Automatic cyclic loading and unloading device for simulating long-term accumulated deformation of storage yard

Abstract

The utility model relates to an automatic cyclic loading and unloading device for simulating long-term accumulated deformation of a storage yard, which is characterized in that the interior of a sample and the interior of a pressure chamber are respectively connected with a pressure controller, and the pressure controller is communicated with the sample through a back pressure drainage pipeline which can be controlled to be switched on and off; the pressure controller is communicated with the pressure chamber through a confining pressure drainage pipeline which can be controlled to be opened and closed, the pressure controller is connected with a data acquisition box, the data acquisition box is connected with data recording and processing equipment, and the sample is connected with a pore pressure sensor. And the pore pressure sensor is connected with the data acquisition box and transmits measured data to the data recording and processing equipment. The device has the advantages that back pressure saturation can be realized in a consolidation test, the saturation of a sample is improved, and a test result is more accurate and reliable; autonomously controlled graded loading can be realized, the test period is shortened, and the influence of human factors is reduced; the control of cyclic loading and unloading can be realized, and the long-term cyclic accumulative strain characteristic of the soil body is researched.

Description

Technical Field

[0001] The utility model relates to the technical field of geotechnical engineering testing, in particular to an automatic cyclic loading and unloading device for simulating the long-term accumulated deformation of a storage yard. Background Art

[0002] The stress-strain relationship of soil is one of the main research topics in soil mechanics, and consolidation test is an important test method to study the deformation characteristics of soil. In 1924, Terzaghi established the one-dimensional unidirectional consolidation theory, and consolidation test began to be widely used in engineering. The consolidation test measures the deformation and pressure of the specimen under the conditions of lateral confinement and axial drainage, and calculates various soil parameters such as the compression coefficient, compression index, rebound index, compression modulus, consolidation coefficient and the initial consolidation pressure of the original soil, providing important design parameters for engineering design. The consolidation test has the advantages of simple theoretical calculation, convenient operation and low cost, and can better simulate and predict the behavior of soil in actual engineering. However, the standard consolidation test generally adopts a graded loading method, the test cycle is long, and it is necessary to observe that the strain reaches stability before the next level of loading or unloading.

[0003] In actual engineering applications, when the groundwater level is high, the soil is generally considered to be in a saturated state. Therefore, using saturated soil for testing can better simulate actual engineering conditions and improve the reliability and applicability of test results. The presence of gas in the soil makes the properties of unsaturated soil far more complex than two-phase saturated soil. Some principles of saturated soil are no longer applicable to unsaturated soil, or need to be re-verified. In consolidation tests, in order to ensure that the sample is in a saturated state, the water tank containing the sample is generally filled with water, and the sample is immersed in water, and the saturation is difficult to ensure. In triaxial tests, back pressure saturation is usually used to increase the saturation of the sample. A back pressure is provided by an external pressure device to press degassed water into the soil sample, thereby increasing the pore water pressure of the sample. When the pore water pressure increases to a certain level, the residual air in the soil sample will dissolve in the water under pressure. A large number of tests have shown that the use of back pressure saturation can make the soil sample reach a higher degree of saturation.

[0004] After infrastructure such as rail transit and storage yards are built and put into use, the foundation is usually subjected to a variety of cyclic loads, such as traffic loads and mechanical vibrations. Measured data from many projects show that soft soil foundations will produce significant additional settlement under long-term cyclic stress, leading to a variety of engineering problems such as bridge head jumping and uneven settlement. Therefore, studying the cumulative deformation of soil under long-term cyclic loads is of great engineering significance. At present, the research on plastic cumulative deformation under long-term cyclic loads mainly uses dynamic triaxial tests, but dynamic triaxial tests are difficult and expensive. When simulating the stress conditions of normal consolidated soil in engineering through dynamic triaxial tests, it is necessary to obtain the static lateral pressure coefficient K0 through other tests, and it is difficult to simulate the changes in lateral pressure during cyclic loading and unloading. Summary of the invention

[0005] The purpose of the utility model is to provide an automatic cyclic loading and unloading device for simulating the long-term cumulative deformation of a storage yard in accordance with the above-mentioned deficiencies of the prior art, which can realize autonomously controlled graded loading and automatically enter the next test process when the conditions are met; by introducing a pressure controller, the device can achieve back pressure saturation and improve the saturation of the sample during the test; at the same time, the control of cyclic loading and unloading can be realized to simulate the long-term cyclic stress effect of projects such as storage yards.

[0006] The purpose of this utility model is achieved by the following technical solutions:

[0007] An automatic cyclic loading and unloading device for simulating the long-term cumulative deformation of a storage yard comprises a testing machine body, a pressure chamber is arranged on the testing machine body, a testing machine crossbeam is arranged above the pressure chamber, a consolidation container is arranged inside the pressure chamber, the inside of the consolidation container is used to place a sample, a loading and unloading device is arranged on the testing machine crossbeam, and the loading and unloading device can load and unload the sample, and is characterized in that: the interior of the sample and the interior of the pressure chamber are respectively connected to a pressure controller, the pressure controller and the sample are connected through a controllable back pressure drainage pipeline, the pressure controller and the pressure chamber are connected through a controllable confining pressure drainage pipeline, the pressure controller is connected to a data acquisition box, the data acquisition box is connected to a data recording and processing device, the sample is connected to a pore pressure sensor, the pore pressure sensor is connected to the data acquisition box and transmits the measurement data to the data recording and processing device.

[0008] The consolidation container includes a lower water-permeable plate, an upper water-permeable plate, and a fixed plate, wherein the fixed plate is fixed to the pressure chamber by fixing screws, the upper water-permeable plate and the lower water-permeable plate are spaced apart in the fixed plate, and the sample is placed between the upper water-permeable plate and the lower water-permeable plate; the lower water-permeable plate is connected to the back-pressure drainage pipeline.

[0009] A guard ring is arranged in the consolidation container, and the guard ring is provided with a rubber ring.

[0010] An exhaust hole is provided on the pressure chamber.

[0011] The back-pressure drainage pipeline is provided with a back-pressure drainage valve, and the back-pressure drainage valve is used to control the on-off of the back-pressure drainage pipeline; the confining pressure drainage pipeline is provided with a confining pressure drainage valve, and the confining pressure drainage valve is used to control the on-off of the confining pressure drainage pipeline.

[0012] The advantages of the utility model are:

[0013] 1) On the basis of the traditional consolidation instrument, a pressure controller is added to saturate the sample with back pressure, improve the saturation of the sample, and make the test results more accurate and reliable.

[0014] 2) The control system of the traditional consolidation instrument has been improved so that it can judge the test conditions and automatically control the test progress according to the changes in pore pressure or deformation, ensuring the continuity and stability of the loading process. At the same time, it minimizes the need for human intervention and improves the efficiency and reliability of the test.

[0015] 3) It has the control function of cyclic loading and unloading: during the loading and unloading process, when the loading or unloading reaches the specified time, or the change of strain within a certain period of time is less than a certain value, the next operation is automatically carried out to realize the control of loading and unloading; the operation of cyclic loading and unloading is realized through the control system, which can more realistically simulate the long-term cumulative deformation of the actual yard; this cyclic loading and unloading control function better simulates the cyclic loading and unloading conditions of long-term loading and unloading in the yard, and more comprehensively evaluates the mechanical properties and deformation characteristics of the soil, providing a reference for infrastructure projects such as yards. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a loading time chart of the utility model;

[0017] Figure 2 It is a schematic diagram of the system composition of the utility model;

[0018] Figure 3 It is a schematic structural diagram of the consolidation container in the utility model. DETAILED DESCRIPTION

[0019] The following is a further detailed description of the features of the present invention and other related features through embodiments in conjunction with the accompanying drawings to facilitate understanding by technicians in the same industry:

[0020] like Figure 1-3 As shown, the symbols in the figure respectively represent: testing machine beam 1, pressure chamber 2, consolidation container 3, lower water-permeable plate 3.1, upper water-permeable plate 3.2, fixing screws 3.3, fixing plate 3.4, ring knife 3.5, protective ring 3.6, rubber ring 3.7, testing machine 4, exhaust hole 5, confining pressure drain valve 6, back pressure drain valve 7, pressure controller 8, pore pressure sensor 9, data acquisition box 10, data recording and processing equipment 11.

[0021] Example: Figures 1 to 3As shown, the automatic cyclic loading and unloading device for simulating the long-term cumulative deformation of the stockpile in this embodiment can automatically perform one-dimensional loading and unloading on the sample, simulate the cyclic loading and unloading conditions of long-term loading and unloading in the stockpile, and measure the deformation and pressure of the sample under the conditions of lateral limit and axial drainage, so as to analyze the soil parameters such as the compression coefficient, compression index, rebound index, compression modulus, initial consolidation pressure and cumulative strain under long-term cyclic loading and unloading.

[0022] Specifically, combined Figures 1 to 3 As shown, the implementation steps and structure of the automatic cycle loading and unloading device in this embodiment are described as follows:

[0023] 1) Prepare the sample using the ring knife 3.5, fill the base of the consolidation container 3 with water, place the guard ring 3.6, the lower water-permeable plate 3.1 and the thin filter paper (not shown in the figure), carefully load the sample with the ring knife 3.5 into the guard ring 3.6, then place the thin filter paper, the upper water-permeable plate 3.2 and the pressure cover plate on the sample, and install the pressure chamber 2. Open the exhaust hole 5, fill the pressure chamber 2 with water, and when the pressure chamber 2 is almost filled with water, reduce the water inlet speed, and when the water overflows from the exhaust hole 5, close the exhaust hole 5. Then apply back pressure at a certain rate through the pressure controller 8 to perform back pressure saturation.

[0024] In this embodiment, back pressure saturation is performed by a pressure controller 8 to improve the saturation of the sample; the pressure controller 8 is connected to the sample soil through a back pressure drainage pipeline provided with a back pressure drainage valve 7, and is also connected to the pressure chamber 2 through a confining pressure drainage pipeline provided with a confining pressure control valve 6. The pressure controller 8 is connected to a data acquisition box 10, and the data acquisition box 10 is connected to a data recording and processing device 11.

[0025] The back pressure inside the soil sample and the pressure in the pressure chamber 2 are controlled by the same pressure controller 8 to avoid errors between different pressure controllers. When the back pressure is saturated, the back pressure drainage valve 8 connected to the pressure controller 8 and the inside of the sample soil is closed, so that the confining pressure remains stable and does not affect the measurement of the pore pressure.

[0026] In this embodiment, a rubber ring 3.7 is provided at the guard ring 3.6, and the rubber ring 3.7 is used to ensure the sealing performance at the ring cutter 3.5 to improve the test accuracy.

[0027] 2) Close the back pressure drain valve 7, use the testing machine 4 to perform graded loading at the specified stress, and measure the strain, stress and pore pressure at the bottom of the sample in real time through the data acquisition box 10. When the strain and pore pressure are stable, the next level of loading is performed until the specified axial initial stress is loaded. The pore pressure measurement of the sample is achieved through the pore pressure sensor 9, and in order to measure its strain and stress, related sensors can also be configured, and unified collection is performed through the data acquisition box 10 and further recording and processing is performed through the data recording and processing equipment 11.

[0028] In this embodiment, loading can be performed in a stress or strain control manner as required. At the same time, the conditions for the next loading can be set, that is, when the change in strain or pore pressure within a certain period of time is less than a certain value, consolidation is considered to be completed and the next level of loading is performed.

[0029] In this embodiment, the testing machine 4 is provided with a testing machine beam 1 above the pressure chamber 2, and a loading and unloading device is provided at the position of the testing machine beam 1 corresponding to the consolidation container 3. The loading and unloading device can be used to pressurize the pressure cover plate above the sample, thereby loading the sample.

[0030] 3) Setting the number of cycles and loading and unloading stress, performing cyclic loading and unloading, and measuring strain and stress in real time through a data acquisition system composed of a data acquisition box 10 and a data recording and processing device 11.

[0031] In this embodiment, the size, number of cycles and duration of each loading and unloading load can be set, and when each loading or unloading step is completed, the next unloading or loading can be automatically performed to simulate the long-term cyclic loading of the yard. Alternatively, the size, number of cycles and conditions for the next loading of each loading and unloading load can be set, and the change of strain can be judged through the control system, and when the strain is stable, the next loading or unloading step can be automatically performed.

[0032] In the specific implementation of this embodiment: the data recording and processing device 11 collects the values ​​of pore pressure and displacement in real time, and uses them to determine whether to proceed to the next step of loading, thereby realizing automation in the process of graded loading.

[0033] The data recording and processing device 11 has a control function of cyclic loading and unloading. After setting the stress and the number of cycles, the entire cyclic loading and unloading process can be controlled by comprehensively judging the changes in strain and pore pressure.

[0034] Although the above embodiments have described the concepts and embodiments of the purpose of the utility model in detail with reference to the accompanying drawings, ordinary technicians in this field can recognize that various improvements and modifications can still be made to the utility model without departing from the scope of the claims, so they are not described one by one here.

Claims

1. An automatic cyclic loading and unloading device for simulating long-term cumulative deformation of a storage yard, comprising a testing machine body, a pressure chamber is arranged on the testing machine body, a testing machine crossbeam is arranged above the pressure chamber, a consolidation container is arranged inside the pressure chamber, the inside of the consolidation container is used to place a sample, a loading and unloading device is arranged on the testing machine crossbeam, and the loading and unloading device can load and unload the sample, characterized in that: The interior of the sample and the interior of the pressure chamber are respectively connected to a pressure controller, the pressure controller and the sample are connected through a controllable on-off back-pressure drainage pipeline, the pressure controller and the pressure chamber are connected through a controllable on-off confining pressure drainage pipeline, the pressure controller is connected to a data acquisition box, the data acquisition box is connected to a data recording and processing device, the sample is connected to a pore pressure sensor, the pore pressure sensor is connected to the data acquisition box and transmits the measurement data to the data recording and processing device.

2. According to claim 1, an automatic cyclic loading and unloading device simulating long-term cumulative deformation of a storage yard is characterized by: The consolidation container includes a lower water-permeable plate, an upper water-permeable plate, and a fixed plate, wherein the fixed plate is fixed to the pressure chamber by fixing screws, the upper water-permeable plate and the lower water-permeable plate are spaced apart in the fixed plate, and the sample is placed between the upper water-permeable plate and the lower water-permeable plate; the lower water-permeable plate is connected to the back-pressure drainage pipeline.

3. The automatic cyclic loading and unloading device simulating the long-term cumulative deformation of a storage yard according to claim 2 is characterized by: A guard ring is arranged in the consolidation container, and the guard ring is provided with a rubber ring.

4. The automatic cyclic loading and unloading device simulating the long-term cumulative deformation of a storage yard according to claim 1 is characterized by: The pressure chamber is provided with an exhaust hole.

5. The automatic cyclic loading and unloading device simulating the long-term cumulative deformation of a storage yard according to claim 1 is characterized in that: The back-pressure drainage pipeline is provided with a back-pressure drainage valve, and the back-pressure drainage valve is used to control the on-off of the back-pressure drainage pipeline; the confining pressure drainage pipeline is provided with a confining pressure drainage valve, and the confining pressure drainage valve is used to control the on-off of the confining pressure drainage pipeline.

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