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CN-116517038-B - Acoustic emission monitoring method for underground rotary spraying effect in construction process

CN116517038BCN 116517038 BCN116517038 BCN 116517038BCN-116517038-B

Abstract

The application discloses an acoustic emission monitoring method for an underground rotary spraying effect in a construction process. The method comprises the steps of burying waveguides inside and outside a pile diameter monitoring area of an underground jet grouting pile target, coupling an acoustic emission sensor at one end of the exposed surface of the waveguides, picking up acoustic emission signals generated by cutting soil bodies by jet grouting media in the construction process in real time, counting acoustic emission characteristic information of the jet grouting pile body at different jet grouting depths and different radial positions of the pile body, uniformly processing the acoustic emission characteristic information counted at different positions by taking the acoustic emission characteristic information counted at the position near the surface and the position away from the center axis and the actual jet grouting frequency at the fixed jet grouting elevation in the construction process as reference values, defining the acoustic emission characteristic information as soil body cutting coefficients, comparing and analyzing the soil body cutting coefficients, grading the jet grouting effect, feeding back grouting conditions and pile forming quality in real time, monitoring the jet grouting effect of the underground jet grouting pile in real time, continuously and quantitatively, realizing visual construction of underground hidden engineering, guaranteeing the construction quality and reducing the construction cost.

Inventors

  • LIN WENLI
  • LIU ANG

Assignees

  • 东南大学

Dates

Publication Date
20260512
Application Date
20230329

Claims (6)

  1. 1. The acoustic emission monitoring method for the underground jet grouting effect in the construction process is characterized by comprising the following steps of: s1, burying waveguide tubes (4) inside and outside a target pile diameter monitoring area of an underground jet grouting pile (1) respectively; s2, coupling an acoustic emission sensor (6) at one end of the waveguide tube (4) exposed out of the earth surface, and connecting the acoustic emission sensor (6) to a preamplifier, a data acquisition system and a data processing software system to build an acoustic emission monitoring system; S3, picking up acoustic emission signals generated by cutting soil body by the jet grouting medium in the construction process, and counting acoustic emission characteristic information of the jet grouting pile (1) at different jet grouting depths and different pile radial positions by utilizing a data processing software system; S4, carrying out homogenization treatment on acoustic emission characteristic information counted at the positions of different rotary spraying depths and different pile radial positions by taking actual rotary spraying times at a fixed rotary spraying depth in the construction process as a reference value, defining the acoustic emission characteristic information as a soil body cutting coefficient, comparing and analyzing the size of the soil body cutting coefficient value to realize the grade division of the rotary spraying effect, and feeding back grouting condition and pile forming quality in real time, wherein the position of the rotary spraying pile (1) near the ground surface and the position of the rotary spraying pile (1) away from the central axis is 1.0-2.0 m below the ground surface and 0.5-0.8 m away from the central axis; the step S1 specifically comprises the following steps: S11, performing hole guiding operation along the central axis of the jet grouting pile (1) according to the pile forming diameter requirement of the jet grouting pile (1), defining a hole A, and burying a slurry pipe (2) in the hole A; s12, performing hole guiding operation along the diameter range and the outer range of the central shaft of the jet grouting pile (1), wherein the hole guiding operation is defined as a hole B, a hole C and a hole D, a waveguide tube (4) is embedded in the hole B, the hole C and the hole D, the waveguide tube (4) is mounted to the designed depth of the pile bottom of the jet grouting pile (1), the waveguide tube (4) is vertical, the end part of the waveguide tube is exposed out of the ground surface by 0.5-1 m, and a sleeve (5) is arranged at one end of the waveguide tube (4) exposed out of the ground surface; the step S2 specifically comprises the following steps: s21, installing an acoustic emission sensor (6) on the surface of one end of the waveguide tube (4) exposed out of the earth surface through strong glue, and connecting a preamplifier, a data acquisition system and a data processing software system; s22, environmental noise testing, namely starting an engine of the rotary spraying device, testing the background noise of the construction environment by using the built acoustic emission monitoring system, and filtering the environmental noise in a data processing software system; The step S3 specifically comprises the following steps: S31, starting a rotary spraying device, clockwise rotating a slurry pipe (2) at a fixed rotary spraying depth, spraying a rotary spraying medium from the slurry pipe (2) at a pressure of 20-50 MPa and spraying a cutting soil body for 5-7 times, recording the actual rotary spraying times N 0 at the fixed rotary spraying depth in the construction process, wherein the rotary spraying medium is a solid-liquid mixture comprising bentonite and cement paste, the dosage of the bentonite is 5-15% of that of the cement paste, the water-cement ratio of the cement paste is 0.8-1.5, and when the rotary spraying medium cuts the soil body, the cut soil body generates local strain or stress concentration and elastic waves; The method comprises the steps of S32, enabling elastic waves to be transmitted to a waveguide tube (4) through surrounding media, enabling the elastic waves to be transmitted to an acoustic emission sensor (6) from underground rapidly through the waveguide tube 4 and to be detected and recorded as acoustic emission signals S, adopting an acoustic emission monitoring device to monitor different jet grouting depths and different pile radial positions in the construction process in real time, and enabling acoustic emission signals S ij of the jet grouting pile 1 at different positions to be picked up, wherein i is 1,2 and 3 respectively, n is the index of different jet grouting depth positions, j is 1,2 and 3 respectively, n is the index of different pile radial positions; the step S4 specifically includes: S41, according to the picked acoustic emission signals, counting acoustic emission energy rates at the positions which are 1.0-2.0 m below the ground surface and 0.5-0.8 m away from the central axis by using a data processing software system, and counting as E 00 ; S42, counting the energy rate and the energy rate wave crest number of acoustic emissions at different radial positions of the pile body at different rotary spraying depths by utilizing the data processing software system, and counting the energy rate and the energy rate wave crest number as E ij and N ij ; S43, normalizing, namely normalizing E ij ,N ij counted in the step S42 by taking N 0 , E 00 acquired in the step S31 and the step S41 as a reference value, and defining soil cutting coefficients R ij and N ij , wherein the concrete calculation formulas of the soil cutting coefficients R ij and N ij are as follows: , ; S44, comparing and analyzing the magnitudes of soil body cutting coefficient values R ij and n ij calculated at different rotary spraying depths and different pile body radial positions of the rotary spraying pile 1, namely distinguishing the strong and weak distribution state and times of cutting soil bodies by the rotary spraying medium, and feeding back grouting conditions and pile forming effects.
  2. 2. The acoustic emission monitoring method for the underground rotary spraying effect in the construction process according to claim 1, wherein a rotary spraying drill bit is arranged at one end of the slurry pipe (2) extending into the hole A, and a group of nozzles (3) are arranged at the drill bit.
  3. 3. The acoustic emission monitoring method for the underground rotary spraying effect in the construction process according to claim 1, wherein a group of acoustic emission sensors (6) are arranged at one end of the waveguide tube (4) exposed out of the earth surface and are used for monitoring acoustic emission signals generated by cutting a soil body by a rotary spraying medium in the construction process and performing contrast verification analysis.
  4. 4. The method for monitoring the underground jet grouting effect in the construction process according to claim 1, wherein the statistical acoustic emission characteristic information is acoustic emission energy rate and energy rate peak number, the acoustic emission energy rate is the area under acoustic emission signal detection envelope curve in 1 second per unit time and reflects the relative energy rate or intensity change of acoustic emission signals, the area under acoustic emission signal detection envelope curve is the time for the jet grouting pile to go through from the beginning to the end of jet grouting, the sampling frequency of an acoustic emission device is deltat, the positive voltage amplitude of the signal measured at the moment t is V + (t), the negative voltage amplitude is V - (t), and the specific calculation formula of the area E MARSE under the envelope curve accumulated from the moment t 1 to the moment t 2 of acoustic emission signal detection is as follows: the energy rate peak number refers to the number of times that the energy rate periodically reaches the maximum value.
  5. 5. The method for monitoring the underground rotary jetting effect in the construction process according to claim 1, wherein the waveguide tube (4) is a solid metal medium material with elastic wave conduction rate of 5000m/s and above, and the sleeve (5) is a soft rubber medium material with elastic wave conduction rate of less than 100 m/s.
  6. 6. The acoustic emission monitoring method for an underground rotary jetting effect in a construction process according to claim 1, wherein: When the soil body cutting coefficient R ij is less than or equal to 1 and the soil body cutting coefficient n ij is less than or equal to 1 and is 0.7, the rotary spraying effect in the construction process is good, the pile forming quality is good, and the cutting grade is classified as grade A; When the soil cutting coefficient R ij is less than or equal to 0.7 and the soil cutting coefficient n ij is less than or equal to 0.7 and is more than or equal to 0.4, the rotary spraying effect in the construction process is medium, the piling quality is medium, and the cutting grade is classified as grade B; when the soil body cutting coefficient R ij is more than or equal to 0.4 and the soil body cutting coefficient n ij is more than or equal to 0.4, the rotary spraying effect in the construction process is poor, the piling quality is poor, and the cutting grade is classified as grade C.

Description

Acoustic emission monitoring method for underground rotary spraying effect in construction process Technical Field The invention relates to the technical field of construction quality detection of jet grouting piles in the field of foundation treatment, in particular to an acoustic emission monitoring method for an underground jet grouting effect in a construction process. Background As a nondestructive testing method, acoustic emission technology can continuously capture elastic waves released by stress concentration in a material under the action of load in real time, and is widely used for quasi-continuous medium materials such as metal, rock, concrete and the like at present. When a material is subjected to an external load, the microscale degradation process inside the material is often accompanied by release of strain energy, which is mostly released in the form of elastic waves, which can be detected and recorded as acoustic emission signals by acoustic emission sensors. The jet grouting pile method is a new technology for reinforcing foundation and preventing water curtain, and has the advantages of wide application range, convenient construction, high efficiency, simple operation, etc. and is suitable for preventing foundation from subsidence, preventing infiltration, reinforcing foundation, etc. the technological principle is that a drilling machine is used to drill jet grouting pipe and nozzle at the designed depth of pile bottom, the slurry prepared in advance is sprayed out from the nozzle at the side of grouting pipe at high speed after obtaining huge energy by means of high pressure generator, so as to form a stream of highly concentrated liquid flow, directly destroy soil body, and during spraying, the slurry and soil body are fully stirred and mixed while the drill pipe is rotated, so that columnar consolidated body with certain diameter is formed in soil, thus reinforcing foundation. The jet grouting pile belongs to underground hidden engineering and has invisible characteristic. At present, conventional detection methods comprise drilling coring, a high-low strain method, a ground penetrating radar, a high-density electric method and the like, but most of the methods belong to pile forming quality detection after injection construction is finished, have guiding significance for remedying engineering defects, but cannot find problems in the construction process and timely adjust and improve the problems. Therefore, in order to timely and accurately find the quality problem of underground high-pressure jet grouting construction, a dynamic detection method is needed to be sought for continuously obtaining the piling effect of the jet grouting pile in real time in the construction process. Chinese patent CN 202010034562.3 discloses an acoustic emission evaluation method for thermal stability of surrounding rock under high temperature condition for underground engineering, which relates to the technical field of thermal damage of surrounding rock, and utilizes rock thermal damage mechanical parameters to carry out inversion, and combines acoustic emission signals generated by thermal cracking to evaluate damage degree and position of the surrounding rock; stress and sound emission information is obtained, and the temperature range of surrounding rock is inverted; the method solves the problem of judging the thermal stability of the surrounding rock in a high-temperature environment, and has the advantages of simplicity and convenience in operation, accurate space-time positioning and the like. The Chinese patent CN 201610034383.3 discloses a multichannel acoustic emission monitoring system and a positioning method in the underground engineering construction process, wherein a plurality of three-dimensional acoustic emission sensing devices are respectively connected with a multichannel acoustic emission synchronous data acquisition device, the multichannel acoustic emission synchronous data acquisition device is connected with an optical fiber network switch through a first photoelectric converter, the optical fiber network switch is connected with an upper computer through a second photoelectric converter, real-time monitoring, waveform display, real-time positioning, signal intensity and data recording of acoustic emission signals can be completed, real-time monitoring of surrounding rock of the underground engineering is realized, damage condition of the rock can be reflected, water burst precursor information can be found timely, and technical support is provided for preventing water burst disaster. Chinese patent CN 201210302216.4 discloses a method for accurately drawing the underground condition of an oil field by acoustic emission positioning monitoring, which comprises the steps of arranging at least 3 signal receivers on the ground around a water injection well at intervals and in any direction, collecting and time difference processing of stratum fracture dynamic signals of the wate