Device and method for jointly testing expansion rate of cement soil and shaft friction resistance

Abstract

The present invention belongs to the technical field of measurement and testing, and particularly relates to a device and a method for jointly testing the expansion rate of cement soil and the side friction resistance of piles. The method includes the following steps: 1: Prepare a model pile with appropriate dimensions and insert it into a cylinder; 2: Prepare a cylindrical elastic membrane, fix it at the bottom of the cylinder, and pour into it cement soil according to a certain ratio; 3: Cover the cylinder lid to form a relatively closed space between the model pile and the elastic membrane; 4: Inject liquid between the elastic membrane and the cylinder to provide confining pressure; 5: Let it stand for 7 - 28 days and measure the expansion rate of the cement soil; 6: Conduct a pile ultimate side friction resistance test on the model pile, draw a τ-S curve using the measured data, and obtain the side friction resistance of the model pile under different confining pressures and cement soil ages. This method can accurately measure the side friction resistance of the model pile and can also measure the expansion rate of the cement soil, and thus can quickly study the influence of cement soil with different ratios on the pile bearing capacity.

Description

Technical Field

[0001] The present invention belongs to the technical field of measurement and testing, and particularly relates to a device and method for jointly testing the expansion rate of cement soil and the side friction resistance of piles. Background Art

[0002] In recent years, it has been an urgent problem to be solved in the pile foundation engineering to develop new pile foundation construction technologies aiming at high bearing capacity, low noise, low vibration and low consumption effect.

[0003] A new type of low-consumption and high-efficiency pile foundation structure with an enlarged pile shoe and synchronous grouting has become a new research hotspot. During the pile driving construction, since the gap between the pile body and the surrounding soil is filled with fluid cement slurry, the penetration resistance required for pile driving construction is greatly reduced. After the construction is completed, on the one hand, the cement slurry on the pile side can enlarge the effective diameter of the pile body, and on the other hand, it can improve the characteristics of the pile-soil contact surface and increase the side friction resistance of the pile. Therefore, it is of great significance to study the influence of the cement soil ratio on the pile bearing capacity improvement. Summary of the Invention

[0004] The purpose of the present invention is to provide a device and method for jointly testing the expansion rate of cement soil and the side friction resistance of piles. This method can test the side friction resistance of piles while detecting the expansion rate of cement soil, and further optimize the cement soil ratio.

[0005] To achieve the above purpose, the following technical solutions are provided: On the one hand, a method for jointly testing the expansion rate of cement soil and the side friction resistance of piles is provided, which includes the following steps:

[0006] Step1: Prepare a model pile with appropriate size and insert it into a cylinder that can only pass through the perforated model pile at the bottom. The cylinder is equipped with a lid that matches its size, and there is also a hole on the lid that can only penetrate the model pile.

[0007] Step2: Prepare a cylindrical elastic membrane, fix its lower end at the bottom of the cylinder, pour cement soil with a certain ratio into it, and stop pouring when the cement soil reaches the same height as the cylinder, and record the volume of the poured cement soil.

[0008] Step3: Take the lid of the cylinder, fix the upper end of the elastic membrane on the lid, and then cover the lid to form a relatively closed space between the model pile and the elastic membrane.

[0009] Step4: Inject liquid between the elastic membrane and the cylinder to provide confining pressure, simulate the situation of the model pile being subjected to soil pressure in the soil layer by controlling different confining pressures, and read the volume of the liquid injected into the cylinder under a specific confining pressure.

[0010] Step 5: Leave the model pile static for 7 - 28 days under the action of cement soil and confining pressure, read the volume of the liquid in the cylinder, and accurately measure the swelling rate of cement soil at different ages according to the ratio of the difference in the change of the liquid volume to the initial volume of the injected cement soil.

[0011] Step 6: Conduct a limit shaft friction test on the model pile using the step - by - step loading method, draw the τ - S curve using the measured data, and obtain the limit shaft friction of the model pile.

[0012] In the above - mentioned technical solution, further, in Step 2, the latex film has ductility. During the consolidation process of the cement soil, when its volume expands, the latex film expands outward, and the volume of the liquid between the cylinder and the latex film changes accordingly.

[0013] In any of the above - mentioned technical solutions, further, in Step 4, a GDS volume controller is used to control the confining pressure generated by the injected liquid. The GDS volume controller is connected to a computer, and the application of the confining pressure is controlled by the computer. Different confining pressures are used to simulate different soil types and soil layer depths.

[0014] On the other hand, a device for jointly testing the swelling rate of cement soil and shaft friction is provided, including a reaction frame, on which a workbench is arranged;

[0015] A cylinder, arranged on the workbench, the bottom of the cylinder has a bottom cover, and the top has a top cover. The top cover and the bottom cover are provided with holes that are coaxial and have the same inner diameter. The holes in the top cover and the bottom cover are used for the two ends of the model pile to pass through; an elastic membrane is arranged around the inner cavity of the cylinder. The elastic membrane divides the inner cavity of the cylinder into an inner cavity and an outer cavity. The inner cavity is used to inject cement soil, and the outer cavity is used to inject liquid;

[0016] A jack, arranged on the reaction frame, providing pressure for the model pile;

[0017] And a GDS volume controller, used to inject liquid into the outer cavity and control the confining pressure generated by the liquid in the outer cavity.

[0018] In any of the above - mentioned technical solutions, further, a displacement meter is arranged below the top of the model pile to detect the vertical displacement of the model pile.

[0019] In any of the above - mentioned technical solutions, further, the elastic membrane is a latex film or a geomembrane.

[0020] In any of the above - mentioned technical solutions, further, there are several groups of cylinders, which are arranged side by side on the workbench, and the jack is arranged on the reaction frame so as to slide along the direction in which the cylinders are arranged side by side;

[0021] The combined testing device further includes:

[0022] A main pipe, which is connected to the GDS volume controller;

[0023] A plurality of branch pipes, the number of which is the same as the number of cylinders, and one end of each branch pipe is connected to the main pipe and the other end is respectively connected to each cylinder and communicated with the outer cavity of the cylinder;

[0024] And a plurality of mass flow meters, the number of which is the same as the number of branch pipes, and are respectively used to detect the volume of the fluid passing through each branch pipe.

[0025] In any of the above technical solutions, further, the mass flow meter is used to detect the volume of the liquid entering the outer cavity from the branch pipe and the volume of the liquid in the outer cavity flowing back from the branch pipe to the main pipe.

[0026] In any of the above technical solutions, further, the cylinder further includes:

[0027] Two sets of support frames are arranged vertically at the middle position outside the cylinder;

[0028] Four adjusting piston rods, two adjusting piston rods are symmetrically arranged on each support frame, and the four adjusting piston rods are circumferentially and evenly distributed outside the cylinder. Adjusting holes are provided on the outer wall of the cylinder opposite to each adjusting piston rod. One end of each adjusting piston rod close to the cylinder is respectively arranged in a sealed and sliding manner on each adjusting hole. One end of the adjusting piston rod extends into the outer cavity and the other end is located on the support frame; the adjusting piston rod is a hollow tubular structure;

[0029] Suction cups are arranged on each of the adjusting piston rods;

[0030] And a vacuum generating device, which is connected to the adjusting piston rod through an air pipe and is used to provide negative pressure suction for the suction cup;

[0031] Wherein, by adjusting the insertion depth of each adjusting piston rod, the suction cups on each adjusting piston rod are respectively abutted or tightened against the outer wall of the elastic membrane to limit and fix the elastic membrane so that it is located at the exact center of the cylinder chamber.

[0032] In any of the above technical solutions, further, the cylinder further includes waterproof barriers arranged on the bottom cover and the top cover, and the upper and lower ends of the elastic membrane are respectively located on the waterproof barrier of the bottom cover and the waterproof barrier of the top cover.

[0033] The beneficial effects of the present invention are:

[0034] 1. A combined test method for controlling the expansion rate of cement soil and the shaft friction resistance under confining pressure provided by the present invention can accurately measure the shaft friction resistance of the model pile and relatively accurately measure the expansion rate of the cement soil, and thus can quickly study the influence of cement soil with different proportions on the pile bearing capacity, greatly reducing the test period.

[0035] 2. In the model test provided by the present invention, confining pressure is applied to the model pile in a cylinder, restoring the stress state of the pipe pile in the actual soil layer and ensuring the accuracy of the test results.

[0036] 3. The method for providing an indoor model test in the present invention is more convenient and has lower costs compared to on-site tests. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a schematic structural diagram of the present invention;

[0038] Figure 2 is a schematic plan view of the present invention;

[0039] Figure 3 is an internal schematic diagram of the cylindrical part structure of the present invention;

[0040] Figure 4 is an internal schematic diagram of the cylinder of the present invention;

[0041] Among them, 10, model pile; 100, reaction frame; 110, workbench; 200, cylinder; 210, bottom cover; 220, top cover; 221, filling port; 222, detection port; 230, elastic membrane; 240, support frame; 241, first connecting rod; 242, second connecting rod; 243, third connecting rod; 244, fourth connecting rod; 245, support rod; 246, hinge seat; 250, adjusting piston rod; 260, suction cup; 270, vacuum generating device; 280, waterproof layer; 300, jack; 310, displacement meter; 400, GDS volume controller; 500, main pipe; 600, branch pipe; 700, mass flow meter. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] Next, the technical solutions in the embodiments of the present application will be clearly described in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present application.

[0043] In the description of the present application, it should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments of the present application. For ease of description, the dimensions of the various parts shown in the drawings are not drawn in actual proportional relationships. Technologies, methods, and devices known to those of ordinary skill in the relevant fields may not be discussed in detail, but where appropriate, such technologies, methods, and devices should be regarded as part of the authorization specification. In all the examples shown and discussed here, any specific value should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar reference numerals and letters denote similar items in the following drawings, and thus, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0044] Embodiment 1:

[0045] A combined test method for the expansion rate of cement soil and the shaft friction resistance of piles, which includes the following steps:

[0046] Step1: Prepare a model pile with appropriate dimensions and insert it into a cylinder whose bottom can only pass through the perforated model pile. The cylinder is equipped with a lid that matches its size, and there is also a hole on the lid that can only penetrate the model pile;

[0047] Step2: Prepare a cylindrical elastic membrane, fix its lower end at the bottom of the cylinder, pour cement soil in a certain ratio into it, and stop pouring when the cement soil reaches the same height as the cylinder, and record the volume of the poured cement soil;

[0048] Step3: Take the lid of the cylinder, fix the upper end of the elastic membrane on the lid, and then cover the lid to form a relatively closed space between the model pile and the elastic membrane;

[0049] Step4: Inject liquid between the elastic membrane and the cylinder to provide confining pressure, simulate the situation of the model pile being subjected to soil pressure in the soil layer by controlling different confining pressures, and read the volume of the liquid injected into the cylinder under a specific confining pressure;

[0050] Step5: Let the model pile stand still for 7 - 28 days under the action of cement soil and confining pressure, read the volume of the liquid in the cylinder, and accurately measure the expansion rate of cement soil at different ages according to the ratio of the difference in the change of the liquid volume to the initial volume of the poured cement soil;

[0051] Step6: Conduct an ultimate shaft friction resistance test on the model pile using the step - by - step loading method, draw a τ - S curve using the measured data, and obtain the ultimate shaft friction resistance of the model pile.

[0052] Optimized. In Step 2, the latex film has ductility. During the consolidation process of the cement soil, its volume expands and causes the latex film to expand outwards, and the volume of the liquid between the cylinder 200 and the latex film changes accordingly.

[0053] Optimized. In Step 4, a GDS volume controller 400 is used to control the confining pressure generated by the injected liquid. The GDS volume controller 400 is connected to a computer, and the application of the confining pressure is controlled by the computer. Different confining pressures are used to simulate different soil types and soil layer depths.

[0054] In this technical solution, there are many current methods for testing the shaft friction of piles, but most of them are actual measurements, that is, on-site test operations, so a large amount of cost is required. Based on this, the applicant provides a model test method that can be carried out indoors. Specifically, by using a self-made cylinder 200 and matching corresponding test instruments, the test can be completed. Of course, the test of the shaft friction of the model pile 10 is not the ultimate goal of this embodiment, but to study the influence of different proportions of cement soil on the bearing capacity of the pile.

[0055] Based on this, the GDS volume controller 400 is used to inject liquid into the cylinder 200. The confining pressure generated by the liquid on the cement soil is used to simulate the influence of different soil types and soil layer depths on the cement soil. The GDS volume controller 400 can accurately control the confining pressure generated by the liquid and the volume of the injected liquid. When the cement soil consolidates, it will expand. After expansion, it will squeeze the surrounding liquid and cause the liquid to flow back, that is, the amount of liquid in the cylinder 200 will decrease. Through this method, the expansion rate of the cement soil after consolidation can be measured more accurately. By preparing cement soil with different proportions and conducting continuous tests, the expansion rates of cement soil with different proportions can be obtained, and under the action of the jack 300, a bearing pressure is provided for the model pile 10, and then the shaft friction between the cement soil with different proportions and the model pile 10 can be obtained.

[0056] Embodiment 2:

[0057] This embodiment provides a combined test device for the expansion rate of cement soil and shaft friction. In addition to including the technical solutions of the above embodiments, it also has the following technical features.

[0058] As Figures 1 - 4 shown, in this embodiment, the combined test device includes: a reaction frame 100, and a workbench 110 is provided on the reaction frame 100;

[0059] A cylinder 200 is disposed on the workbench 110. The bottom of the cylinder 200 has a bottom cover 210, and the top has a top cover 220. The top cover 220 and the bottom cover 210 are provided with holes that are coaxial and have the same inner diameter. The holes on the top cover 220 and the bottom cover 210 are for both ends of the model pile 10 to pass through. An elastic membrane 230 is disposed around the inner cavity of the cylinder 200. The elastic membrane 230 is a latex membrane or a geomembrane. The elastic membrane 230 divides the inner cavity of the cylinder 200 into an inner cavity and an outer cavity. The inner cavity is for injecting cement soil, and the outer cavity is for injecting liquid.

[0060] A jack 300 is disposed on the reaction frame 100 to provide pressure for the model pile 10. A displacement meter 310 is disposed below the top of the model pile 10 to detect the vertical displacement of the model pile 10.

[0061] And a GDS volume controller 400 is for injecting liquid into the outer cavity and controlling the confining pressure generated by the liquid in the outer cavity.

[0062] In this technical solution, based on the test method in Embodiment 1, the applicant provides a self-made test device. Specifically, it includes a reaction frame 100, a cylinder 200, a jack 300, and a GDS volume controller 400. The reaction frame 100 provides an experimental platform for the cylinder 200, the jack 300 provides pressure for the model pile 10, and the GDS volume controller 400 provides confining pressure for the cement soil in the cylinder 200.

[0063] Embodiment 3:

[0064] This embodiment provides a combined test device for the expansion rate of cement soil and the side friction resistance of piles. In addition to including the technical solutions of the above embodiments, it also has the following technical features.

[0065] As Figures 1 - 4 shown, in this embodiment, there are several groups of the cylinders 200, and they are respectively arranged side by side on the workbench 110. The jack 300 is slidably disposed on the reaction frame 100 along the direction in which the cylinders 200 are arranged side by side.

[0066] The combined test device further includes:

[0067] A main pipe 500, which is connected to the GDS volume controller 400.

[0068] There are several branch pipes 600, and the number of them is the same as the number of the cylinders 200. One end of each branch pipe 600 is connected to the main pipe 500 in communication, and the other end is respectively connected to each cylinder 200 and is in communication with the outer cavity of the cylinder 200.

[0069] and a mass flowmeter 700, with a number of them, the number being the same as that of the branch pipes 600, and each being used to detect the volume of the fluid passing through each branch pipe 600. Specifically, the mass flowmeter 700 is used to detect the volume of the liquid entering the outer cavity from the branch pipe 600 and the volume of the liquid in the outer cavity flowing back from the branch pipe 600 to the main pipe 500.

[0070] In this technical solution, since this combined test device is mainly used to study the influence of cement soil with different ratios on the bearing capacity of piles. Therefore, in order to be able to conduct multiple groups of tests simultaneously, reduce the test period, and at the same time control environmental factors and improve test accuracy, a plurality of cylinders 200 are provided on the reaction frame 100, and multiple groups of tests can be realized through the plurality of cylinders 200. Of course, in order to reduce test instruments, that is, reduce the number of GDS volume controllers 400, a main pipe 500 and branch pipes 600 are also provided. One GDS volume controller 400 is adopted, which is connected to the main pipe 500, the main pipe 500 is connected to each branch pipe 600, and the branch pipes 600 are connected to each cylinder 200. When injecting liquid into the outer cavity of the cylinder 200, the pressure of the liquid injected into each cylinder 200 can be controlled by the GDS volume controller 400. After reaching the preset pressure threshold, the GDS controller stops injecting liquid, and then static settlement is carried out. After about a week, when the cement soil consolidates, it will expand. Since the pressure value input by the GDS volume controller 400 is fixed, the liquid in the outer cavity of each cylinder 200 will be squeezed and flow from the branch pipe 600 to the main pipe 500, that is, the GDS volume controller 400 has a backflow. Since the ratios of the cement soil in each cylinder 200 are different, their expansion rates are also different. Because the pressures among the main pipe 500, the branch pipes 600, and the outer cavity of the cylinder 200 are the same, the amount of the liquid flowing back in some cylinders 200 will be more, and the amount of the liquid flowing back in some cylinders 200 will be less. However, for the GDS volume controller 400, it can only display the total volume of the liquid in the outer cavity of each cylinder 200. Therefore, the applicant also separately provides a mass flowmeter 700. By arranging the mass flowmeter 700 on the branch pipe 600, the volume of the liquid entering the branch pipe 600 and the volume of the liquid flowing out of the branch pipe 600 can be detected. By comparing and analyzing the volume of the liquid detected by each mass flowmeter 700 with the volume of the liquid displayed on the GDS volume controller 400, the expansion rate of the cement soil with different ratios can be accurately calculated. Immediately, under the action of the jack 300, pressure data is measured, and using the measured data, a Q-S curve is drawn, and the ultimate bearing capacity and the side friction resistance of the model pile 10 can be obtained.

[0071] Example 4:

[0072] This embodiment provides a combined test device for the expansion rate of cement soil and the side friction of piles. In addition to including the technical solutions of the above embodiments, it also has the following technical features.

[0073] As Figure 3 and Figure 4 shown, in this embodiment, the cylinder 200 further includes:

[0074] Support frames 240, having two groups and arranged vertically at the middle position on the outer side of the cylinder 200;

[0075] Adjusting piston rods 250, having four. Among them, two adjusting piston rods 250 are symmetrically arranged on each support frame 240, and the four adjusting piston rods 250 are circumferentially and evenly distributed on the outer side of the cylinder 200. Adjusting holes corresponding to each adjusting piston rod 250 are opened on the outer wall of the cylinder 200. One end of each adjusting piston rod 250 close to the cylinder 200 is respectively arranged in a sealed and sliding manner on each adjusting hole. One end of the adjusting piston rod 250 extends into the outer cavity, and the other end is located on the support frame 240; the adjusting piston rod 250 is a hollow tubular structure;

[0076] Suction cups 260, arranged on each adjusting piston rod 250;

[0077] And a vacuum generating device 270, connected to the adjusting piston rod 250 through an air pipe, for providing negative pressure suction for the suction cups 260;

[0078] Among them, by adjusting the insertion depth of each adjusting piston rod 250, the suction cups 260 on each adjusting piston rod 250 are respectively made to contact or press tightly against the outer wall of the elastic membrane 230, so as to limit and fix the elastic membrane 230 and make it located at the exact center of the chamber of the cylinder 200.

[0079] In this technical solution, with respect to the elastic membrane 230, it is mainly used to carry the cement soil. After the cement soil is consolidated, the cement soil can wrap the model pile 10 in a columnar structure. In order to enable the cement soil to wrap the model pile 10 without deviation, that is, after the cement soil is consolidated, the model pile 10 is located at the exact middle position of the cement soil, a calibration structure for calibrating the position of the elastic membrane 230 is also provided.

[0080] The calibration structure mainly consists of a support frame 240, an adjusting piston rod 250, a suction cup 260, and a vacuum generating device 270. The specific operation is as follows: The operator first inserts the model pile 10 into the cylinder 200, then puts the annular elastic membrane 230 on the outside of the model pile 10. Immediately afterwards, by pressing the adjusting piston rod 250 on the outside of the cylinder 200, the adjusting piston rod 250 moves inward. At the same time, other adjusting piston rods 250 also move synchronously, and the insertion depth of each adjusting piston rod 250 needs to be the same until the suction cups 260 on each adjusting piston rod 250 all abut against the outer wall of the elastic membrane 230. Subsequently, the vacuum generating device 270 works to generate negative pressure suction on the suction cups 260 to suck the elastic membrane 230 tightly, so that the elastic membrane 230 is in the central position.

[0081] As Figure 3 and Figure 4 shown, to enable the adjusting piston rods 250 on the support frame 240 to move outward or inward simultaneously, while facilitating adjustment and also ensuring that the elastic membrane 230 does not move unidirectionally to one side, for this purpose, the support frame 240 is composed of a first connecting rod 241, a second connecting rod 242, a third connecting rod 243, and a fourth connecting rod 244 that are sequentially hinged. The first connecting rod 241 and the fourth connecting rod 244 are hinged to form a quadrilateral frame structure; the support frame 240 also includes two support rods 245 and four hinge seats 246. The first connecting rod 241, the second connecting rod 242, the third connecting rod 243, and the fourth connecting rod 244 are all arranged on the hinge seats 246. The two support rods 245 respectively slide through the hinge seats 246 between the first connecting rod 241 and the fourth connecting rod 244, and the hinge seats 246 between the second connecting rod 242 and the third connecting rod 243, and then are fixed on the outer wall of the cylinder 200. The ends of the two adjusting piston rods 250 are fixed on the hinge seats 246 between the third connecting rod 243 and the fourth connecting rod 244, and the hinge seats 246 between the first connecting rod 241 and the second connecting rod 242. When pressing one of the adjusting piston rods 250 to move, the other adjusting piston rod 250 also moves synchronously.

[0082] After the positions of the four adjusting piston rods 250 are all adjusted to the set appropriate positions and the suction cups 260 suck the elastic membrane 230 tightly, the elastic membrane 230 presents a state of being tensioned outward. After that, the elastic membrane 230 is not likely to shift easily. Even during the process of pouring cement soil into the elastic membrane 230 and the model pile 10, the position of the elastic membrane 230 is not likely to shift, so that the cement soil can be evenly poured on the outside of the model pile 10.

[0083] Another main factor for the adjustable piston rod 250 to be movably arranged without being locked is that there is no constraint on it. After the cement soil consolidates, it will expand and extrude the elastic membrane 230 outward. Since the adjustable piston rod 250 is not fixed, the elastic membrane 230 can push the adjustable piston rod 250 to move, so that the position where the elastic membrane 230 contacts the adjustable piston rod 250 will not be unable to expand, which ultimately affects the test data of the expansion of the cement soil.

[0084] In this embodiment, preferably, the cylinder 200 further includes a waterproof layer 280 provided on the bottom cover 210 and the top cover 220, and the upper and lower ends of the elastic membrane 230 are respectively located on the waterproof layer 280 of the bottom cover 210 and the waterproof layer 280 of the top cover 220.

[0085] Regarding the process of pouring cement soil between the elastic membrane 230 and the model pile 10, in order to play a sealing role, a waterproof layer 280 is also provided on the bottom cover 210 of the cylinder 200.

[0086] During the test process, the volume parameters of the poured cement soil need to be strictly controlled. In order to enable the cement soil to fill the entire inner cavity, a pouring port 221 and a detection port 222 are provided on the top cover 220. The operation method is as follows: first, open the top cover 220, inject an appropriate amount of cement soil into the inner cavity (the inner cavity is not filled), then cover the top cover 220, and then continue to pour cement soil into the cylinder 200 through the pouring port 221. When the cement soil overflows to the detection port 222, stop pouring. Subsequently, seal the pouring port 221 and the detection port 222.

[0087] As Figure 3 shown, regarding the waterproof layer 280 is also provided on the top cover 220. On the one hand, it is to prevent the cement soil from being fixed to the top cover 220 after consolidation, resulting in difficulty in removing the cement soil and cleaning it subsequently; on the other hand, through the waterproof layer 280, the position of the upper end of the elastic membrane 230 can be sealed to prevent the cement soil from flowing out through the gap. Therefore, a waterproof layer 280 is also provided on the top cover 220. The waterproof layer 280 on the top cover 220 can be fixed by a plastic buckle in a cylindrical structure. Specifically, the plastic buckle is in the shape of the cylinder 200, with a larger lower end and a smaller upper end. The upper end is embedded in the pouring port or the detection port, and the lower end is used to clamp the waterproof layer 280.

[0088] The embodiments of the present application have been described above in conjunction with the accompanying drawings. Without conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application is not limited to the above specific implementation manners. The above specific implementation manners are merely illustrative rather than restrictive. Under the inspiration of the present application, those of ordinary skill in the art can also make many forms without departing from the purpose of the present application and the scope protected by the claims, and all of them belong to the protection scope of the present application.

Claims

1. A combined test method for the expansion rate of cement soil and the shaft friction resistance of piles, characterized in that, Including the following steps: Step 1: Prepare a model pile with appropriate dimensions and insert it into a cylinder that can only pass through the perforated model pile at the bottom. The cylinder is equipped with a cylinder cover that matches its size, and there is also a hole on the cylinder cover that can only penetrate the model pile; Step 2: Prepare a cylindrical elastic membrane, fix its lower end at the bottom of the cylinder, pour cement soil in a certain ratio into it, stop when the poured cement soil reaches the same height as the cylinder, and record the volume of the poured cement soil; Step 3: Take the cylinder cover, fix the upper end of the elastic membrane on the cylinder cover, then cover the cylinder cover to form a relatively enclosed space between the model pile and the elastic membrane; Step 4: Inject liquid between the elastic membrane and the cylinder to provide confining pressure. By controlling different confining pressures, simulate the situation where the model pile is subjected to soil pressure in the soil layer, and read the volume of the liquid injected into the cylinder under a specific confining pressure; Step 5: Let the model pile stand for 7 - 28 days under the action of cement soil and confining pressure, read the volume of the liquid in the cylinder, and accurately measure the swelling rate of cement soil at different ages according to the ratio of the difference in the change of the liquid volume to the initial volume of the poured cement soil; Step 6: Conduct a limit shaft friction test on the model pile using the step - by - step loading method, draw a t - S curve using the measured data, and obtain the limit shaft friction of the model pile.

2. The combined test method for the expansion rate of cement soil and the side friction resistance of piles according to claim 1, characterized in that In Step 2, the elastic membrane has ductility. During the consolidation process of the cement soil, its volume expands, causing the elastic membrane to expand outwards, and the volume of the liquid between the cylinder and the elastic membrane changes accordingly.

3. The combined test method for the expansion rate of cement soil and the shaft friction resistance according to claim 1, wherein, In Step 4, a GDS volume controller is used to control the confining pressure generated by the injected liquid. The GDS volume controller is connected to a computer, and the application of the confining pressure is controlled by the computer. By different confining pressures, simulate the surrounding soil pressures corresponding to different soil types and soil layer depths.

4. A combined test device for the expansion rate of cement soil and the side friction resistance of piles, characterized in that, Including: A reaction frame (100) with a workbench (110) provided thereon; A cylinder (200) disposed on the workbench (110). The bottom of the cylinder (200) has a bottom cover (210), and the top has a top cover (220). The top cover (220) and the bottom cover (210) are provided with coaxial holes with the same inner diameter. The holes on the top cover (220) and the bottom cover (210) are used for both ends of the model pile (10) to pass through. There is a surrounding elastic membrane (230) in the chamber of the cylinder (200). The elastic membrane (230) divides the chamber of the cylinder (200) into an inner cavity and an outer cavity. The inner cavity is used for injecting cement soil, and the outer cavity is used for injecting liquid; A jack (300) disposed on the reaction frame (100) to provide pressure for the model pile (10); And a GDS volume controller (400) for injecting liquid into the outer cavity and controlling the confining pressure generated by the liquid in the outer cavity; The combined test device further includes: A main pipe (500) connected to the GDS volume controller (400); The branch pipes (600) are provided with several pieces, and the number thereof is consistent with the number of the cylinders (200). One end of each branch pipe (600) is communicated with the main pipe (500), and the other ends are respectively connected to the cylinders (200) and communicated with the outer cavity of the cylinders (200). And there are several mass flow meters (700), and the number thereof is consistent with the number of the branch pipes (600), and they are respectively used for detecting the volume of the fluid passing through each branch pipe (600). The mass flow meter (700) is used for detecting the volume of the liquid flowing from the branch pipe (600) into the outer cavity and the volume of the liquid in the outer cavity flowing back from the branch pipe (600) to the main pipe (500).

5. The combined test device for the expansion rate of cement soil and the shaft friction resistance according to claim 4, characterized in that, A displacement meter (310) is arranged below the top of the model pile (10) for detecting the vertical displacement of the model pile (10).

6. The combined test device for the expansion rate of cement soil and the side friction resistance of piles according to claim 4, wherein The elastic membrane (230) is a latex membrane or a geomembrane.

7. A combined test device for cement soil expansion rate and pile side friction resistance according to claim 4, characterized in that, There are several groups of the cylinders (200) for simultaneously measuring the influence of cement soils with different ratios on the shaft friction resistance of the pile. They are respectively arranged side by side on the workbench (110), and the jack (300) is slidably arranged on the reaction frame (100) along the direction in which the cylinders (200) are arranged side by side.

8. A combined test device for the swelling ratio of cement soil and the shaft friction resistance according to any one of claims 4-7, characterized in that, The cylinder (200) further includes: Support frames (240), with two groups, which are arranged up and down at the middle position on the outer side of the cylinder (200); Adjusting piston rods (250), with four pieces. Two adjusting piston rods (250) are symmetrically arranged on each support frame (240), and the four adjusting piston rods (250) are circumferentially and evenly distributed on the outer side of the cylinder (200). Adjusting holes corresponding to the adjusting piston rods (250) are formed on the outer wall of the cylinder (200). One end of each adjusting piston rod (250) close to the cylinder (200) is respectively arranged on each adjusting hole in a sealed and sliding manner. One end of the adjusting piston rod (250) extends into the outer cavity, and the other end is located on the support frame (240); the adjusting piston rod (250) is of a hollow tubular structure; Suction cups (260) are arranged on each adjusting piston rod (250); And a vacuum generating device (270) is connected to the adjusting piston rod (250) through an air pipe for providing negative pressure suction for the suction cups (260); Wherein, by adjusting the insertion depth of each adjusting piston rod (250), the suction cups (260) on each adjusting piston rod (250) are respectively abutted or tightly abutted against the outer wall of the elastic membrane (230) to limit and fix the elastic membrane (230) so that it is located at the exact center of the cavity of the cylinder (200).

9. The combined test device for the expansion rate of cement soil and the shaft friction resistance according to claim 8, characterized in that, The cylinder (200) further includes a waterproof layer (280) arranged on the bottom cover (210) and the top cover (220), and the upper and lower ends of the elastic membrane (230) are respectively located on the waterproof layer (280) of the bottom cover (210) and the waterproof layer (280) of the top cover (220).

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