A static sounding penetration positioning method and a smart static sounding system

Abstract

The present invention relates to a static penetration positioning method and an intelligent static penetration system, comprising the following steps: S1, test preparation: preparing test soil in a test box; S2, performing the first penetration of the static penetration probe to a depth of z max , obtain the cone tip resistance q c , side wall friction f s and pore water pressure u; S3, determine the radius R of the penetration influence range of the static penetration probe at each depth during penetration I , R I The maximum value is recorded as R0; S4, the second static penetration of the static penetration probe is carried out, the distance from the center of the first penetration position is equal to R0, and the depth is z max , obtain the cone tip resistance q c , side wall friction f s and pore water pressure u; S5, calculate the difference in modified cone tip resistance D(q t ) and the difference between the side wall friction resistance D(f s ); S6, correct R0 to obtain the corrected influence range radius R 修 The intelligent static penetration testing system includes a computer program capable of executing the static penetration testing positioning method.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of geotechnical engineering test and measurement technology, in particular to a static cone penetration positioning method and a smart static cone penetration system. BACKGROUND

[0002] Static cone penetration is a kind of in-situ test technology in geotechnical engineering, which penetrates the probe into the soil layer at a constant rate through static force, and can continuously measure the cone tip resistance, side friction resistance and pore water pressure, thereby reflecting the properties of the soil to be tested. Due to its advantages of convenience, high sensitivity, and the ability to obtain continuous data within the penetration depth range, static cone penetration is also widely used in soil model tests, and is usually used to judge the uniformity of the test soil or detect the changes in the properties of the test soil at different positions. Since the process of static cone penetration probe penetrating into the soil will disturb the soil and change the properties of the soil near the penetration point, an influence range of the static cone penetration probe is formed, which is generally represented by a circular range with the probe as the center, also known as the static cone penetration influence range. In the process of model test, the distance between two adjacent static cone penetration points should be greater than the influence range of the static cone penetration, so as to ensure that the static cone penetration data can truly reflect the properties of the soil and are not affected by the disturbance of adjacent static cone penetration.

[0003] In the prior art, multiple static cone penetration tests with different distances are needed in the uniform test soil, and the minimum distance that ensures the same test results is taken as the influence range by comparing the test results of different distances. However, this method is only theoretically feasible, and there are the following problems in actual implementation: (1) Static cone penetration has high sensitivity, and it is inevitable that the test soil will be uneven during preparation, which will make it difficult to obtain the same results even if the distance between two static cone penetrations is greater than the influence range; (2) The results of static cone penetration are continuous curves of each index (cone tip resistance, side friction resistance, and pore water pressure) changing with depth, and there is currently no objective and unified evaluation standard for whether the curves of two static cone penetrations are consistent. In actual operation, the curves are often compared by visual inspection of the curve shape and comparison of landmark points (such as maximum value and inflection point), which highly depends on the personal experience and subjective consciousness of the researchers, resulting in poor reliability of the results; (3) This method requires multiple static cone penetrations, and there needs to be enough distance between different groups of static cone penetrations to avoid mutual influence, so a lot of space is needed, which leads to the need to prepare test soil again for formal test after determining the influence range, which is time-consuming and labor-intensive, and it is difficult to ensure the consistency of the properties of the test soil in two tests. In summary, the prior art cannot obtain an accurate influence range, and in actual test process, the distance between static cone penetration points is often increased as much as possible to avoid mutual influence, which leads to the inability to finely explore the changes in the properties of the test soil. SUMMARY

[0004] In view of the above-mentioned disadvantages of the prior art, the technical problem to be solved by the present application is to provide a static sounding penetration positioning method and a smart static sounding system, which can automatically and accurately determine a penetration influence range and ensure that different static sounding tests do not affect each other.

[0005] To achieve the above-mentioned purpose, the present application provides a static sounding penetration positioning method, comprising the following steps:

[0006] S1, test preparation: preparing test soil in a test box;

[0007] S2, performing first-time penetration of a static sounding probe in the test soil, with a total penetration depth of z max , obtaining cone tip resistance q c , side friction f s and pore water pressure u measured by the static sounding probe during penetration, and obtaining curves of the three variables changing with the penetration depth z;

[0008] S3, determining the radius R I of the penetration influence range of the static sounding probe at each depth during penetration, obtaining an R I -z curve of the penetration influence range radius R I changing with the penetration depth z, and obtaining the maximum value of R I in the R I -z curve, denoted as the maximum range radius R0;

[0009] S4, performing second-time static sounding penetration of the static sounding probe in the test soil, with the distance between the center of the penetration position and the center of the first-time penetration position being equal to R0, the penetration depth being z max , obtaining cone tip resistance q c , side friction f s and pore water pressure u measured by the static sounding probe during penetration, and obtaining curves of the three variables changing with the penetration depth z;

[0010] S5, calculating the difference degrees D(q t ) and D(f s ) of the corrected cone tip resistances of the static sounding probe in the two-time penetrations, , f s1 and f s2 being the side frictions of the static sounding probe in the first-time and second-time penetrations, q t1 and q t2 being the corrected cone tip resistances of the static sounding probe in the first-time and second-time penetrations; wherein the calculation method of the corrected cone tip resistance of the static sounding probe is , a being the ratio of the cross-sectional area of the pressure sensor in the static sounding probe to the cross-sectional area of the probe;

[0011] S6, correcting R0 to obtain a corrected influence range radius R fix = S f R 0 [ 1 + m D ( q t ) + ( 1- m ) D ( f s ) ] where S f is a safety factor, and m is a weight factor of the tip resistance.

[0012] Further, the method further comprises: S7, performing a standard test operation: performing a static sounding test in the test soil, and the center distance between the penetration positions of any two static sounding probes is not less than R 修 .

[0013] Further, in the step S1, a water layer is injected on the surface of the test soil, the depth of the water layer is 3-5 times the length of the tip of the static sounding probe, and the average particle size d 50 of the test soil is not more than 1 / 20 of the diameter d c of the static sounding probe.

[0014] Further, in the steps S2 and S4, before starting the penetration operation, a small bottle containing water is arranged outside the static sounding probe, so that the static sounding probe is immersed in the water in the small bottle, and the small bottle is removed before penetration into the test soil.

[0015] Further, in the steps S2 and S4, the penetration speed v of the static sounding probe is greater than 30c v / d c , c v is the consolidation coefficient of the test soil, and d c is the diameter of the static sounding probe.

[0016] Further, in the step S3, the calculation formula of R I is:

[0017] R I = d c 2 [ ( q t + p 0 ) ( 1 + sin φ ) c ∗ cos φ ] 1 − sin φ 2 sin φ , ,

[0018] where p0 is the overburden pressure, is the internal friction angle of the test soil, c is the cohesion of the test soil, and q t is the corrected tip resistance of the static sounding probe, and a is the cross-sectional area ratio of the pressure sensor to the probe of the static sounding probe.

[0019] Further, in the step S3, when the test soil is saturated soft clay, the calculation formula of R I is where E is the elastic modulus of the test soil, v is the Poisson's ratio of the test soil, and c is the cohesion of the test soil.

[0020] Further, in the step S6, S fTake 1.1, the test soil is non-cohesive soil, m is 0.7, the test soil is cohesive soil, m is 0.5.

[0021] Further, in the step S1, a test area is set in the test soil and a non-test area outside the test area, and the static sounding probe is penetrated in the non-test area in the steps S2 and S4.

[0022] The application further provides a smart static sounding system, comprising a test box, a static sounding probe, a positioning and penetration mechanism and a control mechanism, the positioning and penetration mechanism is connected with the static sounding probe, can drive the static sounding probe to move in the horizontal direction, and can drive the static sounding probe to penetrate into the test soil in the test box, the sensor in the static sounding probe is connected with the control mechanism in communication, and the detection data of the static sounding probe is acquired by the control mechanism; the control mechanism is connected with the positioning and penetration mechanism in control, and the control mechanism comprises a storage medium, the computer program is stored on the storage medium, and the computer program is executed by the processor to realize the static sounding penetration positioning method.

[0023] As described above, the static sounding penetration positioning method and the smart static sounding system have the following beneficial effects:

[0024] 1. A method for predicting the influence range of static sounding in geotechnical model test, which can accurately determine the penetration influence range of the static sounding probe in the test soil before the formal test, and accurately and reliably design the static sounding penetration point according to the penetration influence range, so as to be as close as possible to each other but avoid mutual influence, and can more finely explore the change of the test soil properties.

[0025] 2. The influence range of the static sounding probe in the test soil can be quickly determined by only two times of static sounding penetration, the whole process is realized by calculation, does not need to be judged by comparing whether the two static sounding curves are consistent, does not need to be highly dependent on the personal experience and subjective judgment of researchers, but provides a clear and quantifiable discrimination method for the static sounding influence range, avoids the influence of subjective factors, and the obtained result has good reliability.

[0026] 3. The required penetration times and space are small, the test soil does not need to be prepared again, time is saved, and errors caused by repeated preparation of the test soil are avoided. DETAILED DESCRIPTION

[0027] fig. 1 It is a flowchart of the static sounding penetration positioning method of the application. DETAILED DESCRIPTION

[0028] The following describes the implementation of the present invention through specific embodiments. People skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0029] See also fig. 1 The present invention provides a static penetration positioning method for determining the penetration influence range of the static penetration probe in the test soil and controlling the spacing of the static penetration points accordingly. The static penetration positioning method includes the following steps:

[0030] S1. Test preparation: Prepare the test soil in the test box.

[0031] The test soil requires uniform properties. Preferably, in this embodiment, a certain amount of water is injected into the test soil surface to form a water layer. The depth of the water layer (the distance from the water surface to the test soil surface) is 3 to 5 times the length of the cone tip of the static penetration probe, with a smaller multiple being used for larger static penetration probes. The purpose of the water layer is to maintain saturation in the soil and probe, preventing air from entering the pore pressure sensor strain chamber after liquid loss from the probe, affecting the probe's saturation and ensuring the accuracy of the pore pressure sensor test data. By providing a surface water layer, the static penetration probe is immersed in water before entering the soil layer, ensuring that no air enters the pore pressure strain chamber, keeping the static penetration probe saturated throughout the penetration process.

[0032] Preferably, the average particle size d of the test soil 50 Not exceeding the diameter d of the static penetration probe c The central area of ​​the test soil is set as the test area for subsequent tests. The test area is sufficiently far from the inner wall of the test chamber to ensure that the test area is not affected by boundary effects. The area outside the test area is the non-test area.

[0033] Preferably, the sensor in the static penetration probe is also calibrated, wherein the sensor in the static penetration probe is used to realize the cone tip resistance q c , side wall friction f s The measurement of pore water pressure u is based on a conventional static penetration probe structure. Its structure and principles are well-known and will not be described in detail. During calibration, the static penetration probe is placed in water and saturated with vacuum before subsequent penetration. Pre-calibration and saturation in water ensures that no air in the probe interferes with the pore pressure sensor test results, ensuring stable probe performance during the test and closer-to-realistic measurement results, thereby improving the reliability and effectiveness of the entire static penetration test.

[0034] S2. The first penetration of the static cone penetration probe into the test soil shall be carried out to a total penetration depth not less than the depth of the study area in the test soil and shall be recorded as z max , obtain the cone tip resistance q measured by the static penetration probe during the penetration processc , the side wall friction f s and the pore water pressure u, to obtain curves of the three with the penetration depth z.

[0035] Before the static sounding probe starts the penetration operation, a vial containing water is attached to the static sounding probe, so that the static sounding probe is immersed in the water in the vial. Before the penetration into the test soil, the vial is removed, so as to ensure that the calibrated static sounding probe is kept in a water-saturated state as much as possible before being penetrated into the soil layer, thereby improving the measurement accuracy.

[0036] In the embodiment, the penetration is performed in a non-test area of the test soil, so as to reduce the influence on the subsequent normal test work. Preferably, the penetration speed v of the static sounding probe is greater than 30 cm / s. v c , c v is the consolidation coefficient of the test soil, with the unit of cm 2 / s, which is determined by the properties of the test soil prepared at the time, and can be obtained by the existing conventional measurement method, d c is the diameter of the static sounding probe, with the unit of cm, and the unit of the penetration speed v is cm / s.

[0037] In the embodiment, the static sounding probe is communicatively connected to the control mechanism, and the control mechanism automatically obtains the measurements of the cone tip resistance q c , the side wall friction f s and the pore water pressure u measured by the static sounding probe. The static sounding probe is installed in the positioning and penetration mechanism, and the positioning and penetration mechanism drives the translational positioning and penetration action of the static sounding probe. The control mechanism controls the movement of the positioning and penetration mechanism, so that the penetration depth z of the static sounding probe at a certain time can be determined through the control mechanism, and the corresponding q c —z curve, f s —z curve and u—z curve are obtained accordingly. The control mechanism can include a computer system or other suitable structure, as long as it has the functions of data acquisition, storage, calculation and control instruction sending.

[0038] S3, determining the radius R I of the penetration influence range of the static sounding probe at each depth during the penetration, to obtain the R I —z curve of the penetration influence range radius R I with the penetration depth z; obtaining the maximum value of R I in the R I —z curve, denoted as the maximum range radius R0. For a certain depth, the penetration influence range of the static sounding probe is regarded as a circular area with the static sounding probe as the center, and the penetration influence ranges at different depths are different, that is, the radii R I of the circular areas are different. I ​The maximum value of R is the maximum influence range, and is denoted as the maximum range radius R0.

[0039] In the embodiment, R is preferably I The calculation method of R is as follows:

[0040] R I = d c 2 [ ( q t + p 0 ) ( 1 + sin φ ) c ∗ cos φ ] 1 − sin φ 2 sin φ , ,

[0041] In the formula, p0 is the overburden stress, with a unit of kPa, and p0 is a characteristic of the test soil and is determined according to the test soil parameters, and can be calculated by using the formula , wherein is the unit weight of the test soil, with a unit of kN / m 3 , is the unit weight of water, and is usually 10 kN / m 3 , z is the depth of the calculation point, with a unit of m, and p0 can also be determined by other suitable methods. is the internal friction angle of the test soil, and c is the cohesion of the test soil, with a unit of kPa, and c are both characteristics of the test soil itself, and can be determined according to the parameters during preparation or measured by existing conventional tests; q t is the corrected cone tip resistance of the static cone, with a unit of kPa, and is calculated according to the cone tip resistance q c and the pore water pressure u, and a is the cross-sectional area ratio of the pressure sensor in the static cone to the probe, and is a design parameter of the static cone. Since p0 and q t both vary with the depth, the R I curve with the penetration depth z is obtained. I —z curve.

[0042] In another embodiment, when the test soil is saturated soft clay, R I can also be determined by using the following calculation formula: ,

[0043] In the formula, E is the elastic modulus of the test soil, with a unit of kPa, v is the Poisson's ratio of the test soil, c is the cohesion of the test soil, with a unit of kPa, d c is the diameter of the static cone, with a unit of cm. E, v and c are all characteristics of the test soil itself, and can be determined according to the parameters during preparation or measured by existing conventional tests.

[0044] S4, a second static cone penetration of the static cone is performed in the test soil, the distance between the center of the second penetration position and the center of the first penetration position is R0, and the penetration depth is the same as that of the first time, and is also z max, the cone tip resistance q c , the side friction f s and the pore water pressure u measured by the static cone probe during the penetration process, and obtain the curves of the three parameters varying with the penetration depth z.

[0045] In the embodiment, the static cone probe is also provided with a small bottle containing water before the penetration operation starts, and the static cone probe is immersed in the water in the small bottle. Before the penetration into the test soil, the small bottle is removed, so as to ensure that the calibrated static cone probe is kept in a water-saturated state as much as possible before being penetrated into the soil layer, thereby improving the measurement accuracy. The penetration is also carried out in the non-test area of the test soil, and preferably, the penetration speed of the static cone probe is the same as that in the first penetration, that is, v>30cm / min. v c The detection data of the second penetration of the static cone probe are also obtained automatically by the control mechanism.

[0046] S5, calculate the difference degrees D(q t ) and D(f s ) of the corrected cone tip resistance and the side friction of the static cone probe in the two penetrations, and the calculation formula is:

[0047] ,

[0048] ,

[0049] In the formula, f s1 and f s2 are the side frictions of the static cone probe in the first penetration and the second penetration, q t1 and q t2 are the corrected cone tip resistances of the static cone probe in the first penetration and the second penetration; wherein the corrected cone tip resistances q t of the static cone probe in the two penetrations are calculated according to the formula , and a is the cross-sectional area ratio of the pressure sensor in the static cone probe to the probe.

[0050] In the embodiment, the control mechanism (computer system) automatically calculates the difference degrees D(q t ) and D(f s ) of the corrected cone tip resistance and the side friction according to the measurement data of the two penetrations in steps S2 and S4.

[0051] S6, correct R0 to obtain the corrected influence range radius R 修 , and the correction formula is:

[0052] R fix = S f R 0 [ 1 + m D ( q t ) + ( 1- m ) D ( f s ) ] , ​

[0053] In the formula, S f is a safety factor, which can be selected according to the actual requirements of the measurement work, and is preferably 1.1; m is a weight factor of the cone tip resistance, which can be selected according to the actual requirements of the measurement work, and is preferably 0.7 when the test soil is cohesionless soil and 0.5 when the test soil is cohesive soil.

[0054] S7, normal test work: static cone penetration testing is performed in the test soil, and the center distance between the penetration positions of any two static cone penetration probes is not less than R 修 The penetration points of the static cone penetration probes in the normal test work are located in the test area of the test soil.

[0055] Through the above steps S1-S6, the penetration influence range radius R 修 of the static cone penetration probe in the test soil can be determined, so that in the normal test work, R 修 is taken as the minimum safety spacing constraint to automatically control the positioning and penetration mechanism to move the static cone penetration probe in the horizontal direction, ensuring that the spacing between the static cone penetration penetration points is not less than R 修 , thereby ensuring that the test data is not affected by the disturbance of the adjacent static cone penetration probes and can reflect the true properties of the test soil.

[0056] The present application also provides a smart static cone penetration system, which comprises a test box, a static cone penetration probe, a positioning and penetration mechanism, and a control mechanism. The positioning and penetration mechanism is connected with the static cone penetration probe and can drive the static cone penetration probe to move in the horizontal direction and penetrate into the test soil in the test box. The sensor in the static cone penetration probe is connected with the control mechanism in communication, and the control mechanism obtains the detection data of the static cone penetration probe. The control mechanism is connected with the positioning and penetration mechanism for control, and the test box, the static cone penetration probe, the positioning and penetration mechanism, and the control mechanism can all adopt existing suitable structures. In the present application, the control mechanism comprises a storage medium, and the storage medium stores a computer program. When the computer program is executed by a processor, the above-mentioned static cone penetration penetration positioning method is realized, so that the penetration influence range of the static cone penetration probe in the test soil is automatically obtained, and the spacing between the static cone penetration points in the normal test work is constrained accordingly.

[0057] The static cone penetration penetration positioning method and the smart static cone penetration system of the present application have the following beneficial effects:

[0058] 1. To provide a method for predicting the influence range of static sounding in geotechnical model test, which can accurately determine the influence range of static sounding probe in the test soil before the formal test, and design the static sounding penetration point accurately and reliably, so as to make it as close as possible, but avoid mutual influence, and can more finely explore the change of the test soil properties.

[0059] 2. Only two times of static sounding penetration are needed to quickly determine the influence range of static sounding probe in the test soil, and the whole process is realized by calculation, without the need of judging by comparing whether the two static sounding curves are consistent, and without the need of highly relying on the personal experience and subjective judgment of researchers, but providing a clear and quantifiable method for judging the influence range of static sounding, avoiding the influence of subjective factors, and the obtained result has good reliability.

[0060] 3. The required penetration times and space are small, without the need of preparing the test soil again, saving time and avoiding the error caused by repeatedly preparing the test soil.

[0061] The above examples only exemplarily illustrate the principles and effects of the present application, and are not used to limit the present application. Any person skilled in the art can modify or change the above examples without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes completed by those skilled in the art without departing from the spirit and technical thought disclosed by the present application should be covered by the claims of the present application.

Claims

1. A static penetration positioning method, characterized in that: The following steps are involved: S1. Test preparation: Prepare the test soil in the test box; S2. The first penetration of the static penetration probe into the test soil is carried out to a total penetration depth of z max , obtain the cone tip resistance q measured by the static penetration probe during the penetration process c , side wall friction f s and pore water pressure u, and obtain the curves of the three changing with penetration depth z; S3. Determine the radius R of the penetration range of the static penetration probe at each depth during penetration. I , get the penetration influence range radius R I R changes with penetration depth z I —z curve, R I The calculation formula is , , where p0 is the overburden stress, is the internal friction angle of the test soil, c is the cohesion of the test soil, q t is the modified cone tip resistance of the static penetration probe, a is the cross-sectional area ratio of the pressure sensor to the probe in the static penetration probe; obtain R I —R in the z curve I The maximum value is recorded as the maximum range radius R0; S4. Perform a second penetration of the static penetration probe into the test soil. The distance between the center of the penetration position and the center of the first penetration position is equal to R0. The penetration depth is z max , obtain the cone tip resistance q measured by the static penetration probe during the penetration process c , side wall friction f s and pore water pressure u, and obtain the curves of the three changing with penetration depth z; S5. Calculate the difference in the modified cone tip resistance D(q t ) and the difference between the side wall friction resistance D(f s ), , , f s1 and f s2 are the side wall friction resistance of the first and second penetration of the static penetration probe, q t1 and q t2 are the modified cone tip resistance of the first penetration and the second penetration of the static penetration probe respectively; S6. Correct R0 to obtain the corrected influence range radius , where S f is the safety factor, and m is the weight factor of the cone tip resistance.

2. The static penetration positioning method according to claim 1, characterized in that: Also includes: S7. Normal test work: Conduct static penetration test in the test soil. The center distance between any two penetration positions of static penetration probes shall not be less than R 修 .

3. The static penetration positioning method according to claim 1, characterized in that: In step S1, the surface of the test soil is filled with a water layer, the depth of the water layer is 3 to 5 times the length of the cone tip of the static penetration probe, and the average particle size d of the test soil is 1. 50 Not exceeding the diameter d of the static penetration probe c 1 / 20 of.

4. The static penetration positioning method according to claim 1, characterized in that: In the steps S2 and S4, before the penetration operation of the static penetration probe begins, a small bottle filled with water is provided outside the static penetration probe so that the static penetration probe is immersed in the water in the small bottle. Before penetrating into the test soil, the small bottle is removed.

5. The static penetration positioning method according to claim 1, characterized in that: In the steps S2 and S4, the penetration speed v of the static penetration probe is greater than 30c v / d c , c v is the consolidation coefficient of the test soil, d c is the diameter of the static penetration probe.

6. The static penetration positioning method according to claim 1, characterized in that: In the step S6, S f Take 1.

1. When the test soil is non-cohesive soil, take m as 0.

7. When the test soil is cohesive soil, take m as 0.

5.

7. The static penetration positioning method according to claim 1, characterized in that: In step S1, a test area and a non-test area outside the test area are set in the test soil, and in steps S2 and S4, the static penetration probe is penetrated into the non-test area.

8. An intelligent static penetration sounding system, comprising a test chamber, a static penetration sounding probe, a positioning and penetration mechanism, and a control mechanism. The positioning and penetration mechanism is connected to the static penetration sounding probe and can drive the static penetration sounding probe to move horizontally and penetrate the test soil in the test chamber. The sensor in the static penetration sounding probe is communicatively connected to the control mechanism, which obtains detection data from the static penetration sounding probe. The control mechanism is control-connected to the positioning and penetration mechanism, and is characterized by: The control mechanism includes a storage medium on which a computer program is stored. When the computer program is executed by a processor, the static penetration positioning method according to any one of claims 1 to 7 is implemented.

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