A method for detecting mud behind the top pipe wall using resistivity method

Abstract

This invention discloses a method for detecting mud behind the pipe jacking wall using the resistivity method, comprising the following steps: S1. Steel grouting pipes are pre-embedded at intervals along the circumferential and longitudinal directions inside the pipe jacking wall, and grouting is performed behind the pipe jacking wall through the grouting pipes; S2. Power supply electrodes A and B and measuring electrodes M and N are arranged circumferentially or longitudinally in the area to be tested in the pipe jacking wall; S3. A power supply is set between power supply electrodes A and B to apply an electric field to the mud behind the wall, and the current I between power supply electrodes A and B and the potential difference ΔU between electrodes M and N are measured. MN S4. Calculate the resistivity ρ between power supply electrodes A and B. s S5. The resistivity ρ measured in S4 s The resistivity of the slurry is compared with a pre-measured standard range to determine whether it meets the standard. The entire testing process of this invention is non-destructive and pollution-free to the jacking pipe. Comparison with the standard resistivity range allows for rapid and accurate determination of whether the grouting behind the wall in that area is complete, resulting in high testing efficiency.

Description

Technical Field

[0001] The invention relates to the field of pipe jacking construction, and in particular to a method for detecting mud behind a pipe jacking wall by adopting a resistivity method. Background Art

[0002] As one of the key technologies for long-distance pipe jacking construction, thixotropic mud drag reduction technology plays a vital role in the jacking construction process. Bentonite thixotropic mud is formed by mixing bentonite, water and admixtures in a certain proportion. This slurry has good thixotropic properties and has a good effect in lubricating and reducing drag and supporting the soil behind the wall. The thixotropic mud works by forming a dense and complete mud sleeve outside the pipe wall. However, during the pipe jacking process, the mud sleeve will be destroyed due to water loss, consolidation, friction and shedding with the surrounding soil, so it is necessary to timely detect the formation and distribution of the mud sleeve behind the pipe wall and perform secondary grouting. At present, there are few studies on the detection of the formation and distribution of the thixotropic mud sleeve behind the pipe wall. The traditional detection method is to open the grouting ball valve hole by hole, and check the slurry pressure behind the wall to determine whether to take secondary grouting measures. After the grouting ball valve is opened, the mud turbulently contaminates the inner wall in the jacking pipe, and the loss of mud is easy to cause ground subsidence. For long-distance pipe jacking, this detection method is inefficient and has randomness and uncertainty.

[0003] Resistivity is a characteristic of the mud itself. The resistivity of the damaged mud casing is completely different from that of the intact and dense mud casing. In the prior art, no method for detecting the mud behind the pipe wall using resistivity has been published.

[0004] Therefore, it is necessary to develop a method that is simple in steps and easy to operate to detect the mud behind the top pipe wall using the resistivity method. Without destroying the top pipe structure, the mud condition behind the top pipe wall can be measured conveniently and quickly, so as to deal with the situation of insufficient slurry in time according to the detection results. Summary of the invention

[0005] The purpose of the present invention is to solve the shortcomings of the above-mentioned background technology and to provide a method for detecting mud behind the top pipe wall by resistivity method with simple steps and convenient operation. The method can conveniently and quickly measure the mud condition behind the top pipe wall without destroying the top pipe structure, so as to deal with the situation of insufficient slurry in time according to the detection results.

[0006] The technical solution of the present invention is: a method for detecting mud behind the top pipe wall by using a resistivity method, characterized in that it comprises the following steps:

[0007] S1. Grouting pipes made of steel are pre-buried in the circumferential and longitudinal directions of the top pipe, and grouting is performed behind the top pipe through the grouting pipes;

[0008] S2. Power supply electrode A, power supply electrode B, measuring electrode M and measuring electrode N are arranged circumferentially or longitudinally in the area to be inspected in the top pipe,

[0009] The circumferential setting is as follows: the power supply electrode A and the power supply electrode B are electrically connected to two grouting pipes arranged at intervals in the circumferential direction one by one; in the area on the side where the circumferential distance between the two grouting pipes connected to the power supply electrodes A and B is shorter, two grouting pipes are selected to be electrically connected to the measuring electrode M and the measuring electrode N one by one; the measuring electrodes M and N are arranged in the circumferential direction adjacent to the power supply electrodes A and B respectively;

[0010] The longitudinal arrangement is as follows: the power supply electrode A and the power supply electrode B are electrically connected to two grouting pipes arranged at intervals in the longitudinal direction one by one, and then two grouting pipes are selected between the two grouting pipes connected to the power supply electrodes A and B to be electrically connected to the measuring electrode M and the measuring electrode N one by one, and the measuring electrodes M and N are respectively arranged longitudinally adjacent to the power supply electrodes A and B;

[0011] S3. A power supply is set between power supply electrodes A and B to apply an electric field to the mud behind the wall, and the current I between power supply electrodes A and B is measured, and the potential difference ΔU between electrodes M and N is measured. MN ;

[0012] S4. The resistivity between the power supply electrodes A and B is ρ s

[0013]

[0014] Where K is the device coefficient,

[0015]

[0016] ρ s = the resistivity between the power supply electrodes A and B, in Ω·m;

[0017] ΔU MN =Measure the potential difference between electrodes M and N, in V;

[0018] I = the current I between the power supply electrodes A and B, in A;

[0019] K = device coefficient, in m;

[0020] AM = the distance between the power supply electrode A and the measuring electrode M on the outer wall of the top pipe, in m;

[0021] AN = the distance between the power supply electrode A and the measuring electrode N on the outer wall of the top pipe, in m;

[0022] BM = the distance between the power supply electrode B and the measuring electrode M on the outer wall of the top pipe, in m;

[0023] BN = the distance between the power supply electrode B and the measuring electrode N on the outer wall of the top pipe, in m;

[0024] S5. The resistivity ρ measured by S4 s Compare with the pre-measured standard range of mud resistivity.

[0025] i) If the resistivity ρ s If it is within the standard range of mud resistivity, it means that the mud behind the wall between power supply electrodes A and B is complete and dense and meets the standard;

[0026] ii) If the resistivity ρ s If it is outside the standard range of mud resistivity, it means that the mud behind the wall between power supply electrode A and power supply electrode B is damaged and does not meet the standards, and needs to be supplemented.

[0027] Preferably, in step S1, both ends of each grouting pipe are exposed before being embedded to form a conductive area, and the remaining part is provided with an insulating layer. When each grouting pipe is embedded in the top pipe, the conductive areas at both ends extend from the inner and outer sides of the top pipe wall respectively, and the insulating layer covers at least the contact part between the grouting pipe and the top pipe.

[0028] Furthermore, the conductive area of ​​each grouting pipe is exposed circumferentially and 1-2 cm longitudinally.

[0029] Furthermore, the insulation layer of each grouting pipe is formed by coating an insulating coating.

[0030] Preferably, in step S2, the power supply electrode A, the power supply electrode B, the measuring electrode M and the measuring electrode N are all connected to the corresponding conductive areas at the inner ends of the grouting pipes.

[0031] Preferably, in step S5, the method for determining the standard range of mud resistivity includes: using the same mud as that used for grouting in step S1, performing multiple tests using a resistivity tester, and taking an average value ρ 0 is the standard value of mud resistivity, expressed as [(1-a)ρ 0 , (1+a)ρ 0 ] is the standard range of mud resistivity, where the value of a satisfies 30% ≥ a ≥ 5%.

[0032] Further, a is 20%.

[0033] Preferably, if there are other areas to be inspected on the top pipe, steps S2-S5 are repeated.

[0034] The beneficial effects of the present invention are:

[0035] 1. The principle of the detection of the present invention is: when there is a lack of mud behind the wall between the electrodes, the current of the external electric field will be blocked from passing through the area, resulting in a resistivity greater than the standard resistivity. The steel grouting pipe can transfer the current on the power supply electrode to the mud behind the wall, and the resistivity ρ can be converted by measuring the potential difference between the electrodes. s , no need to open the grouting ball valve to pass through ρs Rapidly characterize behind-the-wall grouting conditions.

[0036] 2. The power supply electrodes and measuring electrodes can be arranged in a circular direction or in a longitudinal direction, and can be flexibly selected according to the scope of the determination area, with wide adaptability.

[0037] 3. The entire test process does not damage or pollute the jacking pipe. By comparing with the standard resistivity range, it is possible to quickly and accurately determine whether the grouting behind the wall in this area is complete, with high detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of the grouting pipe structure

[0039] Figure 2 Schematic diagram of the circular arrangement of power supply electrodes A, B and measuring electrodes M, N

[0040] Figure 3 Schematic diagram of the circular arrangement of power supply electrodes A, B and measuring electrodes M, N

[0041] Figure 4 Schematic diagram of the longitudinal arrangement of power supply electrodes A, B and measuring electrodes M, N

[0042] Among them: 1-top pipe 2-grouting pipe 3-mud 4-stratum 21-conductive area 22-insulating layer. DETAILED DESCRIPTION

[0043] The present invention is further described in detail in the following specific examples. The standard resistivity of S5 in the following examples is measured by a resistivity measuring instrument of model DZL-88A produced by Qingdao Hengtaida Electromechanical Equipment Co., Ltd.

[0044] Example 1

[0045] The present invention provides a method for detecting mud behind a top pipe wall by using a resistivity method, which is characterized by comprising the following steps:

[0046] S1. Grouting pipes 2 made of steel are pre-buried in the circumferential and longitudinal directions of the top pipe 1. When each grouting pipe 2 is pre-buried in the top pipe 1, the axial direction is arranged along the radial direction of the top pipe 1. In this embodiment, the top pipe 1 is a round pipe, and the structure of each grouting pipe 2 is as follows: Figure 1 As shown, the two ends before embedding are exposed to form a conductive area 21, and the remaining part is provided with an insulating layer 22. The conductive area 21 is exposed in an annular direction and along its own longitudinal direction (i.e. Figure 1 The exposed size of the conductive area 21 in the left and right directions is 1-2 cm, the insulating layer 22 is formed by coating insulating paint, and the conductive areas 21 at both ends of the conductive area 21 extend from the inner and outer sides of the top pipe 1 wall when the grouting pipe 2 is pre-buried, and the insulating layer 22 at least covers the contact part between the grouting pipe 2 and the top pipe 1.

[0047] Perform back wall grouting on the top pipe 1 through the grouting pipe 2;

[0048] S2. The power supply electrode A, the power supply electrode B, the measuring electrode M and the measuring electrode N are arranged circumferentially or longitudinally in the area to be detected in the top pipe 1. In this embodiment, the power supply electrode A, the power supply electrode B, the measuring electrode M and the measuring electrode N are arranged circumferentially, specifically:

[0049] The power supply electrodes A and B are electrically connected to the two grouting pipes 2 arranged at intervals in the circumferential direction in a one-to-one correspondence. In the area on the side where the circumferential distance between the two grouting pipes connected by the power supply electrodes A and B is shorter, two grouting pipes 2 are selected to be electrically connected to the measuring electrodes M and N in a one-to-one correspondence. The measuring electrodes M and N are arranged in the circumferential direction adjacent to the power supply electrodes A and B, respectively.

[0050] Ring direction setting Figure 2 or Figure 3 As shown in Figure 2 The right side annular spacing of the two grouting pipes connected by the power supply electrodes A and B is less than the left side annular spacing, so the measuring electrodes M and N are set in the right area. Figure 3 The two grouting pipes connected to the power supply electrodes A and B are located at the radial ends of the top pipe 1, so the measuring electrodes M and N can be set in the left or right area. The power supply electrode A, the power supply electrode B, the measuring electrode M and the measuring electrode N are all located in the top pipe 1 and connected to the conductive area 21 at the inner end of the corresponding grouting pipe 2;

[0051] S3. A power supply is set between the power supply electrode A and the power supply electrode B to apply an electric field to the mud behind the wall, and the current I between the power supply electrodes A and B is measured, and the potential difference ΔU between the measuring electrodes M and N is measured. MN ;

[0052] S4. The resistivity between the power supply electrodes A and B is ρ s

[0053]

[0054] Where K is the device coefficient,

[0055]

[0056] ρ s = the resistivity between the power supply electrodes A and B, in Ω·m;

[0057] ΔU MN =Measure the potential difference between electrodes M and N, in V;

[0058] I = the current I between the power supply electrodes A and B, in A;

[0059] K is the device coefficient, in m;

[0060] AM = the distance between the power supply electrode A and the measuring electrode M on the outer wall of the top pipe, in m;

[0061] AN = the distance between the power supply electrode A and the measuring electrode N on the outer wall of the top pipe, in m;

[0062] BM = the distance between the power supply electrode B and the measuring electrode M on the outer wall of the top pipe, in m;

[0063] BN = the distance between the power supply electrode B and the measuring electrode N on the outer wall of the top pipe, in m;

[0064] S5. The resistivity ρ measured by S4 s The resistivity of the slurry is compared with the standard range of the resistivity of the slurry measured in advance. The method for determining the standard range of the resistivity of the slurry includes: using the same slurry as that used for grouting in step S1, performing multiple tests using a resistivity tester, and taking the average value ρ 0 is the standard value of mud resistivity, expressed as [(1-a)ρ 0 , (1+a)ρ 0 ] is the standard range of mud resistivity, where a satisfies 30% ≥ a ≥ 5%,

[0065] i) If the resistivity ρ s If it is within the standard range of mud resistivity, it means that the mud behind the wall between power supply electrodes A and B is complete and dense and meets the standard;

[0066] ii) If the resistivity ρ s If it is outside the standard range of mud resistivity, it means that the mud behind the wall between power supply electrode A and power supply electrode B is damaged and does not meet the standard, and secondary grouting is required.

[0067] If there are other areas to be inspected on the top pipe 1, steps S2-S5 are repeated.

[0068] The following is a further description of this patent in combination with specific numerical values:

[0069] In this embodiment, I=37A, ΔU MN =24V, AM=1m, AN=3m,

[0070] BM=3m、BN=1m, then the resistivity ρ s =3.05Ω·m.

[0071] In step S5, the standard value of mud resistivity ρ 0 =3.2Ω·m, a = 20%, then the standard value range of mud resistivity is [(1-a)ρ 0 , (1+a)ρ 0 ]=2.56~3.84.

[0072] In this embodiment,s It is in line with the standard range of mud resistivity, so it is determined that the back-wall grouting in the area to be tested in this embodiment meets the requirements.

[0073] Example 2

[0074] The present invention provides a method for detecting mud behind a top pipe wall by using a resistivity method, which is characterized by comprising the following steps:

[0075] S1. Grouting pipes 2 made of steel are pre-buried in the circumferential and longitudinal directions of the top pipe 1. When each grouting pipe 2 is pre-buried in the top pipe 1, the axial direction is arranged along the radial direction of the top pipe 1. In this embodiment, the top pipe 1 is a round pipe, and the structure of each grouting pipe 2 is as follows: Figure 1 As shown, the two ends before embedding are exposed to form a conductive area 21, and the remaining part is provided with an insulating layer 22. The conductive area 21 is exposed in an annular direction and along its own longitudinal direction (i.e. Figure 1 The exposed size of the conductive area 21 in the left and right directions is 1-2 cm, the insulating layer 22 is formed by coating insulating paint, and the conductive areas 21 at both ends of the conductive area 21 extend from the inner and outer sides of the top pipe 1 wall when the grouting pipe 2 is pre-buried, and the insulating layer 22 at least covers the contact part between the grouting pipe 2 and the top pipe 1.

[0076] Perform back wall grouting on the top pipe 1 through the grouting pipe 2;

[0077] S2. The power supply electrode A, the power supply electrode B, the measuring electrode M and the measuring electrode N are arranged circumferentially or longitudinally in the area to be detected in the top pipe 1. In this embodiment, the power supply electrode A, the power supply electrode B, the measuring electrode M and the measuring electrode N are arranged longitudinally, specifically:

[0078] The power supply electrodes A and B are electrically connected to two grouting pipes spaced apart in the longitudinal direction one by one, and then two grouting pipes are selected between the two grouting pipes connected to the power supply electrodes A and B to be electrically connected to the measuring electrodes M and N one by one. The measuring electrodes M and N are respectively arranged longitudinally adjacent to the power supply electrodes A and B.

[0079] Vertical settings such as Figure 4 As shown, Figure 4 The middle vertical direction is the longitudinal direction, and the power supply electrode A, the measuring electrode M, the measuring electrode N, and the power supply electrode B are arranged in sequence from bottom to top. The power supply electrode A, the power supply electrode B, the measuring electrode M, and the measuring electrode N are all located in the top pipe 1 and connected to the conductive area 21 at the inner end of the corresponding grouting pipe 2;

[0080] S3. A power supply is set between the power supply electrode A and the power supply electrode B to apply an electric field to the mud behind the wall, and the current I between the power supply electrodes A and B is measured, and the potential difference ΔU between the measuring electrodes M and N is measured. MN ;

[0081] S4. The resistivity between the power supply electrodes A and B is ρ s

[0082]

[0083] Where K is the device coefficient,

[0084]

[0085] ρ s = the resistivity between the power supply electrodes A and B, in Ω·m;

[0086] ΔU MN =Measure the potential difference between electrodes M and N, in V;

[0087] I = the current I between the power supply electrodes A and B, in A;

[0088] K is the device coefficient, in m;

[0089] AM = the distance between the power supply electrode A and the measuring electrode M on the outer wall of the top pipe, in m;

[0090] AN = the distance between the power supply electrode A and the measuring electrode N on the outer wall of the top pipe, in m;

[0091] BM = the distance between the power supply electrode B and the measuring electrode M on the outer wall of the top pipe, in m;

[0092] BN = the distance between the power supply electrode B and the measuring electrode N on the outer wall of the top pipe, in m;

[0093] S5. The resistivity ρ measured by S4 s The resistivity of the slurry is compared with the standard range of the resistivity of the slurry measured in advance. The method for determining the standard range of the resistivity of the slurry includes: using the same slurry as that used for grouting in step S1, performing multiple tests using a resistivity tester, and taking the average value ρ 0 is the standard value of mud resistivity, expressed as [(1-a)ρ 0 , (1+a)ρ 0 ] is the standard range of mud resistivity, where a satisfies 30% ≥ a ≥ 5%,

[0094] i) If the resistivity ρ s If it is within the standard range of mud resistivity, it means that the mud behind the wall between power supply electrodes A and B is complete and dense and meets the standard;

[0095] ii) If the resistivity ρ s If it is outside the standard range of mud resistivity, it means that the mud behind the wall between power supply electrode A and power supply electrode B is damaged and does not meet the standard, and secondary grouting is required.

[0096] If there are other areas to be inspected on the top pipe 1, steps S2-S5 are repeated.

[0097] The following is a further description of this patent in combination with specific numerical values:

[0098] In this embodiment, I=15A, ΔU MN =24V, AM=2m, AN=4m,

[0099] BM=4m、BN=2m, then the resistivity ρ s =20.1Ω·m.

[0100] In step S5, the standard value of mud resistivity ρ 0 =3.2, a = 20%, then the standard value range of mud resistivity is [(1-a)ρ 0 , (1+a)ρ 0 ]=2.56~3.84.

[0101] In this embodiment, s It does not meet the standard range of mud resistivity, so it is determined that the mud behind the wall of the area to be detected in this embodiment does not meet the requirements and needs to be supplemented with mud.

Claims

1. A method for detecting mud behind the top pipe wall using resistivity method, characterized in that: The following steps are involved: S1. Grouting pipes (2) made of steel are pre-buried in the circumferential and longitudinal directions of the top pipe (1), and grouting is performed behind the wall of the top pipe (1) through the grouting pipes (2); S2. A power supply electrode A, a power supply electrode B, a measuring electrode M and a measuring electrode N are arranged circumferentially or longitudinally in the area to be detected in the top pipe (1), The circumferential arrangement is as follows: the power supply electrode A and the power supply electrode B are electrically connected to two grouting pipes (2) arranged at intervals in the circumferential direction in a one-to-one correspondence; in the area on the side where the circumferential distance between the two grouting pipes connected to the power supply electrodes A and B is shorter, two grouting pipes (2) are selected to be electrically connected to the measuring electrode M and the measuring electrode N in a one-to-one correspondence; the measuring electrodes M and N are arranged in the circumferential direction adjacent to the power supply electrodes A and B respectively; The longitudinal arrangement is as follows: the power supply electrode A and the power supply electrode B are electrically connected to two grouting pipes (2) arranged at intervals in the longitudinal direction in a one-to-one correspondence, and then two grouting pipes (2) are selected between the two grouting pipes (2) connected to the power supply electrodes A and B and are electrically connected to the measuring electrode M and the measuring electrode N in a one-to-one correspondence, and the measuring electrodes M and N are respectively arranged longitudinally adjacent to the power supply electrodes A and B; S3. A power supply is set between the power supply electrode A and the power supply electrode B to apply an electric field to the mud behind the wall, and the current I between the power supply electrodes A and B is measured, and the potential difference ΔU between the measuring electrodes M and N is measured. MN ; S4. The resistivity between the power supply electrodes A and B is ρ s Where K is the device coefficient, ρ s = the resistivity between the power supply electrodes A and B, in Ω·m; ΔU MN =Measure the potential difference between electrodes M and N, in V; I = the current I between the power supply electrodes A and B, in A; K = device coefficient, in m; AM = the distance between the power supply electrode A and the measuring electrode M on the outer wall of the top pipe, in m; AN = the distance between the power supply electrode A and the measuring electrode N on the outer wall of the top pipe, in m; BM = the distance between the power supply electrode B and the measuring electrode M on the outer wall of the top pipe, in m; BN = the distance between the power supply electrode B and the measuring electrode N on the outer wall of the top pipe, in m; S5. The resistivity ρ measured by S4 s Compare with the pre-measured standard range of mud resistivity. i) If the resistivity ρ s If it is within the standard range of mud resistivity, it means that the mud behind the wall between power supply electrodes A and B is complete and dense and meets the standard; ii) If the resistivity ρ s If it is outside the standard range of mud resistivity, it means that the mud behind the wall between power supply electrode A and power supply electrode B is damaged and does not meet the standards, and needs to be supplemented.

2. The method for detecting mud behind the top pipe wall by using the resistivity method as claimed in claim 1, characterized in that: In step S1, before pre-buried, both ends of each grouting pipe (2) are exposed to form a conductive area (21), and the remaining portion is provided with an insulating layer (22). When each grouting pipe (2) is pre-buried, the conductive areas (21) at both ends extend out from the inner and outer sides of the pipe wall of the top pipe (1), respectively, and the insulating layer (22) covers at least the contact portion between the grouting pipe (2) and the top pipe (1).

3. The method for detecting mud behind the top pipe wall by using resistivity method as claimed in claim 2, characterized in that: The conductive area (21) of each grouting pipe (2) is exposed in the circumferential direction and 1-2 cm in the longitudinal direction.

4. The method for detecting mud behind the top pipe wall by using resistivity method as claimed in claim 2, characterized in that: The insulating layer (22) of each grouting pipe (2) is formed by coating an insulating coating.

5. The method for detecting mud behind the top pipe wall by using resistivity method as claimed in claim 2, characterized in that: When each grouting pipe (2) is pre-buried in the top pipe (1), the axial direction is arranged along the radial direction of the top pipe (1).

6. The method for detecting mud behind the top pipe wall by using resistivity method as claimed in claim 1, characterized in that: In step S2, the power supply electrode A, the power supply electrode B, the measuring electrode M and the measuring electrode N are all connected to the corresponding conductive area (21) at the inner end of the grouting pipe (2).

7. The method for detecting mud behind the top pipe wall by using resistivity method as claimed in claim 1, characterized in that: In step S5, the method for determining the standard range of mud resistivity includes: using the same mud as that used for grouting in step S1, performing multiple tests using a resistivity tester, taking the average value ρ0 as the standard value of mud resistivity, and taking [(1-a)ρ0, (1+a)ρ0] as the standard range of mud resistivity, where the value of a satisfies 30% ≥ a ≥ 5%.

8. The method for detecting mud behind the top pipe wall by using the resistivity method as claimed in claim 7, characterized in that: a is 20%.

9. The method for detecting mud behind the top pipe wall by using resistivity method as claimed in claim 1, characterized in that: If there are other areas to be inspected on the top pipe (1), steps S2-S5 are repeated.

10. The method for detecting mud behind the top pipe wall by using resistivity method as claimed in claim 1, characterized in that: The top pipe (1) is a round pipe or a square pipe.

Images