A large depth standard penetration test device and test method

Abstract

This invention discloses a deep standard penetration test apparatus, comprising an umbilical cable, a sheath, an air hammer, and a penetrator. The sheath is open at the top and closed at the bottom, and has at least one vent hole with a one-way valve installed inside. A positioning rod is located inside the sheath, and the air hammer is installed inside the sheath and sleeved on the positioning rod, moving up and down along the positioning rod. The umbilical cable is hollow, with one end sleeved on the positioning rod and connected to the air hammer's air passage, and the other end extending out of the top of the sheath and connected to an external air supply device and data acquisition instrument. The bottom of the sheath is connected to the penetrator, and a pressure sensor and a counter are located between the penetrator and the sheath. A depth sensor is located outside the penetrator. This invention also discloses a deep standard penetration test method. This invention can effectively eliminate energy loss of the probe, improve the test efficiency of the standard penetration test, increase the applicable test depth, and provide accurate measurement results.

Description

Technical Field

[0001] The invention relates to the technical field of standard penetration test, and in particular to a large-depth standard penetration test device and a test method. Background Art

[0002] The standard penetration test is a type of dynamic probing. Its purpose is to use the measured standard penetration hammer number N to judge the compactness of sand or the consistency of clay to determine the allowable bearing capacity of foundation soil, evaluate the vibration liquefaction potential of sand and estimate the bearing capacity of single piles. It can also determine the soil layer profile and take disturbed soil samples for general physical tests. This method has been included in China's national "Code for Design of Foundations for Industrial and Civil Buildings".

[0003] Among the existing technologies, the standard penetration test technology for small depths within 20 meters is mature and widely used. However, for standard penetration tests at large depths exceeding 20 meters, the probe rod of the existing test device is too long and hammering is performed at the wellbore mouth, resulting in excessive energy loss and low test efficiency, which cannot meet the needs of large-depth standard penetration tests. Summary of the invention

[0004] The first technical problem to be solved by the present invention is to provide a large-depth standard penetration test device, which can effectively eliminate the energy loss of the probe rod, is suitable for large-depth standard penetration tests, and has high test efficiency.

[0005] The second technical problem to be solved by the present invention is to provide a large-depth standard penetration test method, which has simple steps, high test efficiency and broad prospects for promotion and application.

[0006] In order to solve the above-mentioned first technical problem, the technical solution adopted by the present invention is as follows:

[0007] A large depth standard penetration test device, characterized in that it comprises an umbilical cable, a sheath, an air hammer and a penetrator, wherein:

[0008] The top end of the sheath is open and the bottom end is closed. The sheath is provided with at least one exhaust hole, a one-way valve is installed in the exhaust hole, and a positioning rod is provided in the sheath;

[0009] The air hammer is installed in the sheath and sleeved on the positioning rod. The air hammer moves up and down along the positioning rod. The air hammer includes a cylinder and a piston. The top end of the cylinder is closed and the bottom end is open. The cylinder is sleeved on the positioning rod. The piston is installed in the cylinder and sleeved on the positioning rod. The piston moves up and down along the inner cavity of the cylinder. A main air chamber for driving the piston to move upward and an excitation air chamber for driving the piston to move downward are provided in the cylinder; a step portion is provided on the inner side of the top end of the cylinder so that the excitation air chamber is formed between the top end of the piston and the top end of the cylinder, and the excitation air chamber is connected to the first air inlet hole opened on the upper part of the positioning rod; the inner cavity of the cylinder between the top end and the bottom end of the piston is the main air chamber, and the main air chamber is connected to the second air inlet hole opened in the middle of the piston and the third air inlet hole opened on the positioning rod;

[0010] The umbilical cable is a hollow structure, one end of the umbilical cable is sleeved on the positioning rod and communicated with the air path of the air hammer, and the other end of the umbilical cable extends out of the top of the sheath and is connected to an external air supply device and a data acquisition instrument;

[0011] The bottom end of the sheath is connected to the penetrator, a pressure sensor and a counter are arranged between the penetrator and the sheath, and a depth sensor is arranged outside the penetrator.

[0012] On the basis of the above technical solution, the present invention can be improved as follows:

[0013] Furthermore, the positioning rod is provided with a first air duct, a second air duct and a cable channel, the port of the first air duct is installed with a solenoid valve, the solenoid valve is connected to the cable in the umbilical cable, the first air duct is communicated with the first air inlet hole, the second air duct is communicated with the third air inlet hole, the cable in the umbilical cable passes through the cable channel, a stop block is provided on the inner side of the bottom end of the cylinder, an air hole is opened at the top end of the cylinder, and an air hammer one-way valve is installed in the air hole.

[0014] Furthermore, the piston includes a top plate, a bottom plate and a connecting tube, the top plate is connected to the top end of the connecting tube, and the bottom plate is connected to the bottom end of the connecting tube, forming an "I"-shaped structure; a stop portion is provided on the bottom side of the top plate for cooperating with the stop block, and the bottom plate cooperates with the stop block on the inner side of the bottom end of the cylinder.

[0015] Furthermore, the top plate, the bottom plate and the connecting pipe are an integrally formed structure or an assembled structure.

[0016] Furthermore, the gas supply equipment is an air compressor and a gas storage cylinder.

[0017] Furthermore, the umbilical cable includes an outer shell, a tensile steel wire layer, a signal line layer and an air pipe which are arranged in sequence from the outside to the inside, and an insulating layer is provided between the tensile steel wire layer and the signal line layer and between the signal line layer and the air pipe.

[0018] Furthermore, the upper end of the air pipe is connected to the air compressor, the lower end of the air pipe is sleeved on the positioning rod, the upper and lower ends of the signal line layer extend out of the outer shell, the upper end of each signal line is connected to the data acquisition instrument, and the lower end of each signal line is respectively connected to the pressure sensor, counter and depth sensor, and the lower end of the tensile steel wire is fixed on the positioning rod or the sheath.

[0019] Furthermore, a screw hole is provided at the bottom end of the sleeve, a stud is provided at the top end of the penetrator, and the screw hole and the stud are threadedly connected to each other.

[0020] To solve the above second technical problem, the technical solution adopted by the present invention is as follows:

[0021] A large depth standard penetration test method, characterized in that the test method is based on the large depth standard penetration test device and comprises the following steps:

[0022] S1: Pre-drill the detection hole and assemble the large-depth standard penetration test device;

[0023] S2: Place the large-depth standard penetration test device at the bottom of the detection hole while keeping the umbilical cable in a relaxed state;

[0024] S3: Start the air compressor to charge the compressed gas into the gas storage bottle and the air hammer respectively;

[0025] S4: After the data acquisition instrument shows that the gas cylinder and the air hammer have reached the set pressure value, an excitation signal is sent out to excite the air hammer to explode and generate impact force;

[0026] S5: Each sensor on the large-depth standard penetration test device transmits the data of impact force, penetration depth and impact times collected to the data acquisition instrument;

[0027] S6: The data acquisition instrument processes the collected data and calculates the bearing capacity of the foundation.

[0028] The working principle of the present invention is:

[0029] Compressed air is filled into the air hammer, and after it is excited, the compressed air in the air hammer is instantly released to form an air explosion, generating an impact force, wherein the downward impact force penetrates the penetrator into the soil, and the reverse impact force causes the air hammer to rush upward along the inner cavity of the jacket, overcoming the gravity of the air hammer, while the impact force spreading to the surroundings is offset by the jacket; after the air hammer rushes to the highest point, it falls back to the bottom of the jacket under the action of its own gravity, and the compressed air generated by the reduction in volume between the air hammer and the bottom of the jacket flows out from the one-way valve, and when the main air chamber is inflated again, the compressed air pushes the piston to move upward and reset, and the air in the exciting air chamber flows out from the one-way valve of the air hammer, restoring the state to be excited; the air hammer cycles the above operation process to achieve multiple air explosions and repeatedly impact the penetrator; by controlling and testing the pressure and volume of compressed air, a corresponding relationship is established between the impact force generated by the air explosion and the hammer force of the air hammer when it falls freely and the hammer force of the standard penetration test, so as to conduct the test in accordance with the existing penetration test specifications.

[0030] Compared with the prior art, the technology of the present invention has the following advantages:

[0031] (1) The test device of the present invention adopts an air hammer with a special structure. The force generated by the air hammer replaces the hammer force of the free fall of the hammer in the prior art, and can hammer at the bottom of the wellbore, effectively eliminating the energy loss of the probe rod and improving the test efficiency of the standard penetration test;

[0032] (2) The test device of the present invention can control the distance between the hammer force application point and the penetrator to always be within a reasonable range, thereby increasing the applicable test depth, achieving accurate measurement results, having a simple overall structure, and having a low manufacturing cost, which is conducive to popularization and use;

[0033] (3) The air hammer used in the test device of the present invention has a simple overall structure and light weight. Compared with the traditional explosive air hammer, it is safer and has greater impact force;

[0034] (4) The experimental method of the present invention has simple steps, high experimental efficiency, and broad prospects for promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Figure 1 It is a structural schematic diagram of a large depth standard penetration test device of the present invention;

[0037] Figure 2 It is a schematic diagram of the structure of the umbilical cable of the present invention;

[0038] Figure 3 It is a structural schematic diagram of the air hammer of the present invention.

[0039] Markings on the accompanying drawings: 1-sheath, 2-air hammer, 2a-cylinder, 2b-piston, 2c-excitation air chamber, 2d-main air chamber, 2e-second air inlet, 3-penetrator, 4-exhaust hole, 5-check valve, 6-positioning rod, 6a-first air inlet, 6b-third air inlet, 6e-first air duct, 6f-second air duct, 6g-cable channel, 7-umbilical cable, 7a-housing, 7b-tensile steel wire layer, 7c-signal line layer, 7d-trachea, 7e-insulating layer, 8-data acquisition instrument, 9-air compressor, 10-gas cylinder, 11-stud, 12-pressure sensor, 13-counter, 14-depth sensor, 15-stop block, 16-air hammer check valve, 17-solenoid valve. DETAILED DESCRIPTION

[0040] See also Figure 1 A large depth standard penetration test device of the present embodiment comprises a jacket 1, an air hammer 2, a penetrator 3 and an umbilical cable 7. The top end of the jacket 1 is open and the bottom end is closed. The jacket 1 is provided with two symmetrically arranged exhaust holes 4. A one-way valve 5 is installed in the exhaust hole 4. The one-way valve 5 opens and closes in one direction toward the outside of the jacket 1. A positioning rod 6 is provided in the jacket 1. The air hammer 2 is installed in the jacket 1 and sleeved on the positioning rod 6. The air hammer 2 moves up and down along the positioning rod 6. The umbilical cable 7 is a hollow structure. One end of the umbilical cable 7 is sleeved on The positioning rod 6 is connected to the air circuit of the air hammer 2, and the other end of the umbilical cable 7 extends out of the top of the sheath 1 and is connected to the external air supply equipment and the data acquisition instrument 8. The air supply equipment in this embodiment is an air compressor 9 and a gas storage bottle 10; a screw hole is provided at the bottom end of the sheath 1, and a stud 11 is provided at the top end of the penetrator 3. The screw hole and the stud 11 are threadedly connected to each other, so that the sheath 1 and the penetrator 3 are connected to each other, and a pressure sensor 12 and a counter 13 are provided between the penetrator 3 and the sheath 1, and a depth sensor 14 is provided on the outside of the penetrator 3.

[0041] When conducting a large-depth standard penetration test, place the test device in the wellbore, keep the umbilical cable 7 in a relaxed state, start the air compressor 9 to charge compressed air into the gas cylinder 10 and the air hammer 2 respectively, and after the data acquisition instrument 8 displays that the inflation reaches the set value, an excitation signal is sent to the air hammer 2, and the air hammer 2 instantly releases a large amount of compressed air in the sheath 1, and the piston 2b moves downward rapidly, generating an impact force downward to make the penetrator 3 penetrate into the soil, and the reaction force of the impact force upwards to make the air hammer 2 move upwards, and a part of the impact force of the gas spreads to the surroundings and is blocked and offset by the sheath 1 to avoid causing the wellbore to collapse; the pressure sensor 12 collects the impact The counter 13 records the number of impacts, the depth sensor 14 collects the penetration depth of the penetrator 3, and the various data obtained are fed back to the data acquisition instrument 8, and the data acquisition instrument 8 processes the data to obtain the foundation bearing capacity; the air hammer 2 in the embodiment can hammer at the bottom of the wellbore, and the distance between the hammer force application point and the penetrator 3 is always kept within a reasonable range. Therefore, the large-depth standard penetration test device in this embodiment effectively eliminates the energy loss of the probe rod, improves the test efficiency of the standard penetration test, increases the applicable test depth, and has accurate measurement results. The overall structure is simple and the manufacturing cost is low, which is conducive to popularization and use.

[0042] See also Figure 2 The umbilical cable 7 in this embodiment includes an outer shell 7a, a tensile steel wire layer 7b, a signal line layer 7c and an air pipe 7d which are arranged in sequence from the outside to the inside. An insulating layer 7e is provided between the tensile steel wire layer 7b and the signal line layer 7c and between the signal line layer 7c and the air pipe 7d. The signal line layer 7c is composed of a plurality of signal lines. The upper end of the air pipe 7d is connected to the air compressor 9, and the lower end of the air pipe 7d is sleeved on the positioning rod 6. The upper and lower ends of the signal line layer 7c extend out of the outer shell 7a. The upper end of each signal line is connected to the data acquisition instrument 8, and the lower end of each signal line is respectively connected to the pressure sensor 12, the counter 13 and the depth sensor 14. The lower end of the tensile steel wire is fixed on the positioning rod 6 or the sheath 1.

[0043] See also Figure 3The air hammer in this embodiment includes a cylinder 2a and a piston 2b. The top end of the cylinder 2a is closed and the bottom end is open. The cylinder 2a is sleeved on the positioning rod 6. The piston 2b is installed in the cylinder 2a and sleeved on the positioning rod 6. The piston 2b moves up and down along the cylinder 2a. A step portion is provided on the inner side of the top end of the cylinder 2a, so that an excitation air chamber 2c is formed between the top end of the piston 2b and the top end of the cylinder 2a. The excitation air chamber 2c is communicated with a first air inlet 6a provided on the upper part of the positioning rod 6. The inner cavity of the cylinder located between the top and the bottom of the piston 2b forms a main air chamber 2d. The main air chamber 2d is communicated with a second air inlet 2e provided on the middle part of the piston 2b and a third air inlet 6b provided on the positioning rod 6. The positioning rod 6 is provided with a first air passage 6e, a second air passage 6f and a cable passage 6g. The port of the first air passage 6e is provided with an electromagnetic valve 17, and the electromagnetic valve 17 is connected to the umbilical cable 7. Cable connection, the first air duct 6e is connected with the first air inlet 6a, the second air duct 6f is connected with the third air inlet 6b, the cable in the umbilical cable 7 passes through the cable channel 6g, a stop block 15 is provided on the inner side of the bottom end of the cylinder 2a to prevent it from escaping from the cylinder 2a, and an air vent is provided on the top end of the cylinder 2a, and an air hammer one-way valve 16 is installed in the air vent, wherein the piston 2b in this embodiment includes a top plate, a bottom plate and a connecting pipe, the top plate is connected to the top end of the connecting pipe, and the bottom plate is connected to the bottom end of the connecting pipe, and is integrally formed to form an "I"-shaped structure. According to actual needs, an "I"-shaped structure can also be formed by assembly; a stop portion for cooperating with the stop block 15 is provided on the bottom side of the top plate, and the bottom plate cooperates with the stop block 15 on the inner side of the bottom end of the cylinder; the air hammer in this embodiment has a simple overall structure and light weight. Compared with traditional explosive air hammers, it has high safety and great impact force.

[0044] The compressed air enters the main air chamber 2d after passing through the third air inlet hole 6b and the second air inlet hole 2e in sequence along the second air passage 6f, and the compressed air pushes the piston 2b to move upward, so that the top end of the piston 2b presses against the step portion of the cylinder 2a, and the bottom end of the piston 2b seals the bottom end of the cylinder 2a; when excited, the solenoid valve 17 is opened, and the compressed air enters the excitation air chamber 2c along the first air passage 6e through the first air inlet hole 6a, and the compressed air pushes the piston 2b to move downward, the bottom end of the cylinder 2a is opened, and the compressed air in the main air chamber 2d is instantly released to the outside of the cylinder 2a, forming an expansion explosion, and the piston 2b moves downward under the impact force of the explosion, and stops when the stop portion on the top plate of the piston 2b cooperates with the stop block 15; according to actual conditions, an air hammer 2 with other structures can also be used, and the air hammer 2 can also form an expansion explosion to push the penetrator 3.

[0045] After the air hammer 2 is pushed up to the highest point by the reaction force, it falls back to the bottom of the sleeve 1 under the action of its own gravity. The compressed air generated by the reduction in volume between the air hammer 2 and the bottom of the sleeve 1 flows out from the one-way valve 5. When the main air chamber 2d is inflated again, the compressed air pushes the piston 2b to move upward and reset, and the air in the exciting air chamber 2c flows out from the air hammer one-way valve 16 to restore the state to be excited; the air hammer 2 cycles the above operation process to achieve multiple air explosions and repeatedly impact the penetrator 3; by controlling and testing the compressed air pressure and volume, a corresponding relationship is established between the impact force generated by the air explosion and the hammer force of the air hammer when it falls freely and the hammer force of the standard penetration test, so that the test is carried out in accordance with the existing penetration test specifications.

[0046] The deep standard penetration test method of this embodiment comprises the following steps:

[0047] (1) Pre-drill detection holes and assemble the large-depth standard penetration test device;

[0048] (2) Place the deep standard penetration test device at the bottom of the detection hole while keeping the umbilical cable in a relaxed state;

[0049] (3) starting the air compressor 9 to charge the compressed gas into the gas cylinder 10 and the air hammer 2 respectively;

[0050] (4) After the data acquisition instrument 8 displays that the gas cylinder 10 and the air hammer 2 have reached the set pressure value, an excitation signal is issued to excite the air hammer 2 to explode and generate impact force;

[0051] (5) Each sensor on the deep standard penetration test device transmits the data collected on the impact force, penetration depth, and impact times to the data acquisition device 8;

[0052] (6) The data acquisition device 8 processes the collected data and calculates the bearing capacity of the foundation.

[0053] After the standard penetration device in this embodiment is sealed by existing sealing and waterproofing measures, it can also be used for underwater testing work. When working underwater, the obtained data needs to be corrected and calibrated in combination with the influencing factors of the water body.

[0054] The above embodiments of the present invention are not intended to limit the protection scope of the present invention, and the implementation modes of the present invention are not limited thereto. All other modifications, replacements or changes made to the above structures of the present invention based on the above contents of the present invention, in accordance with common technical knowledge and customary means in the art, without departing from the above basic technical ideas of the present invention, should fall within the protection scope of the present invention.

Claims

1. A large depth standard penetration test device, characterized in that: It includes umbilical cable, sheath, air hammer and penetrator, among which: The top end of the sheath is open and the bottom end is closed. The sheath is provided with at least one exhaust hole, a one-way valve is installed in the exhaust hole, and a positioning rod is provided in the sheath; The air hammer is installed in the sheath and sleeved on the positioning rod. The air hammer moves up and down along the positioning rod. The air hammer includes a cylinder and a piston. The top end of the cylinder is closed and the bottom end is open. The cylinder is sleeved on the positioning rod. The piston is installed in the cylinder and sleeved on the positioning rod. The piston moves up and down along the inner cavity of the cylinder. A main air chamber for driving the piston to move upward and an excitation air chamber for driving the piston to move downward are provided in the cylinder; a step portion is provided on the inner side of the top end of the cylinder so that the excitation air chamber is formed between the top end of the piston and the top end of the cylinder, and the excitation air chamber is connected to the first air inlet hole opened on the upper part of the positioning rod; the inner cavity of the cylinder between the top end and the bottom end of the piston is the main air chamber, and the main air chamber is connected to the second air inlet hole opened in the middle of the piston and the third air inlet hole opened on the positioning rod; The umbilical cable is a hollow structure, one end of the umbilical cable is sleeved on the positioning rod and communicated with the air path of the air hammer, and the other end of the umbilical cable extends out of the top of the sheath and is connected to an external air supply device and a data acquisition instrument; The bottom end of the sheath is connected to the penetrator, a pressure sensor and a counter are arranged between the penetrator and the sheath, and a depth sensor is arranged outside the penetrator.

2. The large depth standard penetration test device according to claim 1, characterized in that: The positioning rod is provided with a first air duct, a second air duct and a cable channel, a solenoid valve is installed at the port of the first air duct, the solenoid valve is connected to the cable in the umbilical cable, the first air duct is communicated with the first air inlet hole, the second air duct is communicated with the third air inlet hole, the cable in the umbilical cable passes through the cable channel, a stop block is provided on the inner side of the bottom end of the cylinder, an air hole is opened at the top end of the cylinder, and an air hammer one-way valve is installed in the air hole.

3. The large depth standard penetration test device according to claim 2, characterized in that: The piston includes a top plate, a bottom plate and a connecting tube, wherein the top plate is connected to the top end of the connecting tube, and the bottom plate is connected to the bottom end of the connecting tube, forming an "I"-shaped structure; a stop portion for cooperating with the stop block is provided on the bottom side of the top plate, and the bottom plate cooperates with the stop block on the inner side of the bottom end of the cylinder.

4. The large depth standard penetration test device according to claim 3, characterized in that: The top plate, the bottom plate and the connecting pipe are an integrally formed structure or an assembled structure.

5. The large depth standard penetration test device according to any one of claims 1 to 4, characterized in that: The gas supply equipment is an air compressor and a gas storage cylinder.

6. The large depth standard penetration test device according to claim 5, characterized in that: The umbilical cable comprises an outer shell, a tensile steel wire layer, a signal line layer and an air pipe which are arranged in sequence from the outside to the inside, and an insulating layer is arranged between the tensile steel wire layer and the signal line layer and between the signal line layer and the air pipe.

7. The large depth standard penetration test device according to claim 6, characterized in that: The upper end of the air pipe is connected to the air compressor, the lower end of the air pipe is sleeved on the positioning rod, the upper and lower ends of the signal line layer extend out of the shell, the upper end of each signal line is connected to the data acquisition instrument, the lower end of each signal line is respectively connected to the pressure sensor, the counter and the depth sensor, and the lower end of the tensile steel wire is fixed on the positioning rod or the sheath.

8. The large depth standard penetration test device according to claim 7, characterized in that: A screw hole is arranged at the bottom end of the sheath, a stud is arranged at the top end of the penetrator, and the screw hole and the stud are threadedly connected to each other.

9. A test method based on the large depth standard penetration test device according to claim 8, characterized in that: The following steps are involved: S1: Pre-drill the detection hole and assemble the large-depth standard penetration test device; S2: Place the large-depth standard penetration test device at the bottom of the detection hole while keeping the umbilical cable in a relaxed state; S3: Start the air compressor to charge the compressed gas into the gas storage bottle and the air hammer respectively; S4: After the data acquisition instrument shows that the gas cylinder and the air hammer have reached the set pressure value, an excitation signal is sent out to excite the air hammer to explode and generate impact force; S5: Each sensor on the large-depth standard penetration test device transmits the data of impact force, penetration depth and impact times collected to the data acquisition instrument; S6: The data acquisition instrument processes the collected data and calculates the bearing capacity of the foundation.

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