Testing device for simulating influence of dead weight of filling soil and rainfall consolidation on pile foundation

Abstract

The utility model discloses a test device for simulating the influence of filling dead weight and rainfall consolidation on a pile foundation, which belongs to the technical field of foundation engineering and comprises an outer box body, a base is fixed at the bottom of the outer box body, and a support frame is fixed on the base through corner posts; undisturbed soil with the pre-buried height is arranged in the outer box body, and meanwhile, a simulation pile is also pre-buried; a comprehensive soil pressing device is arranged above the undisturbed soil; the comprehensive soil pressing device comprises a plurality of soil pressing plates, and a flexible compression side wall is hinged between every two soil pressing plates; a plurality of micro jacks are further fixedly arranged on the bottom surface of the supporting frame, and the bottoms of telescopic parts of the micro jacks make contact with the top soil pressing plate; a rainfall simulation device is further fixed to the bottom face of the supporting frame. Pressure is applied through the micro jack, the soil pressing plate and the flexible compression side wall are driven to contract downwards, the internal simulation soil filling layer is compressed, and soil filling settlement is simulated. The rainfall simulation device seeps water into the simulated fill stratum; and the influence of rainfall and gravity consolidation of a soil filling layer on the bearing capacity of the existing pile foundation can be studied.

Description

Technical Field

[0001] The utility model belongs to the technical field of foundation engineering, and particularly relates to a test device for simulating the influence of fill deadweight and precipitation consolidation on pile foundations. Background Art

[0002] The statements in this section merely provide background technical information related to the present invention and do not necessarily constitute prior art.

[0003] Pile foundations are the most commonly used foundation type in engineering projects. Their bearing capacity is closely related to the properties of the supporting strata. Negative friction caused by stratum consolidation is one of the main reasons for weakening pile foundation bearing capacity. Increased water content in fill strata can significantly affect ground settlement. To investigate the impact of backfill settlement on pile foundation bearing capacity, experimental methods are an effective way to analyze the effect of negative friction on pile foundation bearing capacity, providing a more intuitive observation.

[0004] Patent CN202311307333.4 describes a test apparatus and method for detecting the negative friction of pile foundations in collapsible loess. The method involves setting up a loess layer and a drainage layer within a test chamber, pre-buried and installing a water pipe in the middle and lower parts of the loess layer, and inserting several simulated piles into the loess layer to complete the test site. The water valve at the water inlet pipe is opened, allowing water to flow through the inlet pipe into the water pipe. Water then flows evenly through the outlet holes in the water pipe into the loess layer. The loess layer sinks after absorbing the water from the pipe, and the test data is recorded.

[0005] However, there are some problems with the above scheme: this method cannot distinguish fill sites. The consolidation of fill sites mainly occurs in the fill layer, and the original soil basically does not consolidate. The fill thickness has a great influence on the degree of consolidation. Therefore, how to accurately simulate the consolidation of the fill layer under rainfall and gravity is of great significance to the study of the impact on the bearing capacity of existing pile foundations. Utility Model Content

[0006] In response to the above problems, the present invention provides a test device for simulating the effects of fill deadweight and precipitation consolidation on pile foundations. By applying pressure through a micro jack, the earth pressure plate and the flexible compression side wall are driven to shrink downward, compressing the simulated fill layer inside, thereby simulating fill settlement. The precipitation simulation device can be vertically extended and retracted, so that the water outlet disc at the bottom can be tightly attached to the simulated fill layer, allowing water to seep into the simulated fill layer. This helps to study the effects of rainfall and gravity consolidation on the bearing capacity of existing pile foundations.

[0007] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0008] The test device for simulating the effects of fill deadweight and precipitation consolidation on pile foundations includes an outer box, the bottom of which is fixedly connected to a base, which is fixedly connected to a support frame via corner columns;

[0009] The outer box is provided with pre-buried undisturbed soil of a certain height and also with pre-buried simulated piles; a comprehensive soil compaction device is provided above the undisturbed soil; the comprehensive soil compaction device comprises a plurality of soil compaction plates, with flexible compression side walls hinged between each two soil compaction plates; the flexible compression side walls can be compressed when pressure is applied;

[0010] A plurality of micro jacks are fixedly arranged on the bottom surface of the support frame, and the bottom of the telescopic part of the micro jack contacts the top soil pressure plate;

[0011] A simulated precipitation device is also fixedly arranged on the bottom surface of the support frame.

[0012] Preferably, the simulation pile is arranged at the inner center position of the outer box; a strain gauge is installed on the simulation pile, and the strain gauge is connected to the computer.

[0013] Preferably, a plurality of support columns are fixedly provided on the bottom surface of the support frame, and the support columns pass through a plurality of soil pressing plates and are slidably connected thereto.

[0014] Preferably, the bottom end of the support column is fixedly connected to the bottom soil pressing plate; the support column cannot be telescopically deformed.

[0015] Preferably, a hole for placing the simulated pile is reserved in the center of the soil pressing plate; the size of the soil pressing plate is slightly smaller than the box size of the outer box, and the edge of the soil pressing plate is wrapped with a rubber pad.

[0016] Preferably, the simulated precipitation device is a multi-layer sleeve structure, the bottom size of the inner sleeve is larger than the top size of the outer sleeve, a water outlet disc is fixedly provided at the bottom of the outermost sleeve, a plurality of water outlets are evenly provided at the bottom of the water outlet disc, and a water inlet is provided at the top.

[0017] Preferably, two symmetrical holes are opened on the outer wall of the bottom of all the sleeves, and the pins are inserted into the holes.

[0018] Preferably, the outer dimension of the water outlet disc is slightly smaller than the inner ring radius of the soil pressure plate, and the inner dimension of the innermost sleeve of the simulated precipitation device is slightly larger than the simulated pile.

[0019] Preferably, the landfill height of the original soil and the fill layer shall not exceed the height of the outer box.

[0020] Preferably, a hydraulic jack is fixedly provided at the center of the top surface of the support frame; the output end of the hydraulic jack passes through the center of the support frame and faces the center of the simulated pile.

[0021] Compared with the prior art, the advantages and positive effects of this utility model are:

[0022] The utility model can simulate the pile body being subjected to the upper structure load by applying pressure through the hydraulic jack; the micro jack applies pressure to drive the pressure plate and the flexible compression side wall to shrink downward, thereby compressing the simulated fill layer inside, which can better simulate the fill settlement and reflect the influence of the fill layer settlement on the bearing capacity of the existing pile foundation; the precipitation simulation device can be vertically extended and retracted, so that the water outlet disc at the bottom can be closely attached to the simulated fill layer, and in the process of water seeping into the simulated fill layer, water will not be spilled onto other components, thereby ensuring the successful conduct of the test and the service life of the device.

[0023] The utility model can simulate the original stratum and the fill layer, which is helpful to study the influence of rainfall and gravity consolidation of the fill layer on the bearing capacity of the existing pile foundation, and is of great significance. At the same time, the device can ensure that the settlement of the two strata is different, and can also more realistically distinguish the water content of different strata, so that the test results are more in line with reality. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation on the present invention.

[0025] Figure 1 This is an overall schematic diagram of the test device of an embodiment of the utility model;

[0026] Figure 2 This is a schematic diagram of the positions of the simulated pile and the hydraulic jack in an embodiment of the utility model;

[0027] Figure 3 This is a schematic diagram of the internal structure of the test device according to an embodiment of the present utility model;

[0028] Figure 4 This is a schematic diagram of the precipitation simulation device according to an embodiment of the present invention when not extended or retracted;

[0029] Figure 5 This is a schematic diagram of the precipitation simulation device of the embodiment of the utility model when it is extended and retracted;

[0030] In the picture:

[0031] 1. Outer box; 2. Base; 3. Support frame; 4. Hydraulic jack; 5. Simulated precipitation device; 6. Earth pressure plate; 7. Flexible compression side wall; 8. Micro jack; 9. Simulated pile; 10. Water outlet disc; 11. Support column. DETAILED DESCRIPTION

[0032] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0033] The present invention will be described in detail below with reference to the accompanying drawings. This embodiment discloses a test device for simulating the effects of fill deadweight and precipitation consolidation on pile foundations. Figure 1 As shown, it includes an outer box body 1, the bottom of the outer box body 1 is fixedly connected to the base 2, the four corners of the base 2 are fixedly connected to four corner columns by bolts, and the tops of the four corner columns are fixedly connected to the support frame 3.

[0034] like Figure 1 、 Figure 5 As shown, the interior of the outer box body 1 is used for pre-filling original soil, and is also used for pre-buried simulation piles 9, which are arranged at the inner center of the outer box body 1; it should be noted that the filling height of the original soil shall not exceed the height of the outer box body 1, because space for the simulated filling layer must be reserved; after the original soil is filled to the preset height, a comprehensive soil compacting device is arranged in the outer box body 1.

[0035] like Figure 1 、 Figure 2 As shown, a hydraulic jack 4 is fixedly mounted at the center of the top surface of support frame 3. The output end of hydraulic jack 4 must pass through the center of support frame 3 and face the center of simulated pile 9. By applying pressure to the simulated pile, the simulated pile is simulated to simulate the superstructure pressure it would experience in actual conditions. Several strain gauges are installed on the simulated pile to monitor the stress and strain values ​​of the simulated pile. By connecting the strain gauges to a computer, changes in stress and strain values ​​can be monitored in real time during the test.

[0036] like Figure 1 、 Figure 3 、 Figure 4 、 Figure 5 As shown, a simulated precipitation device 5 is fixedly installed on the bottom surface of the support frame 3. The simulated precipitation device 5 is a multi-layer sleeve structure, in which the diameter of the innermost sleeve is larger than the diameter of the output end of the hydraulic jack 4, thereby ensuring that the simulated precipitation device 5 can be wrapped around the outside of the output end of the hydraulic jack 4 on the bottom surface of the support frame 3.

[0037] like Figure 1As shown, a plurality of support columns 11 are fixedly provided on the bottom surface of the support frame 3, and the support columns 11 are used to support the comprehensive soil compacting device. The comprehensive soil compacting device includes a plurality of soil compacting plates 6, and the support columns 11 pass through the plurality of soil compacting plates 6. A flexible compression side wall 7 is hinged between every two soil compacting plates 6. Among them, the flexible compression side wall 7 can be compressed when pressure is applied. The flexible compression side wall 7 is connected to the soil compacting plates above and below because, when the upper soil compacting plate 6 is under pressure, the flexible compression side wall 7 below it can be spatially compressed, and the upper soil compacting plate approaches the lower soil compacting plate, thereby realizing the compression of the simulated fill layer between the two soil compacting plates to achieve a settlement effect. In this embodiment, four support columns 11 are used, which are evenly distributed around the circumference of the soil compacting plates to ensure that the comprehensive soil compacting device can be stably supported.

[0038] The number of soil pressing plates 6 is flexibly set according to the actual thickness of the simulated fill layer required for the test; it should be noted that the bottom soil pressing plate 6 is fixed to the bottom end of the support column 11, and the remaining soil pressing plates 6 are all slidingly connected to the support column 11. Under the support of the flexible compression side wall 7, there is a certain distance between the soil pressing plates 6.

[0039] like Figure 1 、 Figure 2 As shown, the bottom surface of the support frame 3 is also fixedly mounted with multiple micro-jacks 8. The bottom of the telescopic portion of the micro-jacks 8 contacts the top pressure plate 6. By activating the micro-jacks 8 to apply pressure to the top pressure plate 6, the soil beneath it is compressed, thereby simulating ground settlement. In this embodiment, there are four micro-jacks 8, evenly distributed around the circumference of the pressure plate, ensuring uniform force in all directions.

[0040] In some other embodiments, the bottom of the micro-jack can be mounted on a pressure plate, and pressure arms fixed to the support frame can be used to apply pressure to the pressure plate, causing the upper pressure plate to squeeze the fill downward. During this process, the support columns ensure the stability of the pressure plate and the flexible compression sidewalls, achieving the effect of simulating fill settlement.

[0041] It's important to note that pressure plate 6 is slightly smaller than the outer box 1 and has rubber pads around its edges to ensure a tight fit. A hole for a simulated pile is located in the center of pressure plate 6, ensuring that the hydraulic jack 4 doesn't affect the pile foundation. Support columns 11 are non-retractable, ensuring the stability of the pressure plate and flexible compression sidewalls after installation.

[0042] like Figure 2 、 Figure 3 、 Figure 4As shown, the simulated precipitation device 5 is a multi-layer sleeve structure, and a water outlet disc 10 is fixedly provided at the bottom of the outermost sleeve. A plurality of water outlets are evenly provided at the bottom of the water outlet disc 10, and a water injection port is provided at the top. Since the simulated precipitation device 5 is a multi-layer sleeve structure, it can be telescopically operated to ensure that the water outlet disc 10 can be closely attached to the simulated fill layer. The water outlet at the bottom of the water outlet disc can continuously seep water into the stratum to simulate the precipitation effect.

[0043] It can be understood that when water seepage is carried out, water can be injected into the water outlet disc, and the injected water can evenly penetrate into the simulated soil layer under the action of several water outlets; the multi-layer sleeve structure of the simulated precipitation device 5 can be expanded and contracted using existing technology. For example, for the sleeves of adjacent layers, a clamping ring is set at the outer bottom of the inner sleeve, and a clamping ring is set at the inner top of the outer sleeve, so as to ensure that the sleeves can slide but will not separate and can be expanded and contracted. It should be noted that the interior of the innermost sleeve is smooth; of course, the bottom size of the inner sleeve can also be larger than the top size of the outer sleeve, but the size of the innermost sleeve must be larger than the size of the simulated pile.

[0044] It can also be understood that two symmetrical holes can be opened on the outer wall of the bottom of all sleeves, and then pins can be inserted into the holes. The pins cannot be pulled out before the test, thereby ensuring that the water outlet disc does not contact the simulated fill layer. When the simulated fill layer is completed, the pins are pulled out, causing the water outlet disc to fall and fit tightly against the top of the simulated fill layer.

[0045] In other embodiments, telescopic devices, such as telescopic cylinders, may be provided on both sides of the top surface of the water outlet disc 10. The fixed end of the telescopic cylinder is provided at the bottom of the support frame 3, and the output ends are provided on both sides of the top surface of the water outlet disc 10. Before the test, the telescopic cylinder can hold the water outlet disc. After the simulated soil layer is filled, the output ends of the telescopic cylinder drive the water outlet disc to fall and closely adhere to the top of the simulated soil layer.

[0046] It should be noted that the outer dimension of the water outlet disc 10 is slightly smaller than the inner ring radius of the soil pressure plate 6, and the inner dimension of the innermost sleeve of the simulated precipitation device 5 is slightly larger than the simulated pile to ensure that other devices will not be contaminated during the seepage process.

[0047] Working principle:

[0048] In the initial stage of the test, the outer box is pre-filled with undisturbed soil and simulated piles. After the undisturbed soil is filled to the preset height, the test device is assembled.

[0049] According to the set height of the fill layer, install the soil pressure plate and flexible compression side wall on the support frame 3, then assemble the micro jack, and install the precipitation simulation device and hydraulic jack in advance, and then install the support frame on the four corner columns;

[0050] Next, fill the outer box with soil in layers until it reaches the top soil pressure plate;

[0051] Then, the hydraulic jack is started to apply pressure to the simulated pile to simulate the pressure from the upper structure;

[0052] Then, four micro-jacks were activated to compress the top soil plate, causing the simulated fill layer to undergo a settlement-like effect. At the same time, the simulated dewatering device was lowered to inject water into the water outlet disc, increasing the moisture content of the simulated fill layer.

[0053] During the test, the numerical changes of the strain gauge on the simulated pile were observed in real time by computer, and the test data were recorded.

[0054] Although the above description of the specific implementation methods of the present invention is combined with the accompanying drawings, it does not limit the scope of protection of the present invention. Technical personnel in the relevant field should understand that on the basis of the technical solution of the present invention, various modifications or deformations that can be made by technical personnel in this field without creative work are still within the scope of protection of the present invention.

Claims

1. A test device for simulating the effects of fill deadweight and precipitation consolidation on pile foundations, characterized in that: It includes an outer box body, the bottom of the outer box body is fixedly connected to the base, and the base is fixedly connected to the support frame through corner columns; The outer box is provided with pre-buried undisturbed soil of a certain height and also with pre-buried simulated piles; a comprehensive soil compaction device is provided above the undisturbed soil; the comprehensive soil compaction device comprises a plurality of soil compaction plates, with flexible compression side walls hinged between each two soil compaction plates; the flexible compression side walls can be compressed when pressure is applied; A plurality of micro jacks are fixedly arranged on the bottom surface of the support frame, and the bottom of the telescopic part of the micro jack contacts the top soil pressure plate; A simulated precipitation device is also fixed on the bottom surface of the support frame.

2. The test device for simulating the effects of fill deadweight and precipitation consolidation on pile foundations according to claim 1, characterized in that: The simulation pile is arranged at the inner center position of the outer box body; a strain gauge is installed on the simulation pile, and the strain gauge is connected to a computer.

3. The test device for simulating the effects of fill deadweight and precipitation consolidation on pile foundations according to claim 1, characterized in that: A plurality of support columns are fixedly provided on the bottom surface of the support frame, and the support columns pass through a plurality of soil pressing plates and are slidably connected therewith.

4. The test device for simulating the effects of fill deadweight and precipitation consolidation on pile foundations according to claim 3, characterized in that: The bottom end of the support column is fixedly connected to the bottom soil pressing plate; the support column cannot be telescopically deformed.

5. The test device for simulating the effects of fill deadweight and precipitation consolidation on pile foundations according to claim 1, characterized in that: A hole for placing a simulated pile is reserved in the center of the soil pressing plate; the size of the soil pressing plate is slightly smaller than the box size of the outer box, and the edge of the soil pressing plate is wrapped with a rubber pad.

6. The test device for simulating the effects of fill deadweight and precipitation consolidation on pile foundations according to claim 1, characterized in that: The simulated precipitation device is a multi-layer sleeve structure, the bottom size of the inner sleeve is larger than the top size of the outer sleeve, a water outlet disc is fixedly provided at the bottom of the outermost sleeve, a plurality of water outlets are evenly provided at the bottom of the water outlet disc, and a water inlet is provided at the top.

7. The test device for simulating the effects of fill deadweight and precipitation consolidation on pile foundations according to claim 6, characterized in that: Two symmetrical holes are opened on the outer wall of the bottom of all the sleeves, and the latches are inserted into the holes.

8. The test device for simulating the effects of fill deadweight and precipitation consolidation on pile foundations according to claim 6, characterized in that: The outer dimension of the water outlet disc is slightly smaller than the inner ring radius of the soil pressure plate, and the inner dimension of the innermost sleeve of the simulated dewatering device is slightly larger than the simulated pile.

9. The test device for simulating the effects of fill deadweight and precipitation consolidation on pile foundations according to claim 1, characterized in that: The landfill height of the original soil and fill layers shall not exceed the height of the outer box.

10. The test device for simulating the effects of fill deadweight and precipitation consolidation on pile foundations according to claim 1, characterized in that: A hydraulic jack is fixedly arranged at the center of the top surface of the support frame; the output end of the hydraulic jack passes through the center of the support frame and faces the center of the simulation pile.

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