CN105863624A - Visual testing method for simulating permeation of slurry into stratum during slurry shielding - Google Patents

Abstract

The invention discloses a visual test method for simulating the penetration of mud-water shield mud in formations, which comprises the following steps: firstly, rotating the rotating shaft, adjusting the opening ratio of the cutter head to 0, and closing the plexiglass right-angle cylinder; then, in the plexiglass model Put the simulated formation prepared by transparent soil into the box, and saturate the formation from bottom to top; then, inject test mud into the plexiglass right-angle cylinder to seal the right-angle cylinder; finally, turn on the air pressure source, turn the shaft, and adjust the opening ratio of the cutter head For a certain value (0%‑50%), conduct a penetration test. This visualization method of mud seepage can observe the seepage form of mud in the formation in real time, and accurately observe the formation type of mud film and the seepage distance in each direction.

Description

A visual test method for simulating the penetration of mud-water shield mud in the formation

technical field

The invention relates to a visual test method for the mud in the pressure cabin to seep into the formation during the excavation process of the mud-water shield. This method can realize the simulation of the mud seepage process under the conditions of visualized formation conditions, different mud pressures and different cutter head opening ratios, and visually observe the mud seepage form in all directions. The invention belongs to the field of underground engineering.

Background technique

In recent years, the mud-water shield method has been widely used in the construction of urban river-crossing subways and cross-river-sea tunnels because of its superior excavation surface control mode. During the forward excavation of the mud-water shield, the mud in the pressure chamber penetrates into the formation to balance the water and soil pressure in the formation and keep the excavation surface stable. At the same time, due to the complex and changeable geological conditions, the shield machine had to be shut down for operations such as opening the cabin for cleaning or maintenance, etc. due to serious wear on the cutter head, cake formation on the cutter head, and mismatch between the cutter and the stratum. Inject mud on the surface to form a mud film to keep the maintenance space stable, such as the maintenance under pressure opening of the Nanjing Yangtze River Tunnel Project in the fine sand and gravel sand formations at the bottom of the river. No matter during the normal excavation process or during the open cabin maintenance under pressure, it is difficult to observe the mud film seeping through the formation, and it is even more difficult to judge the stability of the excavation surface and whether the construction plan is reasonable.

With the development of transparent soil synthesis technology and the development of transparent soil triaxial tests and other physical properties experiments, it has been proved that the transparent soil can be applied to experimental research. At present, it has been gradually applied to shield tunnel research. The internal deformation of the surrounding soil caused by the excavation of the structure, the synchronous grouting model behind the shield tunnel wall, etc.

The present invention designs a transparent soil simulating strata to realize a visualized observation method of mud seeping into the strata under different cutterhead opening ratio conditions. This method can intuitively and easily observe the mud seepage pattern in all directions of the formation under different cutterhead opening ratios, which has guiding significance for mud-water shield construction and mud preparation.

Contents of the invention

The purpose of the present invention is to provide a visualization method for simulating the seepage of mud-water shield mud in formations, which can study the seepage forms of mud in various directions under the conditions of different cutterhead opening ratios.

Technical scheme of the present invention is as follows:

A visual test method for simulating the penetration of mud-water shield mud in the formation,

The visualization device adopted in the test method includes a plexiglass box, a plexiglass right-angle cylinder and an air pressure source for applying pressure; the bottom of the plexiglass box is placed with medium-coarse particle diameter transparent soil for simulating engineering formations, and the machine The upper part of the glass box is provided with a mud overflow tank, and the lower part of the plexiglass box is provided with a water injection port, and the box body of the plexiglass box is provided with a box scale for measuring the thickness of the transparent soil layer; the plexiglass right-angle circle The barrel includes a horizontal glass tube for simulating mud-water shield cutterhead injecting mud into the formation and a vertical glass tube for controlling the amount of mud and applying air pressure; the top of the plexiglass cylinder is sealed by a detachable flange, and the vertical There is a scale on the straight glass tube, the top side wall of the vertical glass tube is connected to the air pressure source, and the bottom side wall is provided with a mud discharge valve;

Described test method comprises the following steps:

Step 1, adjust the opening ratio of the model cutter head: rotate the shaft, adjust the opening ratio of the model cutter head to 0, and separate the plexiglass box and the plexiglass right-angle cylinder to separate the test formation and mud;

Step 2, prepare the stratum: use transparent soil to simulate the medium-coarse sand test stratum; fill the transparent soil into the plexiglass box by layer compaction method to form the test stratum, and then pass through the water injection port at the bottom of the box from bottom to top. Slowly inject calcium bromide solution to saturate the test formation, which is used to prevent the formation from heaving or sand boiling during the saturation process;

Step 3, forming a permeable zone: close the mud discharge valve and the pressure stabilizing valve, inject the test mud from the top of the plexiglass right-angle cylinder, the mud level is located below the air inlet pipe on the upper part of the plexiglass right-angle cylinder, and pass the organic glass through the flange. The top of the glass rectangular cylinder is sealed; open the air pressure source, adjust the air pressure of the air pressure source, adjust the air pressure value on the upper part of the organic glass rectangular cylinder to a predetermined value, and the predetermined value is the soil-water pressure value in the organic glass box; then, rotate the shaft, Adjust the opening ratio of the model cutter head to 20%, and the mud begins to infiltrate into the test formation and form a permeable zone; observe the whole process of infiltration, and when a complete permeable zone is formed, and the calcium bromide solution at the overflow tank flows out stably or does not flow out, turn off the air pressure source , when the infiltration is over, observe the infiltration distance and the infiltration zone form of the mud in all directions in the test formation;

Step 4, control experiment: repeat the above steps 1, 2, and 3 twice, and adjust the opening ratio of the model cutter head in step 3 to 30% and 40%, respectively. Through three sets of comparative experiments, observe the opening ratio of different model cutter heads Permeable zone morphology in all directions under different conditions.

Further, in step 1, the muddy water shield model cutter head is composed of two round soil retaining pieces that are closely attached inside and outside, and the outer soil retaining pieces are fixed on the front end of the horizontal glass tube, and each interval on the outer soil retaining pieces is A fan-shaped opening with a rotation angle of 30° is set at 30°; the inner soil retaining sheet is coaxially connected with the outer soil retaining sheet through the rotating shaft and fixed on the rotating shaft, and a rotation angle of 28° is set at every 32° interval on the inner soil retaining sheet fan-shaped opening.

Further, in step 2, the test formation height is not lower than 25cm, and is located below the position of the mud overflow tank.

Further, in Step 3, the mud is the mud to be used in the actual construction project, and the amount used shall not exceed the air pressure source air inlet at the upper end of the plexiglass rectangular cylinder.

Further, in step 3, the calcium bromide solution permeated and discharged in the plexiglass box flows out from the overflow tank.

Further, in step four, the three groups of experiments should control the test formation height, mud height and predetermined air pressure to remain the same. Technical effect of the present invention:

The invention can observe the mud-water shield excavation process and the whole process of mud seepage in various directions in the formation under the condition of opening the cabin under pressure, and study the mud seepage law by changing the opening ratio of the cutter head, thereby determining the amount of mud used and guiding the shield construction.

Attached to the manual:

Fig. 1: the schematic diagram of the visualized test device of the simulated mud-water shield mud seepage in the stratum used in the present invention;

Fig. 2: Schematic diagram of the outer soil retaining piece of the muddy water shield model cutter head used in the present invention;

Fig. 3: Schematic diagram of the soil retaining piece inside the mud-water shield model cutter head used in the present invention;

Among them: 1. Plexiglass box; 2. Overflow tank; 3. Plexiglass right-angle cylinder; 4. Flange; 5. Model cutter head; 6. Mud discharge valve; 7. Air pressure source; 8. Rotating shaft; , scale; 10, box scale; 11, regulator valve; 12, water inlet.

detailed description

In order to make the purpose and technical solutions of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiments of the present invention. Apparently, the described embodiments are some, not all, embodiments of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Those skilled in the art can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this invention belongs. It should also be understood that terms such as those defined in commonly used dictionaries should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted in an idealized or overly formal sense unless defined as herein Explanation.

The meanings of "inside and outside" in the present invention refer to that relative to the device itself, the direction pointing to the inside of the device is inward, and vice versa, it is not a specific limitation to the device mechanism of the present invention.

The meaning of "connection" in the present invention may be a direct connection between components or an indirect connection between components through other components.

As shown in Figure 1, the visualization device that test method of the present invention adopts comprises plexiglass box 1, plexiglass rectangular cylinder 3 and the air pressure source 7 that is used to apply pressure; Coarse-grained transparent soil, the upper part of the organic glass box is provided with a mud overflow tank 2, the lower part of the organic glass box is provided with a water injection port 12, and the casing of the organic glass box 1 is provided with a device for measuring the thickness of the transparent soil layer. The box scale 10; the plexiglass right-angle cylinder 3 includes a horizontal glass tube for simulating mud-water shield cutterhead injecting mud into the formation and a vertical glass tube for controlling the amount of mud and applying air pressure; the top of the plexiglass cylinder It is sealed by a detachable flange 4, a scale 9 is provided on the vertical glass tube, the top side wall of the vertical glass tube is connected with the air pressure source 7, and a mud discharge valve 6 is provided on the bottom side wall;

The testing method of the visualized device for simulating mud-water shield mud penetration in the stratum of the present invention firstly adjusts the opening ratio of the cutter head to 0, makes the plexiglass rectangular cylinder closed, and then puts it into the plexiglass model box and prepares it with transparent soil. The simulated formation is saturated and the test mud is injected into the plexiglass rectangular cylinder. Finally, the air pressure source is turned on, the rotating shaft is turned, and the penetration experiment is carried out under different cutterhead opening ratios. This visualization method of mud penetration can observe the mud in the formation in real time. The seepage form of the mud film and the formation type of the mud film and the seepage distance in each direction were accurately observed.

The above-mentioned visualization method for studying the penetration of mud-water shield mud in formations specifically includes the following steps:

a. Adjust the opening ratio of the cutter head: firstly turn the rotating shaft and adjust the opening ratio of the cutter head to 0, so that the two cutter heads separate the plexiglass box and the plexiglass right-angle cylinder to prevent the formation and mud from being mixed when the test material is loaded. The two are mixed with each other.

b. Formation preparation: use transparent soil to simulate natural sandy soil, and prepare medium-coarse sand test formations that meet the gradation requirements. Then use layered compaction method to load the test soil, use the scale to control the amount of transparent soil, and then inject calcium bromide solution from bottom to top through the water injection port to saturate the formation. During the saturation process, the formation should be prevented from heaving or sand boiling.

c. Formation of permeable zone: close the mud outlet and pressure stabilizing valve, inject test mud, control the amount of mud with a scale, and seal the device with a flange. Turn the rotating shaft, adjust the opening ratio of the cutter head to 20%, open the air pressure source valve, adjust the air pressure to a predetermined value, the mud begins to penetrate into the test transparent soil layer and form a permeable zone, observe the whole process of infiltration, close the air pressure source valve after a certain period of time, and the infiltration is over , open the mud discharge valve, discharge the excess mud, observe the seepage distance in each direction and the form of the seepage zone.

d. Control experiment: Repeat the above steps a, b, and c twice, and adjust the cutterhead opening ratio in step c to 30% and 40%, respectively. Through three sets of comparative experiments, observe the penetration in all directions under different cutterhead opening ratios Take form and summarize the rules.

In step a, the model cutter head is composed of two circular soil retaining pieces close to each other, the outer soil retaining pieces are fixed, and have fan-shaped openings with a rotation angle of 30° every 30°; The soil slices are connected, and there are fan-shaped openings with a rotation angle of 28° every 32°. The opening ratio can be adjusted by rotating the shaft, and the opening ratio ranges from 0% to 50%.

In step b, the height of the transparent soil layer is not less than 25 cm and is located below the outfall. During the test, transparent soil layers with different gradations can be prepared to study the law of infiltration.

In step c, the mud is the mud to be used in the actual construction project, and the amount used must not exceed the air inlet of the air pressure source.

In step c, the calcium bromide solution discharged by permeation in the plexiglass box flows out from the overflow tank.

In step d, the three groups of experiments should control the test formation height, mud height, predetermined air pressure and other basic quantities except the cutterhead opening ratio to be the same, so as to observe the influence of the cutterhead opening ratio on the shape of the permeable zone in each direction.

The above is only the embodiment of the present invention, and its description is relatively specific and detailed, but it should not be construed as limiting the patent scope of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

Claims (6)

1. A visual test method for simulating mud-water shield mud infiltration in the formation, characterized in that, The visualization device adopted in the test method includes a plexiglass box, a plexiglass right-angle cylinder and an air pressure source for applying pressure; the bottom of the plexiglass box is placed with medium-coarse particle diameter transparent soil for simulating engineering formations, and the machine The upper part of the glass box is provided with a mud overflow tank, and the lower part of the plexiglass box is provided with a water injection port, and the box body of the plexiglass box is provided with a box scale for measuring the thickness of the transparent soil layer; the plexiglass right-angle circle The barrel includes a horizontal glass tube for simulating mud-water shield cutterhead injecting mud into the formation and a vertical glass tube for controlling the amount of mud and applying air pressure; the top of the plexiglass cylinder is sealed by a detachable flange, and the vertical There is a scale on the straight glass tube, the top side wall of the vertical glass tube is connected to the air pressure source, and the bottom side wall is provided with a mud discharge valve; Described test method comprises the following steps: Step 1, adjust the opening ratio of the model cutter head: rotate the shaft, adjust the opening ratio of the model cutter head to 0, and separate the plexiglass box and the plexiglass right-angle cylinder to separate the test formation and mud; Step 2, prepare the stratum: use transparent soil to simulate the medium-coarse sand test stratum; fill the transparent soil into the plexiglass box by layer compaction method to form the test stratum, and then pass through the water injection port at the bottom of the box from bottom to top. Slowly inject calcium bromide solution to saturate the test formation, which is used to prevent the formation from heaving or sand boiling during the saturation process; Step 3, forming a permeable zone: close the mud discharge valve and the pressure stabilizing valve, inject the test mud from the top of the plexiglass right-angle cylinder, the mud level is located below the air inlet pipe on the upper part of the plexiglass right-angle cylinder, and pass the organic glass through the flange. The top of the glass rectangular cylinder is sealed; open the air pressure source, adjust the air pressure of the air pressure source, adjust the air pressure value on the upper part of the organic glass rectangular cylinder to a predetermined value, and the predetermined value is the soil-water pressure value in the organic glass box; then, rotate the shaft, Adjust the opening ratio of the model cutter head to 20%, and the mud begins to infiltrate into the test formation and form a permeable zone; observe the whole process of infiltration, and when a complete permeable zone is formed, and the calcium bromide solution at the overflow tank flows out stably or does not flow out, turn off the air pressure source , when the infiltration is over, observe the infiltration distance and the infiltration zone form of the mud in all directions in the test formation; Step 4, control experiment: repeat the above steps 1, 2, and 3 twice, and adjust the opening ratio of the model cutter head in step 3 to 30% and 40%, respectively. Through three sets of comparative experiments, observe the opening ratio of different model cutter heads Permeable zone morphology in all directions under different conditions. 2. the visualized test method of simulating mud-water shield mud infiltration in formation according to claim 1, it is characterized in that, in step 1, described mud-water shield model cutter head is made of two circles that are close to each other inside and outside The outer soil retaining plate is fixed on the front end of the horizontal glass tube, and a fan-shaped opening with a rotation angle of 30° is opened on the outer soil retaining plate at intervals of 30°; The shaft is connected and fixed on the rotating shaft, and a fan-shaped opening with a rotation angle of 28° is provided at an interval of 32° on the inner soil retaining sheet. 3. the visualized test method of simulating mud-water shield mud infiltration in formation according to claim 1, is characterized in that, in step 2, described test formation height is not less than 25cm, and is positioned at mud overflow tank position below . 4. the visualized test method of simulating mud-water shield mud infiltration in formation according to claim 1, is characterized in that, in step 3, described mud is the mud that plans to use in the actual construction project, and consumption is no more than organic Air pressure source air inlet at the upper end of the glass rectangular cylinder. 5. the visualized test method of simulating mud-water shield mud infiltration in formation according to claim 1, is characterized in that, in step 3, the calcium bromide solution that permeates and discharges in the described plexiglass box flows out by overflow tank . 6. the visualized test method of simulating mud-water shield mud infiltration in formation according to claim 6, is characterized in that, in step 4, three groups of experiments should control test formation height, mud height and predetermined air pressure value to keep identical.