A construction method for mine tunnel without covering soil

Abstract

The present invention provides a construction method for entering a mine tunnel without covering soil, comprising the following steps: S1, dark excavation of the section without covering soil; S2, monitoring and measurement; S3, design and construction of the tunnel body section; S4, design and construction of the back slope at the tunnel entrance. The present invention can shorten the construction period, reduce the engineering cost, and reduce the amount of mountain slope brushing, thereby maintaining the original appearance of the mountain and the surrounding ecological environment, while ensuring construction safety.

Description

Technical Field

[0001] The invention belongs to the technical field of construction, and in particular relates to a mine tunnel construction method without covering soil. Background Art

[0002] Tunnels are a form of human use of underground space. With the rapid development of road traffic, people need to face more and more situations of crossing mountains and ridges. The engineering geological terrain conditions encountered in the process of tunnel construction are becoming more and more complex. The slopes of some tunnel entrance locations are relatively flat. After the surface is cleared and the ground elevation is reviewed, part of the original design of the tunnel vault is in a state of no covering layer or shallow covering. If the traditional tunnel entry method is used, it is necessary to ensure that the tunnel vault has a sufficient covering layer. It is necessary to carry out large-scale and large-scale brushing excavation of the mountain to ensure that the tunnel vault has a sufficiently thick covering layer, and at the same time ensure the safety of blasting excavation when entering the tunnel. However, the disadvantage of this method is that it will cause a large range of damage to the original state of the mountain. The entire construction process is large in engineering volume, long in construction period, and high in investment cost. It will also increase the amount of mountain brushing, causing unnecessary impact and damage to the original appearance of the mountain and the surrounding ecological environment. Summary of the invention

[0003] In view of the defects of the prior art, the present invention provides a mine tunnel construction method without covering soil, which can shorten the construction period, reduce the project cost, and reduce the amount of mountain slope brushing, thereby maintaining the original appearance of the mountain and the surrounding ecological environment while ensuring construction safety.

[0004] The present invention provides a mine tunnel construction method without covering soil, comprising the following steps:

[0005] S1, underground excavation in the hole without covering soil section;

[0006] S2, monitoring and measurement;

[0007] S3, design and construction of tunnel section;

[0008] S4, design and construction of back slope beside tunnel portal.

[0009] In the above technical solution, the present invention can also be improved as follows.

[0010] The preferred technical solution has the additional technical feature that: in the S1, for the design and construction of the arch protection, the tunnel entrance and the use of Φ108×6mm advanced large pipe shed to assist in entering the tunnel, the surrounding rock's own bearing capacity is improved by grouting, the elastic resistance of the rock mass to the structure is improved, and the structural stress conditions are improved; the advanced large pipe shed uses Φ108×6mm hot-rolled seamless steel pipes with an effective length of 30m and a circumferential spacing of 40cm, which are arranged within the range of 120° of the arch, and the part below the advanced large pipe shed is backfilled with stone powder, and the upper part is made of 30cm thick C25 concrete and double-layer steel mesh as the arch protection, and the top of the arch protection is backfilled with soil, and the thickness is controlled at 50cm to 100cm to ensure the safety of the arch during the tunnel blasting excavation process; a C30 concrete 2.0m long guide wall is set at the entrance close to the tunnel entry face, and 4 I18 steel frames and Φ127mm guide pipes are set in the sleeve arch; The construction error of the steel pipe deviating from the design position is required to be no more than 10cm, the number of joints in the same cross section along the longitudinal direction of the tunnel is no more than 50%, and the number of adjacent steel pipe joints must be staggered by at least 1.0m; in order to enhance the rigidity of the steel pipe, the inside of the pipe should be filled with cement mortar after grouting is completed; the external insertion angle of the steel pipe shall not be less than 3°.

[0011] The preferred technical solution has the following additional technical features: in said S1, an inclinometer is used to measure the external insertion angle of the steel pipe. If the external insertion angle is less than 3°, it should be corrected in time to avoid affecting the excavation and support; in order to ensure that the large pipe shelf can fully play the role of stabilizing the surrounding rock, the tail section of the large pipe shelf should be overlapped with the small guide tube grouting advance support of the main tunnel body, and the overlap length should be not less than 5m.

[0012] The preferred technical solution has the additional technical feature that: in the S1, the tunnel blasting drilling is dynamically designed and excavated, the upper step of the tunnel is drilled in turn, the blasting drilling layout is dynamically designed, blasting, slag discharge, support, and the lower step are staggered excavated, and the support system is closed into a loop; the upper step is affected by the actual undulation of the stratum rock surface, and the layout of the blasting drilling needs to be dynamically designed for each cycle to reduce the vibration impact of the blasting on the upper guard arch, and the over-excavation and under-excavation of the tunnel are strictly controlled to ensure a better blasting effect. By dynamically designing the layout and charging of the blasting drilling, the safe and smooth tunnel construction is ensured under the premise of reducing the vibration impact of the tunnel blasting excavation on the upper guard arch.

[0013] The preferred technical solution has the additional technical feature that: in the S2, in order to reduce the adverse effects of the construction on the middle rock wall of the tunnel with small clearance IV grade surrounding rock section, the middle rock wall should be monitored and measured during construction, and in particular, the measurement of blasting vibration during the excavation of the subsequent tunnel should be strengthened, and it is required that the blasting vibration speed at the leading tunnel should be ensured during the construction of the subsequent tunnel: the IV grade surrounding rock is not more than 8cm / s, and the III grade surrounding rock is not more than 10cm / s.

[0014] The preferred technical solution has the additional technical feature that in said S2, the items that must be measured for the middle rock wall include earth pressure of the middle rock wall, displacement inside the surrounding rock, surrounding rock pressure, blasting vibration, surface settlement and tunnel clearance convergence.

[0015] The preferred technical solution has the additional technical feature that: in the S3, the shallow buried section of the Class IV surrounding rock and the deep buried section of the Class IV surrounding rock of the tunnel body are pre-reinforced with Φ50×5mm advanced small guide tubes and D25mm hollow grouting anchor rods, and the middle rock wall reinforcement between the newly built auxiliary tunnel and the existing tunnel is pre-reinforced with a combination of extended D25mm hollow grouting anchor rods and Φ50×5mm advanced small guide tubes; Class II and III surrounding rocks are pre-reinforced with Φ 22 drug-coiled anchor rods, and the middle rock wall reinforcement of Class III surrounding rock is adopted with an extended D25mm hollow grouting anchor rod; the small guide tube is made of Φ50mm hot-rolled seamless steel pipe with a wall thickness of 5mm and an external insertion angle controlled at 10-15°. The tail ends of the advanced grouting small guide tube, hollow grouting anchor rod and drug-coiled anchor rod are supported on the steel frame, and can also be welded to the tail end of the system anchor rod, with a lap length of not less than 1.0m; the grouting liquid is made of cement mortar.

[0016] The preferred technical solution has the additional technical feature that: in S3, the water-cement ratio of the cement mortar W / C=1:1, and the grouting pressure is 0.5-1MPa.

[0017] The preferred technical solution has the additional technical feature that in S4, according to the location of the tunnel portal and the surrounding terrain conditions, prestressed anchor cables and lattice beams are used for support, and the upper part is covered with green to ensure the landscape effect.

[0018] The preferred technical solution has the additional technical feature that: in S4, the tunnel body is located in moderately weathered granite, and the top slope is mainly located in strongly weathered granite.

[0019] The beneficial effects of the present invention are as follows: the present invention adheres to the green and environmentally friendly construction concept, adopts the construction scheme of "entering the tunnel without covering soil", avoids the disturbance of the strata around the tunnel site, saves the construction amount, shortens the construction period, and saves the investment cost. At the same time, the present invention can also reduce the amount of mountain slope brushing, maintain the original appearance of the mountain and the surrounding ecological environment, and reduce the excavation of the mountain. It speeds up the progress and ensures that the conditions for entering the tunnel are quickly met. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the specific embodiments or the description of the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn according to the actual scale.

[0021] Figure 1 It is a schematic diagram of the design and construction of the tunnel entrance section of an embodiment of the present invention.

[0022] Figure 2 It is a schematic diagram of the arrangement of measuring points for surface subsidence monitoring section according to an embodiment of the present invention.

[0023] Figure 3 It is a schematic diagram of the arrangement of measuring points for reserved core soil for circular excavation, step excavation and perimeter convergence of full-section excavation and arch crown sinking in an embodiment of the present invention.

[0024] Figure 4 It is a graph of ground subsidence and displacement within a week according to an embodiment of the present invention.

[0025] Figure 5 It is a graph of the sinking and displacement of the dome in a certain week according to an embodiment of the present invention.

[0026] Figure 6 It is a peripheral convergence and displacement curve diagram within a certain week of an embodiment of the present invention.

[0027] Figure 7 It is a typical cross-sectional schematic diagram of the blasting drilling arrangement of the tunnel entrance section according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to further understand the content, features and effects of the present invention, the following embodiments are given and described in detail as follows:

[0029] See also Figures 1 to 7 This embodiment provides a method for constructing a mine tunnel without covering soil, comprising the following steps:

[0030] S1, underground excavation in the hole without covering soil section;

[0031] S2, monitoring and measurement;

[0032] S3, design and construction of tunnel section;

[0033] S4, design and construction of back slope beside tunnel portal.

[0034] In the S1 of this embodiment, for the design and construction of the arch protection, the tunnel entrance and the use of Φ108×6mm advanced large pipe shed to assist in entering the cave, the bearing capacity of the surrounding rock itself is improved by grouting, the elastic resistance of the rock mass to the structure is improved, and the stress conditions of the structure are improved; the advanced large pipe shed uses Φ108×6mm hot-rolled seamless steel pipes with an effective length of 30m and a circumferential spacing of 40cm, which are arranged within the range of 120° of the arch. The part below the advanced large pipe shed is backfilled with stone powder, and the upper part is made of 30cm thick C25 concrete and double-layer steel mesh as the arch protection, and the top of the arch protection is backfilled with soil, and the thickness is controlled at 50 cm~100cm to ensure the safety of the arch during tunnel blasting and excavation; a 2.0m long guide wall made of C30 concrete is set at the entrance close to the tunnel face, and 4 I18 steel frames and Φ127mm guide pipes are set in the arch; the construction error of the steel pipe deviating from the design position is required to be no more than 10cm, the number of joints in the same cross section along the longitudinal direction of the tunnel is no more than 50%, and the number of adjacent steel pipe joints must be staggered by at least 1.0m; in order to enhance the rigidity of the steel pipe, the inside of the pipe should be filled with cement mortar after grouting; the external insertion angle of the steel pipe shall not be less than 3°.

[0035] The purpose of setting up protection supply is to shorten the construction period, reduce project costs, reduce the amount of mountain slope cleaning, and maintain the original appearance of the mountain and the surrounding ecological environment.

[0036] In S2 of the present embodiment, in S1, an inclinometer is used to measure the external insertion angle of the steel pipe. If the external insertion angle is less than 3°, it should be corrected in time to avoid affecting the excavation and support. In order to ensure that the large pipe shelf can fully play the role of stabilizing the surrounding rock, the tail section of the large pipe shelf should be overlapped with the small guide tube grouting advance support of the main tunnel body, and the overlap length should be not less than 5m.

[0037] In the S1 of the present embodiment, the tunnel blasting drilling is dynamically designed and excavated, the upper step of the tunnel is drilled in turn, the blasting drilling layout is dynamically designed, blasting, slag discharge, support, and the lower step are staggered excavated, and the support system is closed into a loop; the upper step is affected by the actual undulation of the stratum rock surface, and the layout of the blasting drilling needs to be dynamically designed for each cycle to reduce the vibration impact of the blasting on the upper guard arch, and the over-excavation and under-excavation of the tunnel are strictly controlled to ensure a better blasting effect. By dynamically designing the layout and charging of the blasting drilling, the safe and smooth tunnel construction is ensured while reducing the vibration impact of the tunnel blasting excavation on the upper guard arch.

[0038] For tunnel blasting, see Figure 7, the peripheral holes of the upper step are designed according to the hole spacing of 0.5m. When the local or overall surrounding rock properties are incomplete or the lithology is poor, it is adjusted to 0.4m, and the charging line density is adjusted in the range of 0.10kg / m~0.15kg / m; when the lithology is good, it can be adjusted to 0.55m, and the charging line density is adjusted in the range of 0.15kg / m~0.25kg / m. The relative distance between the peripheral hole spacing and the resistance line should be reasonable. Usually, the peripheral hole spacing is reduced, and the contour is formed well after blasting. Affected by the undulation of the stratum rock surface, the relative distance between the peripheral hole layout and the resistance line (rock surface) should be greater than 1.2m. For the excavation of the uncovered section of the tunnel, the layout and charging of the blasting drilling holes are dynamically designed to ensure the safe and smooth tunnel construction under the premise of reducing the vibration effect of the tunnel blasting excavation on the upper arch. The step method is adopted for the excavation of the tunnel section without covering soil, and the blasting excavation, drilling and charging are carried out according to the overall control principle of "short footage, weak blasting". The upper step is affected by the actual undulation of the rock surface. The layout of the blasting drilling holes needs to be dynamically designed in each cycle to reduce the vibration impact of the blasting on the upper arch protection and strictly control the over-excavation and under-excavation of the tunnel to ensure a better blasting effect.

[0039] In addition, a dynamic hole layout design was carried out based on the actual undulation of the rock surface on site, and a reasonable charging method and multi-stage micro-difference detonation technology were adopted to effectively reduce the vibration impact of tunnel blasting and excavation on the upper arch.

[0040] In the S2 of this embodiment, in order to reduce the adverse effects of construction on the middle rock wall of the tunnel with small clearance IV grade surrounding rock section, the middle rock wall should be monitored and measured during construction, and in particular, the measurement of blasting vibration during the excavation of the subsequent tunnel should be strengthened. It is required that during the construction of the subsequent tunnel, the blasting vibration speed at the leading tunnel should be ensured as follows: the IV grade surrounding rock is not more than 8 cm / s, and the III grade surrounding rock is not more than 10 cm / s.

[0041] In S2 of this embodiment, the items that must be measured for the middle rock wall include earth pressure of the middle rock wall, displacement inside the surrounding rock, surrounding rock pressure, blasting vibration, surface settlement and tunnel clearance convergence.

[0042] In addition, during the excavation process, the arch protection structure and surrounding monitoring data (arch crown sinking, surface settlement and tunnel convergence, etc.) were normal and controllable.

[0043] Take tunnel monitoring data for a week as an example, please refer to Figures 5 and 6 :

[0044] 1. Monitoring point layout, tunnel entrance left line surface and arch monitoring

[0045] 1.1. On-site construction situation

[0046] Table 1-1, Tunnel construction progress list

[0047]

[0048] 1.2. On-site monitoring work

[0049] There is no increase or decrease in the number of points, and one group of surrounding convergence monitoring points is set up respectively.

[0050] Table 1-2, Statistics of newly added monitoring sections and total number of sections at the left-line arch of the tunnel entrance this week

[0051]

[0052] 2. Schematic diagram of measurement point layout

[0053] 2.1、Measurement point arrangement of surface subsidence monitoring section: please refer to Figure 5 .

[0054] 2.2、Layout of perimeter convergence and arch subsidence monitoring section survey lines: Please refer to Figure 6 .

[0055] 2.3. Surface subsidence

[0056] The results of this week's surface subsidence monitoring are summarized in Table 2-1 below.

[0057] Table 2-1, Summary of monitoring data of tunnel entrance surface subsidence (unit: mm)

[0058]

[0059]

[0060] Note: Positive numbers indicate elevation, negative numbers indicate subsidence

[0061] 2.4. Vault Sinking

[0062] The results of this week's surface subsidence monitoring are summarized in Table 2-2.

[0063] Table 2-2, Summary of monitoring data of tunnel entrance arch subsidence (unit: mm)

[0064]

[0065] Note: Positive numbers indicate bulges, negative numbers indicate sinking;

[0066] 2.5. Peripheral Convergence

[0067] The results of the surrounding convergence monitoring this week are summarized in Table 2-3 below.

[0068] Table 2-3, Summary of monitoring data of tunnel entrance arch subsidence (unit: mm)

[0069]

[0070] Note: Positive numbers indicate expansion, negative numbers indicate convergence;

[0071] 2.6. Observation inside and outside the tunnel

[0072] (1) The surrounding rock of the left tunnel face is mainly weathered granite of the Yanshanian period. The rock mass is hard and has high strength. The integrity and stability of the surrounding rock are average.

[0073] (2) Where surface subsidence monitoring points have been buried, no obvious cracks or fissures were found at the tunnel entrances.

[0074] 2. Data processing and analysis

[0075] Sedimentation rate this week:

[0076] The maximum cumulative settlement of the left line of the tunnel entrance surface is -2.8mm. At the measuring point ZD1-1, the settlement rate is -0.4mm / d, which is in a slow deformation state and has not reached the alarm value, so normal construction is possible. The maximum cumulative settlement of the left line of the tunnel entrance arch is -2.4mm. At the measuring point ZGD1-1, the settlement rate is -0.34mm / d, which is in a slow deformation state and has not reached the alarm value, so normal construction is possible.

[0077] The maximum cumulative displacement of the left line around the tunnel entrance is -1.42mm. At the measuring point ZSL2-1, the settlement rate this week is -0.2mm / d, which is basically stable and can be constructed normally.

[0078] In this embodiment, according to the monitoring measurement results and reference to the geological forecast, the support is strengthened, and the cyclic footage is strictly followed in accordance with the design specifications to ensure the quality and safety of the construction; to ensure the long-term stability of the tunnel structure, during the blasting construction, the construction is carried out according to the construction specifications and design, the blasting quality is controlled, the disturbance of the blasting to the surrounding rock and the damage of the blasting vibration to other existing structures are reduced, and the three principles of "short footage, weak blasting, and strong support" should be achieved during the construction process to ensure the quality and safety of the construction; the monitoring data show that the surface subsidence rate of the tunnel entrance section is basically within the allowable relative displacement value range of the corresponding surrounding rock level, and does not exceed the limit of 1-5mm / d, and the convergence around all the openings and the sinking of the arch do not exceed the limit of 0.2-1mm / d, and normal construction can be carried out. In order to ensure the timeliness, continuity and accuracy of the data, the monitoring points are protected during the construction process to ensure the continuous collection of data and provide a basis for the controlled situation of the tunnel.

[0079] The above data only provides tunnel monitoring data for a certain week. Subsequent tunnel monitoring data shall be based on actual conditions. The purpose is to ensure continuous data collection and provide a basis for the controlled situation of the tunnel to ensure smooth construction.

[0080] In S3 of the present embodiment, the shallow buried section of the IV grade surrounding rock and the deep buried section of the IV grade surrounding rock of the tunnel body are pre-reinforced with Φ50×5mm advanced small guide tubes and D25mm hollow grouting anchor rods, and the middle rock wall between the newly built auxiliary tunnel and the existing tunnel is pre-reinforced with a combination of lengthened D25mm hollow grouting anchor rods and Φ50×5mm advanced small guide tubes; the II and III grade surrounding rocks are pre-reinforced with Φ22 drug-coiled anchor rods, and the middle rock wall of the III grade surrounding rock is reinforced with a lengthened D25mm hollow grouting anchor rod; the small guide tube is made of Φ50mm hot-rolled seamless steel pipe with a wall thickness of 5mm and an external insertion angle controlled at 10-15°. The tail ends of the advanced grouting small guide tube, hollow grouting anchor rod and drug-coiled anchor rod are supported on the steel frame, and can also be welded to the tail end of the system anchor rod, with a lap length of not less than 1.0m; cement mortar is used as the grouting liquid.

[0081] In S3 of this embodiment, the water-cement ratio of the cement mortar W / C=1:1, and the grouting pressure is 0.5-1 MPa.

[0082] See also Figure 3 and Figure 4 In S4, according to the location of the tunnel portal and the surrounding terrain, prestressed anchor cables and lattice beams are used for support, and the upper part is covered with green to ensure the landscape effect.

[0083] See also Figure 3 and Figure 4 In the S4, the tunnel body is located in moderately weathered granite, and the top slope is mainly located in strongly weathered granite.

[0084] After the implementation of this embodiment, the effect is good, the impact on the surrounding area is small, the excavation of the mountain is reduced, the progress speed is accelerated, and the conditions for entering the tunnel are quickly met.

[0085] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0086] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0087] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0088] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0089] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory. Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and cannot be construed as limitations on the present invention, and those of ordinary skill in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for constructing a mine tunnel without covering soil, characterized in that: The following steps are involved: S1, underground excavation in the hole without covering soil section; S2, monitoring and measurement; S3, design and construction of tunnel section; S4, design and construction of the back slope beside the tunnel portal; In the above S1, for the arch protection design and construction, a Φ108×6mm advanced large pipe shed is used at the tunnel entrance to assist in entering the cave, and the bearing capacity of the surrounding rock itself is improved by grouting, the elastic resistance of the rock mass to the structure is improved, and the stress conditions of the structure are improved; the advanced large pipe shed uses Φ108×6mm hot-rolled seamless steel pipes with an effective length of 30m and a circumferential spacing of 40cm, which are arranged within a 120° range of the arch. The part below the advanced large pipe shed is backfilled with stone powder, and the upper part is made of 30cm thick C25 concrete and double-layer steel mesh as the arch protection, and the top of the arch protection is backfilled with soil. Fill with a thickness of 50cm~100cm to ensure the safety of the arch during tunnel blasting excavation; set a C30 concrete 2.0m long guide wall close to the tunnel entry face at the tunnel entrance, and set 4 I18 steel frames and Φ127mm guide pipes in the arch; the construction error of the steel pipe deviating from the design position is required to be no more than 10cm, the number of joints in the same cross section along the longitudinal direction of the tunnel is no more than 50%, and the number of adjacent steel pipe joints must be staggered by at least 1.0m; in order to enhance the rigidity of the steel pipe, the pipe should be filled with cement mortar after grouting; the external insertion angle of the steel pipe is not less than 3°; In S1, an inclinometer is used to measure the external insertion angle of the steel pipe. If the external insertion angle is less than 3°, it should be corrected in time to avoid affecting excavation and support. In order to ensure that the large pipe shed can fully stabilize the surrounding rock, the tail section of the large pipe shed should be overlapped with the small pipe grouting advance support of the main tunnel body, and the overlap length should not be less than 5m. In the S1, the tunnel blasting drilling is dynamically designed and excavated, the upper step of the tunnel is drilled in turn, the blasting drilling layout is dynamically designed, blasting, slag removal, support, and the lower step are staggered excavated, and the support system is closed into a loop; the upper step is affected by the actual ups and downs of the stratum rock surface, and the layout of the blasting drilling needs to be dynamically designed in each cycle to reduce the vibration effect of the blasting on the upper guard arch, strictly control the over-excavation and under-excavation of the tunnel, so as to ensure a better blasting effect, and through the dynamic design of the layout and charging of the blasting drilling, the tunnel is ensured to be safe and smooth in the hole construction under the premise of reducing the vibration effect of the tunnel blasting excavation on the upper guard arch; In S2, in order to reduce the adverse effects of construction on the middle rock wall of the tunnel with small clearance and grade IV surrounding rock section, monitoring and measurement should be carried out at the middle rock wall during construction, and the measurement of blasting vibration during the excavation of the subsequent tunnel should be strengthened. It is required that the blasting vibration speed at the leading tunnel should be ensured during the construction of the subsequent tunnel: the grade IV surrounding rock should not exceed 8cm / s, and the grade III surrounding rock should not exceed 10cm / s; In the S3, the shallow buried section of the IV grade surrounding rock and the deep buried section of the IV grade surrounding rock of the tunnel body are pre-reinforced with Φ50×5mm advanced small guide tubes and D25mm hollow grouting anchor rods, and the middle rock wall between the newly built auxiliary tunnel and the existing tunnel is pre-reinforced with a combination of extended D25mm hollow grouting anchor rods and Φ50×5mm advanced small guide tubes; the II and III grade surrounding rocks are pre-reinforced with Φ22 drug coil anchor rods, and the middle rock wall of the III grade surrounding rock is reinforced with extended D25mm hollow grouting anchor rods; the small guide tube is made of Φ50mm hot-rolled seamless steel pipe with a wall thickness of 5mm and an external insertion angle controlled at 10-15°. The tail ends of the advanced grouting small guide tube, hollow grouting anchor rod and drug coil anchor rod are supported on a steel frame or welded to the tail end of the system anchor rod, with a lap length of not less than 1.0m; cement mortar is used as the grouting liquid.

2. A mine tunnel construction method without covering soil according to claim 1, characterized in that: In S2, the items that must be measured for the middle rock wall include earth pressure of the middle rock wall, displacement inside the surrounding rock, surrounding rock pressure, blasting vibration, surface settlement and tunnel clearance convergence.

3. A mine tunnel construction method without covering soil according to claim 1, characterized in that: In S3, the water-cement ratio of the cement mortar W / C=1:1, and the grouting pressure is 0.5-1 MPa.

4. A mine tunnel construction method without covering soil according to claim 1, characterized in that: In S4, according to the location of the tunnel portal and the surrounding terrain, prestressed anchor cables and lattice beams are used for support, and the upper part is covered with green to ensure the landscape effect.

5. A mine tunnel construction method without covering soil according to claim 4, characterized in that: In the S4, the tunnel body is located in moderately weathered granite, and the top slope is mainly located in strongly weathered granite.

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