A cement mixing pile detection system and method based on a preset pipe side pressure test

Abstract

The application discloses a cement mixing pile detection system and method based on a preset pipe lateral pressure test, which comprises a preset pipe, a cutting tool, a lateral pressure instrument, a calculation module and a judgment module. The cutting tool is used to release the hoop constraint force of the preset pipe after the cement mixing pile reaches a preset age. The lateral pressure instrument is used to perform a lateral pressure test in the preset pipe and obtain the plastic pressure of the detection point. The calculation module is used to calculate the uniaxial tensile strength and uniaxial compressive strength of the cement mixing pile body detection point according to the obtained plastic pressure. The judgment module is used to judge whether the cement mixing pile is qualified. The detection test is performed in situ in the pile body without drilling and coring, and there are no uncertain influencing factors. Detection data can be obtained at any depth position of the whole length of the pile body. Any pile in the site is provided with a detection hole, and the detection sample is completely randomly selected. The tools and instruments used in the detection test are convenient to carry, and the detection process operation is simple and fast.

Description

TECHNICAL FIELD

[0001] The present application relates to cement mixing pile quality detection, in particular to a cement mixing pile detection system and method based on pre-pipe lateral pressure test. BACKGROUND

[0002] Cement mixing pile is a commonly used soft soil foundation reinforcement pile type, and the pile body strength is a must-check index for engineering acceptance. The conventional method for detection needs drilling, core extraction, uniaxial compression test and other processes. For example, the patent application with the publication number CN110130419A discloses a cement mixing pile construction quality detection device and method, which drills a hole in the center position of the cement mixing pile and then performs inspection. However, there are problems such as great difficulty in drilling and core extraction of the pile body, uncertain core sample taking rate, difficulty in covering the whole pile length with the detection samples, limited number of drilled holes, and insufficient randomness and representativeness of the detection samples. SUMMARY

[0003] The present application provides a cement mixing pile detection system based on pre-pipe lateral pressure test without drilling and core extraction, and the detection samples are random.

[0004] The present application also provides a cement mixing pile detection method based on pre-pipe lateral pressure test.

[0005] Technical scheme: To solve the above problems, the present application adopts a cement mixing pile detection system based on pre-pipe lateral pressure test, which comprises a pre-pipe implanted immediately after the construction of the cement mixing pile, a cutting tool, a lateral pressure instrument, a calculation module, and a judgment module. The cutting tool is used to release the hoop restraint force of the pre-pipe after the cement mixing pile reaches the preset age. The lateral pressure instrument is used to perform lateral pressure test in the pre-pipe with the hoop restraint force released and obtain the plastic pressure of the cement mixing pile body detection point. The calculation module is used to calculate the uniaxial tensile strength and uniaxial compressive strength of the cement mixing pile body detection point according to the obtained plastic pressure. The judgment module is used to judge whether the cement mixing pile is qualified according to the obtained uniaxial tensile strength and uniaxial compressive strength.

[0006] Further, the cutting tool comprises a tool holder, a plurality of blades hinged to the tool holder, and a tool bar driving the blades to rotate. The tool bar is slidingly arranged in the tool holder. The tool bar comprises a first limiting portion and a second limiting portion fixed to the lower end of the first limiting portion. The side of the first limiting portion in contact with the blades is a bevel gradually moving away from the rotation center of the blades from top to bottom. The side of the second limiting portion in contact with the blades is perpendicular to the extension direction of the pre-pipe. When the tool bar moves from top to bottom, it drives the blades to rotate close to the side of the first limiting portion, and the blades are retracted into the tool holder. When the tool bar moves from bottom to top, it drives the blades to rotate close to the second limiting portion, and the blades are extended out of the tool holder. The movement of the tool holder drives the blades to cut the pre-pipe.

[0007] Further, the cutting tool further comprises a nut, a spring and a spring compression pin arranged on the upper end of the tool holder, one end of the spring is fixedly connected with the tool holder, the other end of the spring is fixedly connected with the nut, the tool rod is fixedly connected with the nut, when the spring compression pin is clamped in the tool holder through the nut, the spring is compressed, and the blade contacts the side edge of the first limiting part of the tool rod; when the spring compression pin is pulled out of the tool holder, the spring restores, the tool rod moves upward from bottom to top, and the blade fully contacts the second limiting part.

[0008] Further, the tool holder is cylindrical, the tool holder is sleeved on the outer side of the tool rod, and a plurality of blades are uniformly arranged in the circumferential direction of the tool holder.

[0009] The cement mixing pile detection method based on the pre-set pipe lateral pressure test further comprises the following steps:

[0010] (1) immediately implanting the pre-set pipe after the cement mixing pile construction;

[0011] (2) cutting the pre-set pipe after the cement mixing pile reaches the preset age, and releasing the circumferential constraint force of the pre-set pipe;

[0012] (3) sending the lateral pressure instrument probe into the pre-set pipe with the circumferential constraint force released, starting the lateral pressure test after reaching the predetermined depth, and obtaining the plastic pressure of the cement mixing pile body detection point;

[0013] (4) calculating the uniaxial tensile strength and the uniaxial compressive strength of the cement mixing pile body detection point according to the obtained plastic pressure;

[0014] (5) judging whether the cement mixing pile is qualified according to the obtained uniaxial tensile strength and uniaxial compressive strength.

[0015] Further, when the lateral pressure test is performed in the step (4), the lateral pressure instrument probe pressure and the corresponding probe volume expansion are recorded, the lateral pressure test curve is obtained, the lateral pressure test curve is regarded as an effective test result if the lateral pressure test curve is of a sudden change type, and the plastic pressure is taken as the sudden change point pressure of the lateral pressure test curve.

[0016] Further, the calculation formula of the uniaxial tensile strength R t of the cement mixing pile body detection point is as follows:

[0017]

[0018] wherein r0 is the outer wall radius of the pre-set pipe, p f is the plastic pressure of the pile body detection point, and r bR is the uniaxial compressive strength of the pile body at the detection point, p0 is the initial horizontal pressure at the detection point depth.

[0019] R is the uniaxial compressive strength of the pile body at the detection point c The calculation formula is as follows:

[0020]

[0021] Advantages: compared with the prior art, the present application has the following advantages: 1. The detection test is carried out in situ in the pile body, without the need for drilling and coring, and without uncertain influencing factors; 2. Detection data can be obtained at any depth position of the pile body; 3. Any pile in the site is provided with a detection hole, and the detection sample is completely randomly selected; 4. The test index and the uniaxial compressive strength have a theoretical explicit relationship, and the detection data processing algorithm is established according to the rock mass strength theory; 5. The tools and instruments used in the detection test are convenient to carry, and the detection process is simple and fast. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Fig. 3 shows a cross-sectional view of the cutting tool when the blade is locked in the present application.

[0023] Figure 2 Fig. 4 shows a cross-sectional view of the cutting tool when the blade is unfolded in the present application.

[0024] Figure 3 Fig. 5 shows a flow chart of the cement mixing pile detection method in the present application.

[0025] Figure 4 Fig. 6 shows a schematic diagram of the lateral pressure test curve in the present application.

[0026] Figure 5 Fig. 7 shows a strength calculation principle diagram of the pile body detection point in the present application. DETAILED DESCRIPTION

[0027] The cement mixing pile detection system based on the preset pipe lateral pressure test in the present embodiment comprises a preset pipe, a cutting tool, a lateral pressure instrument, a calculation module and a judgment module, which are implanted immediately after the cement mixing pile construction. The preset pipe is an industrial finished pipe made of PVC material with an outer diameter of 40 mm, a wall thickness of 1.2-1.6 mm and an inner cavity diameter of not less than 36 mm. The cutting tool releases the hoop constraint force of the preset pipe after the cement mixing pile reaches the preset age. The lateral pressure instrument is used to carry out the lateral pressure test in the preset pipe with the released hoop constraint force and obtain the plastic pressure of the cement mixing pile detection point. The calculation module is used to calculate the uniaxial tensile strength and the uniaxial compressive strength of the cement mixing pile detection point according to the obtained plastic pressure. The judgment module is used to judge whether the cement mixing pile is qualified according to the obtained uniaxial tensile strength and uniaxial compressive strength.

[0028] As Figure 1As shown, the cutting tool includes a knife seat 3, a plurality of blades 5 hinged on the knife seat 3, a knife rod 7 for driving the blades to rotate, a nut 2 arranged at the upper end of the knife seat 3, a spring 4, and a spring tightening pin 1. The knife seat 3 is cylindrical, and the knife seat 3 is sleeved on the outside of the knife rod 7. The blade is hinged to the knife seat 3 through a pin 6. A plurality of blades 5 are evenly arranged around the knife seat 3. In this embodiment, four blades are arranged. The diameter of the cylinder of the trigger-type four-blade slitting knife is less than 35 mm in the retracted state to ensure that the blade body can be smoothly delivered to the bottom of the pipe. The diameter of the blade after expansion is 40 to 42 mm. The tip of the blade cuts through the pipe wall and contacts the pile body but does not affect the strength of the pile body.

[0029] The knife rod 7 is slidably set in the knife seat, and the knife rod 7 includes a first limiting portion 71 and a second limiting portion 72 fixed to the lower end of the first limiting portion 71. The side of the first limiting portion 71 in contact with the blade 5 is a bevel that gradually moves away from the rotation center of the blade 5 from top to bottom. The side of the second limiting portion 72 in contact with the blade is perpendicular to the extension direction of the preset tube. When the knife rod 7 moves from top to bottom, it drives the blade to rotate close to the side of the first limiting portion 71, and the blade is retracted into the knife seat 3. When the knife rod 7 moves from bottom to top, it drives the blade to rotate close to the second limiting portion 72, and the blade extends out of the knife seat 3. The movement of the knife seat drives the blade to cut the preset tube.

[0030] One end of the spring 4 is fixedly connected to the knife seat 3, and the other end of the spring 4 is fixedly connected to the nut. The knife rod 7 is fixedly connected to the nut 2. The knife seat 3 is provided with a slot, and the spring locking pin 1 is provided with a retractable locking steel ball 8. When the spring tightening pin 1 passes through the nut 2 and the locking steel ball is stuck in the slot of the knife seat 3, the spring 4 is compressed, and the blade 5 contacts the side of the first limiting portion 71 of the knife rod 7; Figure 2 As shown, when the spring tightening pin 1 is pulled out from the knife seat 3, the spring 4 is restored, and the knife rod 7 moves from bottom to top until the blade completely contacts the second limiting portion 72.

[0031] When the blade is retracted, the tool assumes a cylindrical shape, with an outer diameter smaller than the inner bore of the pipe to be cut. The entire tool can be lowered into the bottom of a vertical pipe. By pulling out the spring-loaded locking pin 1, spring 4 lifts nut 2, bringing the tool bar 7 to its upper working position. The flat surface of tool bar 7 causes blade 5 to pivot around pin 6 and pop out. The tips of the ejected blades 6 are fixed to the inner bore of the plastic pipe wall. Using a steel cable to pull out tool bar 7, the entire tool is extended, and the four ejected blades 6 divide the pipe into four sections.

[0032] Example 2

[0033] like Figure 3 As shown, in this embodiment, a cement mixing pile detection method based on a pre-set pipe side pressure test includes the following steps:

[0034] (1) In the cement mixing pile construction immediately after the implantation of pre-set pipe, at this time the pile body is in a plastic or plastic state, the lower end of the 40mm outer diameter of PVC pipe can be inserted into the bottom of the pile body, the two PVC pipe connection sleeve pipe joint and cementation;

[0035] (2) In the cement mixing pile reaches the preset age of 28 days after cutting the pre-set pipe, the cutting tool of the trigger type four-blade slotting cutter reaches the bottom of the hole, the cutting tool structure is consistent with that described in embodiment 1, which will not be described in this embodiment, the blade triggers the lifting of the cutter body from bottom to top through the full length of the pre-set pipe body, and the pre-set pipe wall is opened at the same time Four through slots, the hoop constraint force of the pre-set pipe is released;

[0036] (3) The diameter of the lateral pressure instrument probe is 33mm, which is sent to the pre-set pipe with the hoop constraint force released, and the lateral pressure test is started after reaching the predetermined depth. Record the lateral pressure instrument probe pressure and the corresponding probe volume expansion until the probe pressure appears the yield characteristics. Obtain the lateral pressure test curve, which is shown as the lateral pressure test curve, and the sudden change point pressure is considered as the effective test result, as shown in Figure 4 , and the intersection pressure value of the straight line segment extension line before and after the curve mutation.

[0037] (4) According to the obtained plastic pressure, the uniaxial tensile strength and uniaxial compressive strength of the cement mixing pile body detection point are calculated; according to the outer wall radius r0 of the precast pipe, the pile body radius r b , the initial horizontal pressure p0 at the detection point depth, the radial stress σ r and the tangential stress σ θ of any point of the hole wall medium are calculated under the condition of linear elastic homogeneous material, as formula (1); when the tangential stress of the medium appears crack, σ θ =0, according to the condition of Δσ r =-Δσ θ , according to the circular hole radius r0 and the pile body radius r b , the relationship between the tensile strength R t of the pile body and the plastic pressure p f in the hole is established as formula (2);

[0038]

[0039]

[0040] According to Griffith strength theory, the ratio m of the compressive strength to the tensile strength of rock is a constant, that is , and the theoretical value is 8, so the compressive strength of the pile body is calculated as formula (3). The value of m is related to the sample method and sample shape of rock tensile strength, which can be determined by sampling and testing on site, which is special for detection site.

[0041]

[0042] (5) According to the obtained uniaxial tensile strength and uniaxial compressive strength, it is judged whether the cement mixing pile is qualified. According to the uniaxial compressive strength value of the pile body detection point obtained by the lateral pressure test data, the pile body quality level is evaluated according to the index required by the design scheme, and the compressive strength value is not less than the index to determine the qualification.

Claims

1. A cement mixing pile detection system based on pre-set pipe side pressure test, characterized in that: It includes a pre-set pipe implanted immediately after the construction of the cement mixing pile, a cutting tool, a lateral pressure meter, a calculation module, and a judgment module; the cutting tool is used to release the circumferential constraint of the pre-set pipe after the cement mixing pile reaches a preset age; the lateral pressure meter is used to perform a lateral pressure test in the pre-set pipe with the circumferential constraint released, and obtain the critical pressure of the cement mixing pile body inspection point; the calculation module is used to calculate the uniaxial tensile strength and uniaxial compressive strength of the cement mixing pile body inspection point according to the obtained critical pressure; the judgment module is used to judge whether the cement mixing pile is qualified according to the obtained uniaxial tensile strength and uniaxial compressive strength.

2. The cement mixing pile detection system according to claim 1, characterized in that: The cutting tool comprises a knife seat (3), a plurality of blades (5) hinged on the knife seat (3), and a knife rod (7) for driving the blades to rotate. The knife rod (7) is slidably arranged in the knife seat. The knife rod (7) comprises a first limiting portion (71) and a second limiting portion (72) fixed to the lower end of the first limiting portion (71). The side of the first limiting portion (71) in contact with the blade (5) is a bevel that gradually moves away from the rotation center of the blade (5) from top to bottom. The side of the second limiting portion (72) in contact with the blade is perpendicular to the extension direction of the preset tube. When the knife rod (7) moves from top to bottom, it drives the blade to rotate close to the side of the first limiting portion (71), and the blade is retracted into the knife seat (3). When the knife rod (7) moves from bottom to top, it drives the blade to rotate close to the second limiting portion (72), and the blade extends out of the knife seat (3). The knife seat moves and drives the blade to cut the preset tube.

3. The cement mixing pile detection system according to claim 2, characterized in that: The cutting tool further includes a nut (2), a spring (4), and a spring tightening pin (1) arranged at the upper end of the knife seat (3); one end of the spring (4) is fixedly connected to the knife seat (3); the other end of the spring (4) is fixedly connected to the nut; the knife rod (7) is fixedly connected to the nut (2); when the spring tightening pin (1) passes through the nut (2) and is stuck in the knife seat (3), the spring (4) is compressed, and the blade (5) contacts the side of the first limiting portion (71) of the knife rod (7); When the spring tightening pin (1) is pulled out from the knife seat (3), the spring (4) is restored, and the knife rod (7) moves from bottom to top until the blade completely contacts the second limiting portion (72).

4. The cement mixing pile detection system according to claim 2 or 3, characterized in that: The knife seat (3) is cylindrical and is sleeved outside the knife rod (7). A plurality of blades (5) are evenly arranged around the knife seat (3).

5. The cement mixing pile detection system according to claim 4, characterized in that: The pre-installed pipe is a PVC pipe with an outer diameter of 40 mm, a wall thickness ranging from 1.2 to 1.6 mm, and an inner diameter of not less than 36 mm. When the blade is received in the knife seat (3), the outer diameter of the knife seat is less than 35 mm, and when the blade extends out of the knife seat, the blade diameter is 40 to 42 mm.

6. A cement mixing pile detection method based on a pre-set pipe side pressure test, characterized in that: The following steps are involved: (1) Immediately after the cement mixing pile is constructed, the pre-placed pipe is implanted; (2) After the cement mixing pile reaches the preset age, the pre-set pipe is cut to release the circumferential constraint of the pre-set pipe; (3) The lateral pressure gauge probe is sent into the pre-set pipe to release the annular constraint. After reaching the predetermined depth, the lateral pressure test is started to obtain the critical pressure of the cement mixing pile body test point; (4) Calculate the uniaxial tensile strength and uniaxial compressive strength of the cement mixing pile at the test point based on the obtained critical plastic pressure; (5) Determine whether the cement mixing pile is qualified based on the obtained uniaxial tensile strength and uniaxial compressive strength.

7. The cement mixing pile detection method according to claim 6, characterized in that: When performing the lateral pressure test in step (4), the lateral pressure gauge probe pressure and the corresponding probe volume expansion are recorded to obtain a lateral pressure test curve. A lateral pressure test curve showing a mutation type is regarded as a valid test result, and the pressure at the mutation point of the lateral pressure test curve is regarded as the critical pressure.

8. The cement mixing pile detection method according to claim 6, characterized in that: Uniaxial tensile strength of cement mixing pile at the testing point The calculation formula is: ； in, is the outer wall radius of the preset tube, is the critical pressure of the pile inspection point, is the pile radius, is the initial horizontal pressure at the depth of the detection point.

9. The cement mixing pile detection method according to claim 8, characterized in that: Uniaxial compressive strength of cement mixing pile at the testing point The calculation formula is: ； Where m is the ratio of the compressive strength to the tensile strength of the rock.

10. The cement mixing pile detection method according to claim 6, characterized in that: In the step (2), a cutting tool is used to cut the preset tube. The cutting tool includes a knife seat (3), a plurality of blades (5) hinged on the knife seat (3), and a knife rod (7) for driving the blades to rotate. The knife rod (7) is slidably arranged in the knife seat. The knife rod (7) includes a first limiting portion (71) and a second limiting portion (72) fixed to the lower end of the first limiting portion (71). The side of the first limiting portion (71) in contact with the blade (5) is a bevel that gradually moves away from the rotation center of the blade (5) from top to bottom. The side of the second limiting portion (72) in contact with the blade is perpendicular to the extension direction of the preset tube. When the knife rod (7) moves from top to bottom, it drives the blade to rotate close to the side of the first limiting portion (71), and the blade is retracted into the knife seat (3). When the knife rod (7) moves from bottom to top, it drives the blade to rotate close to the second limiting portion (72), and the blade extends out of the knife seat (3). The knife seat moves and drives the blade to cut the preset tube.

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