Method for pre-reinforcing strata of mined tunnel and its application

Abstract

The present invention provides a method for pre-reinforcing the strata of a mined tunnel and its application, which relates to the technical field of tunnel engineering. The method for pre-reinforcing the strata of the mined tunnel includes performing double-row deep-hole grouting within the range of 180° of the crown of the tunnel to be excavated; in the phosphoric acid-sodium silicate chemical slurry for the double-row deep-hole grouting, the mass ratio of 75% industrial phosphoric acid, sodium silicate and water is 1:11.5-18.4:33.5-54.3. The above method for pre-reinforcing the strata of the mined tunnel uses phosphoric acid-sodium silicate chemical slurry for grouting. On the premise of having a good sand-solidifying effect, it will not significantly increase the strength of the sand layer, and can ensure that while reinforcing the sand layer in the arch part, it hardly affects the strength of the face soil body and guarantees the excavation efficiency; in addition, through the adjustment of the specific ratio of 75% industrial phosphoric acid, sodium silicate and water in the double-row deep-hole grouting, the present application can form an effective shell structure within the range of 180° of the crown.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel engineering, and in particular to a method for pre-reinforcing strata of a mined tunnel and its application. Background Art

[0002] When constructing a subway by the shallow tunneling method in a water-rich sand layer, in order to prevent safety accidents such as the collapse of the sand layer at the heading face, it is necessary to pre-reinforce the strata. Currently, methods such as advanced small pipe grouting, semi-section long-hole grouting, and full-section long-hole grouting are often used to reinforce the strata before carrying out mined tunneling construction. The slurry injected into the existing pipes is usually phosphoric acid-sodium silicate chemical slurry, but different ratios thereof will also result in different reinforcement effects of the advanced small pipes. The existing grouting ratios are difficult to ensure the reinforcement effect of the advanced pipes in the water-rich sand layer.

[0003] Therefore, it has become very necessary and urgent to research and develop a method for pre-reinforcing strata of a mined tunnel and apply it to the construction process of the shallow tunneling method in a water-rich sand layer to alleviate the problem of poor reinforcement effect of the existing advanced small pipe grouting in the water-rich sand layer.

[0004] In view of this, the present invention is specifically proposed. Summary of the Invention

[0005] The first object of the present invention is to provide a method for pre-reinforcing strata of a mined tunnel. The method for pre-reinforcing strata of a mined tunnel can form an effective shell structure within the range of 180° of the crown of the tunnel to be excavated. On the premise of having a good sand-fixing effect, it will not significantly increase the strength of the sand layer, and can achieve the effect of reinforcing the sand layer in the arch part while hardly affecting the strength of the heading face soil body and ensuring the excavation efficiency.

[0006] The second object of the present invention is to provide an application of the method for pre-reinforcing strata of a mined tunnel in a mined tunnel in a water-rich sand layer. The method for pre-reinforcing strata of a mined tunnel can be widely applied to the construction process of a mined tunnel in a water-rich sand layer.

[0007] In order to achieve the above objects of the present invention, the following technical solutions are specifically adopted:

[0008] The present invention provides a method for pre-reinforcing strata of a mined tunnel, which includes performing double-row long-hole grouting within the range of 180° of the crown of the tunnel to be excavated;

[0009] The slurry for the double-row long-hole grouting is phosphoric acid-sodium silicate chemical slurry, and the phosphoric acid-sodium silicate chemical slurry is mainly composed of 75% industrial phosphoric acid, sodium silicate and water;

[0010] Wherein, the mass ratio of 75% industrial phosphoric acid, sodium silicate and water is 1:11.5-18.4:33.5-54.3.

[0011] Furthermore, the double-row deep-hole grouting includes a first row of grouting holes and a second row of grouting holes;

[0012] Preferably, the first row of grouting holes is located 0.5 m inside the primary support contour line, with a circumferential spacing of 600 mm, a longitudinal spacing of 10 m, a reinforcement length of 12 m, a horizontal overlap of 2 m, and a drilling angle of 6°;

[0013] Preferably, the second row of grouting holes is located 3 - 5 cm inside the primary support contour line, with a circumferential spacing of 600 mm, a longitudinal spacing of 10 m, a reinforcement length of 12 m, a horizontal overlap of 2 m, and a steel pipe with holes angle of 9°.

[0014] According to the different ranges of the formed solidified body thickness, the angles of the two rows of grouting pipes will be different.

[0015] Furthermore, the double-row deep-hole grouting includes advancing drilling grouting and retreating grouting.

[0016] Furthermore, for the advancing drilling grouting, the grouting holes are drilled by the sectional hole guiding method through positioning holes, with each section being 2 m and a total of 6 sections being drilled; the drilling speed is controlled at 0.2 - 0.6 m / min, and the grouting pressure is 0.5 - 1.5 MPa;

[0017] Preferably, the drilling speed is 0.5 m / min and the grouting pressure is 0.8 MPa;

[0018] Preferably, the slurry consumption of a single grouting hole for the advancing drilling grouting is 18.2 L of 75% phosphoric acid, 210 L of water glass, and 611.76 L of water.

[0019] Furthermore, the slurry preparation method for the advancing drilling grouting includes:

[0020] The slurry ratio of the advancing grouting A pipe is 75% industrial phosphoric acid: water = 1:22;

[0021] The slurry ratio of the advancing grouting B pipe is water glass: water = 1:1;

[0022] Mix the slurry of the advancing grouting A pipe and the slurry of the advancing grouting B pipe in a mass ratio of 1:1 to obtain the phosphoric acid - water glass chemical slurry for the advancing drilling grouting.

[0023] Furthermore, the method for the retreating grouting includes:

[0024] Stepwise withdraw the 6 sections of grouting pipes drilled by the advancing drilling grouting, and perform stepwise retreating grouting from the inside to the outside in sequence.

[0025] Furthermore, the slurry preparation method for the retreating grouting includes:

[0026] The slurry ratio of the retreating grouting A pipe is 75% industrial phosphoric acid: water = 1:22 - 35.8;

[0027] The slurry ratio of the backward grouting B pipe is sodium silicate: water = 1:1;

[0028] Mix the slurry of the backward grouting A pipe and the slurry of the backward grouting B pipe in a mass ratio of 1:1 to obtain the phosphoric acid-sodium silicate chemical slurry for the forward grouting.

[0029] Furthermore, the backward grouting includes the following steps:

[0030] (a) When the grouting pipe is not withdrawn, the slurry consumption of a single grouting hole for the backward grouting is 36.48 L of 75% phosphoric acid, 420 L of sodium silicate, and 1223.52 L of water. The drilling speed is controlled at 0.2 - 0.6 m / min, and the grouting pressure is 0.5 - 1.5 MPa;

[0031] Preferably, the drilling speed is 0.5 m / min, and the grouting pressure is 1.0 MPa;

[0032] (b) When the first section of the grouting pipe is withdrawn, the slurry consumption of a single grouting hole for the backward grouting is 25.65 L of 75% phosphoric acid, 315 L of sodium silicate, and 919.35 L of water. The speed is controlled at 0.2 - 0.6 m / min, and the grouting pressure is 0.5 - 1.5 MPa;

[0033] Preferably, the drilling speed is 0.5 m / min, and the grouting pressure is 0.9 MPa;

[0034] (c) When the second section of the grouting pipe is withdrawn, the slurry consumption of a single grouting hole for the backward grouting is 23.94 L of 75% phosphoric acid, 315 L of sodium silicate, and 921.06 L of water. The speed is controlled at 0.2 - 0.6 m / min, and the grouting pressure is 0.5 - 1.5 MPa;

[0035] Preferably, the drilling speed is 0.5 m / min, and the grouting pressure is 0.8 MPa;

[0036] (d) When the third section of the grouting pipe is withdrawn, the slurry consumption of a single grouting hole for the backward grouting is 22.23 L of 75% phosphoric acid, 315 L of sodium silicate, and 922.77 L of water; the speed is controlled at 0.2 - 0.6 m / min, and the grouting pressure is 0.5 - 1.5 MPa;

[0037] Preferably, the drilling speed is 0.5 m / min, and the grouting pressure is 0.8 MPa;

[0038] (e) When the fourth section of the grouting pipe is withdrawn, the slurry consumption of a single grouting hole for the backward grouting is 20.52 L of 75% phosphoric acid, 315 L of sodium silicate, and 924.48 L of water. The speed is controlled at 0.2 - 0.6 m / min, and the grouting pressure is 0.5 - 1.5 MPa;

[0039] Preferably, the drilling speed is 0.5 m / min and the grouting pressure is 0.7 MPa;

[0040] (f) When the 5th grouting pipe is withdrawn, the slurry consumption for each single grouting hole of the backward grouting is 17.1 L of 75% phosphoric acid, 315 L of water glass, and 927.9 L of water, and the speed is controlled at 0.2 - 0.6 m / min, and the grouting pressure is 0.5 - 1.5 MPa;

[0041] Preferably, the drilling speed is 0.5 m / min and the grouting pressure is 0.6 MPa.

[0042] Furthermore, the thickness of the pre - reinforced formation shell formed after the double - row deep - hole grouting is 2 - 3 m, preferably 2.5 m.

[0043] The present invention provides an application of the above - mentioned pre - reinforcement method for the strata of the mined - out tunnel in the mined - out tunnel in water - rich sand strata.

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] The pre - reinforcement method for the strata of the mined - out tunnel provided by the present invention includes double - row deep - hole grouting within the range of 180° of the crown of the tunnel to be excavated; the phosphoric acid - sodium silicate chemical slurry for the double - row deep - hole grouting is composed of 75% industrial phosphoric acid, sodium silicate, and water; among them, the mass ratio of 75% industrial phosphoric acid, sodium silicate, and water is 1:11.5 - 18.4:33.5 - 54.3. The above - mentioned pre - reinforcement method for the strata of the mined - out tunnel uses phosphoric acid - sodium silicate chemical slurry for grouting. On the premise of having a good sand - fixing effect, it will not significantly increase the strength of the sand strata, and can ensure that while strengthening the sand strata at the arch part, it hardly affects the strength of the face soil body, thus ensuring the excavation efficiency; in addition, through the adjustment of the specific ratio of 75% industrial phosphoric acid, sodium silicate, and water in the double - row deep - hole grouting, an effective shell structure can be formed within the range of 180° of the crown.

[0046] The pre - reinforcement method for the strata of the mined - out tunnel provided by the present invention can be widely applied to the construction process of mined - out tunnels in water - rich sand strata. Brief Description of the Drawings

[0047] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0048] Figure 1Front layout view of the shell structure prepared by the pre - reinforcement method for the strata of the mined - out tunnel provided in Embodiment 1 of the present invention;

[0049] Figure 2 Cross - sectional view of the shell structure prepared by the pre - reinforcement method for the strata of the mined - out tunnel provided in Embodiment 1 of the present invention. Detailed implementation manners

[0050] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0051] According to one aspect of the present invention, a pre - reinforcement method for the strata of a mined - out tunnel, the pre - reinforcement method for the strata of the mined - out tunnel includes performing double - row deep - hole grouting within the range of 180° of the crown of the tunnel to be excavated;

[0052] The slurry for the double - row deep - hole grouting is phosphoric acid - sodium silicate chemical slurry, and the phosphoric acid - sodium silicate chemical slurry is mainly composed of 75% industrial phosphoric acid, sodium silicate and water;

[0053] Among them, the mass ratio of 75% industrial phosphoric acid, sodium silicate and water is 1:11.5 - 18.4:33.5 - 54.3.

[0054] The pre - reinforcement method for the strata of the mined - out tunnel provided by the present invention includes performing double - row deep - hole grouting within the range of 180° of the crown of the tunnel to be excavated; the phosphoric acid - sodium silicate chemical slurry for the double - row deep - hole grouting is composed of 75% industrial phosphoric acid, sodium silicate and water; among them, the mass ratio of 75% industrial phosphoric acid, sodium silicate and water is 1:11.5 - 18.4:33.5 - 54.3. The above - mentioned pre - reinforcement method for the strata of the mined - out tunnel uses phosphoric acid - sodium silicate chemical slurry for grouting. On the premise of good sand - fixing effect, it will not significantly increase the strength of the sand layer. It can reinforce the sand layer in the arch part while hardly affecting the strength of the face soil body, ensuring the excavation efficiency; in addition, through the specific ratio adjustment of 75% industrial phosphoric acid, sodium silicate and water in the double - row deep - hole grouting, an effective shell structure can be formed within the range of 180° of the crown.

[0055] In a preferred implementation manner of the present invention, the double - row deep - hole grouting includes a first row of grouting holes and a second row of grouting holes;

[0056] In the above - mentioned preferred implementation manner, the first row of grouting holes is located 0.5 m inside the primary support contour line, with a circumferential spacing of 600 mm, a longitudinal spacing of 10 m, a reinforcement length of 12 m, a horizontal overlap of 2 m, and a drilling angle of 6°;

[0057] In the above preferred embodiment, the second row of grouting holes is located 3 - 5 cm inside the primary support contour line, with a circumferential spacing of 600 mm, a longitudinal spacing of 10 m, a reinforcement length of 12 m, a horizontal overlap of 2 m, and the angle of the perforated steel pipe is 9°.

[0058] As a preferred embodiment, the above double - row deep - hole grouting arranges two rows of grouting holes circumferentially within the 180° range of the arch, and marks the position and drilling angle of the grouting holes with positioning holes within the allowable deviation range. Its specific advantage is that it can form an effective shell structure within the 180° range of the arch crown. Compared with full - section grouting or semi - section grouting, the number of drilling and grouting is significantly reduced.

[0059] In a preferred embodiment of the present invention, the double - row deep - hole grouting includes forward drilling grouting and backward grouting.

[0060] In a preferred embodiment of the present invention, the forward drilling grouting drills the grouting holes by the sectional hole - guiding method through positioning holes, with each section being 2 m and a total of 6 sections being drilled; the drilling speed is controlled at 0.2 - 0.6 m / min, and the grouting pressure is 0.5 - 1.5 MPa; preferably, the drilling speed is 0.5 m / min and the grouting pressure is 0.8 MPa;

[0061] As a preferred embodiment, the requirement for drilling grouting holes by the sectional hole - guiding method through positioning holes is that the hole position deviation is ±3 cm, and the incident angle deviation is not more than 1°.

[0062] It should be noted that in the forward drilling grouting of this application, phosphoric acid - sodium silicate chemical slurry is used during the drilling process, which can fix large - particle - size stones in advance, effectively solve the problem of drill jamming, and greatly improve the success rate of drilling.

[0063] Preferably, the slurry consumption of a single grouting hole for forward drilling grouting is 18.2 L of 75% phosphoric acid, 210 L of sodium silicate, and 611.76 L of water.

[0064] In a preferred embodiment of the present invention, the slurry preparation method for the forward drilling grouting includes:

[0065] The slurry ratio of the forward grouting A pipe is 75% industrial phosphoric acid: water = 1:22;

[0066] The slurry ratio of the forward grouting B pipe is sodium silicate: water = 1:1;

[0067] Mix the slurry of the forward grouting A pipe and the slurry of the forward grouting B pipe in a mass ratio of 1:1 to obtain the phosphoric acid - sodium silicate chemical slurry used for forward grouting.

[0068] In a preferred embodiment of the present invention, the method for backward grouting includes:

[0069] The 6 grouting pipes drilled by the advancing drilling grouting are gradually withdrawn step by step, and the step-by-step backward grouting is carried out in sequence from the inside to the outside.

[0070] In a preferred embodiment of the present invention, the method for preparing the slurry for the backward grouting includes:

[0071] The slurry ratio of the backward grouting A pipe is 75% industrial phosphoric acid: water = 1: 22 - 35.8;

[0072] The slurry ratio of the backward grouting B pipe is sodium silicate: water = 1: 1;

[0073] The slurry of the backward grouting A pipe and the slurry of the backward grouting B pipe are mixed evenly at a mass ratio of 1: 1 to obtain the phosphoric acid - sodium silicate chemical slurry used for the advancing grouting.

[0074] In a preferred embodiment of the present invention, the backward grouting includes the following steps:

[0075] (a), When the grouting pipe is not withdrawn, the slurry consumption of a single grouting hole for the backward grouting is 36.48 L of 75% phosphoric acid, 420 L of sodium silicate, and 1223.52 L of water, the speed is controlled at 0.2 - 0.6 m / min, and the grouting pressure is 0.5 - 1.5 MPa; preferably, the drilling speed is 0.5 m / min and the grouting pressure is 1.0 MPa;

[0076] (b), When the first grouting pipe is withdrawn, the slurry consumption of a single grouting hole for the backward grouting is 25.65 L of 75% phosphoric acid, 315 L of sodium silicate, and 919.35 L of water, the speed is controlled at 0.2 - 0.6 m / min, and the grouting pressure is 0.5 - 1.5 MPa; preferably, the drilling speed is 0.5 m / min and the grouting pressure is 0.9 MPa;

[0077] (c), When the second grouting pipe is withdrawn, the slurry consumption of a single grouting hole for the backward grouting is 23.94 L of 75% phosphoric acid, 315 L of sodium silicate, and 921.06 L of water, the speed is controlled at 0.2 - 0.6 m / min, and the grouting pressure is 0.5 - 1.5 MPa; preferably, the drilling speed is 0.5 m / min and the grouting pressure is 0.8 MPa;

[0078] (d), When the third grouting pipe is withdrawn, the slurry consumption of a single grouting hole for the backward grouting is 22.23 L of 75% phosphoric acid, 315 L of sodium silicate, and 922.77 L of water, the speed is controlled at 0.2 - 0.6 m / min, and the grouting pressure is 0.5 - 1.5 MPa; preferably, the drilling speed is 0.5 m / min and the grouting pressure is 0.8 MPa;

[0079] (e) When the 4th grouting pipe is withdrawn, the slurry consumption for the single-section grouting hole of backward grouting is 20.52 L of 75% phosphoric acid, 315 L of water glass, and 924.48 L of water. The speed is controlled at 0.2 - 0.6 m / min, and the grouting pressure is 0.5 - 1.5 MPa; preferably, the drilling speed is 0.5 m / min and the grouting pressure is 0.7 MPa.

[0080] (f) When the 5th grouting pipe is withdrawn, the slurry consumption for the single-section grouting hole of backward grouting is 17.1 L of 75% phosphoric acid, 315 L of water glass, and 927.9 L of water. The speed is controlled at 0.2 - 0.6 m / min, and the grouting pressure is 0.5 - 1.5 MPa; preferably, the drilling speed is 0.5 m / min and the grouting pressure is 0.6 MPa.

[0081] As a preferred implementation manner, in the process of the above backward grouting, the slurry ratio in different depth ranges is determined according to the setting time of the slurry, and the backward grouting parameters are used for slurry mixing before grouting, which can effectively ensure the formation of an effective shell structure in the 180° range of the vault.

[0082] In a preferred implementation manner of the present invention, the thickness of the pre-reinforced formation shell formed after double-row deep-hole grouting is 2 - 3 m, preferably 2.5 m.

[0083] According to one aspect of the present invention, there is an application of the above-mentioned method for pre-reinforcing the formation of a mined tunnel in a mined tunnel in a water-rich sand layer.

[0084] The method for pre-reinforcing the formation of a mined tunnel provided by the present invention can be widely applied to the construction process of a mined tunnel in a water-rich sand layer.

[0085] Next, the technical solution of the present invention will be further described in conjunction with embodiments.

[0086] Embodiment 1

[0087] A method for pre-reinforcing the formation of a mined tunnel, the method comprising the following steps:

[0088] Note: The construction section using the method for pre-reinforcing the formation of a mined tunnel in this embodiment is the 4th bid section of the general contracting project of the first phase of Xi'an Metro Line 15.

[0089] (1), as Figure 1 、 2 shown, determine the pre-reinforced formation of the tunnel to be excavated. Subsequently, after measuring and setting out the lines, two rows of grouting holes are arranged circumferentially within the 180° range of the arch, and the positions and drilling angles of the grouting holes are marked with positioning holes within the allowable deviation range.

[0090] Parameters of the two rows of grouting holes:

[0091] The first row is located 0.5 m inside the primary support contour line, with a circumferential spacing of 600 mm, a longitudinal spacing of 10 m, a reinforcement length of 12 m, a horizontal lap of 2 m, and a drilling angle of 6°.

[0092] The second row uses steel flower pipe grouting (also serving as the function of an advanced small guide pipe), located 5 cm inside the vicinity of the primary support contour line, with a circumferential spacing of 600 mm, a longitudinal spacing of 10 m, a reinforcement length of 12 m, a horizontal lap of 2 m, a steel flower pipe angle of 9°, and a grouted shell with a thickness of 2.5 m is formed.

[0093] (2) Advance drilling grouting: Prepare the slurry according to the advance drilling grouting parameters as follows:

[0094] The slurry preparation method for the advance drilling grouting includes:

[0095] The slurry ratio of the advance grouting A pipe is 75% industrial phosphoric acid: water = 1:22;

[0096] The slurry ratio of the advance grouting B pipe is sodium silicate: water = 1:1;

[0097] Mix the slurry of the advance grouting A pipe and the slurry of the advance grouting B pipe in a mass ratio of 1:1 to obtain the phosphoric acid - sodium silicate chemical slurry used for advance grouting.

[0098] Subsequently, drill the grouting holes by the sectional hole - leading method through the positioning holes using a double - pipe grouting rig according to the position and drilling angle of the grouting holes. Each section is 2 m, and a total of 6 sections are drilled. The slurry is a chemical slurry of phosphoric acid and sodium silicate. The hole position deviation is required to be ±3 cm, and the incident angle deviation is not more than 1°;

[0099] Among them, the drilling speed is controlled at 0.5 m / min, the grouting pressure is 0.8 MPa, and the slurry consumption for advance grouting of a single grouting hole is 18.2 L of 75% phosphoric acid, 210 L of sodium silicate, and 611.76 L of water.

[0100] (3) Retreating grouting: The retreating grouting includes the following steps:

[0101] a. When the grouting pipe is not withdrawn, the slurry preparation method for the retreating grouting includes:

[0102] The slurry ratio of the retreating grouting A pipe is 75% industrial phosphoric acid: water = 1:22;

[0103] The slurry ratio of the retreating grouting B pipe is sodium silicate: water = 1:1;

[0104] Mix the slurry of the retreating grouting A pipe and the slurry of the retreating grouting B pipe in a mass ratio of 1:1 to obtain the phosphoric acid - sodium silicate chemical slurry used for advance grouting.

[0105] When the grouting pipe is not withdrawn, the slurry consumption for each grouting hole in the backward grouting is 36.48 L of 75% phosphoric acid, 420 L of water glass, and 1223.52 L of water. The speed is controlled at 0.5 m / min, and the grouting pressure is 1.0 MPa.

[0106] b. When the first grouting pipe is withdrawn, the slurry preparation method for the backward grouting includes:

[0107] The slurry ratio of the backward grouting A pipe is 75% industrial phosphoric acid: water = 1:23.5;

[0108] The slurry ratio of the backward grouting B pipe is water glass: water = 1:1;

[0109] Mix the slurry of the backward grouting A pipe and the slurry of the backward grouting B pipe in a mass ratio of 1:1 to obtain the phosphoric acid-sodium silicate chemical slurry used for the forward grouting.

[0110] When the first grouting pipe is withdrawn, the slurry consumption for each grouting hole in the backward grouting is 25.65 L of 75% phosphoric acid, 315 L of water glass, and 919.35 L of water. The speed is controlled at 0.5 m / min, and the grouting pressure is 0.9 MPa.

[0111] c. When the second grouting pipe is withdrawn, the slurry preparation method for the backward grouting includes:

[0112] The slurry ratio of the backward grouting A pipe is 75% industrial phosphoric acid: water = 1:25.3;

[0113] The slurry ratio of the backward grouting B pipe is water glass: water = 1:1;

[0114] Mix the slurry of the backward grouting A pipe and the slurry of the backward grouting B pipe in a mass ratio of 1:1 to obtain the phosphoric acid-sodium silicate chemical slurry used for the forward grouting.

[0115] When the second grouting pipe is withdrawn, the slurry consumption for each grouting hole in the backward grouting is 23.94 L of 75% phosphoric acid, 315 L of water glass, and 921.06 L of water. The speed is controlled at 0.5 m / min, and the grouting pressure is 0.8 MPa.

[0116] d. When the third grouting pipe is withdrawn, the slurry preparation method for the backward grouting includes:

[0117] The slurry ratio of the backward grouting A pipe is 75% industrial phosphoric acid: water = 1:27.3;

[0118] The slurry ratio of the backward grouting B pipe is water glass: water = 1:1;

[0119] Mix the slurry of the backward grouting A pipe and the slurry of the backward grouting B pipe in a mass ratio of 1:1 to obtain the phosphoric acid-sodium silicate chemical slurry used for the forward grouting.

[0120] When extracting the third grouting pipe, the slurry consumption for the single grouting hole of backward grouting is 22.23 L of 75% phosphoric acid, 315 L of water glass, and 922.77 L of water. The speed is controlled at 0.5 m / min, and the grouting pressure is 0.8 MPa.

[0121] e. When extracting the fourth grouting pipe, the slurry preparation method for the backward grouting includes:

[0122] The slurry ratio of the backward grouting A pipe is 75% industrial phosphoric acid: water = 1:29.7;

[0123] The slurry ratio of the backward grouting B pipe is water glass: water = 1:1;

[0124] Mix the slurry of the backward grouting A pipe and the slurry of the backward grouting B pipe in a mass ratio of 1:1 to obtain the phosphoric acid - water glass chemical slurry used for forward grouting.

[0125] When extracting the fourth grouting pipe, the slurry consumption for the single grouting hole of backward grouting is 20.52 L of 75% phosphoric acid, 315 L of water glass, and 924.48 L of water. The speed is controlled at 0.5 m / min, and the grouting pressure is 0.7 MPa.

[0126] f. When extracting the fifth grouting pipe, the slurry preparation method for the backward grouting includes:

[0127] The slurry ratio of the backward grouting A pipe is 75% industrial phosphoric acid: water = 1:35.8;

[0128] The slurry ratio of the backward grouting B pipe is water glass: water = 1:1;

[0129] Mix the slurry of the backward grouting A pipe and the slurry of the backward grouting B pipe in a mass ratio of 1:1 to obtain the phosphoric acid - water glass chemical slurry used for forward grouting.

[0130] When extracting the fifth grouting pipe, the slurry consumption for the single grouting hole of backward grouting is 17.1 L of 75% phosphoric acid, 315 L of water glass, and 927.9 L of water. The speed is controlled at 0.5 m / min, and the grouting pressure is 0.6 MPa.

[0131] The above backward grouting is completed by step - by - step back - extraction of the six grouting pipes drilled by forward drilling grouting, and then step - by - step backward grouting is completed from the inside to the outside in sequence. In this embodiment, the backward grouting adjusts the slurry ratio and slurry consumption in different depth ranges according to the setting time, and thus an effective shell structure is formed in the 180° range of the arch crown.

[0132] Effect verification

[0133] To demonstrate that the pre - reinforcement method for the strata of the mined - out tunnel in this application can form an effective shell structure within the 180° range of the crown of the tunnel to be excavated. On the premise of having a good sand - fixing effect, it will not significantly increase the strength of the sand layer. It can reinforce the sand layer in the arch part while hardly affecting the strength of the face soil mass, ensuring the excavation efficiency, and thus alleviating the problem of poor reinforcement effect of the existing advanced small - duct grouting in water - rich sand layers.

[0134] The applicant conducted sampling inspections on the pre - reinforcement shells of the mined - out tunnel strata prepared in the above - mentioned Example 1. The specific method is as follows:

[0135]

[0136] The specific inspection results are shown in the following table:

[0137]

[0138] Comparative Example 1

[0139] A pre - reinforcement method for the strata of the mined - out tunnel by semi - section deep - hole grouting. The method includes the following steps:

[0140] Note: The construction section using semi - section deep - hole grouting in this comparative example is Section 4 of the general contracting project of the first - phase project of Xi'an Metro Line 15.

[0141] (1). Determine the pre - reinforcement strata of the tunnel to be excavated. Then, after measuring and setting out the lines, arrange three rows of grouting holes circumferentially within the 180° range of the arch, and mark the positions and drilling angles of the grouting holes with positioning holes within the allowable deviation range.

[0142] Parameters of the three rows of grouting holes:

[0143] The first row is located 1.0 m inside the primary support contour line, with a circumferential spacing of 600 mm, a longitudinal spacing of 10 m, a reinforcement length of 12 m, a horizontal overlap of 2 m, and a drilling angle of 2°51’45;

[0144] The second row is located 1.0 m inside the primary support contour line, with a circumferential spacing of 600 mm, a longitudinal spacing of 10 m, a reinforcement length of 12 m, a horizontal overlap of 2 m, and a drilling angle of 5°42’38”;

[0145] The third row uses steel - flower - tube grouting (also serving as the function of the advanced small - duct), located 5 cm inside the primary support contour line, with a circumferential spacing of 600 mm, a longitudinal spacing of 10 m, a reinforcement length of 12 m, a horizontal overlap of 2 m, and an angle of the steel - flower tube of 8°31’51”;

[0146] The remaining grouting holes are drilled horizontally with a spacing of 1.0 m and arranged in a plum - blossom pattern.

[0147] (2). Advance drilling and grouting: Prepare the grout according to the advance - drilling - grouting parameters, specifically as follows:

[0148] The slurry preparation method for forward drilling grouting includes:

[0149] The slurry ratio of the forward grouting A pipe is 75% industrial phosphoric acid: water = 1:22;

[0150] The slurry ratio of the forward grouting B pipe is sodium silicate: water = 1:1;

[0151] Mix the slurry of the forward grouting A pipe and the slurry of the forward grouting B pipe in a mass ratio of 1:1 to obtain the phosphoric acid - sodium silicate chemical slurry for forward grouting.

[0152] Subsequently, according to the position and driving angle of the grouting hole, use a double - pipe grouting rig to drill the grouting hole by the sectional pilot - hole method through the positioning hole. Each section is 2m, and a total of 6 sections are drilled. The slurry is a chemical slurry of phosphoric acid and sodium silicate. The hole position deviation is required to be ±3cm, and the incident angle deviation is not more than 1°;

[0153] Among them, the drilling speed is controlled at 0.5m / min, the grouting pressure is 0.8MPa, and the slurry consumption for forward grouting in a single grouting hole is 18.2L of 75% phosphoric acid, 210L of sodium silicate, and 611.76L of water.

[0154] (3) Backward grouting: The backward grouting includes the following steps:

[0155] a. When the grouting pipe is not withdrawn, the slurry preparation method for backward grouting includes:

[0156] The slurry ratio of the backward grouting A pipe is 75% industrial phosphoric acid: water = 1:22;

[0157] The slurry ratio of the backward grouting B pipe is sodium silicate: water = 1:1;

[0158] Mix the slurry of the backward grouting A pipe and the slurry of the backward grouting B pipe in a mass ratio of 1:1 to obtain the phosphoric acid - sodium silicate chemical slurry for forward grouting.

[0159] When the grouting pipe is not withdrawn, the slurry consumption for a single - section grouting hole in backward grouting is 36.48L of 75% phosphoric acid, 420L of sodium silicate, and 1223.52L of water. The speed is controlled at 0.5m / min, and the grouting pressure is 1.0MPa;

[0160] b. When the first - section grouting pipe is withdrawn, the slurry preparation method for backward grouting includes:

[0161] The slurry ratio of the backward grouting A pipe is 75% industrial phosphoric acid: water = 1:23.5;

[0162] The slurry ratio of the backward grouting B pipe is sodium silicate: water = 1:1;

[0163] Mix the grout in the backward grouting A pipe and the grout in the backward grouting B pipe in a mass ratio of 1:1 to obtain the phosphoric acid-sodium silicate chemical grout for the forward grouting.

[0164] When extracting the first section of the grouting pipe, the slurry consumption of a single grouting hole for backward grouting is 25.65 L of 75% phosphoric acid, 315 L of sodium silicate, and 919.35 L of water. The speed is controlled at 0.5 m / min, and the grouting pressure is 0.9 MPa.

[0165] c. When extracting the second section of the grouting pipe, the slurry preparation method for the backward grouting includes:

[0166] The ratio of the slurry in the backward grouting A pipe is 75% industrial phosphoric acid: water = 1:25.3;

[0167] The ratio of the slurry in the backward grouting B pipe is sodium silicate: water = 1:1;

[0168] Mix the grout in the backward grouting A pipe and the grout in the forward grouting B pipe in a mass ratio of 1:1 to obtain the phosphoric acid-sodium silicate chemical grout for the forward grouting.

[0169] When extracting the second section of the grouting pipe, the slurry consumption of a single grouting hole for backward grouting is 23.94 L of 75% phosphoric acid, 315 L of sodium silicate, and 921.06 L of water. The speed is controlled at 0.5 m / min, and the grouting pressure is 0.8 MPa.

[0170] d. When extracting the third section of the grouting pipe, the slurry preparation method for the backward grouting includes:

[0171] The ratio of the slurry in the backward grouting A pipe is 75% industrial phosphoric acid: water = 1:27.3;

[0172] The ratio of the slurry in the backward grouting B pipe is sodium silicate: water = 1:1;

[0173] Mix the grout in the backward grouting A pipe and the grout in the backward grouting B pipe in a mass ratio of 1:1 to obtain the phosphoric acid-sodium silicate chemical grout for the forward grouting.

[0174] When extracting the third section of the grouting pipe, the slurry consumption of a single grouting hole for backward grouting is 22.23 L of 75% phosphoric acid, 315 L of sodium silicate, and 922.77 L of water. The speed is controlled at 0.5 m / min, and the grouting pressure is 0.8 MPa.

[0175] e. When extracting the fourth section of the grouting pipe, the slurry preparation method for the backward grouting includes:

[0176] The ratio of the slurry in the backward grouting A pipe is 75% industrial phosphoric acid: water = 1:29.7;

[0177] The ratio of the slurry in the backward grouting B pipe is sodium silicate: water = 1:1;

[0178] Mix the grout of the backward grouting A pipe and the grout of the backward grouting B pipe in a mass ratio of 1:1 to obtain the phosphoric acid-sodium silicate chemical grout used for the forward grouting.

[0179] When the 4th grouting pipe is withdrawn, the slurry consumption of a single grouting hole for backward grouting is 20.52 L of 75% phosphoric acid, 315 L of sodium silicate, and 924.48 L of water, the speed is controlled at 0.5 m / min, and the grouting pressure is 0.7 MPa;

[0180] f. When the 5th grouting pipe is withdrawn, the slurry preparation method for the backward grouting includes:

[0181] The slurry ratio of the backward grouting A pipe is 75% industrial phosphoric acid: water = 1:35.8;

[0182] The slurry ratio of the backward grouting B pipe is sodium silicate: water = 1:1;

[0183] Mix the grout of the backward grouting A pipe and the grout of the backward grouting B pipe in a mass ratio of 1:1 to obtain the phosphoric acid-sodium silicate chemical grout used for the forward grouting.

[0184] When the 5th grouting pipe is withdrawn, the slurry consumption of a single grouting hole for backward grouting is 17.1 L of 75% phosphoric acid, 315 L of sodium silicate, and 927.9 L of water, the speed is controlled at 0.5 m / min, and the grouting pressure is 0.6 MPa.

[0185] The above backward grouting is carried out by stepwise withdrawing the 6 grouting pipes drilled by the forward drilling grouting, and then the stepwise backward grouting is completed in sequence from the inside to the outside. In this embodiment, the backward grouting adjusts the slurry ratio and slurry consumption in different depth ranges according to the setting time, and thus an effective shell structure is formed in the 180° range of the arch crown.

[0186] Technical comparison

[0187] The applicant compares Example 1 and Comparative Example 1 in terms of the unconfined compressive strength of the reinforced body, the total grouting volume, and the construction efficiency.

[0188] (1) Comparison of the unconfined compressive strength of the reinforced body:

[0189] For Example 1, only 2 core samples were taken from the arch crown and the arch waist for inspection. For Comparative Example 1, core samples were taken from 3 locations: the arch crown, the arch waist, and the heading face. The comparison results are shown in the following table.

[0190]

[0191]

[0192] As can be seen from the table, under the semi-section deep-hole grouting technology, the unconfined compressive strengths of the reinforced bodies at the vault and the arch waist are not much different, and the unconfined compressive strength at the heading face is slightly lower; under the arch deep-hole grouting technology, the unconfined compressive strength of the reinforced body at a shallower depth is similar to that of the semi-section deep-hole grouting reinforcement, but there is an obvious attenuation phenomenon of the strength with the increase of depth.

[0193] (2) Comparison of the total grouting volume:

[0194] The main grouting materials are water, phosphoric acid and water glass, and the Baume degree of water glass Be = 45.

[0195] For the comparison between Example 1 and Plan Example 1, the comparison of the usage amounts of each grouting material is shown in the following table in detail.

[0196] <![CDATA[Water glass (m 3 )]]> <![CDATA[Phosphoric acid (m 3 )]]> <![CDATA[Water (m 3 )]]> Example 1 81.59 6.07 238.62 Comparative Example 1 138.92 10.34 406.29

[0197] As can be seen from the table, the amount of materials required for the arch deep-hole grouting is about 60% of that required for the semi-section deep-hole grouting.

[0198] (3) Comparison of construction efficiency

[0199] At the site, a double-shift operation system of day and night shifts is adopted every day. The test section is constructed by the bench method, including one deep-hole grouting reinforcement, excavation and support of 10 m for each of the upper and lower benches. The comparison of the construction time is shown in the following table in detail.

[0200]

[0201] As can be seen from the table, the time-consuming for the grouting reinforcement, excavation and support of the semi-section deep-hole grouting is significantly higher than that of the arch deep-hole grouting. The former has 63 grouting holes, 26 more than the latter. And during the excavation process, the strength of the upper bench stratum after reinforcement is relatively high, and the excavation efficiency is relatively low.

[0202] (4) Summary of the comparison

[0203] According to the comparison of the three parameters of the unconfined compressive strength, the total grouting volume and the construction efficiency of the reinforced body under the two grouting technologies, although the strength of the reinforced body of the arch deep-hole grouting has an attenuation phenomenon with the increase of depth, it is still sufficient to maintain the stability of the stratum after attenuation; in the other two aspects, the arch deep-hole grouting saves 40% of the grouting materials compared with the semi-section deep-hole grouting, and the construction efficiency is far ahead; therefore, the arch deep-hole grouting technology has more advantages than the semi-section deep-hole grouting.

[0204] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for pre - reinforcing the strata of a mined - out tunnel, characterized in that, the method for pre - reinforcing the strata of the mined - out tunnel includes performing double - row deep - hole grouting within the range of 180° of the crown of the tunnel to be excavated; the double - row deep - hole grouting includes a first row of grouting holes and a second row of grouting holes; the first row of grouting holes is located 0.5 m inside the primary support contour line, with a circumferential spacing of 600 mm, a longitudinal spacing of 10 m, a reinforcement length of 12 m, a horizontal overlap of 2 m, and a drilling angle of 6°; the second row of grouting holes is located 3 - 5 cm inside the primary support contour line, with a circumferential spacing of 600 mm, a longitudinal spacing of 10 m, a reinforcement length of 12 m, a horizontal overlap of 2 m, and a steel - flower - tube angle of 9°; the double - row deep - hole grouting includes advancing - hole drilling grouting and retreating grouting; the advancing - hole drilling grouting drills the grouting holes by the sectional hole - guiding method through positioning holes, with each section being 2 m and a total of 6 sections being drilled; the drilling speed is controlled at 0.2 - 0.6 m / min, and the grouting pressure is 0.5 - 1.5 MPa; the slurry consumption of a single grouting hole for advancing - hole drilling grouting is 18.2 L of 75% phosphoric acid, 210 L of water glass, and 611.76 L of water; the method of retreating grouting includes the following steps: (a) When the grouting pipe is not withdrawn, the slurry consumption of a single grouting hole for retreating grouting is 36.48 L of 75% phosphoric acid, 420 L of water glass, and 1223.52 L of water, with the speed controlled at 0.2 - 0.6 m / min and the grouting pressure at 0.5 - 1.5 MPa; (b) When the first section of the grouting pipe is withdrawn, the slurry consumption of a single grouting hole for retreating grouting is 25.65 L of 75% phosphoric acid, 315 L of water glass, and 919.35 L of water, with the speed controlled at 0.2 - 0.6 m / min and the grouting pressure at 0.5 - 1.5 MPa; (c) When the second section of the grouting pipe is withdrawn, the slurry consumption of a single grouting hole for retreating grouting is 23.94 L of 75% phosphoric acid, 315 L of water glass, and 921.06 L of water, with the speed controlled at 0.2 - 0.6 m / min and the grouting pressure at 0.5 - 1.5 MPa; (d) When the third section of the grouting pipe is withdrawn, the slurry consumption of a single grouting hole for retreating grouting is 22.23 L of 75% phosphoric acid, 315 L of water glass, and 922.77 L of water, with the speed controlled at 0.2 - 0.6 m / min and the grouting pressure at 0.5 - 1.5 MPa; (e) When the fourth section of the grouting pipe is withdrawn, the slurry consumption of a single grouting hole for retreating grouting is 20.52 L of 75% phosphoric acid, 315 L of water glass, and 924.48 L of water, with the speed controlled at 0.2 - 0.6 m / min and the grouting pressure at 0.5 - 1.5 MPa; (f) When the fifth section of the grouting pipe is withdrawn, the slurry consumption of a single grouting hole for retreating grouting is 17.1 L of 75% phosphoric acid, 315 L of water glass, and 927.9 L of water, with the speed controlled at 0.2 - 0.6 m / min and the grouting pressure at 0.5 - 1.5 MPa.

2. The method for pre - reinforcing the strata of a mined - out tunnel according to claim 1, characterized in that, the method for preparing the slurry for advancing - hole drilling grouting includes: The slurry ratio of the advancing grouting A pipe is 75% industrial phosphoric acid: water = 1:22; The slurry ratio of the advancing grouting B pipe is sodium silicate: water = 1:1; Mix the slurry of the advancing grouting A pipe and the slurry of the advancing grouting B pipe in a mass ratio of 1:1 to obtain the phosphoric acid-sodium silicate chemical slurry used for advancing grouting.

3. The pre-reinforcement method for the strata of the mined tunnel according to claim 1, characterized in that, the method for preparing the slurry for the backward grouting includes: The slurry ratio of the backward grouting A pipe is 75% industrial phosphoric acid: water = 1:22 - 35.8; The slurry ratio of the backward grouting B pipe is sodium silicate: water = 1:1; Mix the slurry of the backward grouting A pipe and the slurry of the backward grouting B pipe in a mass ratio of 1:1 to obtain the phosphoric acid-sodium silicate chemical slurry used for backward grouting.

4. The pre-reinforcement method for the strata of the mined tunnel according to claim 1, characterized in that, the thickness of the strata pre-reinforcement shell formed after the double-row deep-hole grouting is 2 - 3 m.

5. The pre-reinforcement method for the strata of the mined tunnel according to claim 4, characterized in that, the thickness of the strata pre-reinforcement shell formed after the double-row deep-hole grouting is 2.5 m.

6. The application of the pre-reinforcement method for the strata of the mined tunnel according to any one of claims 1 - 5 in the mined tunnel in the water-rich sand layer.

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