A method for determining the surrounding rock pressure after backfilling a tunnel ground collapse

Abstract

The present invention provides a method for determining the surrounding rock pressure after backfilling a tunnel ground collapse, which includes the following steps: 1. Determine the top surface radius, bottom surface radius and height of the collapse pit; 2. Calculate the soil thickness; 3. Determine the unit weight of the backfill material in the collapse pit and the unit weight of the loose soil at the bottom of the pit; 4. Determine the inclination angle of the side wall of the collapse pit; 5. Determine the internal friction angle and the unstable angle of the backfill material; 6. Determine the volume of the unstable part at the collapse pit; 7. Calculate the surrounding rock pressure exerted by the unstable part of the backfill material on the lining; 8. Calculate the surrounding rock pressure exerted by the loose soil at the collapse pit on the lining; 9. Calculate the total surrounding rock pressure. The design of the present invention is reasonable. By calculating the surrounding rock pressure including the self-weight of the loose soil and the self-weight of the unstable part of the backfill material, the total surrounding rock pressure is obtained, which has the advantages of simple structure, convenient implementation and reliable results.

Description

Technical Field

[0001] The present invention relates to a method for determining the surrounding rock pressure after backfilling a tunnel ground collapse. Background Art

[0002] When a tunnel is constructed in poor geological conditions, water and mud inrush disasters may occur, forming a cavity above the vault. If the water and mud inrush cannot be stopped in time, the mud inrush may extend to the ground surface, and then the ground surface collapses, forming a pit. Usually, a certain material is used for backfilling treatment later, and drainage ditches are built around the pit to prevent surface water from flowing into the interior. After the pit is backfilled, the surrounding rock pressure acting on the lining has changed greatly compared with that before the water and mud inrush. So far, there is no reliable theoretical method to determine the surrounding rock pressure after the pit is backfilled. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a method for determining the surrounding rock pressure after backfilling a tunnel ground collapse, to solve the problems existing in the above technical solutions, and has the advantages of strong processability, simple structure and reliable results.

[0004] The present invention is implemented as follows: A method for determining the surrounding rock pressure after backfilling a tunnel ground collapse includes the following steps:

[0005] Step S1: Determine the top surface radius a, bottom surface radius b of the collapse pit and the height H of the pit 1 ;

[0006] Step S2: Determine the elevation Z at the bottom of the collapse pit 1 , the elevation Z of the vault 2 , calculate and determine the soil thickness H within the range above the vault at the collapse pit 2 , the soil thickness H 2 The calculation formula is as follows:

[0007] H 2 =Z 1 -Z 2 ;

[0008] Step S3: Determine the unit weight γ of the backfill material for the collapse pit 1 ;

[0009] Step S4: Determine the unit weight γ of the loose soil at the bottom of the collapse pit 2 ;

[0010] Step S5: Calculate and determine the inclination angle α of the side wall of the collapse pit, that is, the angle between the side wall and the horizontal plane. The calculation formula for the inclination angle α is as follows:

[0011]

[0012] Step S6: Determine the internal friction angle of the backfill material

[0013] Step S7: Determine the unstable angle β of the backfill material: If then β = α; if then

[0014] Step S8: Calculate and determine the volume V of the unstable part at the collapse pit. The calculation formula for the volume V is as follows:

[0015]

[0016] Step S9: Determine the surrounding rock pressure p exerted by the unstable part of the backfill material on the lining 1 , the surrounding rock pressure p 1 The calculation formula is as follows:

[0017]

[0018] Step S10: Calculate and determine the surrounding rock pressure p exerted by the loose soil mass at the collapse pit on the lining 2 , the surrounding rock pressure p 2 The calculation formula is as follows:

[0019] p 2 = γ 2 H 2 ;

[0020] Step S11: Calculate and determine the total surrounding rock pressure p exerted on the lining after backfilling the collapse pit. The calculation formula for the total surrounding rock pressure p is as follows:

[0021] p = p 1 + p 2 .

[0022] Furthermore, in Step S1: Use a total station to measure the top surface radius a, bottom surface radius b, and the height H of the collapse pit 1 .

[0023] Furthermore, in Step S2: Use RTK to measure the elevation Z at the bottom of the collapse pit 1 , and determine the crown elevation Z 2 according to the tunnel design data.

[0024] Furthermore, in Step S3: If the backfill is made of soil, γ 1 is taken as 20 kN / m3; if the backfill is made of concrete, γ 1 is taken as 25 kN / m3.

[0025] Further, in step S4: Use a drill to bore a hole at the collapsed pit, take the undisturbed soil sample, transport it back to the laboratory, then use the cutting ring method to measure its density, and multiply it by the acceleration of gravity to obtain its unit weight γ. 2 .

[0026] Further, in step S6: Transport the typical backfill material back to the laboratory, conduct a direct shear test, and measure the internal friction angle of the backfill material.

[0027] Compared with the prior art, the present invention has the following beneficial effects: It is reasonably designed. By calculating the surrounding rock pressure including the self-weight of the loose soil and the self-weight of the unstable part of the backfill material, the total surrounding rock pressure is obtained, which has the advantages of simple structure, convenient implementation, and reliable results. Specific Embodiments

[0028] The present invention will be further described below through embodiments.

[0029] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs.

[0030] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0031] This embodiment provides a method for determining the surrounding rock pressure after backfilling a tunnel ground collapse, including the following steps:

[0032] Step S1: Determine the top radius a, bottom radius b, and height H of the collapsed pit. 1 ;

[0033] Step S2: Determine the elevation Z at the bottom of the collapsed pit, the elevation Z at the crown, and calculate and determine the thickness H of the soil above the crown in the area of the collapsed pit. 1 , the elevation Z at the crown 2 , calculate and determine the thickness H of the soil above the crown in the area of the collapsed pit. 2 , the thickness H of the soil 2 The calculation formula is as follows:

[0034] H 2 = Z 1 - Z 2 ;

[0035] Step S3: Determine the unit weight γ of the backfill material for the collapsed pit 1 ;

[0036] Step S4: Determine the unit weight γ of the loose soil at the bottom of the collapsed pit 2 ;

[0037] Step S5: Calculate and determine the inclination angle α of the side wall of the collapsed pit, that is, the angle between the side wall and the horizontal plane. The calculation formula for the inclination angle α is as follows:

[0038]

[0039] Step S6: Determine the internal friction angle of the backfill material

[0040] Step S7: Determine the unstable angle β of the backfill material: If then β = α; if then

[0041] Step S8: Calculate and determine the volume V of the unstable part at the collapsed pit. The calculation formula for the volume V is as follows:

[0042]

[0043] Step S9: Determine the surrounding rock pressure p exerted by the unstable part of the backfill material on the lining 1 , and the surrounding rock pressure p 1 has the following calculation formula:

[0044]

[0045] Step S10: Calculate and determine the surrounding rock pressure p exerted by the loose soil at the collapsed pit on the lining 2 , and the surrounding rock pressure p 2 has the following calculation formula:

[0046] p 2 = γ 2 H 2 ;

[0047] Step S11: Calculate and determine the total surrounding rock pressure p exerted on the lining after backfilling the collapsed pit. The calculation formula for the total surrounding rock pressure p is as follows:

[0048] p = p 1 + p 2 .

[0049] In this embodiment, in Step S1: Use a total station to measure the top radius a, bottom radius b, and height H of the collapsed pit 1 .

[0050] In this embodiment, in step S2: The elevation Z of the bottom of the subsidence pit is measured by RTK. 1 , and according to the tunnel design data, the elevation Z of the vault is determined. 2 .

[0051] In this embodiment, in step S3: If soil is used for backfilling, γ 1 is taken as 20 kN / m3; if concrete is used for backfilling, γ 1 is taken as 25 kN / m3.

[0052] In this embodiment, in step S4: A drill is used to drill holes at the subsidence pit, and undisturbed soil samples are taken. After transporting them back to the laboratory, the density is measured by the cutting ring method, and then multiplied by the acceleration of gravity to obtain the unit weight γ 2 .

[0053] In this embodiment, in step S6: Typical backfill materials are transported back to the laboratory for direct shear tests to measure the internal friction angle of the backfill materials.

[0054] The working principle of the present invention is that after the subsidence pit is backfilled, the surrounding rock pressure acting on the lining has two parts. One part is caused by the self-weight of the previously fallen loose soil mass, and the other part is caused by the self-weight of the backfill materials. Due to the internal friction angle of the backfill materials, the self-weight of the stable part acts on the side walls, and the self-weight of the unstable part acts on the bottom of the pit and also on the fallen loose soil mass, further causing the surrounding rock pressure. Therefore, the surrounding rock pressure acting on the lining is caused by the sum of the self-weight of the loose soil mass and the self-weight of the unstable part of the backfill materials.

[0055] Implementation case

[0056] For a certain railway tunnel, when constructing in poor geological conditions, a water and mud inrush disaster occurred. The mud inrush flowed rapidly in the tunnel, causing damage to mechanical equipment. Three months after the mud inrush, a subsidence pit appeared on the ground surface of the mountain top, and the construction party quickly carried out backfilling. In order to determine the surrounding rock pressure acting on the primary lining after backfilling, the method of the present invention was used for prediction.

[0057] Technicians went to the subsidence pit on the mountain top and used a total station to measure that the top radius a of the subsidence pit was 15.9 m, the bottom radius b was 6.2 m, and the height H 1 of the pit was 10.7 m; the elevation Z of the bottom of the subsidence pit was measured by RTK 1 as 462.4 m, and according to the tunnel design data, the elevation Z of the vault was determined 2 as 324.6 m; the thickness H 2 of the soil mass above the vault at the subsidence pit was further determined as 137.8 m; soil was used for on-site backfilling, γ1 Take it as 20 kN / m3; Use a drilling rig to drill holes at the collapsed pit, take undisturbed soil samples, transport them back to the laboratory, then use the cutting ring method to measure its density, and then multiply by the acceleration of gravity to obtain the unit weight γ of the loose soil at the bottom of the collapsed pit. 2 It is 16.7 kN / m3; Determine the inclination angle α of the side wall of the collapsed pit to be 47.8°; Transport the typical backfill material back to the laboratory, conduct a direct shear test, and measure the internal friction angle of the backfill material. It is 26.4°; Since Determine the unstable angle β of the backfill material to be 47.8°; Determine the volume V of the unstable part at the collapsed pit to be 4365.8 m3; Determine the surrounding rock pressure p exerted by the unstable part of the backfill material on the lining. 1 It is 536.0 kPa; Determine the surrounding rock pressure p exerted by the loose soil at the collapsed pit on the lining. 2 It is 2301.3 kPa; Determine the total surrounding rock pressure p exerted on the lining after backfilling the collapsed pit to be 2837.2 kPa.

[0058] For any of the technical solutions disclosed in the present invention as described above, unless otherwise stated, if it discloses a numerical range, then the disclosed numerical range is a preferred numerical range. Any person skilled in the art should understand that the preferred numerical range is only the numerical values with relatively obvious technical effects or representativeness among many feasible numerical values. Since there are too many numerical values to list exhaustively, the present invention only discloses some numerical values to illustrate the technical solutions of the present invention. Moreover, the numerical values listed above should not constitute a limitation on the protection scope of the present invention.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the specific implementation manners of the present invention or perform equivalent replacements on some technical features; Without departing from the spirit of the technical solutions of the present invention, they should all be covered within the scope of the technical solutions claimed by the present invention.

Claims

1. A method for determining the surrounding rock pressure after backfilling a tunnel floor collapse, characterized in that, it includes the following steps: Step S1: Determine the top surface radius a, bottom surface radius b of the sunken pit, and the height H of the pit 1 ; Step S2: Determine the elevation Z of the bottom of the collapsed pit 1 , the elevation Z of the vault 2 , calculate and determine the thickness H of the soil mass within the range above the vault at the collapsed pit 2 , the soil mass thickness H 2 The calculation formula is as follows: H 2 = Z 1 -Z 2 ; Step S3: Determine the unit weight γ of the backfill material for the collapsed pit 1 ; Step S4: Determine the unit weight γ of the loose soil at the bottom of the collapsed pit 2 ; Step S5: Calculate and determine the inclination angle α of the side wall of the collapse pit, that is, the angle between the side wall and the horizontal plane. The calculation formula for the inclination angle α is as follows: Step S6: Determine the internal friction angle of the backfill material Step S7: Determine the unstable angle β of the backfill material: If then β = α; if then Step S8: Calculate and determine the volume V of the unstable part at the collapse pit. The calculation formula for the volume V is as follows: Step S9: Determine the surrounding rock pressure p exerted by the unstable part of the backfill material on the lining 1 , the surrounding rock pressure p 1 The calculation formula is as follows: Step S10: Calculate and determine the surrounding rock pressure p exerted by the loose soil mass at the collapsed pit on the lining 2 , the surrounding rock pressure p 2 has the following calculation formula: p 2 = γ 2 H 2 ; Step S11: Calculate and determine the total surrounding rock pressure p acting on the lining after backfilling the collapse pit. The calculation formula for the total surrounding rock pressure p is as follows: p = p 1 +p 2 。 2. The method for determining the surrounding rock pressure according to claim 1, characterized in that, In step S1: Use a total station to measure the top surface radius a, the bottom surface radius b, and the height H of the subsidence pit 1 .

3. The method for determining the surrounding rock pressure according to claim 1, characterized in that, In step S2: Use RTK to measure the elevation Z of the bottom of the subsidence pit 1 , and determine the elevation Z of the vault according to the tunnel design data 2 .

4. The method for determining the surrounding rock pressure according to claim 1, characterized in that, In step S3: If the soil is used for backfilling, γ 1 is taken as 20 kN / m3; if the concrete is used for backfilling, γ 1 is taken as 25 kN / m3.

5. The method for determining the surrounding rock pressure according to claim 1, characterized in that, In step S4: Use a drill to drill holes at the subsidence pit, take undisturbed soil samples, transport them back to the laboratory, then use the cutting ring method to measure their density, and then multiply it by the acceleration of gravity to obtain their unit weight γ 2 .

6. The method for determining the surrounding rock pressure according to claim 1, characterized in that, In step S6: Transport the typical backfill material back to the laboratory for direct shear tests to measure the internal friction angle of the backfill material

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