A device for testing multi-directional deformation and expansion force of expansive soil

Abstract

The present invention discloses a device capable of testing the multi-directional deformation and expansion force of expansive soil. The present invention mainly comprises a test box, a water injection device and a measuring device arranged on the test box. A sample placement chamber is arranged in the test box. The sample placement chamber is a square box structure including a bottom plate and four side baffles. A displacement sensor I for measuring horizontal displacement is arranged between the inner wall of the test box and the side baffles. A displacement sensor II for measuring vertical displacement is arranged between the cantilever cross bar extending from the top of the box and the top plate. When performing the expansion force test, the displacement sensor is replaced with a spiral pressure rod, and a stress sensor is arranged at the end of the spiral pressure rod. The present invention has a novel structure, is easy to install, and is convenient to operate. It can effectively measure the expansion deformation in multiple directions and the corresponding expansion force of the expansive soil after it absorbs water and expands.

Description

Technical Field

[0001] The invention belongs to the technical field of civil engineering, and in particular relates to a device capable of testing multi-directional deformation and expansion force of expansive soil. Background Art

[0002] Expansive soil is widely distributed in my country, mainly in central, southern and southwestern China. Expansive soil is often in a relatively hard state in its natural state, and its properties will change greatly after absorbing water. It is highly sensitive to climate and hydrological factors. Expansive soil is very harmful and can easily cause uneven vertical or horizontal deformation of buildings or structures, causing cracking, tilting and even damage to the structure. Therefore, in order to solve a series of engineering problems caused by the expansion and contraction of expansive soil, it is necessary to conduct in-depth experimental research on the expansibility of expansive soil, explore the changing laws of its expansion deformation and expansion force, and guide engineering design and construction.

[0003] The current method for determining the expansion rate of expansive soil is to immerse the expansive soil sample in water under certain pressure conditions in a lateral confinement compression instrument, and after the expansion is stable, measure the increased height of the sample and compare it with the original height of the sample to obtain the expansion rate. The limitation of this method is that the horizontal deformation of the sample is constrained, and only the vertical deformation of the sample can be observed. In fact, expansive soil will undergo multi-directional expansion deformation under the condition of no lateral constraint, which cannot be measured by existing instruments. At present, the main methods for testing the expansion force are the expansion counter-pressure method, the pressurized expansion method, and the balanced pressurization method. The principle of these methods is to first expand the sample, and then compress the sample to the initial state by applying a compressive load. The size of the compression load at this time is the size of the expansion force. These methods are to reverse the expansion force by ensuring that the expansion deformation and the artificial compression deformation are completely consistent, but ignore the influence of the stress path and the different stress states of the sample. In addition, the expansion pressure of the sample needs to be measured under the condition of keeping the sample volume unchanged. These traditional test methods cannot keep the sample volume constant during the test, and the practice of expanding first and then compressing the sample causes too much disturbance to the sample, which will cause artificial deviation in the test results. Therefore, how to design a new device that can not only measure the expansion deformation in multiple directions when the expansive soil expands, but also truly measure the magnitude of the expansion force without disturbing the expansive soil sample, is of great academic value and engineering significance. Summary of the invention

[0004] The purpose of the present invention is to provide a device which can effectively measure the multi-directional deformation and expansion force around and on the top of expansive soil in view of the deficiencies of the prior art.

[0005] The objective of the present invention is achieved through the following technical scheme: the device capable of testing the multi-directional deformation and expansion force of expansive soil comprises a test box and a water injection device and a measuring device arranged on the test box, and is characterized in that: the test box is a hollow box with a square bottom and an open top; a sample placement chamber is arranged at the center of the bottom surface of the test box, and the sample placement chamber is a square box structure comprising a bottom plate and four side baffles; the bottom plate of the sample placement chamber is provided with slide grooves in the normal direction of the four inner walls of the test box, and the bottoms of the four side baffles are provided with slide groove connectors connected to the bottom plate slide grooves, so that the side baffles can pass through the test box. The connecting piece through the slide groove can slide along the slide groove of the bottom plate; an inter-plate slide groove is arranged on the inner right side of each side baffle plate, and a roller is arranged in the inter-plate slide groove; a telescopic side plate is arranged at the inner left end of each side baffle plate, and a clamping shaft is arranged at the height position corresponding to the outer end of the telescopic side plate and the roller center hole in the inter-plate slide groove; the clamping shaft at the outer end of the telescopic side plate of each side baffle plate is inserted into the roller center hole in the inner inter-plate slide groove of the adjacent side baffle plate, so that the four side baffle plates are enclosed to form a sample placement chamber whose volume increases as the sample expands with water; a groove is arranged on the bottom plate of the sample placement chamber, and a water-permeable plate is added in the groove, and the top surface of the water-permeable plate is flush with the top surface of the bottom plate. A drainage hole is provided at the bottom of the groove, which is connected to a drainage pipe and leads to the outside of the box; the water injection device includes a water storage container, a water delivery pipe, a drip valve, and a drip top plate. The water storage container is fixed to the top of one side of the test box, one end of the water delivery pipe is connected to the lower part of the water storage container, and the other end is connected to the drip top plate, and the drip top plate is arranged directly above the sample in the sample placement chamber; the measuring device includes a sensor bracket horizontally installed on the inner walls around the test box, one end of the displacement sensor I for measuring the horizontal displacement of the sample is fixedly installed on the sensor bracket, and the other end is connected to the outer side of the side baffle of the sample placement chamber; the measuring device also includes a test An inverted concave component that fits with the top of the side wall of the box is arranged on the top of the other side of the box, and a horizontal cantilever cross bar is fixed to the upper part of the component by bolts. A downward vertical sensor bracket is arranged at the end of the cross bar, and a displacement sensor II for measuring the vertical displacement of the sample is connected to the sensor bracket, and the displacement sensor II is connected to the top surface of the dripping top plate; or, instead of installing the sensor bracket on the above-mentioned sensor bracket, a spiral pressure rod is installed, and a stress sensor bracket is arranged at the end of the spiral pressure rod, and a stress sensor is arranged on the stress sensor bracket, and the stress sensor is tightly fitted to the side baffle or the dripping top plate by adjusting the length of the spiral pressure rod and fixing it.

[0006] Specifically, the width of the four side baffles of the sample placement chamber is greater than the width of the sample, and a scale is provided on the inner wall thereof.

[0007] Specifically, the telescopic side panels of the four side baffles of the sample placement chamber are arranged in the left end panel of the side baffle, the telescopic side panels are slightly smaller than the side baffles, and a slideway is arranged between the side baffles and the upper and lower panels of the telescopic side panels.

[0008] Specifically, the drip top plate is provided with an upper and lower layer, the upper layer is provided with a through hole connected to a water pipe, and the lower layer is provided with a plurality of water-permeable holes, through which water is allowed to evenly penetrate into the sample.

[0009] The invention has novel structure, is easy to install and convenient to operate, can effectively observe the deformation of the surrounding and top of the expansive soil after it absorbs water and expands, provides reaction force through the side wall of the box body and the top cantilever structure, and ensures constant volume during the expansion force test. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a vertical cross-sectional view of an embodiment of the present invention.

[0011] Figure 2 Based Figure 1 Top view of the .

[0012] Figure 3 Based Figure 1 Schematic diagram of the three-dimensional structure of the middle side baffle. DETAILED DESCRIPTION

[0013] See also Figure 1 , Figure 2 , Figure 3 The device of this embodiment can test the multi-directional deformation and expansion force of expansive soil, which includes a test box 1 and a water injection device and a measuring device arranged on the test box 1. Figure 1 , Figure 2 It can be seen that the test box 1 is a hollow box with a square bottom and an open top. A sample placement chamber 4 is provided at the center of the bottom surface of the test box 1. The sample placement chamber 4 is a square box structure including a bottom plate 2 and four side baffles 5. The bottom plate 2 of the sample placement chamber 4 is provided with two slide grooves 3 along the normal direction of the four inner walls of the test box 1. The bottom of the four side baffles 5 is provided with slide groove connectors connected to the slide grooves 3 of the bottom plate 2, so that the side baffles 5 can slide along the slide grooves 3 of the bottom plate 2 through the slide groove connectors. Figure 3It can be seen that an inter-plate chute 6 is provided on the right side of the inner side of each side baffle 5, and a roller 7 is provided in the inter-plate chute 6. A telescopic side plate 8 is provided in the inner left end plate of each side baffle 5. The size of the telescopic side plate 8 is slightly smaller than that of the side baffle 5. A slideway 10 is provided between the upper and lower plates of the side baffle 5 and the telescopic side plate 8. A clamping shaft 9 is provided at the height position corresponding to the center hole of the roller 7 in the inter-plate chute 6. The clamping shaft 9 at the outer end of the telescopic side plate 8 of each side baffle 5 is inserted into the center hole of the roller 7 in the inter-plate chute 6 of the adjacent side baffle 5. Each side baffle 5 can move outward along the chute 3 on the bottom plate 2 as the sample expands with water, and at the same time, it can drive the stretching of the telescopic side plate 8 and the movement of the side baffles along the expansion direction of the sample through the inter-plate chute 6, so that the volume of the sample placement chamber 4 changes with the volume change of the sample after immersion in water and expansion; the width of the four side baffles 5 is greater than the width of the sample, and a scale is provided on its inner wall for easy observation. The bottom plate 2 of the sample placement chamber 4 is provided with a groove, in which a water-permeable plate 11 is added, and the top surface of the water-permeable plate 11 is flush with the top surface of the bottom plate 2. A drainage hole is provided at the bottom of the groove, and the drainage hole is connected to a drainage pipe 12 and leads to the outside of the box. A water-stop clamp 13 is provided outside the box. Figure 1 It can be seen that the water injection device includes a water storage container 20, a water delivery pipe 21, a drip valve 22, and a drip top plate 23. The water storage container 20 is fixed to the top right side of the test box 1. The upper end of the water delivery pipe 21 is connected to the lower part of the water storage container 20, and the lower end is connected to the drip top plate 23. The drip top plate 23 is arranged directly above the sample in the sample placement chamber 4; the drip top plate 23 is provided with an upper and lower layer, the upper layer is provided with a through hole connected to the water delivery pipe 21, and the lower layer is provided with a plurality of water permeable holes, through which water can evenly penetrate into the sample. The measuring device includes a sensor bracket 14 horizontally installed on the inner walls around the test box 1, one end of the displacement sensor I15 for measuring the horizontal displacement of the sample is fixedly installed on the sensor bracket 14, and the other end is connected to the outer side of the side baffle 5 of the sample placement chamber 4; the displacement generated around the sample can be measured by the displacement sensor I15; the measuring device also includes an inverted concave component 16 arranged on the top of the left side of the test box 1 and fitting with the top of the box side wall, a horizontal cantilever cross bar 18 is fixed to the upper part of the component 16 by bolts 17, and a downward vertical sensor bracket 14 is arranged at the end of the cross bar 18, and a displacement sensor II19 for measuring the vertical displacement of the sample is connected to the sensor bracket 14, and the displacement sensor II19 is connected to the top surface of the drip top plate 23; the displacement sensor II can measure the vertical displacement of the top of the sample; the above measuring device can be used to test the expansion rate of multi-directional deformation of expansive soil. Alternatively, when used to test the multi-directional expansion force of expansive soil, the sensor bracket is not installed on the above-mentioned sensor bracket 14, but a spiral pressure rod is installed, a stress sensor bracket is set at the end of the spiral pressure rod, and a stress sensor is set on the stress sensor bracket. The stress sensor is tightly fitted to the side baffle or the drip top plate by adjusting the length of the spiral pressure rod and fixing it.

[0014] The specific steps of the expansion rate experiment are as follows:

[0015] Place a permeable plate in the groove of the bottom plate of the sample placement chamber, stick filter paper on each surface of the sample, place the prefabricated sample on the bottom plate of the sample placement chamber, move the side baffles around to make the side baffles close to the sample, place a dripping top plate above the sample, install displacement sensor I for measuring horizontal displacement on the sensor brackets around the box, and install displacement sensor II for measuring vertical displacement on the top, add distilled water to the water storage container, connect the water storage container and the dripping top plate through a water pipe, so that water can evenly penetrate the sample through the dripping top plate. After the sample absorbs water and expands, the displacement generated around and on the top of the sample is measured by the displacement sensor.

[0016] The specific steps of the expansion force experiment are as follows:

[0017] The displacement sensor on the sensor bracket is replaced with a spiral pressure rod, and the other end of the spiral pressure rod is connected to the stress sensor bracket. The other end of the stress sensor bracket is connected to a stress sensor. By adjusting the spiral pressure rod, a certain pressure is generated on the sample, and the stress sensor at the rod end is close to the outer wall of the side baffle. The spiral pressure rod is fixed, and a drip top plate is placed on the top of the sample. A spiral pressure rod and a stress sensor are arranged under the cantilever cross bar on the top of the box. When the stress sensor contacts the top plate, the length of the spiral pressure rod is fixed, and the reaction force provided by the side wall of the box and the cantilever on the top of the box makes the volume of the sample placement chamber fixed. After the sample is water-permeable and swells, the force generated by the water absorption and expansion is transmitted to the stress sensor, and the expansion force generated around and on the top of the sample is measured by the stress sensor.

Claims

1. A device for testing the multi-directional deformation and expansion force of expansive soil, characterized in that: It comprises a test box and a water injection device and a measuring device arranged on the test box, and is characterized in that: the test box is a hollow box with a square bottom and an open top; a sample placement chamber is arranged at the center of the bottom surface of the test box, and the sample placement chamber is a square box structure including a bottom plate and four side baffles; the bottom plate of the sample placement chamber is provided with slide grooves along the normal direction of the four inner walls of the test box, and the bottoms of the four side baffles are provided with slide groove connectors connected to the bottom plate slide grooves, so that the side baffles can slide along the bottom plate slide grooves through the slide groove connectors; a plate spacer is arranged on the right side of the inner side of each side baffle A slide groove, rollers are arranged in the slide grooves between the plates, a telescopic side plate is arranged at the inner left end of each side baffle plate, and a clamping shaft is arranged at the height position corresponding to the center hole of the roller in the slide groove between the plates; the clamping shaft at the outer end of the telescopic side plate of each side baffle plate is inserted into the center hole of the roller in the slide groove between the inner plates of the adjacent side baffle plates, so that the four side baffle plates are enclosed to form a sample placement chamber whose volume increases as the sample expands with the addition of water; a groove is arranged on the bottom plate of the sample placement chamber, a water-permeable plate is added in the groove, the top surface of the water-permeable plate is flush with the top surface of the bottom plate, a drainage hole is arranged at the bottom of the groove, and the drainage hole is connected to the drainage pipe and leads to the outside of the box; the water injection device includes a water storage container, a water delivery pipe, a drip valve, and a drip top plate. The water storage container is fixed to the top of one side of the test box, one end of the water delivery pipe is connected to the lower part of the water storage container, and the other end is connected to the drip top plate, and the drip top plate is arranged directly above the sample in the sample placement room; the measuring device includes a sensor bracket horizontally installed on the inner wall around the test box, one end of the displacement sensor I for measuring the horizontal displacement of the sample is fixedly installed on the sensor bracket, and the other end is connected to the outer side of the side baffle of the sample placement room; the measuring device also includes a sensor bracket arranged on the top of the other side of the test box An inverted concave member that fits with the top of the side wall of the box body, a horizontal cantilever cross bar is fixed to the upper part of the member by bolts, a downward vertical sensor bracket is arranged at the end of the cross bar, a displacement sensor II for measuring the vertical displacement of the sample is connected to the sensor bracket, and the displacement sensor II is connected to the top surface of the dripping top plate; or, instead of installing the sensor bracket on the above-mentioned sensor bracket, a spiral pressure rod is installed, a stress sensor bracket is arranged at the end of the spiral pressure rod, and a stress sensor is arranged on the stress sensor bracket, and the stress sensor is closely fitted to the side baffle or the dripping top plate by adjusting the length of the spiral pressure rod and fixing it; The width of the four side baffles of the sample placement chamber is greater than the width of the sample, and a scale is provided on the inner wall; The telescopic side panels of the four side baffles of the sample placement chamber are arranged in the left end panel of the side baffle, the size of the telescopic side panel is slightly smaller than the side baffle, and a slideway is arranged between the side baffle and the upper and lower panels of the telescopic side panel; The drip top plate is provided with an upper and lower layer, the upper layer is provided with a through hole connected to a water pipe, and the lower layer is provided with a plurality of water-permeable holes, through which water can evenly penetrate into the interior of the sample.

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