Top and bottom double force structure ball-type penetration instrument device and vertical consolidation coefficient testing method

Abstract

The application relates to the technical field of soil parameter detection, in particular to a top-and-bottom double-force-structure ball-type penetration instrument device and a vertical consolidation coefficient testing method. The device comprises a loading probe rod and a spherical probe, the spherical probe comprises a middle spherical instrument and a lower spherical instrument, the middle spherical instrument and the lower spherical instrument form a sphere, the middle spherical instrument is located above the lower spherical instrument, the top of the middle spherical instrument is provided with an upper force measuring mechanism, and the bottom of the middle spherical instrument and the lower spherical instrument are connected through a lower force measuring mechanism; a signal transmission cable penetrates through the middle spherical instrument, and the signal connection of the upper force measuring mechanism and the lower force measuring mechanism is realized. The measured penetration resistance value is stable and high in precision, the vertical consolidation coefficient of soil can be measured, the measurement cost is greatly reduced, and the operation time is shortened.

Description

Technical Field

[0001] This invention relates to the field of soil parameter detection technology, and in particular to a top-and-bottom dual-force-measuring spherical penetrator device and a method for testing the vertical consolidation coefficient. Background Technology

[0002] Structural soft soils are widely distributed in coastal and lacustrine sedimentary areas. Due to the significant disturbance during sampling, sampling test indicators cannot reflect in-situ characteristics. Therefore, developing high-precision in-situ testing methods is crucial for accurately evaluating the parameters of this type of soil. The consolidation coefficient is an important parameter in geotechnical engineering design, divided into horizontal and vertical consolidation coefficients. The vertical consolidation coefficient is a key parameter for calculating foundation settlement. Domestic and international scholars have conducted relevant theoretical and experimental research on in-situ testing methods for the consolidation coefficient. The spherical probe has advantages over traditional cone-shaped static penetration probes, including higher sensitivity, no need for stress correction, and a larger penetration area, making it more suitable for soft soil measurement. Developing a method for evaluating the consolidation coefficient of structural soft soil based on the spherical probe has significant engineering value.

[0003] Existing spheroidometers equipped with pore pressure sensors have the following drawbacks:

[0004] (1) Since the consolidation process is also a pore pressure dissipation process, the existing in-situ test methods for the consolidation coefficient are all based on the spherical instrument with added pore pressure sensor. However, the accuracy of the pore pressure dissipation test results depends on the saturation effect of the permeable ring. The permeable ring needs to be saturated after one use. The saturation process usually takes at least 12 hours (the saturation effect is judged by the pore pressure response detection. If the saturation effect is not up to standard, it needs to be saturated again), which increases the operation time and labor cost.

[0005] (2) Pore pressure sensors are more easily damaged than pressure sensors, and the cost of a pore pressure sensor with the same accuracy is more than 10 times that of a pressure sensor.

[0006] (3) In order to protect the pore pressure sensor, the pore pressure sensor is usually set at the equator. However, the consolidation at the equator is mainly horizontal dissipation consolidation, so the inversion result is the horizontal consolidation coefficient. However, for problems such as foundation settlement, the vertical consolidation coefficient is the result that is needed. At present, the horizontal consolidation coefficient is mainly converted into the vertical consolidation coefficient through theoretical conversion formula. The ratio of the horizontal consolidation coefficient to the vertical consolidation coefficient is generally between 3.5 and 10. The coefficients in the conversion formula depend on multiple soil parameters, and it is difficult to determine the coefficients in the conversion formula in actual operation.

[0007] In summary, existing pore pressure spherical testers suffer from problems such as long operating time, large saturation workload, easy damage to pore pressure sensors, high cost of pore pressure sensors, test results being horizontal consolidation coefficients, uncertain conversion formula coefficients, and unsuitability for aerated soils. Summary of the Invention

[0008] The purpose of this invention is to overcome the above-mentioned defects in the existing technology and to propose a double-bottom double-force-measuring spherical penetrator device and a method for testing the vertical consolidation coefficient. The penetrating resistance value measured by the invention is stable and highly accurate, and the vertical consolidation coefficient of the soil can be measured, which greatly reduces the measurement cost and shortens the operation time.

[0009] The technical solution of this invention is: a spherical penetrator device with a double-bottom, double-force-measuring structure, comprising a loading probe and a spherical probe, wherein,

[0010] The spherical probe consists of a middle spherical probe and a lower spherical probe, which together form a sphere. The middle spherical probe is located above the lower spherical probe. The top of the middle spherical probe is equipped with an upper force measuring mechanism, and the bottom of the middle spherical probe and the lower spherical probe are connected through the lower force measuring mechanism.

[0011] The signal transmission cable runs through the middle spherical instrument, enabling signal connection between the upper force measuring mechanism and the lower force measuring structure.

[0012] In this invention, the upper force measuring mechanism includes a first pressure sensor, and the first pressure sensor is provided with several strain gauges;

[0013] The bottom surface of the first pressure sensor is fixed with a first connecting thread.

[0014] The top of the central spherical instrument is provided with a groove, the first pressure sensor is disposed in the groove, and the first connecting thread is threadedly connected to the top of the central spherical instrument.

[0015] The lower force measuring mechanism includes a second pressure sensor, which contains several strain gauges.

[0016] The top surface of the second pressure sensor is fixed with a second connecting thread, and the bottom surface of the second pressure sensor is fixed with a third connecting thread.

[0017] The bottom of the central spherical instrument is provided with a groove, the second pressure sensor is installed in the groove, the second connecting thread is threaded to the bottom of the central spherical instrument, and the third connecting thread is threaded to the lower spherical instrument, thereby realizing a fixed connection between the central spherical instrument and the lower spherical instrument.

[0018] The coaxial cable passes sequentially through the through hole in the first connecting thread, the wiring hole at the center of the spherical instrument, and the through hole in the second connecting thread to connect the first pressure sensor and the second pressure sensor.

[0019] The loading probe is equipped with a signal transmission cable, and the first pressure sensor is connected to the signal transmission cable.

[0020] The loading probe is fixedly connected to the top surface of the first pressure sensor.

[0021] The present invention also includes a method for testing the vertical consolidation coefficient using the above-mentioned double-bottom, double-force-measuring spherical penetrator device, comprising the following steps:

[0022] S1, press the spherical probe into the test soil at a uniform speed;

[0023] S2, the first pressure sensor at the top of the spherical probe obtains the penetration resistance q1 during the penetration test, and the test result of the second pressure sensor is q2. After the spherical probe stops penetrating, the pressure dissipation of the test soil is tested through the second pressure sensor.

[0024] S3, normalize the penetration resistance to obtain the curve between the dissipation percentage C and the dissipation time t;

[0025] S4, normalizes the time:

[0026] Obtain the dissipation percentage C and the normalized time T * The curves between the two soil types, after being normalized by the penetration time, completely overlap the penetration resistance dissipation curves of different soil types.

[0027] S5. Based on the dissipation percentage C detected in the actual production environment, substitute it into the C-t curve in step S3 to obtain the corresponding dissipation time t, and then substitute it into the CT obtained in step S4. * The curve yields the corresponding normalized time T. * Substituting the value of into formula (3), we obtain the vertical consolidation coefficient c in the actual production environment. v :

[0028]

[0029] The data recorded in step S1 is processed into a data format where the vertical axis represents the dissipation percentage C and the horizontal axis represents time t. The expression for the dissipation percentage C is as follows:

[0030]

[0031] Where, q 2ini q represents the initial penetration resistance; 2sta This represents the penetration resistance when entering the stable phase, achieving normalization of the penetration resistance.

[0032] The vertical consolidation coefficient c of different soils obtained through one-dimensional consolidation tests v * The penetration time was normalized using formula (2) respectively.

[0033]

[0034] Among them, T * Here, t represents the normalized time, t represents the dissipation time, and r represents the radius of the spherical probe.

[0035] The beneficial effects of this invention are:

[0036] Based on the principle that the force acting on the structure decreases during the consolidation process of porous media in the process of pore pressure dissipation, this application proposes a spherical instrument with a lower force measuring structure. This application overcomes the problems and limitations of existing pore pressure sensor probes, such as saturation, easy wear and tear and low testing accuracy of pore pressure sensors, the fact that pore pressure sensors are only suitable for fully saturated soils, and the fact that existing structures can only test the horizontal consolidation coefficient. The device structure and vertical consolidation coefficient testing method proposed in this application can be applied to the vertical consolidation coefficient testing of various soils, providing a reference for the prediction of settlement of marine gas-bearing soil foundations.

[0037] Indoor model tests were conducted using the apparatus and method proposed in this application. The test results show that the penetration resistance data obtained by the apparatus is stable and accurate, and has good value for promotion and application.

[0038] This device can achieve the same measurement accuracy as existing spheroidometers, and its cost is significantly reduced compared to existing spheroidometers.

[0039] During the measurement experiment using this device, there is no need for saturation operation, which greatly shortens the operation time.

[0040] The vertical consolidation coefficient of soil can be measured using this device and method. Attached Figure Description

[0041] Figure 1 This is a cross-sectional structural schematic diagram of a spherical penetrator with a top and bottom dual force measuring structure;

[0042] Figure 2 This is a schematic diagram of the upper force measuring mechanism;

[0043] Figure 3 This is a schematic diagram of the lower force-measuring mechanism;

[0044] Figure 4 The curves show the indoor penetration test results of the second sensor in the lower force measuring mechanism for standard kaolin and air-containing kaolin.

[0045] Figure 5 This is the curve obtained after normalizing the penetration resistance of the second pressure sensor.

[0046] Figure 6 This curve is obtained after time normalization of the second pressure sensor.

[0047] In the diagram: 1. Signal transmission cable; 2. Probe; 3. Connecting rod; 4. First pressure sensor; 5. First connecting thread; 7. Wiring hole; 8. Second connecting thread; 9. Second pressure sensor; 10. Third connecting thread; 11. Top groove; 12. Middle spheroidizer; 13. Coaxial cable; 14. Bottom groove; 15. Lower spheroidizer; 17. First strain gauge; 18. Second strain gauge; 21. Third strain gauge; 22. Fourth strain gauge. Detailed Implementation

[0048] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0049] Specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many ways other than those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0050] like Figures 1 to 3 As shown, the spherical penetrator device with a top and bottom dual force measuring structure according to the present invention includes a loading probe, a spherical probe, an upper force measuring structure, and a lower force measuring mechanism. The upper force measuring mechanism is located at the top of the spherical probe, and the lower force measuring mechanism is located at the bottom of the spherical probe.

[0051] The spherical probe includes a middle spherical probe 12 and a lower spherical probe 15, which together form a sphere. The middle spherical probe 12 is located above the lower spherical probe 15. An upper force-measuring mechanism is provided on the top of the middle spherical probe 12, and the bottom of the middle spherical probe 12 is connected to the lower spherical probe 15 via the lower force-measuring mechanism. In this embodiment, the diameter of the top surface of the lower spherical probe 15 is 3 / 4 of the diameter of the upper spherical probe 12.

[0052] The loading probe includes a probe 2 and a connecting shaft 3. One end of the connecting shaft 3 is fixedly connected to the probe 2, and the other end of the connecting shaft 3 is connected to the central spherical instrument 12.

[0053] The upper force measuring mechanism includes a first pressure sensor 4, which is a strain gauge pressure sensor. Therefore, the first pressure sensor 4 has several strain gauges inside. During the pressure test, the strain gauges will generate corresponding strain deformation. The first pressure sensor 4 measures the penetration resistance based on the deformation of the strain gauges. In this embodiment, the first pressure sensor 4 has two strain gauges inside, including a first strain gauge 17 and a second strain gauge 18.

[0054] The top of the central spherical shape measuring instrument 12 is provided with a top groove 11, and the first pressure sensor 4 is located in the top groove 11. The bottom of the first pressure sensor 4 is fixedly connected to the first connecting thread 5, and the first connecting thread 5 is fixedly connected to the central spherical shape measuring instrument 12 by means of a threaded connection. Therefore, the first pressure sensor 4 is fixedly connected to the central spherical shape measuring instrument 12 through the first connecting thread 5.

[0055] The lower force measuring mechanism includes a second pressure sensor 9, which is a strain gauge pressure sensor. Therefore, the second pressure sensor 9 has several strain gauges inside. During the pressure test, the strain gauges will generate corresponding strain deformation. The second pressure sensor 9 measures the penetration resistance based on the deformation of the strain gauges. In this embodiment, the second pressure sensor 9 has two strain gauges inside, including a third strain gauge 21 and a fourth strain gauge 22.

[0056] The bottom of the central spherical probe 12 has a bottom groove 14, and the second pressure sensor 9 is located in the bottom groove 14. The top of the second pressure sensor 9 is fixedly connected to the second connecting thread 8, and its bottom is fixedly connected to the third connecting thread 3. The second connecting thread 8 is fixedly connected to the central spherical probe 12 by a threaded connection, and the third connecting thread 3 is fixedly connected to the lower spherical probe 15 by a threaded connection. Therefore, the second pressure sensor 9 is fixedly connected to the central spherical probe 12 by the second connecting thread 8, and the second pressure sensor 9 is fixedly connected to the lower spherical probe 15 by the third connecting thread 3.

[0057] In this application, the resistance values ​​measured by the first pressure sensor 4 and the second pressure sensor 9 are transmitted through the signal transmission cable 1. The signal transmission cable 1 passes through the probe rod 2, connects the thin rod 3 and the central spherical probe 12, and during the passage process, it achieves the connection between the signal transmission cable 1 and the first pressure sensor 4, as well as the connection between the signal transmission cable 1 and the second pressure sensor 9.

[0058] In this embodiment, the probe rod 2 and the connecting rod 3 are provided with through holes. The signal transmission cable 1 passes through the through holes in the probe rod 2 and the connecting rod 3 and is electrically connected to the first pressure sensor 4.

[0059] Both the first connecting thread 5 and the second connecting thread 8 have through holes, and the central spheroidizer 12 has a wiring hole 7 in the middle. One end of the coaxial cable 13 is connected to the first pressure sensor 4, passes through the through hole of the first connecting thread 5, and sequentially passes through the wiring hole 7 in the middle of the central spheroidizer 12 and the through hole in the second connecting thread 8 to be electrically connected to the second pressure sensor 9.

[0060] The resistance values ​​measured by the first pressure sensor 4 and the second pressure sensor 9 are output through the signal transmission cable 1, and the resistance values ​​are then processed.

[0061] Under constant deformation conditions, the force acting on the structure gradually decreases during the soil consolidation process. Therefore, the change in force corresponds to the consolidation process, and the consolidation coefficient can be inferred from the force-time curve. During the soil consolidation process, the forces acting on both the upper and lower parts of the full-flow spherical probe show a decreasing trend. Therefore, this device is equipped with a lower pressure sensor to measure the decrease in vertical pressure over time.

[0062] This application also includes a method for testing the vertical consolidation coefficient using the above-described apparatus, the method comprising the following steps.

[0063] The first step is to install the spherical probe in the device on the loading probe rod according to the test requirements, and then press the spherical probe into the soil at a uniform speed.

[0064] In this step, different test soils are selected, and the spherical probe is pressed into each soil at a uniform speed. In this embodiment, two different test soils are selected, including standard kaolin and aerated kaolin.

[0065] The second step involves obtaining the penetration resistance q1 during the full-flow penetration test using the first pressure sensor 4 at the top of the spherical probe. During this process, the second pressure sensor 9 measures q2, thus determining the vertical stress Δσ of the soil layer during penetration. v =1.78q2-q1.

[0066] After the spherical probe stops penetrating, the pressure dissipation is tested using the second pressure sensor 9. Figure 4 The results are from the test of the second pressure sensor.

[0067] The third step is to normalize the penetration resistance.

[0068] The data recorded in the second step is processed into a data format where the vertical axis represents the dissipation percentage C and the horizontal axis represents time t. The expression for the dissipation percentage C is as follows:

[0069]

[0070] Where, q 2ini q represents the initial penetration resistance; 2sta This represents the penetration resistance when entering the steady-state phase; this process is commonly referred to as penetration resistance normalization. Figure 4 The standard kaolin curve and the gas-bearing kaolin curve were successively normalized for penetration resistance using formula (1), and the resulting Ct curve is shown below. Figure 5 As shown.

[0071] The fourth step is to normalize the penetration time.

[0072] The standard kaolin curve and the vertical consolidation coefficient c of air-bearing kaolin obtained through one-dimensional consolidation tests will be used. v * The penetration time was normalized using formula (2) respectively.

[0073]

[0074] Among them, T * represents the normalized time; t represents the dissipation time, where t gradually increases at a frequency of 0.01s; r represents the radius of the spherical probe.

[0075] The result obtained after time normalization is as follows Figure 6 As shown in the figure, the penetration resistance dissipation curves of aerated kaolin and standard kaolin completely overlap after time normalization. The complete overlap of the penetration resistance dissipation curves for different soil types indicates the reliability of the proposed treatment method.

[0076] The fifth step is to combine the dissipation percentage C obtained in the fourth step with the normalized time T. * The curve relationship between them is applied to the actual production environment. Based on the dissipation percentage C detected in the actual production environment, the CT obtained in step four is used... * The curve relationship yields the corresponding normalized time T. * The value of the dissipation time t is obtained by using the Ct curve relationship obtained in step three.

[0077] The obtained normalized time T * Substituting the dissipation time t into the following formula (3), the vertical consolidation coefficient c in the actual production environment is calculated. v .

[0078]

[0079] The foregoing has provided a detailed description of the top-and-bottom dual-force-measuring spherical penetrator device and the vertical consolidation coefficient testing method provided by this invention. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from the principles of this invention, and these improvements and modifications also fall within the protection scope of the claims of this invention. The above description of the disclosed embodiments enables those skilled in the art to implement or use this invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of this invention. Therefore, this invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A spherical penetrator device with a top and bottom dual force measuring structure, comprising a loading probe and a spherical probe, characterized in that, The spherical probe consists of a middle spherical probe and a lower spherical probe, which together form a sphere. The middle spherical probe is located above the lower spherical probe. The top of the middle spherical probe is equipped with an upper force measuring mechanism, and the bottom of the middle spherical probe and the lower spherical probe are connected through the lower force measuring mechanism. The signal transmission cable runs through the middle spherical instrument to realize the signal connection between the upper force measuring mechanism and the lower force measuring structure; The upper force measuring mechanism includes a first pressure sensor, and the loading probe is fixedly connected to the top surface of the first pressure sensor. The first pressure sensor is equipped with several strain gauges. The penetration resistance of the full-flow penetration test during the penetration process is tested through the first pressure sensor. The lower force measuring mechanism includes a second pressure sensor, which contains several strain gauges. After the spherical probe stops penetrating, the pressure dissipation is tested through the second pressure sensor.

2. The spherical penetrator device with a top and bottom dual force measuring structure according to claim 1, characterized in that, The bottom surface of the first pressure sensor is fixed with a first connecting thread.

3. The spherical penetrator device with a top and bottom dual force measuring structure according to claim 2, characterized in that, The top of the central spherical instrument is provided with a groove, the first pressure sensor is disposed in the groove, and the first connecting thread is threadedly connected to the top of the central spherical instrument.

4. The spherical penetrator device with a top and bottom dual force measuring structure according to claim 1, characterized in that, The top surface of the second pressure sensor is fixed with a second connecting thread, and the bottom surface of the second pressure sensor is fixed with a third connecting thread.

5. The spherical penetrator device with a top and bottom dual force measuring structure according to claim 4, characterized in that, The bottom of the central spherical instrument is provided with a groove, the second pressure sensor is installed in the groove, the second connecting thread is threaded to the bottom of the central spherical instrument, and the third connecting thread is threaded to the lower spherical instrument, thereby realizing a fixed connection between the central spherical instrument and the lower spherical instrument.

6. The spherical penetrator device with a top and bottom dual force measuring structure according to claim 5, characterized in that, The coaxial cable passes sequentially through the through hole in the first connecting thread, the wiring hole in the center of the spherical instrument, and the through hole in the second connecting thread to connect the first pressure sensor and the second pressure sensor. The loading probe is equipped with a signal transmission cable, and the first pressure sensor is connected to the signal transmission cable.

7. A method for testing the vertical consolidation coefficient using the top-bottom dual-force-measuring spherical penetrator device as described in any one of claims 1-6, characterized in that, Includes the following steps, S1, press the spherical probe into the test soil at a uniform speed; S2, the first pressure sensor at the top of the spherical probe obtains the penetration resistance during the test penetration process. The test results of the second pressure sensor are as follows: After the spherical probe stops penetrating, the pressure dissipation of the test soil is tested by the second pressure sensor. S3, normalize the penetration resistance to obtain the curve between the dissipation percentage C and the dissipation time t; S4, normalizes the penetration time: Obtain the dissipation percentage C and normalized time. The curves between the two soil types, after being normalized by the penetration time, completely overlap the penetration resistance dissipation curves of different soil types. S5. Based on the dissipation percentage C detected in the actual production environment, substitute it into the Ct curve obtained in step S3 to obtain the corresponding dissipation time t, and then substitute it into the value obtained in step S4. The curve yields the corresponding normalized time. Substituting the numerical value into formula (3), we obtain the vertical consolidation coefficient in the actual production environment. : （3） r represents the radius of the spherical probe.

8. The method according to claim 7, characterized in that, The data recorded in step S2 is processed into a data format where the vertical axis represents the dissipation percentage C and the horizontal axis represents time t. The expression for the dissipation percentage C is as follows: （1）； in, Indicates the initial penetration resistance; This represents the penetration resistance when entering the stable phase, achieving normalization of the penetration resistance.

9. The method according to claim 7, characterized in that, Vertical consolidation coefficients of different soils obtained through one-dimensional consolidation tests Formula (2) is used respectively. The penetration time was normalized. (2); in, Here, t represents the normalized time, t represents the dissipation time, and r represents the radius of the spherical probe.

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