Performance test method for soft soil foundation
By setting up reinforced drainage nets and drainage holes in the sample chamber, the drainage rate and consolidation settlement rate of soft soil foundation were measured, which solved the problem that existing technologies could not measure them simultaneously, and achieved efficient consolidation drainage control and data measurement.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-25
- Publication Date
- 2026-04-10
AI Technical Summary
Existing technologies cannot simultaneously measure the drainage rate and reinforcement effect of soft soil foundations, and traditional methods suffer from problems such as long consolidation time and uncontrollable drainage direction.
A reinforced drainage net and drainage holes were set up in the sample chamber. Force was applied by the loading unit to consolidate the clay layer. The drainage rate and consolidation settlement rate were measured by the reinforced drainage net and drainage holes. Data were obtained by combining displacement sensors and drainage measurement units.
It significantly improves the efficiency of consolidation drainage, and can simultaneously measure the average consolidation settlement rate, drainage rate and final bearing capacity, thereby improving the efficiency and accuracy of the test.
Smart Images
Figure CN121830246A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of indoor geotechnical testing technology, and in particular relates to a performance testing method for soft soil foundations. Background Technology
[0002] In soft soil foundation treatment, horizontal sand cushion layers are often laid. Although this method can promote drainage consolidation and 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. Therefore, the consolidation effect is not significant in large-scale applications. Composite geogrids can provide unobstructed drainage paths for the soil, significantly improving consolidation and drainage efficiency.
[0003] Traditional performance tests for soft soil foundations can only measure the consolidation settlement rate, and cannot simultaneously measure the drainage rate and reinforcement effect. Summary of the Invention
[0004] Based on the above analysis, the present invention aims to provide a performance testing method for soft soil foundations to solve the problem in the prior art that it is impossible to simultaneously measure the drainage rate and reinforcement effect of soft soil foundations.
[0005] The objective of this invention is mainly achieved through the following technical solutions:
[0006] This invention provides a performance testing method for soft soil foundations, comprising the following steps:
[0007] Step 1: Fill the sample chamber with the clay layer, reinforced drainage net and sand cushion layer from the actual project in sequence to obtain the sample. Then, bring the loading unit and the sample displacement sensor into contact with the upper surface of the sand cushion layer.
[0008] Step 2: Turn on the loading unit. The loading unit applies and maintains the loading force on the sample. The sand cushion layer and clay layer are compacted. The clay layer is consolidated. Water in the clay layer seeps out from the clay layer and is discharged into the drainage measurement unit through the drainage holes opened in the side wall of the sample chamber along the reinforced 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.
[0009] 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.
[0010] Step 4: Increase the loading force of the loading unit, repeat steps 2 to 3, and perform graded loading on the sample until the sand cushion layer is destroyed;
[0011] Step 5: Obtain the consolidation settlement rate and drainage rate corresponding to each stage, as well as the final bearing capacity of the sample;
[0012] 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.
[0013] Furthermore, step 5 is followed by the following steps:
[0014] Step 7: Change the thickness of the sand cushion layer, the thickness of the clay layer, and / or the aperture of the reinforced drainage net, and repeat steps 1 to 6 to obtain a process data table consisting of multiple data on the thickness of the sand cushion layer, the thickness of the clay layer, the aperture of the reinforced drainage net, the average consolidation settlement rate, the average drainage rate, and the maximum bearing capacity.
[0015] Furthermore, in step 4, 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.
[0016] Furthermore, the diameter of the sample is not less than 600 mm, and the height of the sample is not less than 1200 mm.
[0017] Furthermore, the diameter of the sample is 650–800 mm, and the height of the sample is 1200–1500 mm.
[0018] Furthermore, the ratio of the diameter of the drainage hole to the height of the sample is 1:40 to 60.
[0019] Furthermore, the ratio of the axial length of the drainage hole to the diameter of the sample is 1:20 to 60.
[0020] Furthermore, the reinforced drainage mesh is located below the lower edge of the drainage hole.
[0021] Furthermore, the distance between the reinforced drainage net and the lower edge of the drainage hole is 10mm to 20mm.
[0022] Furthermore, there are multiple drainage holes, drainage volume measuring units, and displacement sensors; each drainage hole, drainage volume measuring unit, and displacement sensor corresponds to another.
[0023] Compared with the prior art, the present invention can achieve at least the following beneficial effects:
[0024] The performance testing method for soft soil foundations provided by this invention is simple to operate. By setting a reinforced drainage net between the sand cushion layer and the clay layer, and setting corresponding drainage holes at the positions corresponding to the reinforced drainage net, water in the clay layer seeps out from the clay layer and flows along the reinforced drainage net through the drainage holes opened in the side wall of the sample chamber to the drainage measurement unit. This allows for better control of the drainage direction of the clay layer, significantly improving the consolidation drainage efficiency. At the same time, the average consolidation settlement rate, average drainage rate, and final bearing capacity are measured, thereby improving the test efficiency.
[0025] 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
[0026] 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.
[0027] Figure 1 This is a front view of the performance testing apparatus used in the performance testing method for determining soft soil foundations provided in Embodiment 1 of the present invention.
[0028] Figure 2 This is a top view of the performance testing apparatus used in the performance testing method for determining soft soil foundations provided in Embodiment 1 of the present invention.
[0029] Figure 3 This is a schematic diagram of the first structure of the adjustable drainage hole in the test method for determining the performance of soft soil foundation provided in Embodiment 1 of the present invention;
[0030] Figure 4 This is a schematic diagram of the second structure of the adjustable drainage hole in the test method for determining the performance of soft soil foundation provided in Embodiment 1 of the present invention;
[0031] Figure 5 This is a flowchart of a test method for determining the performance of soft soil foundations provided in Embodiment 1 of the present invention.
[0032] Figure label:
[0033] 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
[0034] 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.
[0035] Example 1
[0036] This embodiment provides a performance testing method for soft soil foundations. (See also...) Figure 5 It includes the following steps:
[0037] 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.
[0038] Step 2: The loading unit is turned on. 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 undergoes consolidation settlement. The water in the clay layer 2 seeps out from the clay layer 2 and is discharged into the drainage measurement unit through the drainage hole 4 opened in the side wall of the sample chamber 1 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).
[0039] The reinforced drainage mesh 3 is located below the lower edge of the drainage hole 4. For example, the distance between the reinforced drainage mesh 3 and the lower edge of the drainage hole 4 is 10mm to 20mm.
[0040] 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.
[0041] 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.
[0042] 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;
[0043] Step 5: Obtain the consolidation settlement rate and drainage rate corresponding to each stage, as well as the final bearing capacity of the sample;
[0044] 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.
[0045] Compared with the prior art, the performance test method for soft soil foundation provided in this embodiment is simple to operate. By setting a reinforced drainage net 3 between the sand cushion layer 6 and the clay layer 2, and setting corresponding drainage holes 4 at the positions corresponding to the reinforced drainage net 3, water in the clay layer 2 seeps out from the clay layer 2 and is discharged into the drainage measurement unit through the drainage holes 4 opened on the side wall of the sample chamber 1 along the reinforced drainage net 3. This allows for better control of the drainage direction of the clay layer 2, significantly improving the consolidation drainage efficiency. At the same time, the average consolidation settlement rate, average drainage rate, and final bearing capacity are measured, thereby improving the test efficiency.
[0046] In order to better guide practical applications with the experimental results, the following steps are included after step 6 above:
[0047] 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.
[0048] 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.
[0049] To effectively reduce the size effect of the specimens, for example, the diameter of the specimens is not less than 600 mm (e.g., 650–800 mm), and the height of the specimens is not less than 1200 mm (e.g., 1200–1500 mm). This allows for a larger specimen size to better reflect the drainage consolidation state of the specimen in actual engineering, effectively reducing the size effect and making the indoor test results obtained by the above-mentioned soft soil foundation performance testing method more accurate and valuable for reference.
[0050] 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 is 1:40 to 60, and the ratio of the axial length of the drainage hole 4 to the diameter of the sample is 1:20 to 60.
[0051] For example, the structure of the soft soil foundation performance testing device used in the above-mentioned soft soil foundation performance testing method is as follows:
[0052] See Figures 1 to 2 The performance testing device for soft soil foundation includes a sample chamber 1 (e.g., a cylindrical body of tempered glass), a loading unit, a sample displacement sensor 8, and a drainage measurement unit. Drainage holes 4 are opened on the side wall of the sample chamber 1 and are connected to the drainage measurement unit. The sample is placed in the sample chamber 1 and 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.
[0053] To facilitate drainage of the drainage holes 4, there are multiple drainage holes 4, for example, 4 to 6. The multiple drainage holes 4 are evenly arranged along the axial direction of the sample chamber 1. Correspondingly, there are also multiple drainage measurement units. The drainage holes 4 correspond one-to-one with the drainage measurement units. When calculating the drainage volume in the subsequent process, the total drainage volume measured by the multiple drainage measurement units is calculated, which is the total drainage volume of the sample.
[0054] Accordingly, there are multiple displacement sensors, each corresponding to a drain hole 4, and the displacement sensors are located above the drain holes 4.
[0055] 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.
[0056] In order to improve the accuracy of the above-mentioned performance test method for soft soil foundation, 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.
[0057] 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.
[0058] 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.
[0059] In order to obtain a more accurate drainage time and improve the accuracy of drainage rate calculation, the drainage measurement unit also 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 the loading process of the loading unit applying the loading force, the drainage sensor 12 monitors the water flow in the guide pipe 13 in real time. If water flows through, the timing controller controls the timer 11 to start and start calculating the drainage time. If the water flow in the guide pipe 13 is measured to be zero, the timing controller controls the timer 11 to turn off and records the time measured by the timer 11.
[0060] This is because, in the existing technology, the starting point of drainage is usually determined by human subjective judgment and the timer 11 is manually turned on. This obviously affects the accuracy of drainage time measurement. In this embodiment, by setting a drainage sensor 12 and a timer controller, the drainage sensor 12 senses whether water flows through and the timer controller controls the timer 11 to turn on, thereby realizing automatic control of drainage time measurement, reducing the influence of human subjective factors and improving the accuracy of drainage time measurement.
[0061] 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 above-mentioned soft soil foundation performance test device 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.
[0062] 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:
[0063] The first method, see [link / reference] Figure 3 The aforementioned soft soil foundation performance testing device also includes a clamping rod 20, a cover plate 15, and a slide rail. The drainage hole 4 is a vertically elongated strip. The cover plate 15 covers the drainage hole 4 and has a circular plate hole 19. 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, and 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 edge of the reinforced drainage net 3, and the other end of the clamping rod 20 is fixedly connected to the cover plate 15. A slide groove is opened on the side of the cover plate 15 facing the sample chamber 1, and the slide rail is inserted into the slide groove and cooperates with the slide groove.
[0064] In practice, the cover plate 15 is fixedly connected to the edge of the reinforced drainage net 3 by the clamping rod 20, so that the two can move synchronously. When the position of the reinforced drainage net 3 drops, the clamping rod 20 will drive the cover plate 15 to drop. Correspondingly, the position of the circular plate hole 19 will also drop. Since the drainage hole 4 is a vertically set elongated strip, the circular plate hole 19 can still be connected to the drainage hole 4 at this time, so as to achieve the adjustment of the drainage position while ensuring smooth drainage.
[0065] 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.
[0066] The second method, see Figure 4 The aforementioned soft soil foundation performance testing device 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 vertically elongated strip. The cover plate 15 covers the drainage hole 4 and has a circular plate hole 19. The water inlet of the circular plate hole 19 is connected to the inner cavity of the sample chamber 1 through the drainage hole 4, and the water outlet 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 is provided on the side of the cover plate 15 away from the sample chamber 1. The rack 18 meshes with the gear 17, and the gear 17 is fixedly connected to the output shaft of the drive motor.
[0067] 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.
[0068] Specifically, the vertical length of the drain hole 4 is 300-500mm, and the diameter of the circular plate hole 19 is 20-35mm.
[0069] 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 performance testing method for soft soil foundations, characterized in that, Includes the following steps: Step 1: Fill the sample chamber with the clay layer, reinforced drainage net and sand cushion layer from the actual project in sequence to obtain the sample. Then, bring the loading unit and the sample displacement sensor into contact with the upper surface of the sand cushion layer. Step 2: Activate the loading unit. The loading unit applies and maintains the loading force on the sample. The sand cushion layer and clay layer are compacted. The clay layer is consolidated. Water in the clay layer seeps out from the clay layer and is discharged into the drainage measurement unit through the drainage holes opened in the side wall of the sample chamber along the reinforced 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. 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. Step 4: Increase the loading force of the loading unit, repeat steps 2 to 3, and perform graded loading on the sample until the sand cushion layer is destroyed; Step 5: Obtain the consolidation settlement rate and drainage rate corresponding to each stage, as well as the final bearing capacity of the sample; 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.
2. The performance testing method for soft soil foundation according to claim 1, characterized in that, Following step 6, the following steps are also included: Step 7: Change the thickness of the sand cushion layer, the thickness of the clay layer, and / or the aperture of the reinforced drainage net, and repeat steps 1 to 6 to obtain a process data table consisting of multiple data on the thickness of the sand cushion layer, the thickness of the clay layer, the aperture of the reinforced drainage net, the average consolidation settlement rate, the average drainage rate, and the maximum bearing capacity.
3. The performance testing method for soft soil foundation according to claim 1, characterized in that, In step 4, 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.
4. The performance testing method for soft soil foundation according to claim 1, characterized in that, The diameter of the sample is not less than 600 mm and the height of the sample is not less than 1200 mm.
5. The performance testing method for soft soil foundation according to claim 4, characterized in that, The diameter of the sample is 650-800 mm, and the height of the sample is 1200-1500 mm.
6. The performance testing method for soft soil foundation according to claim 1, characterized in that, The ratio of the diameter of the drainage hole to the height of the sample is 1:40 to 60.
7. The performance testing method for soft soil foundation according to claim 1, characterized in that, The ratio of the axial length of the drainage hole to the diameter of the sample is 1:20 to 60.
8. The performance testing method for soft soil foundation according to claim 1, characterized in that, The reinforced drainage net is located below the lower edge of the drainage hole.
9. The performance testing method for soft soil foundation according to claim 8, characterized in that, The distance between the reinforced drainage net and the lower edge of the drainage hole is 10mm to 20mm.
10. The performance testing method for soft soil foundation according to claim 1, characterized in that, The number of drainage holes, drainage volume measurement units, and displacement sensors are all multiple; The drainage hole, drainage volume measurement unit, and displacement sensor are all in one-to-one correspondence.