A method for predicting the water plugging grouting pressure of an inflatable bag

Abstract

The present invention provides a method for predicting the water plugging grouting pressure of an inflatable bag. By obtaining relevant parameters, such as the diameter d and cross-sectional area A at the gushing water outlet, the length L of the inflatable bag after inflation, the undrained shear strength c of the soil around the gushing outlet, u the water pressure U at the gushing outlet, the inflation pressure p1 inside the inflatable bag, and the friction coefficient f between the inflatable bag and the surrounding soil; calculating the pushing external force generated by the gushing water on the inflatable bag, the grouting pressure controlled by the friction force of the inflatable bag, and the grouting pressure controlled by the soil strength; and finally determining the grouting pressure, which has the advantages of simple structure, convenient use and reliable results.

Description

Technical Field

[0001] The present invention relates to the field of infrastructure construction, and particularly to a method for predicting the water plugging grouting pressure of an inflatable bag. Background Art

[0002] During the construction of underground projects such as foundation pits and tunnels, sudden water inrush is a relatively common disaster. After sealing with an inflatable bag, water cannot gush out, and then high-pressure grouting is carried out behind the inflatable bag to fill the lost soil, which is an ideal and fast method. Usually, after filling the inflatable bag with gas at a certain pressure, high-pressure grouting is carried out behind it. The grouting pressure is an important parameter for controlling the stability of the inflatable bag. If the grouting pressure is too high, the inflatable bag will be pushed out; if the grouting pressure is insufficient, the grouting effect will be affected. At present, the control of the grouting pressure basically relies on construction experience, and there is no accurate and effective method. Summary of the Invention

[0003] The main object of the present invention is to overcome the above-mentioned defects in the prior art, and propose a method for predicting the water plugging grouting pressure of an inflatable bag, which has the advantages of simple structure, convenient use and reliable results.

[0004] The present invention adopts the following technical solutions:

[0005] A method for predicting the water plugging grouting pressure of an inflatable bag, comprising:

[0006] (1) Obtaining the diameter d and cross-sectional area A at the sudden water inrush port;

[0007] (2) Obtaining the length L of the inflatable bag after inflation;

[0008] (3) Determining the undrained shear strength c of the soil around the sudden water inrush port u ;

[0009] (4) Determining the water pressure U at the sudden water inrush port;

[0010] (5) According to the construction plan, obtaining the inflation pressure p1 in the inflatable bag;

[0011] (6) Using a large direct shear test to measure the friction coefficient f between the inflatable bag and the surrounding soil;

[0012] (7) Calculating the pushing external force F generated by the sudden water inrush on the inflatable bag;

[0013] F = AU

[0014] (8) Calculating the grouting pressure p2 controlled by the friction force of the inflatable bag;

[0015] p2 = πdLp1f / A - U

[0016] (9) Calculate the grouting pressure p3 controlled by the soil strength;

[0017]

[0018] (10) Determine the grouting pressure p;

[0019] p = min(p2, p3)

[0020] Where, min is the function to take the minimum value.

[0021] Specifically, obtain the diameter d and cross-sectional area A at the gushing water outlet, specifically:

[0022] Use a ruler to measure the diameter horizontally and vertically at the gushing water outlet, and take the average of the two as the diameter d at the gushing water outlet, and further calculate its cross-sectional area

[0023] Specifically, determine the undrained shear strength c of the soil around the gushing outlet u , specifically:

[0024] Use a miniature vane shear tester to conduct in-situ shear tests around the gushing outlet to determine its undrained shear strength c u .

[0025] Specifically, determine the water pressure U at the gushing outlet, specifically:

[0026] Use a pressure gauge installed on the grouting pipe in the inflatable bag to measure the water pressure U at the gushing water.

[0027] As can be seen from the above description of the present invention, compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention proposes a method for predicting the grouting pressure of water plugging with an inflatable bag. By obtaining relevant parameters, such as the diameter d and cross-sectional area A at the gushing water outlet, the inflated length L of the inflatable bag, the undrained shear strength c of the soil around the gushing outlet u , the water pressure U at the gushing outlet, the inflation pressure p1 in the inflatable bag, and the friction coefficient f between the inflatable bag and the surrounding soil; calculate the pushing external force generated by the gushing water on the inflatable bag, the grouting pressure controlled by the friction force of the inflatable bag, and the grouting pressure controlled by the soil strength; finally determine the grouting pressure, which has the advantages of simple structure, convenient use and reliable results. Description of the Drawings

[0029] Figure 1 It is a flowchart of a method for predicting the grouting pressure of water plugging with an inflatable bag provided by an embodiment of the present invention.

[0030] The present invention will be further described in detail below with reference to the drawings and specific embodiments. Specific implementation manner

[0031] The working principle of the present invention is that when the inflatable bag is inflated to seal the gushing water outlet, the inflatable bag is subjected to the pressure of the gushing water and the grouting pressure. The sum of the two pressures causes the inflatable bag to generate an outward pushing force along the bag edge, and the frictional force at the edge of the inflatable bag prevents the inflatable bag from pushing outward; on the other hand, when the inflatable bag pushes outward, it may also cause damage along the surrounding soil mass, and the soil strength provides an outward resistance force. Considering the most unfavorable conditions, take the smaller value of either the resistance force provided by the inflatable bag along the perimeter or the resistance force provided by the soil strength to control the grouting pressure

[0032] Such as Figure 1 , is the flow chart of the technical solution adopted by the present invention, specifically including:

[0033] (1) Determine the diameter d and cross-sectional area A at the gushing water outlet.

[0034] Use a ruler to measure the diameter horizontally and vertically at the gushing water outlet, and take the average of the two as the diameter d at the gushing water outlet, and further calculate its cross-sectional area

[0035] (2) Determine the length L of the inflatable bag after inflation.

[0036] Determine the length L of the inflatable bag after inflation according to the designed geometric dimensions of the inflatable bag.

[0037] (3) Determine the undrained shear strength c of the soil around the gushing water outlet u .

[0038] Use a miniature vane shear tester to conduct in-situ shear tests around the gushing water outlet to determine its undrained shear strength c u .

[0039] (4) Determine the water pressure U at the gushing water outlet.

[0040] Use the pressure gauge installed on the grouting pipe in the inflatable bag to measure the water pressure U at the gushing water area.

[0041] (5) Determine the inflation pressure p1 in the inflatable bag.

[0042] Determine the inflation pressure p1 in the inflatable bag according to the construction plan.

[0043] (6) Determine the friction coefficient f between the inflatable bag and the surrounding soil.

[0044] Use a large direct shear test to measure the friction coefficient f between the inflatable bag and the surrounding soil.

[0045] (7) Determine the outward pushing external force F generated by the gushing water on the inflatable bag.

[0046] F = AU

[0047] (8) Determine the grouting pressure p2 controlled by the friction force of the inflatable bag.

[0048] p2 = πdLp1f / A - U

[0049] (9) Determine the grouting pressure p3 controlled by the soil strength.

[0050]

[0051] (10) Determine the grouting pressure p considering the most unfavorable conditions.

[0052] p = min(p2, p3)

[0053] Where min is the function to take the minimum value.

[0054] Specific case:

[0055] When a tunnel was excavated in a certain city in China, water inrush and gushing occurred at the tunnel face. An inflatable bag was used for sealing, and high-pressure grouting treatment was carried out behind the inflatable bag. In order to determine the grouting pressure and prevent the inflatable bag from being pushed out, the method of the present invention was used to predict the grouting pressure.

[0056] Use a ruler to measure the diameter horizontally and vertically at the water inrush and gushing outlet, take the average of the two to determine the diameter d at the water inrush and gushing outlet is 0.46 m, and further calculate its cross-sectional area A is 0.17 m 2 ; According to the designed geometric dimensions of the inflatable bag, determine the inflated length L of the inflatable bag is 1.0 m; Use a miniature vane shear tester to conduct in-situ shear tests around the water inrush and gushing outlet to determine the undrained shear strength c of the soil around the water inrush and gushing outlet u is 47.5 kPa; Use the pressure gauge installed on the grouting pipe in the inflatable bag to measure the water pressure U at the water inrush and gushing place is 1211 kPa; According to the construction plan, determine the inflation pressure p1 in the inflatable bag is 2500 kPa; Use a large direct shear test to measure the friction coefficient f between the inflatable bag and the surrounding soil is 0.26; Determine the pushing external force F generated by the water inrush and gushing on the inflatable bag is 205.9 kN; Determine the grouting pressure p2 controlled by the friction force of the inflatable bag is 4311.7 kPa; Determine the grouting pressure p3 controlled by the soil strength is 600.1 kPa; Determine the grouting pressure p considering the most unfavorable conditions is 600.1 kPa.

[0057] The present invention proposes a method for predicting the water plugging grouting pressure of an inflatable bag. By obtaining relevant parameters, the diameter d and cross-sectional area A at the water inrush and gushing outlet, the inflated length L of the inflatable bag, and the undrained shear strength c of the soil around the water inrush and gushing outlet u, the water pressure U at the gushing outlet, the inflation pressure p1 in the inflatable bag, and the friction coefficient f between the inflatable bag and the surrounding soil mass; calculate the pushing external force generated by the gushing water on the inflatable bag, the grouting pressure controlled by the friction force of the inflatable bag, and the grouting pressure controlled by the soil strength; finally determine the grouting pressure, which has the advantages of simple structure, convenient use and reliable results.

[0058] The above is only the specific implementation manner of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantive modification of the present invention using this concept shall fall within the scope of infringement of the protection scope of the present invention.

Claims

1. A method for predicting the water plugging grouting pressure of an inflatable bag, characterized in that, Including: (1) Obtain the diameter d and cross-sectional area A at the gushing water outlet; (2) Obtain the length L after inflation of the inflatable bag; (3) Determine the undrained shear strength c of the soil around the bursting outlet u ; (4) Determine the water pressure U at the gushing opening; (5) According to the construction plan, obtain the inflation pressure p1 inside the inflatable bag; (6) Use a large direct shear test to measure the friction coefficient f between the inflatable bag and the surrounding soil; (7) Calculate the pushing external force F generated by the gushing water on the inflatable bag; F = AU (8) Calculate the grouting pressure p2 controlled by the friction force of the inflatable bag; p2 = πdLp1f / A - U (9) Calculate the grouting pressure p3 controlled by the soil strength; (10) Determine the grouting pressure p; p = min(p2, p3) where min is the function to take the minimum value.

2. The method for predicting the water plugging grouting pressure of an inflatable bag according to claim 1, wherein To obtain the diameter d and cross-sectional area A at the gushing water outlet, specifically: Use a ruler to measure the diameter horizontally and vertically at the gushing water outlet, and take the average of the two as the diameter d at the gushing water outlet, and further calculate its cross-sectional area.

3. A method for predicting the water plugging grouting pressure of an inflatable bag according to claim 1, characterized in that Determine the undrained shear strength c of the soil around the bursting outlet u , specifically as follows: Using a miniature vane shear apparatus, in-situ shear tests were carried out around the gushing point to determine its undrained shear strength c u .

4. A method for predicting the water plugging grouting pressure of an inflatable bag according to claim 1, characterized in that, To determine the water pressure U at the gushing opening, specifically: Use the pressure gauge installed on the grouting pipe inside the inflatable bag to measure the water pressure U at the gushing water location.

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