A micro-pile probe and an in-situ bearing capacity testing method thereof

Abstract

The application discloses a kind of micro pile probe and its in-situ bearing capacity test method, wherein micro pile probe, including the pressure plate for bearing external force and being pressed into soil layer, the upper loading chamber of fixed installation in the bottom of pressure plate, the side resistance component of active installation on the upper loading chamber and along its axis sliding to measure pile side resistance, the lower loading chamber of fixed installation in the bottom of upper loading chamber, and the end resistance component of installation in the inside of lower loading chamber and below axis and for measuring pile end resistance.The application can carry out pile foundation bearing capacity in-situ test, can directly measure the side resistance and end resistance of each section of pile foundation, and simultaneously measure the displacement corresponding to side resistance and end resistance, based on side resistance and end resistance and corresponding displacement, the load displacement curve of each section of pile foundation can be obtained, and the bearing capacity of pile foundation can be obtained by load transfer method, with high measurement accuracy and reliable measurement result.

Description

Technical Field

[0001] This invention belongs to the field of civil engineering foundation bearing capacity testing technology, specifically relating to a micropile probe and its in-situ bearing capacity testing method. Background Technology

[0002] Pile foundations are widely used in high-rise buildings, long-span bridges, and other structures, and their bearing capacity directly determines the safety of the superstructure. To ensure the absolute safety and reliability of pile foundations, bearing capacity testing is necessary. Currently, traditional methods for testing the bearing capacity of pile foundations in civil engineering mainly include the surcharge method, the anchor pile method, and the self-balancing method. These methods directly measure the pile bearing capacity through loading, and cannot directly obtain the end resistance and side resistance of each pile section. When testing the bearing capacity of deep foundations in complex environments such as deep water, steep slopes, and narrow terrain, these traditional testing methods become even more difficult, and the cost of testing ultra-large and ultra-high-tonnage deep foundations is high. Overcoming these technical bottlenecks has become a technical challenge in the industry. Furthermore, in-situ testing is required before designing the bearing capacity of pile foundations. In-situ testing often uses the CPTU method; however, the CPTU method can only roughly estimate the pile bearing capacity and cannot obtain the load-displacement curve of each pile segment, thus making it impossible to accurately calculate the pile bearing capacity in advance. Summary of the Invention

[0003] Purpose of the invention: The first purpose of this invention is to provide a micropile probe that can directly obtain the pile end resistance and pile side resistance of the cross section.

[0004] The second objective of this invention is to provide an in-situ bearing capacity testing method for micropile probes.

[0005] Technical Solution: The present invention discloses a micropile probe, comprising a bearing plate for bearing external forces and pressing into the soil layer, an upper loading chamber fixedly installed at the bottom of the bearing plate, a side resistance assembly movably installed on the upper loading chamber and sliding along its axis to measure the pile side resistance, a lower loading chamber fixedly installed at the bottom of the upper loading chamber, and an end resistance assembly installed inside the lower loading chamber and below its axis for measuring the pile end resistance; the side resistance assembly includes a moving part that moves along the axis of the upper loading chamber and contacts the soil layer, a first load sensor disposed in the upper loading chamber for measuring the frictional force between the moving part and the soil layer, and a first displacement meter disposed in the upper loading chamber for measuring the displacement of the moving part.

[0006] Furthermore, the upper loading chamber has several parallel guide slots along its axial direction; the moving component includes a friction sleeve sleeved on the outer periphery of the upper loading chamber for contact with the soil layer, a force transmission plate slidably connected to the guide slots, one end fixedly connected to the inner wall of the friction sleeve and the other end extending into the upper loading chamber, an upper pad and a lower pad fixedly connected to the top and bottom of the force transmission plate respectively, and a first annular jack fixedly installed in the upper loading chamber for driving the friction sleeve to move, the first load sensor fixedly installed between the upper pad and the output end of the first annular jack, and the first displacement gauge fixedly installed in the upper loading chamber, with the telescopic rod of the first displacement gauge in contact with the lower pad.

[0007] Furthermore, the friction sleeve is provided with chamfers at the top and bottom to assist its movement in the soil layer; the friction sleeve is provided with a first annular groove at the upper inner wall and the lower inner wall, and a first sealing ring is installed in the first annular groove.

[0008] Furthermore, the outer periphery of the upper loading chamber is provided with a stepped surface for limiting the initial position of the friction sleeve.

[0009] Furthermore, the end resistance assembly includes a second annular jack installed inside the lower loading chamber, a second load sensor fixedly connected to the output end of the second annular jack, a conical head fixedly connected to the bottom of the second load sensor and moving under the drive of the second annular jack, and a second displacement meter fixedly installed inside the lower loading chamber, with the telescopic rod in contact with the conical head and used to measure the displacement of the conical head, wherein the conical head is slidably connected to the lower loading chamber.

[0010] Furthermore, a protective sleeve is provided at the top of the conical head, the top of the protective sleeve extends into the lower loading chamber and slides in contact with the inner wall of the lower loading chamber; a second annular groove is provided on the outer periphery of the protective sleeve, and a second sealing ring is installed in the second annular groove.

[0011] Furthermore, it also includes a pressure bar mounted on top of the pressure plate for contact with external drive equipment.

[0012] Based on the same inventive concept, this invention also discloses an in-situ bearing capacity testing method for a micropile probe, comprising the following steps:

[0013] S1: Set the test depth to below ground level Place;

[0014] S2: After pressing the micropile probe into the test depth using the pressure rod, adjust the first annular jack to drive the friction sleeve downwards, and adjust the first annular jack to drive the conical head downwards.

[0015] S3: The first load sensor measures the lateral friction force experienced by the friction sleeve during its downward movement at the current test depth; the first displacement gauge measures the displacement of the friction sleeve during its downward movement at the current test depth; the second load sensor measures the end resistance experienced by the conical head during its downward movement at the current test depth; and the second displacement gauge measures the displacement of the conical head during its downward movement at the current test depth.

[0016] S4: Reset the first and second annular jacks so that the friction sleeve returns to its initial position relative to the upper loading chamber and the conical head returns to its initial position relative to the lower loading chamber;

[0017] S5: Let the test depth be... Return to step S2; until Reaching the preset value Then proceed to the next step;

[0018] S6: Obtain the side friction force data measured by the first load sensor and the displacement data measured by the first displacement gauge at all test depths, and plot the side resistance load-displacement curve of the micropile probe.

[0019] S7: Obtain the test depth. The end resistance data measured by the second load sensor and the displacement data measured by the second displacement gauge are used to plot the end resistance load-displacement curve of the micropile probe with displacement s as the abscissa and end resistance p as the ordinate. The end resistance load-displacement curve is then restored to obtain the end resistance restored curve.

[0020] S8: Based on the pile end dimensions of the cast-in-place pile in actual application, the restoration curve is corrected to obtain the corrected real load-displacement curve of the cast-in-place pile in actual application.

[0021] S9: Based on the actual load-displacement curve, the load transfer method is used to plot the pile end load-settlement curve of the cast-in-place pile.

[0022] Furthermore, the method for restoring the end resistance load displacement curve in step S6 is as follows:

[0023] The starting point of the end resistance load displacement curve is denoted as point A, and the ending point is denoted as point C;

[0024] Before the end resistance load displacement curve reaches the inflection point, extend it to obtain the extended straight line AJ, and the extended straight line AJ intersects the end resistance load displacement curve at point B.

[0025] Draw the tangent line BD at point B on the end resistance load displacement curve, and denote the tangent modulus of BD at point B as . ;

[0026] Draw a perpendicular line BF at point B, perpendicular to the tangent line BD, and denote the angle between the extended line AJ and the perpendicular line BF as . ;

[0027] Draw a horizontal line BE at point B, and denote the angle between the horizontal line BE and BD as . ;

[0028] Let the angle between the extended line AJ and the horizontal axis be denoted as . ;

[0029] Calculated based on geometric relationships =90°+ - and based on calculate ;

[0030] Assume the actual load-displacement curve of the end resistance on the cast-in-place pile conforms to a hyperbola, and the model of the hyperbola is as follows: ,in , , This represents the ultimate limit of the end resistance that the cast-in-place pile can withstand.

[0031] Draw the tangent line OG of the hyperbola at its starting point O, and denote the tangent modulus OG at point O as . ;

[0032] Draw a perpendicular line OH at point O, perpendicular to the tangent OG. The angle between the tangent OG and the perpendicular line OH is denoted as . ,and The theoretical value is 90°.

[0033] make The initial value is and based on Calculate the included angle The actual value.

[0034] judge If the actual value is 90°, adjust the value of a and return to step S611 until... The actual value is equal to the theoretical value; retain The value of 'a' when the actual value equals the theoretical value is used to obtain the hyperbola. This is the restoration curve.

[0035] Furthermore, the correction process for the restoration curve in step S7 is as follows:

[0036] The additional stress in the soil at the bottom of the pile tip of the cast-in-place pile is calculated using the method of calculating the additional stress coefficient of the foundation. The settlement at different depths at the bottom of the pile tip is then calculated using the tangent modulus method, resulting in the corrected settlement value for the cast-in-place pile in practical applications. ;

[0037] Using Prandtl's upper bound solution method Make corrections to obtain the corrected version. ;

[0038] The corrected true load-displacement curve is .

[0039] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: This invention enables in-situ testing of pile foundation bearing capacity, directly measuring the lateral and end resistance of each pile segment, and simultaneously measuring the displacement corresponding to these resistances. Based on the lateral and end resistances and their corresponding displacements, the load-displacement curve of each pile segment can be obtained. The pile bearing capacity can then be obtained through the load transfer method, resulting in high measurement accuracy and reliable results. Furthermore, this invention can reconstruct and correct the load-displacement curve of the end resistance based on actual cast-in-place piles, which is beneficial for further improving the accuracy and reliability of the final true load-displacement curve of the end resistance. The invention has a compact overall structure and occupies little space, making it suitable for complex environments such as deep water, steep slopes, and narrow terrain. Moreover, the invention is easy to operate during testing, effectively reducing testing costs and saving on testing expenses. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the structure of the present invention;

[0041] Figure 2 This is a front view of the upper loading chamber of the present invention;

[0042] Figure 3 This is a cross-sectional view of the friction sleeve of the present invention;

[0043] Figure 4 This is a schematic diagram of the force transmission plate of the present invention;

[0044] Figure 5 This is a cross-sectional view of the present invention;

[0045] Figure 6 This is a cross-sectional view of the lower loading chamber of the present invention;

[0046] Figure 7 This is a cross-sectional view of the conical head and the protective sleeve of the present invention;

[0047] Figure 8 This is a schematic diagram of the end resistance load displacement curve and hyperbola in an embodiment of the present invention;

[0048] Figure 9 This is a schematic diagram of the hyperbola and the actual load-displacement curve in an embodiment of the present invention. Detailed Implementation

[0049] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0050] Example 1

[0051] This invention discloses a micropile probe, such as Figure 1 As shown, the system includes a pressure plate 1, an upper loading chamber 2, a lower loading chamber 3, a friction sleeve 5, a force transmission plate 6, an upper pad 7, a lower pad 8, a first load sensor 9, a first annular jack 10, a first displacement gauge 11, a second annular jack 14, a second load sensor 15, a conical head 16, a second displacement gauge 17, a protective casing 18, and a pressure rod 20. The pressure plate 1 is used to bear external forces and press into the soil layer. The upper loading chamber 2 is fixedly installed on the bottom of the pressure plate 1, and is a cylindrical structure with open ends. The lower loading chamber 3 is fixedly installed on the bottom of the upper loading chamber 2, and is a cylindrical structure with an open bottom. Preferably, the lower loading chamber 3 and the upper loading chamber 2 are connected by a threaded connection. The pressure rod 20 is installed on the top of the pressure plate 1 and is used to contact external driving equipment. Preferably, the pressure rod 20 is connected to the top of the upper loading chamber 2 by a threaded connection.

[0052] like Figures 1 to 5 As shown, the friction sleeve 5, force transmission plate 6, upper pad 7, lower pad 8, first load sensor 9, first annular jack 10, and first displacement gauge 11 constitute a side resistance assembly. This assembly is movably mounted on the upper loading chamber 2 and slides along its axis to measure the pile side resistance. The friction sleeve 5, force transmission plate 6, upper pad 7, lower pad 8, and first annular jack 10 constitute a moving component. This component moves along the axis of the upper loading chamber 2 and contacts the soil layer. Figure 2 As shown, the upper loading chamber 2 has several parallel guide grooves 4 along its axial direction; the friction sleeve 5 is sleeved on the outer periphery of the upper loading chamber 2 and is used to contact the soil layer, such as... Figure 3 As shown, the friction sleeve 5 has chamfers at both the top and bottom to assist its movement in the soil. Figure 2 As shown, the outer periphery of the upper loading chamber 2 is provided with a stepped surface 13 to limit the initial position of the friction sleeve 5. Figure 3 As shown, the friction sleeve 5 has a first annular groove 12 on both the upper and lower inner walls, and a first sealing ring is installed in the first annular groove 12. The first sealing strip can prevent external substances from entering the upper loading chamber 2 during the movement of the friction sleeve 5. Preferably, when the friction sleeve 5 is in the initial displacement and when it moves to the maximum stroke, the guide groove 4 is located between the two first annular grooves 12.

[0053] The force transmission plate 6 is slidably connected to the guide groove 4, and one end of the force transmission plate 6 is fixedly connected to the inner wall of the friction sleeve 5, while the other end passes through the guide groove 4 and extends into the upper loading chamber 2; the upper pad 7 is a circular plate structure, located inside the upper loading chamber 2 and fixedly connected to the top of the force transmission plate 6, preferably by bolt connection; the lower pad 8 is a circular plate structure, located inside the upper loading chamber 2 and fixedly connected to the bottom of the force transmission plate 6, preferably by bolt connection; the first load sensor 9 is located above the upper pad 7 and is fixedly installed on... The top of the upper pad 7 is preferably installed using bolts. The first annular jack 10 is located above the first load sensor 9. The first annular jack 10 is fixedly connected to the inner wall of the upper loading chamber 2, and the output end of the first annular jack 10 is fixedly connected to the upper pad 7. The connection between the first annular jack 10 and the upper pad 7 is preferably bolted. The first annular jack 10 is used to drive the friction sleeve 5 to move. The first displacement gauge 11 is used to measure the displacement of the friction sleeve 5, and the first displacement gauge 11 is fixedly installed inside the upper loading chamber 2. The telescopic rod of the first displacement gauge 11 is in contact with the lower pad 8. In use, the first annular jack 10 drives the upper pad 7 to move downward through the first load sensor 9. The upper pad 7 and the force transmission plate 6 drive the friction sleeve 5 to move downward synchronously. The first load sensor 9 measures the frictional resistance experienced by the friction sleeve 5 when it moves downward, which is the load on the friction sleeve 5. The first displacement gauge 11 measures the downward displacement of the friction sleeve 5.

[0054] like Figure 1 , Figure 6 and Figure 7 As shown, the second annular jack 14, the second load sensor 15, the conical head 16, the second displacement gauge 17, and the casing 18 constitute an end resistance assembly. The end resistance assembly is installed inside the lower loading chamber 3 and below the shaft, and is used to measure the pile end resistance. The second annular jack 14 includes components installed inside the lower loading chamber 3. The second load sensor 15 is located below the second annular jack 14 and is fixedly connected to the output end of the second annular jack 14. The connection between the second load sensor 15 and the second annular jack 14 is preferably a threaded connection. The conical head 16 is slidably connected to the lower loading chamber 3 and is fixedly connected to the bottom of the second load sensor 15. The connection between the conical head 16 and the second load sensor 15 is preferably a bolted connection. The conical head 16 moves under the drive of the second annular jack 14. The second displacement gauge 17 is fixedly installed inside the lower loading chamber 3, and the telescopic rod of the second displacement gauge 17 contacts the conical head 16. The second displacement gauge 17 is used to measure the displacement of the conical head 16.

[0055] like Figure 1 and Figure 7As shown, the protective sleeve 18 is fixedly mounted on the top of the conical head 16, and the top of the protective sleeve 18 extends into the lower loading chamber and slides in contact with the inner wall of the lower loading chamber 3. The protective sleeve 18 is integrally formed from a first ring 21, an annular frustum 22, and a second ring 23. The first ring 21 is fixedly mounted on the top of the conical head 16, and the outer diameter of the first ring 21 is the same as the diameter of the top of the conical head 16. The annular frustum 22 is fixedly mounted on the top of the first ring 21, and the outer diameter of the bottom of the annular frustum 22 is the same as the outer diameter of the first ring 21. The outer diameter of the annular frustum 22 gradually decreases from bottom to top, and the inner diameter of the annular frustum 22 is the same as the inner diameter of the first ring 21. The second ring 23 is fixedly mounted on the top of the annular frustum 22, and the outer diameter of the second ring 23 is the same as the outer diameter of the top of the annular frustum 22, the inner diameter of the second ring 23 is the same as the inner diameter of the annular frustum 22, and the outer diameter of the second ring 23 is the same as the inner diameter of the lower loading chamber 3. The outer periphery of the casing 18 is provided with a second annular groove 19, and a second sealing ring is installed in the second annular groove 19. The sealing ring is preferably installed on the second ring 23. The second sealing ring can prevent external substances from entering the interior of the lower loading chamber.

[0056] In use, the second ring jack 14 drives the conical head 16 to move downward through the second load sensor 15. The second load sensor 15 measures the end resistance that the conical head 16 experiences when it moves downward, which is also the load on the conical head 16. The second displacement meter 17 measures the displacement of the conical head 16 as it moves downward.

[0057] The pressure rod 20, the pressure plate 1, the upper pad 7, the lower pad 8, and the lower loading chamber 3 are all provided with a through hole for the power supply cable to pass through, so as to facilitate the connection of the first load sensor 9, the first annular jack 10, the first displacement meter 11, the second annular jack 14, the second load sensor 15, and the second displacement meter 17 with external cables, transmission cables, hydraulic pipes, etc.

[0058] Before measurement, the entire assembly is pressed into the set depth using the pressure rod 20. Then, the first annular jack 10 is adjusted to drive the friction sleeve 5 downward, and the second annular jack 14 is adjusted to drive the conical head 16 downward, and the soil layer is measured. The side friction and end resistance were measured; after the measurement, the first annular jack 10 and the second annular jack 14 were reset; pressure was applied to the pressure rod 20 again to press the whole thing into the set depth. Repeat the above steps to adjust the first annular jack 10 and the second annular jack 14, and measure the soil layers. The side friction and end resistance; repeat the above steps until the design depth is reached. The side friction and end resistance of each soil layer are measured according to the requirements. The measured side friction and end resistance of different soil layers are processed using the pile foundation load transfer method to generate the pile top load displacement curve. The bearing capacity of the pile foundation is obtained through the pile top load displacement curve.

[0059] Traditional in-situ pile foundation bearing capacity testing devices require not only strong vertical and horizontal reactions during measurement, but also reinforcement bars within the pile body to indirectly calculate side and end resistance. Compared to traditional testing methods, this invention solves the problem that traditional in-situ testing cannot obtain the load-displacement curves for each pile segment. Furthermore, this invention overcomes the challenge of CPT in-situ testing failing to obtain the load-displacement curves for each pile segment's sides and ends.

[0060] Example 2

[0061] This invention discloses an in-situ bearing capacity testing method for a micropile probe, comprising the following steps:

[0062] S1: Set the test depth to below ground level In practical applications, the first ring jack 10 and the second ring jack 14 can be connected to an external controller for convenient and precise control of the first ring jack 10 and the second ring jack 14. The first load sensor 9, the first displacement meter 11, the second load sensor 15 and the second displacement meter 17 can be connected to an external data acquisition instrument for convenient data acquisition.

[0063] S2: After pressing the micropile probe into the test depth using the pressure rod 20, adjust the first annular jack 10 to drive the friction sleeve 5 downward and adjust the first annular jack 10 to drive the conical head 16 downward.

[0064] S3: The first load sensor 9 measures the lateral friction force experienced by the friction sleeve 5 during its downward movement at the current test depth; the first displacement meter 11 measures the displacement of the friction sleeve 5 during its downward movement at the current test depth; the second load sensor 15 measures the end resistance experienced by the conical head 16 during its downward movement at the current test depth; and the second displacement meter 17 measures the displacement of the conical head 16 during its downward movement at the current test depth.

[0065] S4: Reset the first annular jack 10 and the second annular jack 14 so that the friction sleeve 5 returns to its initial position relative to the upper loading chamber 2 and the conical head 16 returns to its initial position relative to the lower loading chamber 3.

[0066] S5: Let the test depth be... Return to step S2; until Reaching the preset value Then proceed to the next step.

[0067] S6: Obtain the side friction force data measured by the first load sensor 9 and the displacement data measured by the first displacement meter 11 at all test depths, and plot the side resistance load-displacement curve of the micropile probe.

[0068] S7: Obtain the test depth. The end resistance data measured by the second load sensor 15 and the displacement data measured by the second displacement gauge 17 are used to plot the end resistance load-displacement curve of the micropile probe, with displacement s as the abscissa and end resistance p as the ordinate. The end resistance load-displacement curve is then restored to obtain the restored end resistance curve. The end resistance load-displacement curve is shown below. Figure 8 As shown by the red curve ABC in the figure, and Figure 8 In The test depth is At that time, the initial position of the conical head 16 before the second annular jack 14 was activated.

[0069] This invention uses the micropile probe from Example 1 for testing. The test results of the micropile probe differ from those of actual cast-in-place piles: the load-displacement curves at the micropile probe tip and the cast-in-place pile tip are different. The micropile probe penetrates the soil at a certain rate, and the soil bearing capacity at the probe tip remains at its limit state. However, the actual pile tip loading process involves a linear stage, a plastic stage, and ultimate failure. The micropile probe differs significantly in size from the actual cast-in-place pile, and size effects also exist. The shape and size of the foundation are closely related to the stress on the foundation bottom surface. Compared to the cast-in-place pile tip, the micropile probe acts like a concentrated force or a localized surface load. The additional stress in the soil at the bottom of the micropile probe differs significantly from the additional stress at the bottom of the cast-in-place pile. Therefore, it is necessary to restore and correct the end-resistance load-displacement curve of the micropile probe test results.

[0070] like Figure 8 As shown, the method for restoring the end resistance load displacement curve is as follows:

[0071] S71: Denote the starting point of the end resistance load displacement curve as point A and the ending point as point C. For example... Figure 8 The red curve ABC is shown in the image.

[0072] S72: Extend the end resistance load displacement curve before it enters the inflection point to obtain the extended straight line AJ, and the extended straight line AJ intersects the end resistance load displacement curve at point B.

[0073] S73: Draw the tangent line BD at point B on the end resistance load displacement curve, and denote the tangent modulus of BD at point B as... .

[0074] S74: Draw a perpendicular line BF at point B, perpendicular to the tangent line BD, and denote the angle between the extended line AJ and the perpendicular line BF as . .

[0075] S75: Draw a horizontal line BE at point B, and denote the angle between the horizontal line BE and BD as . .

[0076] S76: The angle between the extended line AJ and the horizontal axis is denoted as... The angle between the extended straight line AJ and the horizontal line BE is also . .

[0077] S77: Calculated based on geometric relationships =90°+ - and based on calculate .

[0078] S78: Assume that the actual load-displacement curve of the end resistance of the cast-in-place pile conforms to a hyperbola, and the model of the hyperbola is as follows: ,in , , This represents the ultimate end resistance value that the cast-in-place pile can withstand.

[0079] S79: Draw the tangent line OG of the hyperbola at its starting point O, and denote the tangent modulus of OG at point O as... .

[0080] S710: Draw a perpendicular line OH at point O, perpendicular to the tangent OG. The angle between the tangent OG and the perpendicular line OH is denoted as . ,and The theoretical value is 90°.

[0081] S711: Order The initial value is and based on Calculate the included angle The actual value.

[0082] S712: Judgment If the actual value is 90°, adjust the value of a and return to step S611 until... The actual value is equal to the theoretical value; retain The value of 'a' when the actual value equals the theoretical value is used to obtain the hyperbola. This is the restoration curve.

[0083] S8: Based on the pile end dimensions of the cast-in-place pile in actual application, the restoration curve is corrected to obtain the corrected true load-displacement curve of the cast-in-place pile in actual application.

[0084] like Figure 9 As shown, the method for correcting the restoration curve is as follows:

[0085] The additional stress in the soil at the bottom of the pile tip of the cast-in-place pile is calculated using the method of calculating the additional stress coefficient of the foundation. The settlement at different depths at the bottom of the pile tip is then calculated using the tangent modulus method, resulting in the corrected settlement value for the cast-in-place pile in practical applications. Among them, the method for calculating the additional stress coefficient of the foundation and the tangent modulus method are existing mature algorithms.

[0086] Using Prandtl's upper bound solution method Make corrections to obtain the corrected version. Among them, Prandtl's upper bound solution is a mature existing algorithm.

[0087] The corrected true load-displacement curve is .

[0088] S9: Based on the actual load-displacement curve, the load transfer method is used to plot the pile end load-settlement curve of the cast-in-place pile. The load transfer method is a mature existing algorithm.

Claims

1. A micro-pile probe, characterized in that: The system includes a bearing plate (1) for bearing external forces and pressing into the soil layer, an upper loading chamber (2) fixedly installed at the bottom of the bearing plate (1), a side resistance assembly movably installed on the upper loading chamber (2) and sliding along its axis to measure the pile side resistance, a lower loading chamber (3) fixedly installed at the bottom of the upper loading chamber (2), and an end resistance assembly installed inside the lower loading chamber (3) and below its axis for measuring the pile end resistance; the side resistance assembly includes a movable part that moves along the axis of the upper loading chamber (2) and contacts the soil layer, and is disposed inside the upper loading chamber (2). A first load sensor (9) for measuring the frictional force between the moving part and the soil layer, and a first displacement gauge (11) for measuring the displacement of the moving part, disposed in the upper loading chamber (2); the upper loading chamber (2) has a plurality of parallel guide slots (4) arranged along its axial direction; the moving part includes a friction sleeve (5) sleeved on the outer periphery of the upper loading chamber (2) for contacting the soil layer, and a force transmission plate (6) slidably connected to the guide slots (4), one end of which is fixedly connected to the inner wall of the friction sleeve (5) and the other end of which extends into the interior of the upper loading chamber (2). The first load sensor (9) is fixedly installed between the upper plate (7) and the output end of the first ring jack (10), respectively, and is fixedly installed inside the upper loading chamber (2) for driving the friction sleeve (5) to move. The first displacement gauge (11) is fixedly installed inside the upper loading chamber (2), and the telescopic rod of the first displacement gauge (11) is in contact with the lower plate (8). The end resistance assembly includes an upper plate (7) and a lower plate (8) fixedly connected to the top and bottom of the force transmission plate (6), respectively, and a first annular jack (10) fixedly installed inside the upper loading chamber (2) for driving the friction sleeve (5) to move. The second annular jack (14) is installed inside the lower loading chamber (3), the second load sensor (15) is fixedly connected to the output end of the second annular jack (14), the conical head (16) is fixedly connected to the bottom of the second load sensor (15) and moves under the drive of the second annular jack (14), and the second displacement meter (17) is fixedly installed inside the lower loading chamber (3), the telescopic rod contacts the conical head (16) and is used to measure the displacement of the conical head (16), and the conical head (16) is slidably connected to the lower loading chamber (3).

2. The micropile probe according to claim 1, characterized in that: The friction sleeve (5) is provided with chamfers at the top and bottom to assist its movement in the soil layer; the friction sleeve (5) is provided with a first annular groove (12) at the upper end inner wall and the lower end inner wall, and a first sealing ring is installed in the first annular groove (12).

3. The micropile probe according to claim 1, characterized in that: The outer periphery of the upper loading chamber (2) is provided with a stepped surface (13) for limiting the initial position of the friction sleeve (5).

4. The micropile probe according to claim 1, characterized in that: The top of the conical head (16) is provided with a protective sleeve (18), the top of the protective sleeve (18) extends into the lower loading chamber and slides in contact with the inner wall of the lower loading chamber (3); a second annular groove (19) is provided on the outer periphery of the protective sleeve (18), and a second sealing ring is installed in the second annular groove (19).

5. The micropile probe according to claim 1, characterized in that: It also includes a pressure bar (20) mounted on top of the pressure plate (1) and used for contact with external drive equipment.

6. A method for testing the in-situ bearing capacity of a micropile probe according to claim 5, characterized in that: Includes the following steps, S1: Set the test depth to below ground level Place; S2: After pressing the micropile probe into the test depth by the pressure rod (20), adjust the first annular jack (10) to drive the friction sleeve (5) to move downward, and adjust the first annular jack (10) to drive the conical head (16) to move downward. S3: The first load sensor (9) measures the lateral friction force experienced by the friction sleeve (5) during its downward movement at the current test depth; the first displacement meter (11) measures the displacement of the friction sleeve (5) during its downward movement at the current test depth; the second load sensor (15) measures the end resistance experienced by the conical head (16) during its downward movement at the current test depth; and the second displacement meter (17) measures the displacement of the conical head (16) during its downward movement at the current test depth. S4: Reset the first annular jack (10) and the second annular jack (14) so ​​that the friction sleeve (5) returns to its initial position relative to the upper loading chamber (2) and the conical head (16) returns to its initial position relative to the lower loading chamber (3); S5: Let the test depth be... Return to step S2; until Reaching the preset value Then proceed to the next step; S6: Obtain the side friction force data measured by the first load sensor (9) and the displacement data measured by the first displacement meter (11) at all test depths, and plot the side resistance load displacement curve of the micropile probe; S7: Obtain the test depth. The end resistance data measured by the second load sensor (15) and the displacement data measured by the second displacement meter (17) are used to plot the end resistance load-displacement curve of the micropile probe with displacement s as the abscissa and end resistance p as the ordinate. The end resistance load-displacement curve is then restored to obtain the end resistance restoration curve. S8: Based on the pile end dimensions of the cast-in-place pile in actual application, the restoration curve is corrected to obtain the corrected real load-displacement curve of the cast-in-place pile in actual application. S9: Based on the actual load-displacement curve, the load transfer method is used to plot the pile end load-settlement curve of the cast-in-place pile.

7. The in-situ bearing capacity testing method for the micropile probe according to claim 6, characterized in that: The method for restoring the end resistance load displacement curve in step S6 is as follows: The starting point of the end resistance load displacement curve is denoted as point A, and the ending point is denoted as point C. Before the end resistance load displacement curve reaches the inflection point, extend it to obtain the extended straight line AJ, and the extended straight line AJ intersects the end resistance load displacement curve at point B. Draw the tangent line BD at point B on the end resistance load displacement curve, and denote the tangent modulus of BD at point B as . ; Draw a perpendicular line BF at point B, perpendicular to the tangent line BD, and denote the angle between line AJ and the perpendicular line BF as . ; Draw a horizontal line BE at point B, and denote the angle between the horizontal line BE and BD as . ; Let the angle between the extended line AJ and the horizontal axis be denoted as . ; Calculated based on geometric relationships =90°+ - and based on calculate ; Assume the actual load-displacement curve of the end resistance on the cast-in-place pile conforms to a hyperbola, and the model of the hyperbola is as follows: ,in , , This represents the ultimate limit of the end resistance that the cast-in-place pile can withstand. Draw the tangent line OG of the hyperbola at its starting point O, and denote the tangent modulus OG at point O as . ; Draw a perpendicular line OH at point O, perpendicular to the tangent OG. The angle between the tangent OG and the perpendicular line OH is denoted as . ,and The theoretical value is 90°; make The initial value is and based on Calculate the included angle The actual value; judge If the actual value is 90°, adjust the value of a and return to step S611 until... The actual value is equal to the theoretical value; retain The value of 'a' when the actual value equals the theoretical value is used to obtain the hyperbola. This is the restoration curve.

8. The in-situ bearing capacity testing method for the micropile probe according to claim 7, characterized in that: The correction process for the restoration curve in step S7 is as follows: The additional stress in the soil at the bottom of the pile tip of the cast-in-place pile is calculated using the method of calculating the additional stress coefficient of the foundation. The settlement at different depths at the bottom of the pile tip is then calculated using the tangent modulus method, resulting in the corrected settlement value for the cast-in-place pile in practical applications. ; Using Prandtl's upper bound solution method Make corrections to obtain the corrected version. ; The corrected actual load-displacement curve at the pile tip is as follows .

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