A combined test device and method for consolidating settlement and reinforcement effects

Abstract

The application discloses a combined test device and method for consolidation settlement and reinforcement effect, and belongs to the technical field of indoor geotechnical test, and aims to solve the problem that the drainage rate and reinforcement effect cannot be simultaneously measured in the prior art. The device comprises a sample chamber, a loading unit, a sample displacement sensor and a drainage measurement unit. A drainage hole is formed in the side wall of the sample chamber, the drainage hole is connected with the drainage measurement unit, a sample is arranged in the sample chamber, the sample comprises a sand cushion layer, a reinforced drainage net and a clay layer which are sequentially stacked from top to bottom, the loading unit and the sample displacement sensor are both in contact with the upper surface of the sand cushion layer, the loading unit is used for applying a loading force to the whole sample, and the displacement sensor is used for measuring the displacement of the upper surface of the sample. The application can be used for the combined test of the consolidation settlement and reinforcement effect of a soft soil foundation sample.

Description

Technical Field

[0001] This invention belongs to the field of indoor geotechnical testing technology, and in particular relates to a combined test device and method for consolidation settlement and reinforcement effect. Background Technology

[0002] In soft soil foundation treatment and dam filling projects, horizontal sand cushion layers are often laid. The main purpose is to accelerate soil consolidation, improve the bearing capacity of the foundation, and thus give full play to the engineering properties of the consolidated soil. Although this method can improve the bearing capacity of the foundation, it has problems such as long consolidation time, uncontrollable drainage direction, and many factors affecting the consolidation rate. When applied on a large scale, the consolidation effect is not significant.

[0003] Composite geonet is a composite geosynthetic material that combines isolation, drainage, and reinforcement functions. The geonet core has a unique three-dimensional porous structure, which can provide unobstructed drainage paths for the soil and significantly improve the consolidation drainage efficiency. At the same time, composite geonet can withstand high vertical loads during use, further improving the foundation bearing capacity of the consolidated soil.

[0004] Traditional soil consolidation testing equipment can only measure the consolidation settlement rate and cannot simultaneously measure the drainage rate and reinforcement effect. Summary of the Invention

[0005] In view of the above analysis, the present invention aims to provide a combined test device and method for consolidation settlement and reinforcement effect, so as to solve the problem that the drainage rate and reinforcement effect cannot be measured simultaneously in the prior art.

[0006] The objective of this invention is mainly achieved through the following technical solutions:

[0007] This invention provides a combined testing device for consolidation settlement and reinforcement effect, including a sample chamber, a loading unit, a sample displacement sensor, and a drainage measurement unit. The side wall of the sample chamber has drainage holes, which are connected to the drainage measurement unit. The sample is placed in the sample chamber and includes a sand cushion layer, a reinforced drainage net, and a clay layer stacked from top to bottom. The loading unit and the sample displacement sensor are both in contact with the upper surface of the sand cushion layer. The loading unit is used to apply a loading force to the entire sample, and the displacement sensor is used to measure the displacement of the upper surface of the sample.

[0008] Furthermore, the loading unit includes an inverted hydraulic cylinder, a load sensor, and a loading plate. The loading plate is placed on the upper surface of the sample. The inverted hydraulic cylinder abuts against the loading plate through the load sensor, and the sensing end of the displacement sensor contacts the upper surface of the loading plate.

[0009] Furthermore, the loading plate is circular in shape, and its diameter is smaller than the inner diameter of the sample chamber.

[0010] Furthermore, the sample chamber, loading unit, and sample are arranged coaxially.

[0011] Furthermore, the drainage measurement unit includes a guide pipe and a measuring cylinder connected in sequence to the drainage hole.

[0012] Furthermore, the drainage measurement unit also includes a drainage sensor, a timing controller, and a timer. The sensing end of the drainage sensor is located in the guide pipe. During the loading process, the drainage sensor monitors the water flow in the guide pipe in real time. If water flows through, the timing controller controls the timer to start and calculates the drainage time. If the water flow in the guide pipe is measured to be zero, the timing controller controls the timer to stop and records the time measured by the timer.

[0013] Furthermore, it also includes a filter screen, which is located at the water inlet end of the guide pipe, and the sample chamber is connected to the guide pipe through the filter screen.

[0014] Furthermore, the mesh size of the filter screen is smaller than the smallest particle size in the sand cushion layer.

[0015] Furthermore, there are multiple drainage holes, which are evenly arranged along the axial direction of the sample chamber.

[0016] The present invention also provides a combined test method for consolidation settlement and reinforcement effect, characterized in that the above-mentioned combined test device is used to test the consolidation settlement and reinforcement effect of soft soil foundation samples.

[0017] Compared with the prior art, the present invention can achieve at least the following beneficial effects:

[0018] The combined test device for consolidation settlement and reinforcement effect provided by the present invention has a simple structure and is easy to operate. A reinforced drainage net is set between the sand cushion layer and the clay layer, and corresponding drainage holes are set at the positions corresponding to the reinforced drainage net. This allows for better control of the drainage direction of the clay layer, significantly improving the consolidation drainage efficiency. It can simultaneously measure the consolidation settlement rate and the drainage rate, thereby improving the test efficiency.

[0019] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0020] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0021] Figure 1 This is a front view of the combined test apparatus for measuring consolidation settlement and reinforcement effect provided in Embodiment 1 of the present invention;

[0022] Figure 2 This is a top view of the combined test apparatus for measuring consolidation settlement and reinforcement effect provided in Embodiment 1 of the present invention;

[0023] Figure 3 This is a schematic diagram of the first structure of the adjustable drainage hole in the combined test device for measuring consolidation settlement and reinforcement effect provided in Embodiment 1 of the present invention.

[0024] Figure 4 This is a schematic diagram of the second structure of the adjustable drainage hole in the combined test device for measuring consolidation settlement and reinforcement effect provided in Embodiment 1 of the present invention.

[0025] Figure label:

[0026] 1-Sample chamber; 2-Clay layer; 3-Reinforced drainage net; 4-Drainage hole; 5-Filter screen; 6-Sand cushion layer; 7-Loading plate; 8-Sample displacement sensor; 9-Inverted hydraulic cylinder; 10-Load sensor; 11-Timer; 12-Drainage sensor; 13-Guide pipe; 14-Measuring cylinder; 15-Cover plate; 16-Drainage net displacement sensor; 17-Gear; 18-Rack; 19-Circular plate hole; 20-Clamping rod. Detailed Implementation

[0027] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of the present invention and are used together with the invention to illustrate the principles of the invention.

[0028] Example 1

[0029] This embodiment provides a combined test device for consolidation settlement and reinforcement effect. See [link to relevant documentation]. Figures 1 to 2 The system includes a sample chamber 1, a loading unit, a sample displacement sensor 8, and a drainage measurement unit. A drainage hole 4 is provided on the side wall of the sample chamber 1, and the drainage hole 4 is connected to the drainage measurement unit. The sample is placed in the sample chamber 1. The sample includes a sand cushion layer 6, a reinforced drainage net 3 (e.g., a composite geonet), and a clay layer 2 (e.g., soft clay) stacked from top to bottom. The loading unit and the sample displacement sensor 8 are both in contact with the upper surface of the sand cushion layer 6. The loading unit is used to apply a loading force to the entire sample, and the displacement sensor is used to measure the displacement of the upper surface of the sample. The reinforced drainage net 3 is located below the lower edge of the drainage hole 4. For example, the distance between the reinforced drainage net 3 and the lower edge of the drainage hole 4 is 10 mm to 20 mm.

[0030] In practice, the consolidation settlement and reinforcement effect tests of the samples using the above-mentioned combined sample apparatus include the following steps:

[0031] Step 1: Fill the sample chamber 1 with the clay layer 2, reinforced drainage net 3 and sand cushion layer 6 from the actual project in sequence to obtain the sample. Then, bring the loading unit and the sample displacement sensor 8 into contact with the upper surface of the sand cushion layer 6.

[0032] Step 2: Activate the loading unit. The loading unit applies and maintains the loading force on the sample. The sand cushion layer 6 and the clay layer 2 are compacted. The clay layer 2 is consolidated. Water in the clay layer 2 seeps out from the clay layer 2 and is discharged into the drainage measurement unit along the reinforced drainage net 3. The displacement sensor collects the displacement of the upper surface of the sample until the displacement of the upper surface of the sample per hour is less than the threshold (e.g., 0.01 mm).

[0033] Step 3: Calculate the consolidation settlement rate based on the displacement and displacement time of the upper surface of the sample, and calculate the drainage rate based on the drainage volume and drainage time.

[0034] Step 4: Increase the loading force of the loading unit and repeat steps 2 to 3 to perform graded loading on the sample until the sand cushion layer 6 is damaged, that is, the loading plate 7 of the loading unit damages the surface of the sand cushion layer 6.

[0035] For example, the loading levels are 7, corresponding to loading forces of 12.5 kPa, 25 kPa, 50 kPa, 100 kPa, 200 kPa, 300 kPa and 400 kPa respectively;

[0036] Step 5: Obtain the consolidation settlement rate and drainage rate corresponding to each stage, as well as the final bearing capacity of the sample;

[0037] Step 6: Calculate the average consolidation settlement rate and average drainage rate based on the number of loading stages, the consolidation settlement rate corresponding to each stage, and the drainage rate.

[0038] Compared with the prior art, the combined test device for consolidation settlement and reinforcement effect provided in this embodiment has a simple structure and is easy to operate. A reinforced drainage net 3 is set between the sand cushion layer 6 and the clay layer 2, and corresponding drainage holes 4 are set at the positions corresponding to the reinforced drainage net 3. This can better control the drainage direction of the clay layer 2, significantly improve the consolidation drainage efficiency, and simultaneously measure the consolidation settlement rate and drainage rate, thereby improving the test efficiency.

[0039] To facilitate drainage, there are multiple drainage holes 4, for example, 4 to 6. These multiple drainage holes 4 are evenly arranged along the axial direction of the sample chamber 1. Correspondingly, there are also multiple drainage measurement units. Each drainage hole 4 corresponds to a drainage volume measurement unit. When calculating the drainage volume in the subsequent process, the total drainage volume measured by the multiple drainage volume measurement units is calculated, which is the total drainage volume of the sample.

[0040] Accordingly, there are multiple displacement sensors, each corresponding to a drain hole 4, and the displacement sensors are located above the drain holes 4.

[0041] To reduce the size effect of the specimens, the specimen chamber 1 is, for example, a cylindrical body of tempered glass with a diameter of not less than 600 mm (e.g., 650–800 mm) and a height of not less than 1200 mm (e.g., 1200–1500 mm). This allows for a larger specimen chamber 1, better reflecting the drainage consolidation state of the specimens in actual engineering, effectively reducing the size effect, and making the indoor test results obtained from the combined test device for consolidation settlement and reinforcement effects more valuable.

[0042] In order to further reduce the size effect of the sample, the ratio of the diameter of the drainage hole 4 to the height of the sample chamber 1 is 1:40 to 60, and the ratio of the axial length of the drainage hole 4 to the inner diameter of the sample chamber 1 is 1:20 to 60.

[0043] Specifically, the loading unit includes an inverted hydraulic cylinder 9, a load sensor 10, and a loading plate 7. Considering the uniform distribution of loading force, the loading plate 7 is circular in shape and is placed on the upper surface of the sample. The inverted hydraulic cylinder 9 abuts against the loading plate 7 through the load sensor 10, and the sensing end of the displacement sensor contacts the upper surface of the loading plate 7. The overall displacement of the sample is reflected by measuring the displacement of the loading plate 7.

[0044] In order to improve the accuracy of the above tests, the diameter of the loading plate 7 is smaller than the inner diameter of the sample chamber 1, so as to better simulate the effect of the structure on the soft soil foundation.

[0045] From the perspective of uniform stress distribution, the sample chamber 1, the loading unit (i.e., the loading plate 7) and the sample (i.e., the sand cushion layer 6, the reinforced drainage net 3 and the clay layer 2) are all coaxially arranged.

[0046] Specifically, the structure of the drainage measurement unit includes a guide tube 13 (e.g., a rubber guide tube 13) and a measuring cylinder 14 connected in sequence to the drainage hole 4, wherein the minimum graduation of the measuring cylinder 14 is at least 0.5 ml.

[0047] To obtain accurate drainage time for calculating drainage rate, the drainage measurement unit further includes a drainage sensor 12, a timing controller, and a timer 11. The sensing end of the drainage sensor 12 is located in the guide pipe 13. During loading, the drainage sensor 12 monitors the water flow rate in the guide pipe 13 in real time. If water flows through, the timing controller controls the timer 11 to start and calculate the drainage time. If the measured water flow rate in the guide pipe 13 is zero, the timing controller controls the timer 11 to stop and records the time measured by the timer 11. This is because, in the prior art, drainage timing is usually determined by human subjective judgment of the drainage start point and the timer 11 is manually started, which obviously affects the accuracy of drainage timing. This embodiment, by setting a drainage sensor 12 and a timing controller, allows the drainage sensor 12 to sense whether water flows through and the timing controller to control the start of the timer 11, thereby achieving automatic control of drainage time measurement, reducing the influence of human subjective factors, and improving the accuracy of drainage time measurement.

[0048] In practical applications, particles in the sand cushion layer 6 will inevitably flow out from the drainage hole 4, which will lead to errors in the measurement of drainage volume. Therefore, the combined test device for consolidation settlement and reinforcement effect also includes a filter screen 5. The filter screen 5 is located at the water inlet end of the guide pipe 13. The sample chamber 1 is connected to the guide pipe 13 through the filter screen 5. The mesh size of the filter screen 5 is smaller than the smallest particle size in the sand cushion layer 6.

[0049] It is worth noting that as the loading force increases, the clay layer 2 will consolidate and compress, and correspondingly, the position of the reinforced drainage net 3 will also decrease. In order to ensure that the drainage holes 4 can also be adjusted accordingly with the position of the reinforced drainage net 3, the following two methods are adopted, for example:

[0050] The first method, see [link / reference] Figure 3The combined test device for consolidation settlement and reinforcement effect also includes a clamping rod 20, a cover plate 15, and a slide rail. The drainage hole 4 is a long strip that is set vertically. The cover plate 15 covers the drainage hole 4. A circular plate hole 19 is opened on the cover plate 15. The water inlet end of the circular plate hole 19 is connected to the inner cavity of the sample chamber 1 through the drainage hole 4. The water outlet end of the circular plate hole 19 is connected to the drainage measurement unit. The diameter of the circular plate hole 19 is smaller than the vertical length of the drainage hole 4. One end of the clamping rod 20 clamps the reinforced drainage net 3. The other end of the clamping rod 20 is fixedly connected to the cover plate 15. A slide groove that cooperates with the slide rail is opened on the side of the cover plate 1 facing the sample chamber 1. During implementation, the clamping rod 20 enables the cover plate 15 and the reinforced drainage net 3 to move synchronously. When the reinforced drainage net 3 descends, the clamping rod 20 will drive the cover plate 15 to descend, and correspondingly, the position of the circular plate hole 19 will also descend. Since the drainage hole 4 is a vertically arranged elongated shape, the circular plate hole 19 can still be connected to the drainage hole 4, thereby enabling the adjustment of the drainage position while ensuring smooth drainage.

[0051] It should be noted that in practical applications, the reinforced drainage net 3 in a certain area will also be subject to the tension of the surrounding reinforced drainage net 3. By adopting the above adjustment method, a certain tension can be applied to the reinforced drainage net 3 through the clamping rod 20, thereby further improving the accuracy of the test.

[0052] The second method, see Figure 4 The combined test device for consolidation settlement and reinforcement effect also includes a drainage net displacement sensor 16, a cover plate 15, a gear 17, a drive motor and a drive controller. The drainage hole 4 is a long strip that is set vertically. The cover plate 15 covers the drainage hole 4. A circular plate hole 19 is opened on the cover plate 15. The water inlet end of the circular plate hole 19 is connected to the inner cavity of the sample chamber 1 through the drainage hole 4. The water outlet end of the circular plate hole 19 is connected to the drainage measurement unit. The diameter of the circular plate hole 19 is smaller than the vertical length of the drainage hole 4. A rack 18 that cooperates with the gear 17 is provided on the side of the cover plate 15 away from the sample chamber 1. The gear 17 is fixedly connected to the output shaft of the drive motor. When the reinforced drainage net 3 descends, the drainage net displacement sensor 16 acquires the displacement of the reinforced drainage net 3 in real time and transmits it to the drive controller. The drive controller drives the drive motor and gear 17 to rotate synchronously. The rotation of gear 17 drives rack 18 to move downward, thereby driving cover plate 15 to descend. Correspondingly, the position of circular plate hole 19 will also descend. Since drainage hole 4 is a vertically arranged elongated shape, at this time, circular plate hole 19 can still be connected to drainage hole 4, so as to achieve drainage position adjustment while ensuring smooth drainage.

[0053] Specifically, the vertical length of the drain hole 4 is 300-500mm, and the diameter of the circular plate hole 19 is 20-35mm.

[0054] Example 2

[0055] This embodiment provides a combined experimental method for consolidation settlement and reinforcement effect, using the combined experimental apparatus for consolidation settlement and reinforcement effect provided in Embodiment 1. The combined experimental method includes the following steps:

[0056] Step 1: Fill the sample chamber 1 with the clay layer 2, reinforced drainage net 3 and sand cushion layer 6 from the actual project in sequence to obtain the sample. Then, bring the loading unit and the sample displacement sensor 8 into contact with the upper surface of the sand cushion layer 6.

[0057] Step 2: Turn on the loading unit. The loading unit applies and maintains the loading force on the sample. The sand cushion layer 6 and the clay layer 2 are compacted. The clay layer 2 is consolidated. Water in the clay layer 2 seeps out from the clay layer 2 and is discharged into the drainage measurement unit along the drainage net. The displacement sensor collects the displacement of the upper surface of the sample until the displacement of the upper surface of the sample per hour is less than the threshold (e.g., 0.01 mm).

[0058] Step 3: Calculate the consolidation settlement rate based on the displacement and displacement time of the upper surface of the sample, and calculate the drainage rate based on the drainage volume and drainage time.

[0059] Step 4: Increase the loading force of the loading unit and repeat steps 2 to 3 to perform graded loading on the sample until the sand cushion layer 6 is damaged, that is, the loading plate 7 of the loading unit damages the surface of the sand cushion layer 6.

[0060] For example, the loading levels are 7, corresponding to loading forces of 12.5 kPa, 25 kPa, 50 kPa, 100 kPa, 200 kPa, 300 kPa and 400 kPa respectively;

[0061] Step 5: Obtain the consolidation settlement rate and drainage rate corresponding to each stage, as well as the final bearing capacity of the sample;

[0062] Step 6: Calculate the average consolidation settlement rate and average drainage rate based on the number of loading stages, the consolidation settlement rate corresponding to each stage, and the drainage rate.

[0063] Compared with the prior art, the beneficial effects of the combined test method for consolidation settlement and reinforcement effect provided in this embodiment are basically the same as those of the combined test device for consolidation settlement and reinforcement effect provided in Embodiment 1, and will not be described in detail here.

[0064] In order to better guide practical applications with the experimental results, the following steps are included after step 5 above:

[0065] Step 7: Change the thickness of the sand cushion layer 6, the thickness of the clay layer 2, and / or the aperture of the reinforced drainage net 3, and repeat steps 1 to 6 to obtain a process data table consisting of multiple data on the thickness of the sand cushion layer 6, the thickness of the clay layer 2, the aperture of the reinforced drainage net 3, the average consolidation settlement rate, the average drainage rate, and the maximum bearing capacity.

[0066] Step 8: Determine the average consolidation settlement rate, average drainage rate, and maximum bearing capacity according to actual requirements. Then, find the corresponding thickness of the sand cushion layer 6, the thickness of the clay layer 2, and the pore size of the reinforced drainage net 3 in the process data table based on the average consolidation settlement rate, average drainage rate, and maximum bearing capacity for actual construction.

[0067] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A combined experimental device for consolidation settlement and reinforcement effect, characterized in that, Includes a sample chamber, a loading unit, a sample displacement sensor, and a drainage measurement unit; The sample chamber has drainage holes on its side wall, which are connected to a drainage measurement unit. The sample is placed in the sample chamber and consists of a sand cushion layer, a reinforced drainage net, and a clay layer stacked from top to bottom. The loading unit and the sample displacement sensor are both in contact with the upper surface of the sand cushion layer. The loading unit is used to apply a loading force to the entire sample, and the sample displacement sensor is used to measure the displacement of the upper surface of the sample. The drainage measurement unit includes a drainage sensor, a timing controller, and a timer. The sensing end of the drainage sensor is located in the guide pipe. During loading, the drainage sensor monitors the water flow rate in the guide pipe in real time. If water flows through, the timing controller controls the timer to start and calculates the drainage time. If the water flow rate in the guide pipe is measured to be zero, the timing controller controls the timer to stop and records the time measured by the timer. The reinforced drainage mesh is located below the lower edge of the drainage hole; The sample chamber is a cylindrical body with a diameter of 650-800 mm and a height of not less than 1200 mm; the ratio of the diameter of the drain hole to the height of the sample chamber is 1:40-60, and the ratio of the axial length of the drain hole to the inner diameter of the sample chamber is 1:20-60. The loading unit includes an inverted hydraulic cylinder, a load sensor, and a loading plate. The loading plate is placed on the upper surface of the sample. The inverted hydraulic cylinder abuts against the loading plate through the load sensor. The sensing end of the sample displacement sensor contacts the upper surface of the loading plate. The diameter of the loading plate is smaller than the inner diameter of the sample chamber. The combined testing device also includes a clamping rod, a cover plate, and a slide rail. The drainage hole is a vertically elongated strip. The cover plate covers the drainage hole and has a circular hole. The inlet end of the circular hole is connected to the sample chamber cavity through the drainage hole, and the outlet end of the circular hole is connected to the drainage measurement unit. The diameter of the circular hole is smaller than the vertical length of the drainage hole. One end of the clamping rod clamps a reinforced drainage net, and the other end of the clamping rod is fixedly connected to the cover plate. The cover plate has a groove on the side facing the sample chamber that cooperates with the slide rail.

2. The combined test apparatus for consolidation settlement and reinforcement effect according to claim 1, characterized in that, The loading plate is circular in shape, and its diameter is smaller than the inner diameter of the sample chamber.

3. The combined test apparatus for consolidation settlement and reinforcement effect according to claim 1, characterized in that, The sample chamber, loading unit, and sample are arranged coaxially.

4. The combined test apparatus for consolidation settlement and reinforcement effect according to claim 1, characterized in that, The drainage measurement unit also includes a guide pipe and a measuring cylinder that are connected in sequence to the drainage hole.

5. The combined test apparatus for consolidation settlement and reinforcement effect according to claim 4, characterized in that, It also includes a filter screen, which is located at the water inlet end of the guide pipe, and the sample chamber is connected to the guide pipe through the filter screen.

6. The combined test apparatus for consolidation settlement and reinforcement effect according to claim 5, characterized in that, The mesh size of the filter screen is smaller than the smallest particle size in the sand cushion layer.

7. The combined test apparatus for consolidation settlement and reinforcement effect according to claim 1, characterized in that, The number of drainage holes is multiple, and the multiple drainage holes are evenly arranged along the axial direction of the sample chamber.

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