Grouting ring construction method and construction method for gushing water section of deep buried tunnel in environmentally sensitive area

Abstract

The present application relates to the technical field of tunnel construction, and provides a construction method for a deep-buried tunnel gushing water section in an environmentally sensitive area, comprising the following steps: building a waterproof rock wall close to a working face at the working face; constructing a grouting ring in front of the arch crown of the working face according to a grouting ring construction method; drilling a hole at a position where an advanced pilot tunnel is to be excavated in front of the working face according to a second drilling method, and grouting; excavating the advanced pilot tunnel after the mechanical properties of the grouting meet the requirements; performing annular drilling and grouting along the radial direction of the tunnel in the advanced pilot tunnel, and then excavating the area outside the advanced pilot tunnel. The present application not only prevents the loss of underground water from having a negative impact on the hydrogeological environment of the environmentally sensitive area, but also provides a theoretical basis for the required thickness of the grouting ring, avoids excessive increase in the thickness of the grouting ring, and thus reduces construction costs, improves construction efficiency, and makes the treatment of the gushing water section of the tunnel more targeted.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tunnel construction, in particular to a grouting ring construction method and a construction method for a water gushing section of a deep-buried tunnel in an environmentally sensitive area. BACKGROUND

[0002] In deep-buried long tunnel construction, when the tunnel passes through an environmentally sensitive area, due to the large tunnel depth and large underground water storage space, the underground water gushing from the tunnel face has the characteristics of high water head and high water pressure, and there is a high risk of water gushing. When the tunnel face appears water gushing, not only will it cause delays in the construction period, equipment losses and personnel construction risks, but also due to the excessive discharge of underground water, it will cause a certain negative impact on the hydrogeological environment of the environmentally sensitive area, and even cause damage to the underground water environment and death of surface vegetation due to lack of water.

[0003] Therefore, when the tunnel passes through a water gushing section in a sensitive environment area during deep-buried tunnel construction, the method of "mainly blocking and controlling discharge" is often used to prevent excessive loss of underground water. At present, a grouting ring is often constructed in the vault of the tunnel face to block the underground water, and the thickness of the grouting ring determines the amount of water flowing into the tunnel. Although the structure and thickness of the grouting ring will be designed specifically during the survey and design stage, due to the complexity of geological bodies and the non-uniformity of rock bodies, the specific location of the water gushing section, the water gushing characteristics and the underground water pressure will all deviate from the original design during actual construction. Therefore, the thickness of the grouting ring also needs to be determined again according to the actual situation during construction.

[0004] The current research mainly focuses on the grouting blocking effect based on fluid-structure coupling, but lacks research on the stability of the grouting ring under high water pressure, and lacks a basis for determining the required thickness of the grouting ring. Although increasing the thickness of the grouting ring can reduce the amount of water flowing into the tunnel, if the thickness of the grouting ring is excessively increased, it will not only cause high grouting costs and increase construction costs, but also reduce construction efficiency and prolong the construction period. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a grouting ring construction method and a construction method for a water gushing section of a deep-buried tunnel in an environmentally sensitive area, to obtain a basis for determining the required thickness of the grouting ring, and to make the treatment of the water gushing section of the tunnel more targeted.

[0006] The technical solution adopted by the present application to solve the technical problem is: a grouting ring construction method, comprising the following steps: obtaining the water head height of the underground water of the tunnel face; drilling a hole in the vault of the tunnel face along the extension direction of the tunnel according to a first drilling method and grouting to form a grouting ring; the safety thickness of the grouting ring is determined according to formula (1);

[0007]

[0008] wherein, delta is the safety thickness of the grouting circle, unit is m; k is the safety factor; r is the inner radius of the grouting circle, unit is m; c is the cohesion of the grouting circle, unit is kPa; is the internal friction angle of the grouting circle, unit is °; rho is the density of the underground water, unit is kg / m 3 ; g is the gravity acceleration, unit is m / s 2 ; h is the water head height of the underground water at the working face, unit is m.

[0009] Further, the method for obtaining the water head height of the underground water at the working face comprises the following steps: drilling an advanced borehole in front of the working face, revealing the outburst of underground water, and measuring the outburst water flow; and calculating the water head height of the underground water at the working face according to formula (2).

[0010]

[0011] wherein, h is the water head height of the underground water at the working face, unit is m; d is the hole diameter of the advanced borehole, unit is m; Q is the outburst water flow, unit is m 3 / s; g is the gravity acceleration, unit is m / s 2 .

[0012] The construction method for the water outburst section of the deep-buried tunnel in the environmentally sensitive area comprises the following steps: building a waterproof rock wall close to the working face at the working face; constructing a grouting circle in front of the vault of the working face according to the grouting circle construction method; drilling a hole at the position where the advanced pilot tunnel is to be excavated in front of the working face according to the second drilling mode, and grouting, and then excavating the advanced pilot tunnel after the grouting body meets the mechanical performance requirements; and drilling a hole along the radial direction of the tunnel in the advanced pilot tunnel and grouting, and then excavating the region outside the advanced pilot tunnel.

[0013] Further, when drilling the hole along the radial direction of the tunnel in the advanced pilot tunnel, the upper hole should be deep into the vault by at least 5 m, and the lower hole should be deep into the inverted arch by 3-4 m.

[0014] Further, the advanced pilot tunnel is excavated in sections; after the excavation of each section of the advanced pilot tunnel is completed, a hole is drilled along the radial direction of the tunnel in the section of the advanced pilot tunnel and grouting is performed; and after the excavation of the next section of the advanced pilot tunnel is completed, the excavation of the region outside the previous section of the advanced pilot tunnel is completed.

[0015] The beneficial effects of the present application are:

[0016] The grouting circle construction method provided by the embodiments of the present application can determine the safety thickness of the grouting circle according to the water head height of the underground water at the working face, provide a theoretical basis for the required thickness of the grouting circle, avoid excessive increase of the thickness of the grouting circle, and thus reduce the construction cost and improve the construction efficiency.

[0017] The construction method for water inrush sections of deep-buried tunnels in environmentally sensitive areas provided by this invention can not only prevent the loss of groundwater from negatively impacting the hydrogeological environment of environmentally sensitive areas, but also provide a theoretical basis for the required thickness of the grouting ring, avoiding excessive increase in the thickness of the grouting ring, thereby reducing construction costs, improving construction efficiency, and making the treatment of water inrush sections of tunnels more targeted. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 It is a cross-sectional view of the tunnel face;

[0020] Figure 2 This is the main longitudinal section view of the tunnel face;

[0021] Figure 3 This is a diagram showing the state of the groundwater level when drilling ahead of the working face.

[0022] The attached diagram is labeled as follows: 1-grouting ring, 2-working face, 3-water-resistant rock wall, 4-pre-tunnel. Detailed Implementation

[0023] To enable those skilled in the art to better understand the present invention, it will be further described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0024] The grouting ring construction method provided in this embodiment of the invention includes the following steps: obtaining the water head height of the groundwater at the tunnel face; drilling a hole along the tunnel extension direction at the tunnel face arch according to the first drilling method, and grouting to form a grouting ring; the safe thickness of the grouting ring is determined according to formula (1);

[0025]

[0026] Where δ is the safe thickness of the grouting ring, in meters (m); k is the safety factor; r is the inner radius of the grouting ring, in meters (m); and c is the cohesion of the grouting ring, in kPa. ρ is the internal friction angle of the grouting ring, in degrees (°); ρ is the density of groundwater, in kg / m³. 3 g is the acceleration due to gravity, and its unit is m / s². 2h is the water head of the face groundwater, and the unit is m.

[0027] The grouting ring 1 is a grouting body formed by drilling a plurality of holes in a ring shape along the tunnel extension direction of the tunnel roof and grouting in each hole. The drilling manner determines the mechanical properties of the grouting ring 1. That is, during the construction of the grouting ring, different drilling manners correspond to different mechanical properties of the grouting ring 1. In the embodiment, the grouting ring 1 is formed by drilling and grouting according to the first drilling manner, and the cohesion and internal friction angle of the grouting ring 1 can be obtained by sampling the grouting body and conducting mechanical tests after solidification. The first drilling manner mainly includes drilling diameter, drilling length, drilling angle, and spacing between adjacent holes, and the specific data can be adjusted according to the actual situation, which is not limited here. The inner radius of the grouting ring 1 can be directly determined during design; for example, the inner radius of the grouting ring 1 can be equal to the radius of the tunnel, or can be greater than the radius of the tunnel. k is a safety factor, and generally takes a value of 1.3-1.5.

[0028] The grouting ring 1 of the tunnel is assumed to be an annular elastic ring, and according to the elastic theory, the most unfavorable position of the grouting ring 1 is located at the inner ring of the grouting ring 1, and the stress of the inner ring of the grouting ring 1 under the action of groundwater pressure is:

[0029]

[0030] σ3=0 (4)

[0031] Wherein, σ1 is the maximum principal stress, the unit is kPa; r is the inner radius of the grouting ring, the unit is m; δ' is the calculated thickness of the grouting ring, the unit is m; f is the pressure of the face groundwater, the unit is kPa; σ3 is the minimum principal stress, the unit is kPa.

[0032] When the most unfavorable point of the outer ring of the grouting ring 1 is in the limit equilibrium, the Mohr-coulomb criterion linear expression is satisfied as formula (5), then the inner ring of the grouting ring 1 is in the limit state.

[0033]

[0034] Wherein, c is the cohesion of the grouting ring, the unit is kPa; is the internal friction angle of the grouting ring, the unit is °.

[0035] Substituting formula (3), (4) into formula (5), we can get:

[0036]

[0037] The calculated thickness δ of the grouting ring 1 ′The limit thickness under the action of groundwater pressure f is h = k f / g, wherein k is a coefficient, and f is the groundwater pressure. ′ The expression of converting the pressure f of the underground water of the working face into the water head height h of the underground water of the working face is f = 0.001 rho gh, wherein rho is the density of the underground water, the unit is kg / m 3 ; g is the gravity acceleration, the unit is m / s 2 ; h is the water head height of the underground water of the working face, the unit is m; and the safe thickness of the grouting ring 1 is h = k f / g.

[0038]

[0039] For convenience of calculation, rho = 1000 kg / m 3 , g = 10 m / s 2 , and the formula (1) can be simplified as h = k f / g.

[0040]

[0041] The grouting ring construction method provided by the embodiment of the application can determine the safe thickness of the grouting ring according to the water head height of the underground water of the working face, provide a theoretical basis for the required thickness of the grouting ring, avoid excessive increase of the thickness of the grouting ring under the condition of ensuring safety, and further reduce the construction cost and improve the construction efficiency.

[0042] The water head height of the underground water of the working face can be obtained by using the existing method, for example, the method disclosed in the application publication No. CN113269714A; another method for obtaining the water head height of the underground water of the working face is provided in the embodiment of the application.

[0043] The embodiment of the application provides a method for obtaining the water head height of the underground water of the working face, which comprises the following steps: referring to Figure 3 , the advanced drilling is performed in front of the working face 2, the underground water is revealed to flow out, and the flow rate of the outflowing water is measured; and the water head height of the underground water of the working face is calculated according to formula (2).

[0044]

[0045] , wherein h is the water head height of the underground water of the working face, the unit is m; d is the hole diameter of the advanced drilling, the unit is m; Q is the flow rate of the outflowing water, the unit is m 3 / s; and g is the gravity acceleration, the unit is m / s 2 .

[0046] Referring to Figure 3 , the underground water flows out from the advanced drilling after the advanced drilling of the working face; wherein the water head pressure obtained by the unit length water column in the advanced drilling under the action of the high water head pressure is F = gamma h A (8).

[0047] F = gamma h A (8)

[0048] Wherein, F is water head pressure, unit is kN; gamma is the unit weight of groundwater, unit is kN / m 3 ; h is the water head height of the working face underground water, unit is m; A is the cross-sectional area of the advanced borehole, unit is m 2 .

[0049] The water column in the advanced borehole obtains the speed v from static in the length l range, and according to the kinetic energy law, the following formula (8) can be obtained:

[0050]

[0051] Wherein, v is the speed of water column gushing out from the advanced borehole, unit is m / s; m is the mass of water column in the advanced borehole, unit is kg; l is the length of the advanced borehole, unit is m.

[0052] According to formula (8), (9), the following formula (9) can be obtained:

[0053]

[0054] The volume of water gushing out from the advanced borehole is V=Qt=vAt; wherein, Q is the gushing water flow, unit is m 3 / s; t is time, unit is s; the following formula (11) can be obtained by combining formula (10):

[0055]

[0056] Wherein, m=ρAl, gamma=ρg, A=πd 2 / 4, then formula (11) can be converted into:

[0057]

[0058] In order to facilitate calculation, g=10m / s 2 , pi=3.14, then formula (2) can be simplified as:

[0059]

[0060] The grouting ring construction method provided by the embodiment of the application only needs to perform advanced borehole in front of the working face 2 to reveal the gushing of underground water, measures the gushing water flow by using pipeline flow meter and other tools on site, and then the water head height of the working face underground water can be quickly and accurately calculated through formula (2).

[0061] Embodiment:

[0062] The tunnel hole body radius is 4.5m, the inner radius of the set grouting ring 1 is equal to the tunnel hole body radius, the advance drilling is performed in front of the working face 2 before the construction of the grouting ring, the hole diameter d of the advance drilling is 0.08m, the water column is jetted out from the working face 2 by the underground water when drilling 3m, and then the water flow Q of the jetted water is measured by using the pipe flow meter and is 0.1m 3 / s; g=10m / s 2 , π=3.14, the water head height of the underground water of the working face can be calculated according to formula (2):

[0063] The tunnel water gushing section is a fault fracture zone, the rock mass is extremely broken, and is in a state of fragmentation to powder, the tunnel water gushing section is located in a nature reserve and is an environmentally sensitive area, the grouting plugging mode is used to cross the water gushing section, the thickness of the grouting ring is determined by using formula (1); specifically, the first drilling mode is used to drill and grout at the working face vault, the test result is obtained by sampling after the grouting body is solidified: c=120Kpa, K=1.3, ρ=1000kg / m 3 ; the safe thickness of the grouting ring is calculated according to formula (1): Then the first drilling mode is used to drill and grout at the working face vault, and the thickness of the grouting ring 1 meets the requirement of 4.55m.

[0064] Referring to Figure 1 , Figure 2 , the construction method of the deep buried tunnel water gushing section in the environmentally sensitive area provided by the embodiment of the application comprises the following steps: the waterproof rock wall 3 close to the working face 2 is built at the working face 2; on the basis that the waterproof rock wall 3 can guarantee the stability of the working face 2, the grouting ring 1 is constructed in front of the working face 2 vault according to the above grouting ring construction method; the drilling and grouting are performed at the position of the advance pilot tunnel 4 to be excavated in front of the working face according to the second drilling mode, the advance pilot tunnel 4 is excavated after the mechanical properties of the grouting body meet the requirements; the pilot tunnel is excavated; the annular drilling and grouting are performed along the tunnel radial direction in the advance pilot tunnel 4, and then the excavation of the area outside the advance pilot tunnel 4 is completed. When the drilling is performed along the tunnel radial direction in the advance pilot tunnel 4, the upper drilling should be at least 5m deep into the vault, and the lower drilling should be 3-4m deep into the inverted arch.

[0065] Drilling holes at the position of the advanced pilot tunnel 4 to be excavated in front of the working face, the drilling mode determines the mechanical properties of the grouting body formed after grouting. That is, different drilling modes correspond to different mechanical properties of the grouting body. In the embodiment, the holes are drilled at the position of the advanced pilot tunnel 4 to be excavated in front of the working face according to the second drilling mode, and grouting is performed, and then the grouting body is sampled and pressure water test is performed, when the test result of the permeability is ≤2Lu and the compressive strength is >1MPa, it indicates that the mechanical properties of the grouting body meet the requirements. The second drilling mode mainly includes drilling diameter, drilling length, drilling angle, adjacent drilling spacing, etc., and the specific data can be adjusted according to the actual situation, which is not limited here. In the embodiment, the diameter of the advanced pilot tunnel 4 is 3-4m.

[0066] To further improve the safety of construction, preferably, the advanced pilot tunnel 4 is excavated in sections; after each section of the advanced pilot tunnel 4 is excavated, annular drilling and grouting are performed along the radial direction of the tunnel in the section of the advanced pilot tunnel 4; wherein after the excavation of the next section of the advanced pilot tunnel is completed, the excavation of the area outside the previous section of the advanced pilot tunnel is completed.

[0067] For example, referring to Figure 2 , the advanced pilot tunnel 4 is excavated in three sections; the advanced pilot tunnel 4 in region ① is excavated first, after the excavation of this section is completed, annular drilling and grouting are performed along the radial direction of the tunnel in region ①; then the advanced pilot tunnel 4 in region ② is excavated, after the excavation of this section is completed, annular drilling and grouting are performed along the radial direction of the tunnel in region ②; then the excavation of region ③, which is the remaining area outside the advanced pilot tunnel 4 in region ①, is performed; then the advanced pilot tunnel 4 in region ④ is excavated, after the excavation of this section is completed, annular drilling and grouting are performed along the radial direction of the tunnel in region ④; then the excavation of region ⑤, which is the remaining area outside the advanced pilot tunnel 4 in region ②, is performed.

[0068] The construction method for the water inrush section of the deep-buried tunnel in the environmentally sensitive area provided by the embodiment of the present application not only prevents the negative impact of the loss of underground water on the hydrogeological environment of the environmentally sensitive area, but also provides a theoretical basis for the required thickness of the grouting ring, avoids excessive increase in the thickness of the grouting ring, and further reduces the construction cost and improves the construction efficiency, so that the treatment of the water inrush section of the tunnel is more targeted.

[0069] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of installing a grout collar, characterised in that, The method comprises the following steps: obtaining the water head of the tunnel face groundwater; drilling and grouting in the vault of the tunnel face according to a first drilling mode to form a vault grouting ring, wherein the first drilling mode comprises setting the drilling diameter, drilling length, drilling angle and adjacent drilling spacing; and the safety thickness of the grouting ring is determined according to formula (1). wherein, δ is the safety thickness of the grouting circle, unit is m; k is the safety factor; r is the inner radius of the grouting circle, unit is m; c is the cohesion of the grouting circle, unit is kPa; is the inner friction angle of the grouting circle, unit is °; ρ is the density of the underground water, unit is kg / m 3 ; g is the acceleration of gravity, unit is m / s 2 ; h is the water head height of the underground water at the working face, unit is m.

2. The method of claim 1, wherein, The method for obtaining the water head of the tunnel face groundwater comprises the following steps: drilling ahead of the tunnel face to reveal the outflow of groundwater and measuring the outflow; and calculating the water head of the tunnel face groundwater according to formula (2). where h is the water head of the water in the working face, in meters; d is the diameter of the advanced borehole, in meters; and Q is the water inflow, in cubic meters per second 3 g is the acceleration of gravity, in meters per second squared 2 .

3. The construction method of the deep-buried tunnel gushing water section in the environmentally sensitive area, characterized in that, The method comprises the following steps: building a waterproof rock wall close to the tunnel face at the tunnel face; constructing a grouting ring in front of the vault of the tunnel face according to the grouting ring construction method in claim 1 or 2; drilling and grouting in the position where the advanced pilot tunnel is to be excavated in front of the tunnel face according to a second drilling mode to reinforce the advanced pilot tunnel area, wherein the second drilling mode comprises setting the drilling diameter, drilling length, drilling angle and adjacent drilling spacing, and the advanced pilot tunnel is excavated after the mechanical properties of the grouting body meet the requirements; and performing annular drilling and grouting in the advanced pilot tunnel along the radial direction of the tunnel, and then completing the excavation of the area outside the advanced pilot tunnel.

4. The construction method of a water inrush section of an environmental sensitive area deep-buried tunnel according to claim 3, characterized in that, When drilling in the advanced pilot tunnel along the radial direction of the tunnel, the upper drilling should be at least 5 m deep into the vault, and the lower drilling should be 3-4 m deep into the inverted arch.

5. The construction method of a water inrush section of an environmental sensitive area deep-buried tunnel according to claim 3 or 4, characterized in that, The advanced pilot tunnel is excavated in sections; after the excavation of each section of the advanced pilot tunnel is completed, annular drilling and grouting are performed in the section of the advanced pilot tunnel along the radial direction of the tunnel; and after the excavation of the next section of the advanced pilot tunnel is completed, the excavation of the area outside the previous section of the advanced pilot tunnel is completed. The advanced pilot tunnel is excavated in sections; after the excavation of each section of the advanced pilot tunnel is completed, annular drilling and grouting are performed in the section of the advanced pilot tunnel along the radial direction of the tunnel; and after the excavation of the next section of the advanced pilot tunnel is completed, the excavation of the area outside the previous section of the advanced pilot tunnel is completed.

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