on the deformation of foundation soil can be judged according to the test results.

[0007] To achieve the above object, the present invention provides the following solutions: The present invention provides a geotechnical test device for simulating different construction rates and dry-wet cycle changes, including a microcomputer processing system, a sample loading, fixing and reading device, and a water injection and pumping device; The microcomputer processing system is responsible for inputting the test project and sample information, setting the loading and unloading sequence, collecting and processing the data during the test, including controlling the loading and unloading pressure on the sample, and recording the sample deformation readings; The specimen is a ring-knife specimen with a ring knife on the outside; The sample loading, fixing and reading device comprises a sample loading container, a pressurizing device and a reading device. The sample loading container is used to load the sample, inject water or pump water. The reading device is used to measure the deformation of the sample during the test and convert the deformation information of the sample into a signal, which is transmitted to the microcomputer processing system for recording and processing. The pressurizing device is used to load the sample. The water injection and pumping device is used to inject water into or pump water into the sample container, and the deformation of the simulated sample under different water content conditions is achieved by injecting water into and pumping water into the sample container.

[0008] Preferably, the microcomputer processing system includes a pressure controller, a water injection and pumping controller, a data acquisition box and processing software. The pressure controller, the water injection and pumping controller and the processing software are integrated on a computer and connected to the acquisition box via a data cable, and the acquisition box is connected to the reading device via a data cable.

[0009] Preferably, it also includes a base and a loading frame, the pressurizing device is arranged on the top of the base, the sample container is arranged on the top of the pressurizing device, the loading frame is arranged on the top of the base, and the loading frame is used to assist in applying a load to the sample; the reading device includes a dial indicator and a bracket for fixing the dial indicator, and the reading device is connected to the sample in the sample container by fixing bolts.

[0010] Preferably, the sample container comprises from bottom to top a lower guide ring, a lower permeable stone, a protective ring, a lower filter paper, a sample, an upper guide ring, an upper filter paper, an upper permeable stone and a pressure cover, and the top of the pressure cover contacts the bottom of the fixing bolt.

[0011] Preferably, the water injection and pumping device includes a water container, a water injection pump, a water injection conduit, a water injection switch, a water pump, a water pumping pipe and a water pumping switch; the water container is connected to the sampling container via the water injection conduit; the water injection pump and the water injection switch are arranged on the water injection conduit; the water container is connected to the sampling container via the water pumping pipe; the water pump and the water pumping switch are arranged on the water pumping pipe.

[0012] Based on the above geotechnical test device for simulating different construction rates and dry-wet cycle changes, the present invention also provides a geotechnical test method for simulating different construction rates and dry-wet cycle changes, comprising the following steps: 1) Stable pressure dry-wet cycle compression test 1.1) Sample preparation Take a piece of original soil to make a ring knife test block, ensure that the sample is uniform and has no gaps, and carry out moisture content, density and specific gravity tests at the same time; 1.2) Test process: Load the prepared sample into the sample loading and reading device, adjust the reading device, set the loading sequence through the microcomputer processing system, start pressurization from 25kPa, and the pressurization sequence is 25kPa, 50kPa, 100kPa, 200kPa, 300kPa, 400kPa, 500kPa. At a pressure of 500kPa, the sample reaches a stable state; After the deformation of the sample reaches stability under the pressure of 500kpa, water is injected into the sample surface by using the water injection and pumping device to start the dry-wet cycle process; the reading is recorded once at the set time interval, and the test is terminated after multiple readings are taken. During the whole process, the microcomputer processing system continuously collects and records the deformation data of the sample; Drain the water in the container, take out the sample, weigh the sample immediately, and then conduct a moisture content test; Export test data to a table for processing and analysis; 2) Dry-wet cycle compression test under combined loading and unloading 2.1) Sample preparation Take a piece of original soil to make a ring knife test block, ensure that the sample is uniform and has no gaps, and carry out moisture content, density and specific gravity tests at the same time; 2.2) Test process: Load the sample into the sample loading fixture and reading device. After adjusting the reading device, set the initial loading sequence through the microcomputer processing system. Start pressurizing from 25kPa, and pressurize to 500kPa in the sequence of 25kPa, 50kPa, 100kPa, 200kPa, 300kPa, 400kPa, 500kPa. After the deformation of the sample is stable, water is injected to cover the surface of the sample. Then, the unloading operation is performed, and the pressure is released to 400kPa, 300kPa, 200kPa, 100kPa, and 50kPa in sequence, and then reverse loading is performed, and the pressure is increased to 100kPa, 200kPa, 300kPa, 400kPa, and 500kPa; after the sample reaches stability again under the pressure of 500kPa, the water in the container is drained by using the water injection and pumping device; After that, the pressure is released again to 400kPa, 300kPa, 200kPa, 100kPa, 50kPa, and then the pressure is increased to 100kPa, 200kPa, 300kPa, 400kPa, 500kPa. During the whole process, the sample reaches the set deformation stability standard at each pressure level before the next pressure increase or pressure relief is carried out. The microcomputer processing system controls the loading and unloading operations and records the deformation data of the sample. Take out the sample, weigh the sample immediately, and then conduct a moisture content test; Import test data into a table for processing and analysis; 3) Compression test of natural moisture content under different loading rates 3.1) Sample preparation Take one piece of original soil to make eight ring knife test blocks, ensure that the sample is uniform and has no gaps, and carry out moisture content, density and specific gravity tests at the same time to ensure the consistency of its physical properties so as to carry out comparative tests; 3.2) Test process: Take 4 samples and put them into different sample containers in turn, and conduct tests at different time intervals under the natural moisture content state. Each test block always maintains the natural moisture content state. During the natural state test, the test block is not filled with water during the entire test process; The pressurization and depressurization sequence of the test is consistent, which is: pressurization of 25kPa, 50kPa, 100kPa, 200kPa, 300kPa, 400kPa, 500kPa, then depressurization to 400kPa, 300kPa, 200kPa, 100kPa, 50kPa, and then pressurization to 100kPa, 200kPa, 300kPa, 400kPa, 500kPa again; during the whole process, the specimen reaches the set deformation stability standard at each level of pressure before the next level of pressurization or depressurization is carried out. During the test, the microcomputer processing system collects and records the deformation data of each test block, so as to compare and analyze the influence of different loading rates and dry-wet cycles on the deformation of the soil layer below the foundation later; Take out the sample, weigh the sample immediately, and then conduct a moisture content test; Export test data to a table for processing and analysis 4) Compression test of water injection state under different loading rates 4.1) Sample preparation Same as experiment 3); Test process: Take 4 samples and put them into different sample containers in turn, and conduct tests at different time intervals under water filling state respectively; before the test starts, fill each sample container with water through water filling and pumping device, and set it to automatically fill water to cover the sample when the water sample is lower than a certain water level. Each sample is kept in the water filling state until the end of the test; The pressurization and depressurization sequence of the test is consistent, which is: pressurization of 25kPa, 50kPa, 100kPa, 200kPa, 300kPa, 400kPa, 500kPa, then depressurization to 400kPa, 300kPa, 200kPa, 100kPa, 50kPa, and then pressurization to 100kPa, 200kPa, 300kPa, 400kPa, 500kPa again; during the whole process, the specimen reaches the set deformation stability standard at each level of pressure before the next level of pressurization or depressurization is carried out. During the test, the microcomputer processing system collects and records the deformation data of each test block, so as to compare and analyze the influence of different loading rates and dry-wet cycles on the deformation of the soil layer below the foundation later; Drain the water in the container, take out the sample, weigh the sample immediately, and then conduct a moisture content test; Export test data to a table for processing and analysis; 5) Experimental data processing 5.1) Data export After the test, the deformation data recorded in the microcomputer acquisition and processing system is exported to Excel and other data Processing software; 5.2) Calculation of void ratio According to the parameters such as moisture content, density, specific gravity of the sample measured before the test, combined with the pressure and sample deformation data during the test, the porosity ratio at each pressure is calculated using the relevant formula; 5.3) Curve drawing and analysis The porosity ratio-pressure curve is plotted with pressure as the horizontal axis and porosity ratio as the vertical axis. By comparing and analyzing the curves under different test methods, the compression modulus, deformation characteristics, etc. of different soils under different construction rates and dry-wet cycle conditions are evaluated to determine the influence mode, main influencing factors and influence amplitude of the two factors on the deformation of foundation soil. The deformation law of foundation soil at different loading rates and dry-wet cycle stages is analyzed.

[0013] Preferably, the sample loading process is as follows: Check whether the specimen loading and fixing and reading devices can be used normally, including whether the parts are intact and complete, and whether the dial indicator pointer can rotate normally; Place the lower guide ring, lower permeable stone, protective ring, lower filter paper, sample, upper guide ring, upper filter paper, upper permeable stone and pressure cover in the sample container from bottom to top; Place the sample container filled with the sample on the pressurizing machine base, and tighten the fixing bolts to make it in close contact with the pressurizing cover without applying additional pressure; Turn the bracket that fixes the dial indicator so that the dial indicator pointer is near the center of the upper edge of the fixing bolt; Enter the project name and sample number information on the microcomputer processing system.

[0014] Compared with the prior art, the present invention has achieved the following technical effects: 1) It can accurately simulate the influence of seasonal fluctuations in water level or extreme precipitation on the deformation of soil layers near the water level after the excavation of the foundation pit or the construction of the lower foundation structure under the specified foundation pit depth. Whether it is clay, silt or sand, this test method can accurately test the change law of its compression modulus and porosity under this specific working condition.

[0015] 2) It can accurately simulate the influence of seasonal fluctuations in water levels or extreme precipitation on the deformation of soil layers near the water level during excavation or construction of lower foundation structures of foundation pits of different depths.

[0016] 3) It can accurately simulate the influence of different construction rates on the deformation of the foundation soil layer during the excavation or construction of the lower foundation structure of foundation pits of different depths under the condition that the surrounding water level does not change much.

[0017] 4) It can accurately simulate the comprehensive impact of different construction rates and moisture contents on the deformation of foundation soil layers when the surrounding groundwater levels of foundation pits of different depths vary significantly.

[0018] The above working conditions realize the sequential superposition of three influencing factors: deep foundation pit, construction rate and moisture content change. Through comparative analysis, it helps engineers to gain a deeper understanding of the stability and deformation trend of foundation soil under different construction conditions.

[0019] This test can clearly show the mechanical response of foundation soil under the influence of multiple factors, provide a reliable basis for analyzing deformation phenomena such as settlement and uplift during the construction process, and help optimize the construction plan and take effective foundation reinforcement measures. Through experimental research, it can provide a reference for the reasonable control of construction speed and stop time of groundwater control measures for foundation pits of different depths in actual projects, avoid problems such as excessive deformation or uplift of foundation soil caused by extreme precipitation weather and too fast construction speed, provide key data support for engineering structure design, and effectively optimize the design and construction plan. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 It is a schematic diagram of the structure of the geotechnical test device for simulating different construction rates and dry-wet cycle changes in the present invention; In the figure: 1. microcomputer processing system; 2. sample loading, fixing and reading device; 3. water filling and pumping device; 4. sample container; 5. pressurizing device; 6. pressurizing machine base; 7. collection box; 8. computer; 9. base; 10. loading frame; 11. reading device; 12. bracket; 13. dial indicator; 14. lower guide ring; 15. lower permeable stone; 16. guard ring; 17. lower filter paper; 18. sample; 19. upper guide ring; 20. upper filter paper; 21. upper permeable stone; 22. pressurizing cover; 23. fixing bolt; 24. water container; 25. water filling conduit; 26. water filling switch; 27. pumping pipe; 28. pumping switch. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The object of the present invention is to provide a geotechnical test device and method for simulating different construction rates and dry-wet cycle changes, so as to solve the problems existing in the prior art.

[0024] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] The geotechnical test device in this embodiment simulates different construction rates and dry-wet cycle changes, such as Figure 1 As shown, it includes a microcomputer processing system 1, a sample loading, fixing and reading device 2 and a water injection and pumping device 3; The specimen 18 involved is a ring-knife specimen with a ring knife on the outside; The microcomputer processing system 1 is responsible for inputting the test project and the information of the sample 18, setting the loading and unloading sequence, collecting and processing the data during the test, including controlling the loading and unloading pressure of the sample 18, and recording the deformation reading of the sample 18; The sample loading, fixing and reading device 2 comprises a sample loading container 4, a pressurizing device 5 and a reading device 11. The sample loading container 4 is used to load the sample 18. The reading device 11 is used to measure the deformation of the sample 18 during the test and convert the deformation information of the sample 18 into a signal, which is transmitted to the microcomputer processing system 1 for recording and processing. The pressurizing device 5 is used to load the sample 18. The water injection and pumping device 3 is used to inject water into or pump water into the sample container 4 , and the deformation of the simulated sample 18 under different water content conditions is achieved by injecting water into or pumping water into the sample container 4 .

[0026] In this specific embodiment, the microcomputer processing system 1 includes a pressure controller, a water injection and pumping controller, a data acquisition box 7 and processing software. The pressure controller, the water injection and pumping controller and the processing software are integrated on a computer 8 and connected to the acquisition box 7 through a data line, and the acquisition box 7 is connected to the reading device 11 through a data line. The microcomputer processing system 1 accurately controls the sequence, value size, time interval and other parameters of pressure loading and unloading according to the requirements of different test methods through a preset program. During the test, the deformation data from the test loading fixture and reading device 11 is received in real time, and stored and preliminarily processed for subsequent data processing and analysis.

[0027] In this specific embodiment, a base 9 and a loading frame 10 are also included. The pressure device 5 is arranged on the top of the base 9, the sample container 4 is arranged on the top of the pressure device 5, and the loading frame 10 is arranged on the top of the base 9 to assist in applying a load to the sample 18. The bracket 12 is used to support and fix the dial gauge 13, and the reading device 11 is connected to the sample 18 in the sample container 4 through the fixing bolts 23. After the sample 18 is placed in the sample container 4, the initial state of the reading device 11 is adjusted. Under the control of the microcomputer system, the water level is set and different loading and unloading pressures are endured. The device converts the deformation information of the sample 18 into an electrical signal or other identifiable signal, and transmits it to the microcomputer processing system 1 for recording and processing.

[0028] In this specific embodiment, the sample container 4 includes, from bottom to top, a lower guide ring 14, a lower permeable stone 15, a guard ring 16, a lower filter paper 17, a sample 18, an upper guide ring 19, an upper filter paper 20, an upper permeable stone 21 and a pressure cover 22. The guard ring 16 and the upper guide ring 19 are provided on the outside of the sample 18, and the top of the pressure cover 22 contacts the fixing bolts 23.

[0029] In this specific embodiment, the water injection and pumping device 3 includes a water container 24, a water injection pump, a water injection conduit 25, a water injection switch 26, a water pump, a water pumping switch 27 and a water pumping switch 28. The water container 24 is connected to the sample container 4 through the water injection conduit 25, the water injection pump and the water injection switch 26 are arranged on the water injection conduit 25, the water container 24 is connected to the sample container 4 through the water pumping switch 27, and the water pump and the water pumping switch 28 are arranged on the water pumping switch 27.

[0030] Based on the above geotechnical test device for simulating different construction rates and dry-wet cycle changes, the present invention also provides a geotechnical test method for simulating different construction rates and dry-wet cycle changes, comprising the following steps: 1) Stable pressure dry-wet cycle compression test 1.1) Preparation of Sample 18 Take a piece of original soil to make a ring knife test block (diameter greater than or equal to 80mm, height 200mm), ensure that the sample 18 is uniform and has no gaps, and carry out moisture content, density and specific gravity tests at the same time; 1.2) Test process: According to the above sample loading process, the prepared sample 18 is loaded into the sample loading, fixing and reading device 2 (2), and the reading device 11 is adjusted. The loading sequence is set by the microcomputer processing system 1 (1), starting from 25kPa, and the pressurization sequence is 25kPa, 50kPa, 100kPa, 200kPa, 300kPa, 400kPa, 500kPa (including other pressurization sequences and pressure intervals, and final pressure). Under the pressure of 500kPa, the sample 18 reaches a stable state (the stable state can be judged according to indicators such as the deformation rate of the sample 18, such as the deformation amount is extremely small (not more than 0.01mm) within a certain period of time).

[0031] After the deformation of the sample 18 reaches stability under the pressure of 500 kPa, water is injected into the sample 18 surface by using the water injection and pumping device 3 (3), and the dry-wet cycle process begins. The reading is recorded once every 1 hour (or other set time interval), and the test is terminated after five (or more) readings are taken. During the whole process, the microcomputer processing system 1 continuously collects and records the deformation data of the sample 18.

[0032] Drain the water in the container, take out the sample 18, weigh the mass of the sample 18 immediately, and then conduct a moisture content test; Export test data to a table for processing and analysis; 2) Dry-wet cycle compression test under combined loading and unloading 2.1) Preparation of Sample 18 Take a piece of original soil to make a ring knife test block, ensure that the sample 18 is uniform and has no gaps, and carry out moisture content, density and specific gravity tests at the same time; 2.2) Test process: Load the sample 18 into the sample loading and fixing and reading device 2. After adjusting the reading device 11, set the initial loading sequence through the microcomputer processing system 1. Start pressurizing from 25 kPa, and pressurize to 500 kPa in the sequence of 25 kPa, 50 kPa, 100 kPa, 200 kPa, 300 kPa, 400 kPa, and 500 kPa. After the deformation of the sample 18 is stable, water is injected to cover the surface of the sample 18. Then, the unloading operation is performed, and the pressure is released to 400 kPa, 300 kPa, 200 kPa, 100 kPa, and 50 kPa in sequence, and then reverse loading is performed, and the pressure is increased to 100 kPa, 200 kPa, 300 kPa, 400 kPa, and 500 kPa; after the sample 18 reaches stability again under the pressure of 500 kPa, the water in the container is drained by using the water injection and pumping device 3; After that, the pressure is released again to 400kPa, 300kPa, 200kPa, 100kPa, and 50kPa, and then the pressure is continued to be increased to 100kPa, 200kPa, 300kPa, 400kPa, and 500kPa. During the whole process, the sample 18 reaches the set deformation stability standard at each pressure level before the next pressure is increased or released. The microcomputer processing system 1 controls the loading and unloading operations and records the deformation data of the sample 18. Take out sample 18, weigh the mass of sample 18 immediately, and then conduct a moisture content test; Import test data into a table for processing and analysis; 3) Compression test of natural moisture content under different loading rates 3.1) Preparation of Sample 18 Take one piece of original soil to make 8 ring knife test blocks, ensure that the sample 18 is uniform and has no gaps, and carry out moisture content, density and specific gravity tests at the same time to ensure the consistency of its physical properties so as to carry out comparative tests; 3.2) Test process: Take 4 samples 18 and put them into different sample containers 4 in sequence, and conduct tests at different time intervals (1 hour, 2 hours, 5 hours, 10 hours, etc.) under the natural moisture content state. Each test block always maintains the natural moisture content state. When conducting the natural state test, for example, when conducting the 1-hour natural state test, the test block is not filled with water during the entire test process; The pressurization and depressurization sequence of the test is consistent, which is: pressurization of 25kPa, 50kPa, 100kPa, 200kPa, 300kPa, 400kPa, 500kPa, then depressurization to 400kPa, 300kPa, 200kPa, 100kPa, 50kPa, and then pressurization to 100kPa, 200kPa, 300kPa, 400kPa, 500kPa again; during the whole process, the sample 18 reaches the set deformation stability standard at each level of pressure before the next level of pressurization or depressurization is carried out. During the test, the microcomputer processing system 1 collects and records the deformation data of each test block, so as to compare and analyze the influence of different loading rates and dry-wet cycles on the deformation of the soil layer below the foundation later; Take out sample 18, weigh the mass of sample 18 immediately, and then conduct a moisture content test; Export test data to a table for processing and analysis 5) Compression test of water injection state under different loading rates 4.1) Preparation of Sample 18 Same as experiment 3); Test process: Take 4 samples 18 and put them into different sample containers 4 in turn, and conduct tests at different time intervals (1 hour, 2 hours, 5 hours, 10 hours, etc.) under the water filling state; before the test starts, fill each sample container 4 with water through the water filling and pumping device 3, and set it to automatically fill water to cover the sample 18 when the water sample is lower than a certain water level, and each sample 18 is kept in the water filling state until the end of the test; The pressurization and depressurization sequence of the test is consistent, which is: pressurization of 25kPa, 50kPa, 100kPa, 200kPa, 300kPa, 400kPa, 500kPa, then depressurization to 400kPa, 300kPa, 200kPa, 100kPa, 50kPa, and then pressurization to 100kPa, 200kPa, 300kPa, 400kPa, 500kPa again; during the whole process, the sample 18 reaches the set deformation stability standard at each level of pressure before the next level of pressurization or depressurization is carried out. During the test, the microcomputer processing system 1 collects and records the deformation data of each test block, so as to compare and analyze the influence of different loading rates and dry-wet cycles on the deformation of the soil layer below the foundation later; Drain the water in the container, take out the sample 18, weigh the mass of the sample 18 immediately, and then conduct a moisture content test; Export test data to a table for processing and analysis; 5) Experimental data processing 5.1) Data export After the test, the deformation data recorded in the microcomputer acquisition and processing system is exported to Excel and other data Processing software; 5.2) Calculation of void ratio According to the parameters such as the moisture content, density, and specific gravity of the sample 18 measured before the test, combined with the pressure during the test and the deformation data of the sample 18, the porosity ratio at each pressure is calculated using the relevant formula; 5.3) Curve drawing and analysis With pressure as the horizontal axis and porosity as the vertical axis, the porosity-pressure curve is plotted; by comparing and analyzing the curves under different test methods, the compression modulus, deformation characteristics, etc. of different soils under different construction rates (simulated by different loading rates) and dry-wet cycles (simulated by water injection and pumping) are evaluated; the influence mode, main influencing factors and influence amplitude of the two factors on the deformation of foundation soil are determined; the deformation law of foundation soil at different loading rates and dry-wet cycle stages is analyzed.

[0033] The sample loading process is as follows: Check whether the sample loading and fixing and reading device 2 can be used normally, including whether the parts are intact and complete, and whether the dial indicator pointer can rotate normally; Place the lower guide ring 14, the lower permeable stone 15, the protective ring 16, the lower filter paper 17, the sample 18, the upper guide ring 19, the upper filter paper 20, the upper permeable stone 21, and the pressure cover 22 in the sample container 4 from bottom to top; Place the sample container 4 filled with the sample 18 on the pressurizing base 6, and tighten the fixing bolts 23 to make it in close contact with the pressurizing cover 22 without applying additional pressure; Rotate the bracket 12 that fixes the dial gauge 13 so that the pointer of the dial gauge 13 is located near the center of the upper edge of the fixing bolt 23; Input the project name and sample 18 number information on the microcomputer processing system 1.

[0034] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A geotechnical test device for simulating different construction rates and dry-wet cycle changes, characterized in that: It includes a microcomputer processing system, a sample loading and fixing and reading device, and a water injection and pumping device; The specimen is a ring-knife specimen with a ring knife on the outside; The microcomputer processing system is responsible for inputting the test project and sample information, setting the loading and unloading sequence, collecting and processing the data during the test, including controlling the loading and unloading pressure and time interval of the sample, and recording the sample deformation reading; The sample loading, fixing and reading device comprises a sample loading container, a pressurizing device and a reading device. The sample loading container is used to load the sample, inject water or pump water. The reading device is used to measure the deformation of the sample during the test and convert the deformation information of the sample into a signal, which is transmitted to the microcomputer processing system for recording and processing. The pressurizing device is used to load the sample. The water injection and pumping device is used to inject water into or pump water into the sample container, and the deformation of the simulated sample under different water content conditions is achieved by injecting water into and pumping water into the sample container.

2. The geotechnical test device for simulating different construction rates and dry-wet cycle changes according to claim 1, characterized in that: The microcomputer processing system includes a pressure controller, a water injection and pumping controller, a data acquisition box and processing software. The pressure controller, the water injection and pumping controller and the processing software are integrated on a computer and connected to the acquisition box via a data line, and the acquisition box is connected to the reading device via a data line.

3. The geotechnical test device for simulating different construction rates and dry-wet cycle changes according to claim 1, characterized in that: It also includes a base and a loading frame, wherein the pressurizing device is arranged on the top of the base, the sample container is arranged on the top of the pressurizing device, and the loading frame is arranged on the top of the base, and the loading frame is used to assist in applying a load to the sample; the reading device includes a dial indicator and a bracket for fixing the dial indicator, and the reading device is connected to the sample in the sample container by fixing bolts.

4. The geotechnical test device for simulating different construction rates and dry-wet cycle changes according to claim 3, characterized in that: The sample container is provided with a lower guide ring, a lower permeable stone, a protective ring, a lower filter paper, a sample, an upper guide ring, an upper filter paper, an upper permeable stone and a pressure cover from bottom to top, and the top of the pressure cover contacts the fixing bolt.

5. The geotechnical test device for simulating different construction rates and dry-wet cycle changes according to claim 1, characterized in that: The water injection and pumping device includes a water container, a water injection pump, a water injection conduit, a water injection switch, a water pump, a water pumping pipe and a water pumping switch. The water container is connected to the sample container via the water injection conduit, and the water injection pump and the water injection switch are arranged on the water injection conduit. The water container is connected to the sample container via the water pumping pipe, and the water pump and the water pumping switch are arranged on the water pumping pipe.

6. A geotechnical test method for simulating different construction rates and dry-wet cycle changes, using the geotechnical test device for simulating different construction rates and dry-wet cycle changes according to any one of claims 1 to 5, comprising the following steps: 1) Stable pressure dry-wet cycle compression test 1.1) Sample preparation Take a piece of original soil to make a ring knife test block, ensure that the sample is uniform and has no gaps, and carry out moisture content, density and specific gravity tests at the same time; 1.2) Test process: Load the prepared sample into the sample loading and reading device, adjust the reading device, set the loading sequence through the microcomputer processing system, start pressurization from 25kPa, and the pressurization sequence is 25kPa, 50kPa, 100kPa, 200kPa, 300kPa, 400kPa, 500kPa. At a pressure of 500kPa, the sample reaches a stable state; After the deformation of the sample reaches stability under the pressure of 500kpa, water is injected into the sample surface by using the water injection and pumping device to start the dry-wet cycle process; the reading is recorded once at the set time interval, and the test is terminated after multiple readings are taken. During the whole process, the microcomputer processing system continuously collects and records the deformation data of the sample; Drain the water in the container, take out the sample, weigh the sample immediately, and then conduct a moisture content test; Export test data to a table for processing and analysis; 2) Dry-wet cycle compression test under combined loading and unloading 2.1) Sample preparation Take a piece of original soil to make a ring knife test block, ensure that the sample is uniform and has no gaps, and carry out moisture content, density and specific gravity tests at the same time; 2.2) Test process: Load the sample into the sample loading fixture and reading device. After adjusting the reading device, set the initial loading sequence through the microcomputer processing system. Start pressurizing from 25kPa, and pressurize to 500kPa in the sequence of 25kPa, 50kPa, 100kPa, 200kPa, 300kPa, 400kPa, 500kPa. After the deformation of the sample is stable, water is injected to cover the surface of the sample. Then, the unloading operation is performed, and the pressure is released to 400kPa, 300kPa, 200kPa, 100kPa, and 50kPa in sequence, and then reverse loading is performed, and the pressure is increased to 100kPa, 200kPa, 300kPa, 400kPa, and 500kPa; after the sample reaches stability again under the pressure of 500kPa, the water in the container is drained by using the water injection and pumping device; After that, the pressure is released again to 400kPa, 300kPa, 200kPa, 100kPa, 50kPa, and then the pressure is increased to 100kPa, 200kPa, 300kPa, 400kPa, 500kPa. During the whole process, the sample reaches the set deformation stability standard at each pressure level before the next pressure increase or pressure relief is carried out. The microcomputer processing system controls the loading and unloading operations and records the deformation data of the sample. Take out the sample, weigh the sample immediately, and then conduct a moisture content test; Import test data into a table for processing and analysis; 3) Compression test of natural moisture content under different loading rates 3.1) Sample preparation Take one piece of original soil to make eight ring knife test blocks, ensure that the sample is uniform and has no gaps, and carry out moisture content, density and specific gravity tests at the same time to ensure the consistency of its physical properties so as to carry out comparative tests; 3.2) Test process: Take 4 samples and put them into different sample containers in turn, and conduct tests at different time intervals under the natural moisture content state. Each test block always maintains the natural moisture content state. During the natural state test, the test block is not filled with water during the entire test process; The pressurization and depressurization sequence of the test is consistent, which is: pressurization of 25kPa, 50kPa, 100kPa, 200kPa, 300kPa, 400kPa, 500kPa, then depressurization to 400kPa, 300kPa, 200kPa, 100kPa, 50kPa, and then pressurization to 100kPa, 200kPa, 300kPa, 400kPa, 500kPa again; during the whole process, the specimen reaches the set deformation stability standard at each level of pressure before the next level of pressurization or depressurization is carried out. During the test, the microcomputer processing system collects and records the deformation data of each test block, so as to compare and analyze the influence of different loading rates and dry-wet cycles on the deformation of the soil layer below the foundation later; Take out the sample, weigh the sample immediately, and then conduct a moisture content test; Export test data to a table for processing and analysis 4) Compression test of water injection state under different loading rates 4.1) Sample preparation Same as experiment 3); Test process: Take 4 samples and put them into different sample containers in turn, and conduct tests at different time intervals under water filling state respectively; before the test starts, fill each sample container with water through water filling and pumping device, and set it to automatically fill water to cover the sample when the water sample is lower than a certain water level. Each sample is kept in the water filling state until the end of the test; The pressurization and depressurization sequence of the test is consistent, which is: pressurization of 25kPa, 50kPa, 100kPa, 200kPa, 300kPa, 400kPa, 500kPa, then depressurization to 400kPa, 300kPa, 200kPa, 100kPa, 50kPa, and then pressurization to 100kPa, 200kPa, 300kPa, 400kPa, 500kPa again; during the whole process, the specimen reaches the set deformation stability standard at each level of pressure before the next level of pressurization or depressurization is carried out. During the test, the microcomputer processing system collects and records the deformation data of each test block, so as to compare and analyze the influence of different loading rates and dry-wet cycles on the deformation of the soil layer below the foundation later; Drain the water in the container, take out the sample, weigh the sample immediately, and then conduct a moisture content test; Export test data to a table for processing and analysis; 5) Experimental data processing 5.1) Data export After the test, the deformation data recorded in the microcomputer acquisition and processing system is exported to Excel data Processing software; 5.2) Calculation of void ratio According to the sample moisture content, density and specific gravity parameters measured before the test, combined with the pressure and sample deformation data during the test, the porosity ratio at each pressure is calculated using the relevant formula; 5.3) Curve drawing and analysis The porosity ratio-pressure curve is plotted with pressure as the horizontal axis and porosity ratio as the vertical axis. By comparing and analyzing the curves under different test methods, the compression modulus and deformation characteristics of different soils under different construction rates and dry-wet cycle conditions are evaluated to determine the influence mode, main influencing factors and influence amplitude of the two factors on the deformation of foundation soil. The deformation law of foundation soil at different loading rates and dry-wet cycle stages is analyzed.

7. The geotechnical test method for simulating different construction rates and dry-wet cycle changes according to claim 6, characterized in that: The sample loading process is as follows: Check whether the specimen loading and fixing and reading devices can be used normally, including whether the parts are intact and complete, and whether the dial indicator pointer can rotate normally; Place the lower guide ring, lower permeable stone, protective ring, lower filter paper, sample, upper guide ring, upper filter paper, upper permeable stone and pressure cover in the sample container from bottom to top; Place the sample container filled with the sample on the pressurizing machine base, and tighten the fixing bolts to make it in close contact with the pressurizing cover without applying additional pressure; Turn the bracket that fixes the dial indicator so that the dial indicator pointer is near the center of the upper edge of the fixing bolt; Enter the project name and sample number information on the microcomputer processing system.

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