CN103234839A - In-situ direct shear tester for soil bodies - Google Patents

Abstract

The invention discloses an in-situ direct shear tester for soil, which comprises: a steel frame; a vertical oil cylinder arranged on the steel frame; a cylinder arranged horizontally at the power output end of the vertical oil cylinder; an oil cylinder, arranged on the steel frame; a push bowl, arranged at the power output end of the horizontal oil cylinder, for applying a horizontal thrust to the cylinder and moving the cylinder a predetermined distance; wherein, A displacement sensor for measuring displacement and a first pressure sensor for measuring thrust are also arranged on the horizontal oil cylinder, and a second pressure sensor for measuring lateral pressure is also arranged on the vertical oil cylinder. The invention uses vertical oil cylinders and horizontal oil cylinders to automatically apply horizontal and vertical loads step by step, and obtains soil cohesion, internal friction angle standard values, and pressure-deformation curves through shear experiments. The tester is accurate, flexible in operation, and reliable in results.

Description

Soil In Situ Direct Shear Tester

technical field

The invention relates to the technical field of soil in-situ testing, in particular to an in-situ soil shearing test instrument.

Background technique

Soil shear strength test values are currently divided into indoor shear experiments, field shear experiments, and cross shear experiments. The basic principles and theoretical basis for determination are the same. The key to the availability of the results lies in the selection of test methods The determination of body shear strength mainly includes direct shear test and in-situ direct shear test.

The direct shear test is a method for measuring the shear strength of soil. The common method is to use 4 samples, respectively, under different vertical pressures, to apply horizontal shear force for shearing, to obtain the shear stress at the time of failure, and then according to Coulomb's law determines the shear strength parameters of soils, internal friction and cohesion.

There are three methods of direct shear test: fast shear, consolidation fast shear, and slow shear. Whether it is triaxial shear or conventional direct shear test, it is required to collect undisturbed soil samples on site, and then test them under different pressures, drainage conditions and conditions. The test is carried out under the environment to determine the value of the soil. The indoor direct shear test artificially controls the shear plane, and the drainage conditions are also difficult to control, so that the stress state is quite different from the natural state of the soil, and because there are many requirements for the sample, It is difficult to ensure the consistency and uniformity of the soil sample state.

The method mentioned above also has the disadvantage of taking soil from local areas, and the shear surface of the soil sample is too small, resulting in the weakness of "point to surface".

Contents of the invention

Aiming at the problems existing in the prior art, the object of the present invention is to provide a soil in-situ direct shear tester, which is not only light and simple in pressurization, but also can test at multiple points at different depths, and is suitable for various soils to obtain stress -Strain curve and cohesion, internal friction angle and other parameters.

A kind of soil in-situ direct shear tester of the present invention comprises:

steel frame;

A vertical oil cylinder is arranged on the steel frame;

The cylinder is horizontally movable and arranged at the power output end of the vertical oil cylinder;

A horizontal oil cylinder is arranged on the steel frame;

The push bowl is arranged at the power output end of the horizontal oil cylinder, and is used to apply a horizontal thrust to the cylinder and move the cylinder a predetermined distance;

Wherein, a displacement sensor for measuring displacement and a first pressure sensor for measuring thrust are also arranged on the horizontal oil cylinder, and a second pressure sensor for measuring lateral pressure is also arranged on the vertical oil cylinder.

The invention uses vertical oil cylinders and horizontal oil cylinders to automatically apply horizontal and vertical loads step by step, and obtains soil cohesion, internal friction angle standard values, and pressure-deformation curves through shear experiments. The tester is accurate, flexible in operation, and reliable in results.

Description of drawings

Fig. 1 is a direct shear experiment plan view of the present invention;

Fig. 2 is a schematic bottom view of Fig. 1 .

Detailed ways

As shown in Figures 1 and 2, the present invention includes: a steel frame 1, a vertical oil cylinder 2, a horizontal oil cylinder 3 and a cylinder 4. The vertical oil cylinder 2 is arranged on the steel frame 1, and the cylinder 4 is arranged on the power output end of the vertical oil cylinder 2 through the horizontal slide rail 12 to be movable horizontally; the horizontal oil cylinder 3 is arranged on the steel frame 1; the push bowl 11 is arranged on the horizontal oil cylinder 3 The power output end of the cylinder 4 is used to apply a horizontal thrust to the cylinder 4 and move the cylinder 4 a predetermined distance to shear the soil inside the cylinder 4 and the soil outside the cylinder 4.

In addition, a displacement sensor 6 for measuring the displacement of the soil and a first pressure sensor 7 for measuring the thrust of the soil are also arranged on the horizontal oil cylinder 3, and a pressure sensor 7 for measuring the simulated side pressure of the soil is also arranged on the vertical oil cylinder 2. The second pressure sensor 8.

The data measured by the displacement sensor 6 , the first pressure sensor 7 and the second pressure sensor 8 are transmitted to the processing unit 10 for storage and processing. Vertical oil cylinder 2 and horizontal oil cylinder 3 are controlled by hydraulic pump 9.

In addition, a camera (not shown) for photographing the in-situ ring shearing process of the entire soil mass can also be arranged on the steel frame 1 .

When the present invention is used,

1) Choose steel tanks with higher rigidity for testing experiments;

2) Fill the tank with simulated soil;

3) The hydraulic cylinder vertically presses the cylinder 4 into the soil below 10mm;

4) Manually shovel out the surrounding soil;

5) The horizontal oil cylinder 3 drives the push bowl 11 to apply force to the cylinder 4. Due to the guiding effect of the horizontal slide rail 12, the joint surface between the soil body and the bulk soil body in the cylinder 4 is only subjected to pure shear force, and the horizontal oil cylinder 3 Stretch out at a speed of 1mm, take real-time sampling and monitoring, record the relationship between force and displacement, until the soil is sheared and destroyed, and obtain parameters such as cohesion and internal friction angle.

6) The visual equipment on the tester records the whole process of the extension and retraction of the support bar, the combination of the pendulum rotation and the load application and the test, so as to achieve the visualization of the whole test process.

Since the in-situ direct shear test of the present invention is carried out on the spot, there is no slight disturbance of transportation and no change in water content, and the natural state of the soil structure can be kept to the greatest extent, ensuring that the stress state of the soil does not change , and its stress path can also be determined according to the actual engineering situation, so it is more in line with the natural state than the indoor test.

In addition, the present invention can also apply horizontal thrust along the sliding direction, and can directly fix the shearing surface on the sliding surface for shearing. The shearing area is large and representative, so the in-situ shearing test can truly reflect the nature of the soil. actual shear strength.

Since the in-situ direct shear test is generally measured by digging a shaft, the test environment is very poor. At the same time, the error of human reading is a large source of measurement error, and the system measurement error largely depends on the operator's operating level and test Skills, in order to improve the test environment of the in situ test and reduce human error. The hydraulic pump 9 automatically applies a vertical load to compress the soil downward step by step, and uses stress and displacement sensors to monitor the stress and deformation of the soil, and automatically collects and stores test data, and measures the plasticity and failure strength parameters of each soil layer; test The visual equipment on the instrument records the whole process of the extension of the support bar, the application of the load and the test, so as to achieve the visualization of the whole test process.

Claims (1)

1. A soil in situ direct shear tester, characterized in that it comprises: steel frame; A vertical oil cylinder is arranged on the steel frame; The cylinder is horizontally movable and arranged at the power output end of the vertical oil cylinder; A horizontal oil cylinder is arranged on the steel frame; The push bowl is arranged at the power output end of the horizontal oil cylinder, and is used to apply a horizontal thrust to the cylinder and move the cylinder a predetermined distance; Wherein, a displacement sensor for measuring displacement and a first pressure sensor for measuring thrust are also arranged on the horizontal oil cylinder, and a second pressure sensor for measuring lateral pressure is also arranged on the vertical oil cylinder.

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