阅读说明：本技术 一种泥浆成膜性能现场检测方法 (Slurry film forming performance on-site detection method ) 是由 刘中欣 王东欣 张庆军 杨云 牛得草 吴立朋 赵世永 辛松鹤 焦磊 张玉龙 李桂 于 2021-09-16 设计创作，主要内容包括：本发明涉及一种泥浆成膜性能现场检测方法,属于隧道施工技术领域。包括以下步骤：首先在泥水盾构的压力舱内固定若干特制的聚波器,再将泥浆注入压力舱并保持特定范围压力,然后进行声发射信号采集。通过频谱分析,选取指定特征范围内的声发射信号进行统计,得到累计撞击数时程曲线,经由分析该曲线的增长趋势,判定泥浆成膜性能的优劣。所需的聚波器制作简单,费用低,试验表明该方法的测试结果和相同配比泥浆的工程现场成膜性能具有很好的一致性。(The invention relates to a field detection method for slurry film-forming performance, and belongs to the technical field of tunnel construction. The method comprises the following steps: firstly, fixing a plurality of specially-made wave collectors in a pressure chamber of a slurry shield, then injecting slurry into the pressure chamber and keeping the pressure in a specific range, and then carrying out acoustic emission signal acquisition. And (3) selecting acoustic emission signals in a specified characteristic range for statistics through spectral analysis to obtain an accumulated impact number time-course curve, and judging the quality of the slurry film-forming performance by analyzing the increasing trend of the curve. The required wave condenser is simple to manufacture and low in cost, and tests show that the test result of the method has good consistency with the engineering site film-forming performance of the slurry with the same proportion.)

1. The field detection method for the film forming performance of the slurry is characterized by comprising the following steps:

the method comprises the following steps: fixing an acoustic emission instrument and a plurality of wave collectors in a pressure chamber of the slurry shield, wherein the wave collectors are symmetrically arranged on a circumferential line at a radius from the center 2/3 of the pressure chamber; the wave condenser comprises a wave-collecting cover (1) arranged at the front part, and a sound wave guide rod (2) made of the same material is arranged at the tail part of the wave-collecting cover (1); a broadband acoustic emission sensor (3) is fixed at the rear end of the acoustic guide rod (2), and the frequency range of the acoustic emission sensor covers the frequency range of 20 kHz-300 kHz;

step two: pressing the pressure chamber into the slurry, pressurizing to 1.05-1.1 times of working pressure, and keeping the pressure; rotating the cutter head for 10-20 circles at the rotating speed of 0.5-1.4 revolutions per minute, and then starting to collect acoustic emission signals sent by an acoustic emission instrument through an acoustic emission sensor (3);

step three: carrying out spectrum analysis on the waveform of the acoustic emission signal, and selecting the acoustic emission signal with the first peak frequency and the second peak frequency of 20-70 kHz; selecting signals with the maximum amplitude value of 30-50 dB from the signals screened for the first time, and counting to obtain the accumulated impact number, namely, once an acoustic emission signal is received by the acoustic emission sensor (3), the signal is called impact;

step four: time history curve for making accumulated impact number

Selecting 5-10 time points at equal intervals in a test time period, calculating coordinates of each point and sequentially recording the coordinates as t according to the size₁,t₂,……t_nN is a natural number of 1-10; and connecting each point with the origin of coordinates to obtain a corresponding straight line, wherein if the slope of the straight line continuously becomes small, the film forming performance of the slurry is gradually improved along with the time extension, otherwise, the gas blocking performance of the slurry is poor, and the proportion needs to be adjusted.

2. The on-site detection method for the film-forming performance of the slurry according to claim 1, characterized in that: 4-6 wave collectors fixed in the pressure chamber of the slurry shield.

3. The on-site detection method for the film-forming performance of the slurry according to claim 1, characterized in that: the wave-focusing cover (1) is conical, the conical angle is 120-150 degrees, the diameter is 30-40 cm, and the material is brass.

4. The on-site detection method for the film-forming performance of the slurry according to claim 1, characterized in that: the diameter of the sound wave guide rod (2) is 2-3 cm, and the length of the sound wave guide rod is 5-8 cm.

5. The on-site detection method for the film-forming performance of the slurry according to claim 1, characterized in that: the acoustic emission sensor (3) is a soft island RS-2w type acoustic emission sensor; the acoustic emission instrument is a DS5-8B acoustic emission instrument.

Technical Field

The invention relates to a field detection method for slurry film-forming performance, and belongs to the technical field of tunnel construction.

Background

In the last two decades, the construction of the traffic infrastructure and the hydraulic engineering in China is rapid, and the construction method becomes the country with the most shield construction application. The shield is a preferred construction mode of the existing river-crossing tunnel engineering because the shield integrates excavation, supporting and slag discharge. Compared with an earth pressure balanced shield, the slurry shield is more applied to complex geological working conditions such as large cross section, water body passing and the like. When the slurry shield works, the cutter is driven by the cutter disc rotating at a low speed to cut the front rock-soil mass, then the rock-soil mass enters the slurry cabin and is mixed with bentonite, water and a performance adjusting material, and the mixture is conveyed to the outside of the tunnel by the slurry pump and the pipeline. And the slurry mixed with rock and soil bodies is injected into the muddy water cabin again for recycling after the steps of filtering, precipitating, modifying and the like. The slurry shield uses slurry to balance the water and soil pressure of the excavation surface. The mud can form a layer of mud film with very low permeability on the excavation surface, and the quality of the performance of the mud film directly influences the excavation safety and the construction progress. The current tests for mud performance are mainly conducted in the laboratory. Because the field condition is different from the laboratory condition, the test result of the laboratory often can not completely reflect the field performance, so the development of the slurry performance test method suitable for the field, in particular the slurry film-forming performance test method, has important practical significance.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a field detection method for the film forming performance of the slurry, which comprises the steps of designing and manufacturing a corresponding wave condenser, amplifying and collecting acoustic emission signals generated by fluid leakage in the process of forming a mud film, carrying out screening statistics on the acoustic emission signals mixed with various noises according to a certain standard, and judging the quality of the film forming performance of the slurry through analysis of the increasing trend of an impact number time-course curve.

In order to solve the problems, the invention adopts the following technical scheme:

a field detection method for slurry film-forming performance specifically comprises the following steps:

the method comprises the following steps: fixing an acoustic emission instrument and a plurality of wave collectors in a pressure chamber of the slurry shield, wherein the wave collectors are symmetrically arranged on a circumferential line at a radius from the center 2/3 of the pressure chamber; the wave condenser comprises a wave-collecting cover arranged at the front part, and the tail part of the wave-collecting cover is provided with a sound wave guide rod made of the same material; a broadband acoustic emission sensor is fixed at the rear end of the acoustic wave guide rod, and the frequency range of the acoustic emission sensor covers the frequency range of 20 kHz-300 kHz;

step two: pressing the pressure chamber into the slurry, pressurizing to 1.05-1.1 times of working pressure, and keeping the pressure; rotating the cutter head for 10-20 circles at the rotating speed of 0.5-1.4 revolutions per minute, and then starting to collect acoustic emission signals sent by an acoustic emission instrument through an acoustic emission sensor;

step three: carrying out spectrum analysis on the waveform of the acoustic emission signal, and selecting the acoustic emission signal with the first peak frequency and the second peak frequency of 20-70 kHz; selecting signals with the maximum amplitude value of 30-50 dB from the signals screened for the first time, and counting to obtain the accumulated impact number, namely, once an acoustic emission signal is received by the acoustic emission sensor, the acoustic emission sensor is called as one-time impact;

step four: time history curve for making accumulated impact number

Selecting 5-10 time points at equal intervals in a test time period, calculating coordinates of each point and sequentially recording the coordinates as t according to the size₁,t₂,……t_nN is a natural number of 1-10; and connecting each point with the origin of coordinates to obtain a corresponding straight line, wherein if the slope of the straight line continuously becomes small, the film forming performance of the slurry is gradually improved along with the time extension, otherwise, the gas blocking performance of the slurry is poor, and the proportion needs to be adjusted.

Furthermore, 4-6 wave collectors are fixed in the pressure chamber of the slurry shield.

Furthermore, the wave-collecting cover is conical, the conical angle of the wave-collecting cover is 120-150 degrees, the diameter of the wave-collecting cover is 30-40 cm, and the wave-collecting cover is made of brass.

Furthermore, the diameter of the acoustic waveguide rod is 2-3 cm, and the length of the acoustic waveguide rod is 5-8 cm.

Furthermore, the acoustic emission sensor is a soft island RS-2w type acoustic emission sensor; the acoustic emission instrument is a DS5-8B acoustic emission instrument.

Adopt the produced beneficial effect of above-mentioned technical scheme to lie in:

the method obtains the slope change index reflecting the film forming performance of the measured mud by measuring the change of an acoustic emission signal generated by fluid leakage in the mud film forming process over time. The required wave condenser is simple to manufacture and low in cost, and tests show that the test result of the method has good consistency with the engineering site film-forming performance of the slurry with the same proportion.

Drawings

For a clearer explanation of the solution of the invention, the following brief description of the drawings required for this solution is given:

FIG. 1 is a schematic diagram of a wave condenser for use in the present invention;

FIG. 2 is a graph showing the time history of cumulative impact and the slope thereof according to the present invention.

Detailed Description

The technical solutions in the implementation of the present invention will be clearly and completely described below with reference to fig. 1-2 of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than those described herein, and it will be apparent to those of ordinary skill in the art that the present invention may be practiced without departing from the spirit and scope of the present invention, and therefore the present invention is not limited to the examples disclosed below.

And a slurry pressure type shield is used for constructing a tunnel passing through a river in the north and the Hu. The slurry mixing proportion adopted in the test section is as follows: 1000g of water, 126g of bentonite, 85g of silt, 0.16g of carboxymethyl cellulose and 220g of fine sand with the particle size of 0.075-0.25 mm. 6 brass wave collectors were used, the cone angle of the wave collector was 120 °, the diameter was 40cm, the diameter of the acoustic waveguide was 2cm, and the length was 5 mm. A soft island RS-2w type acoustic emission sensor and a DS5-8B acoustic emission instrument are selected.

As shown in fig. 1-2, the method for on-site detecting the film-forming property of the slurry of the embodiment specifically includes the following steps:

the method comprises the following steps: fixing an acoustic emission instrument and 6 wave collectors in a pressure chamber of the slurry shield, wherein the wave collectors are symmetrically arranged on a circumferential line at a radius of 2/3 from the center of the pressure chamber as shown in FIG. 1; the wave condenser comprises a wave-collecting cover 1 arranged at the front part, the wave-collecting cover 1 is conical, and a sound wave guide rod 2 made of the same material is arranged at the tail part of the wave-collecting cover 1; a broadband acoustic emission sensor 3 is fixed at the rear end of the acoustic guide rod 2, and the frequency range of the acoustic emission sensor covers the frequency range of 20 kHz-300 kHz;

step two: pressing the pressure chamber into the slurry, pressurizing to 1.05 times of working pressure, and maintaining the pressure; rotating the cutter head for 20 circles at the rotating speed of 0.6 r/min, and then starting to acquire an acoustic emission signal sent by an acoustic emission instrument through the acoustic emission sensor 3;

step three: carrying out spectrum analysis on the waveform of the acoustic emission signal, and selecting the acoustic emission signal with the first peak frequency and the second peak frequency of 20-70 kHz; selecting signals with the maximum amplitude value of 30-50 dB from the signals screened for the first time, and counting to obtain the accumulated impact number, namely, once an acoustic emission signal is received by the acoustic emission sensor 3, the signal is called as one-time impact;

step four: time history curve (horizontal axis unit: second; vertical axis unit: unit) of accumulated impact number is made

Selecting 8 time points at equal intervals in the test time period, calculating coordinates of each point and sequentially recording the coordinates as t according to the size₁,t₂,……t₈(ii) a Connecting each point with the origin of coordinates to obtain a corresponding straight line, wherein the slope is shown in table 1, and the slope is continuously reduced, which shows that the film-forming property of the slurry is gradually improved along with the time extension; furthermore, the slope of the first three characteristic points is reduced very quickly, which reflects that the film forming speed is fast, and the mud has good film forming performance in the tested stratum.

TABLE 1 actually measured cumulative impact number time history curve slope at each characteristic point

The technical scheme provided by the invention is described in detail above. The foregoing description of the embodiments is provided merely as an aid in understanding the invention, and it will be appreciated by those skilled in the art that changes may be made in this invention without departing from the principles and spirit of the invention, the invention also falling within the scope of the appended claims.