Construction method for full-weathered granite shallow-buried tunnel with eccentric pressure

Abstract

This invention provides a method for constructing a shallow-buried, bias-pressure tunnel entrance for completely weathered granite, belonging to the technical field of tunnel construction. The method includes: S1, slope protection and construction of a drainage system; S2, construction of slope protection along the tunnel entrance; S3, construction of entrance retaining walls and installation of jet grouting piles to lower the groundwater level; S4, selection of tunnel pre-support based on the water content, moisture content, and overburden thickness of the completely weathered granite; and S5, excavation of the tunnel using the CD method, selecting initial support and secondary lining based on the water content, moisture content, and overburden thickness of the completely weathered granite. This method ensures the safety of the tunnel entrance for shallow-buried, bias-pressure tunnels made of completely weathered granite and effectively prevents tunnel entrance disasters.

Description

Technical Field

[0001] This invention belongs to the technical field of tunnel construction, and specifically discloses a method for the construction of a shallow-buried bias-pressure tunnel in fully weathered granite. Background Technology

[0002] The terrain at the entrance of mountain tunnels is highly undulating and complex. Shallow burial and biased pressure are very common in such mountain tunnels. After the tunnel is excavated, the entrance will be subjected to significant unbalanced forces. As the throat of the tunnel, the entrance is the weak point of the tunnel and is very susceptible to structural damage under the action of unbalanced forces.

[0003] Completely weathered granite is loose and easily disintegrates, expands when exposed to water, and has extremely poor self-stabilizing ability. Tunnel entrance slopes and side slopes are prone to collapse and landslides under this stratum. Completely weathered granite becomes soft plastic when exposed to water, making it difficult to form the tunnel outline and prone to collapse during excavation; completely weathered granite that has been soaked in water for a long time becomes fluid plastic, increasing the amount of foundation settlement of the tunnel.

[0004] At the entrance of a shallow-buried, bias-pressure tunnel in completely weathered granite, the tunnel body experiences excessive settlement due to both unfavorable topographical and geological factors, making the tunnel structure susceptible to damage. Therefore, effective support and protection measures are required at the tunnel entrance, along with the selection of appropriate entry and construction methods. Summary of the Invention

[0005] To ensure the safety of the entrance to a shallow-buried, bias-pressure tunnel made of completely weathered granite and to prevent tunnel entrance disasters, this invention provides a method for constructing an entrance to a shallow-buried, bias-pressure tunnel made of completely weathered granite.

[0006] The above-mentioned method for constructing a shallow-buried, bias-pressure tunnel in completely weathered granite includes the following steps:

[0007] S1, slope and construct drainage system

[0008] The drainage system includes the slope drainage system and the slope surface drainage system;

[0009] Slope drainage system: Drainage holes are excavated on the uphill slope at the entrance of the tunnel according to the preset spacing and preset inclination angle, and the drainage holes are inclined downwards;

[0010] Slope surface drainage system: dig a water interception ditch inside the slope platform and a drainage ditch at the toe of the slope next to the opening;

[0011] S2, Construct slope protection along the tunnel entrance.

[0012] t1, Lay flexible steel wire mesh on the slope surface at the entrance of the tunnel;

[0013] t2, Insert the drain pipe into the drain hole, with the top end of the drain pipe inside the slope of the hole and the bottom end outside the slope of the hole as the drain end;

[0014] t3, spray the first layer of concrete and cure it;

[0015] t4, Drill grouting holes at preset intervals. The grouting holes are drilled vertically into the slope of the opening through the first layer of concrete and flexible wire mesh, and are staggered with the drainage pipe. The part located in the slope of the opening is opened with a grouting pre-reserved hole.

[0016] t5, insert the side slope anchor into the grouting hole, and sleeve the anchor holding component and anchor locking component on the end of the anchor outside the grouting hole. The anchor locking component tightly abuts the anchor holding component against the first layer of concrete to seal the grouting hole, and then grout is injected;

[0017] t6, lay a rigid steel mesh on the first layer of concrete;

[0018] t7, spray a second layer of concrete onto the rigid steel mesh and cure it; the second layer of concrete seals the anchor bolt support components and anchor bolt locking components.

[0019] S3, construct retaining walls and protection at the tunnel entrance, install jet grouting piles, and lower the groundwater level.

[0020] Constructing retaining walls and protective barriers at the tunnel entrance:

[0021] t1, Install anti-slide piles

[0022] Shallow-buried anti-slide piles and deep-buried anti-slide piles are installed on the shallow-buried side and the deep-buried side of the slope at the entrance of the tunnel, respectively, and shallow-buried side baffles are built between the shallow-buried anti-slide piles.

[0023] t2, Install a guide pipe above the tunnel entrance. The guide pipe passes horizontally through the shallow-buried anti-slide pile and the original slope toe of the tunnel entrance side slope. The first end is sealed to the deep-buried anti-slide pile, and the second end is flush with the shallow-buried anti-slide pile.

[0024] t3, pass the grouting pipe through the guide pipe and the deep-buried side anti-slide pile, insert it into the slope of the tunnel entrance, and open the grouting pre-reserved hole in the part located in the slope of the tunnel entrance;

[0025] t4, insert the anchor rod at the opening into the grouting pipe, and sleeve the anchor rod holding component and anchor rod locking component at the end of the anchor rod located outside the grouting pipe. The anchor rod locking component tightly abuts the anchor rod holding component against the shallow buried anti-slide pile to seal the grouting pipe and guide pipe, and then grouting is performed;

[0026] t5, fill the space between the original slope toe, shallow-buried anti-slide piles and deep-buried anti-slide piles on the slope of the tunnel entrance, and lay a waterproof layer on the top surface of the fill that is flush with the shallow-buried anti-slide piles.

[0027] The above-mentioned construction method for shallow buried biased tunnels in completely weathered granite also includes S0, clearing unstable objects on the slope at the tunnel entrance and performing preliminary leveling of the slope surface at the tunnel entrance.

[0028] In S1, the width of the slope platform is 1-1.2m. When the height of the side slope is greater than 5m, a stepped slope is adopted, and the height of each step is controlled at 4-6m.

[0029] The inclination angle of the drain hole is 8-10°, and the distance between adjacent drain holes is 80-120cm;

[0030] The intercepting ditch and the drainage ditch are 50cm wide and 60cm high, respectively.

[0031] In S2, the slope protection of the tunnel entrance is constructed layer by layer from bottom to top, and the tunnel is moved laterally in an S-shaped route.

[0032] t1, Flexible wire mesh is laid on the slope surface of the opening side using a flexible wire mesh fixing device;

[0033] The flexible steel wire mesh fixing device includes anti-detachment steel pins, anti-detachment barbs, anti-detachment barb hinges, anti-detachment steel pin washers, and anti-detachment steel pin locks;

[0034] Anti-detachment steel rods are driven through the flexible steel wire mesh and into the slope at the entrance of the tunnel.

[0035] The anti-detachment barb is connected to the anti-detachment steel rod through the anti-detachment barb hinge. It closes when the anti-detachment steel rod is driven into the slope of the hole and opens when the anti-detachment steel rod is pulled outward.

[0036] An anti-detachment steel plug gasket and an anti-detachment steel plug lock are fitted at the end of the anti-detachment steel plug located outside the slope of the opening. The anti-detachment steel plug lock sleeve tightly abuts the anti-detachment steel plug gasket against the flexible steel wire mesh.

[0037] t2, After the drainage pipe is laid, the drainage end is temporarily sealed;

[0038] t3, the first layer of concrete uses C20 concrete, and the concrete thickness is 10-15cm;

[0039] For t5, 6m and 9m anchor bolts are selected for the slope anchor bolts. When the moisture content of the completely weathered granite is less than 18%, 6m anchor bolts are used, and when it is higher than 18%, 9m anchor bolts are used. The anchor bolt locking component is threaded to the end of the anchor bolt of the slope anchor bolt. The ratio of cement to sand in the grout is 1:1. Ordinary Portland cement is used for cement. The maximum particle size of sand is less than 2.5mm. The strength of cement mortar is not less than 25Mpa. The ratio of water to cement is 0.36:1-0.43:1.

[0040] t7, the second layer of concrete uses C20 concrete, with a thickness of 15-20cm.

[0041] In S3

[0042] t1, the spacing between shallow-buried anti-slide piles is 1.5-2m, the spacing between deep-buried anti-slide piles is 1.5-2m, and the thickness of the shallow-buried baffle is 0.8-1.5m;

[0043] t2, A sealing rubber gasket is installed between the first end of the guide tube and the deeply buried anti-slide pile;

[0044] t4, the anchor bolt locking component is threadedly connected to the end of the anchor bolt at the opening. The anchoring depth of the anchor bolt at the opening is the length from the outside of the deep-buried anti-slide pile to the potential sliding surface plus the length inserted into the sliding bed. The length inserted into the sliding bed is 7-8m.

[0045] t5, the filling material is plain concrete.

[0046] In S3

[0047] Jet grouting piles are installed: double rows of jet grouting piles are installed on the deep buried side of the tunnel, and single rows of jet grouting piles are installed on the shallow buried side of the tunnel. The diameter of the double rows of jet grouting piles is 50cm and the spacing is 50cm. The diameter of the single rows of jet grouting piles is 60cm and the spacing is 40cm.

[0048] Lowering the groundwater level by drilling dewatering wells at the bottom of the tunnel entrance can be categorized into three situations:

[0049] The completely weathered granite remains unwaterlogged year-round, so no measures to lower groundwater levels are necessary.

[0050] The completely weathered granite is in a state of phased water immersion. During the rainy season, the diameter of the dewatering well is 20cm, the spacing between the dewatering wells is 2m, and the depth of the dewatering well is 1.5m below the tunnel invert.

[0051] The completely weathered granite is submerged in water year-round. The diameter of the dewatering wells is 30cm, the spacing between the dewatering wells is 1.5m, and the depth of the dewatering wells is 1.5m below the tunnel invert.

[0052] The above-mentioned construction method for shallow-buried, biased-pressure tunnels made of completely weathered granite also includes S4, which selects tunnel pre-support based on the degree of water immersion, moisture content, and overburden thickness of the completely weathered granite.

[0053] When the completely weathered granite is in a non-waterlogged state throughout the year, with a cover thickness of more than 20m and a moisture content of 6%-18% or less than 6%, tunnel pre-support is not required.

[0054] When the completely weathered granite is in a non-waterlogged state throughout the year, with a cover thickness of less than 20m and a moisture content of 6%-18%, advanced large pipe roof is used for tunnel advance support.

[0055] When the completely weathered granite is in a state of phased water immersion, and the cover thickness is less than 28m during the rainy season, the tunnel advance support is carried out by combining horizontal jet grouting and advanced large pipe roof.

[0056] When the completely weathered granite is soaked in water all year round, the tunnel advance support is carried out by combining horizontal jet grouting, advanced pipe roof, and pre-lining support.

[0057] The construction method for advanced large pipe sheds includes the following steps:

[0058] t1, at the tunnel entrance, a casting cavity is constructed by a bottom formwork, a top formwork, and an end formwork, as well as an arch frame and pipe roof sleeve located within the casting cavity. The pipe roof sleeve includes an outer layer pipe roof sleeve installed on the outside of the arch frame and an inner layer pipe roof sleeve installed on the inside of the arch frame.

[0059] t2, pour arch concrete into the cavity, cure, remove formwork, and the arch formed by the pouring is connected with the shallow and deep anti-slide piles to form an integral whole;

[0060] t3, pass the outer and inner pipe roof guide pipes through the outer and inner pipe roof sleeves and insert them into the slope at the opening, and then grout.

[0061] In S4,

[0062] t1, the arch frame includes a transverse I-beam frame, longitudinal connectors and transverse connectors;

[0063] Multiple horizontal I-beam frames are spaced apart;

[0064] Multiple longitudinal connectors are spaced apart perpendicular to the transverse I-beams, longitudinally connecting multiple transverse I-beams;

[0065] Adjacent longitudinal connecting parts are connected by multiple transverse connecting parts;

[0066] The density of pipe roof sleeves on the deep-buried side of the tunnel is several times that on the shallow-buried side of the tunnel.

[0067] t2, the arch concrete is C25 concrete, and the concrete slump is in the range of 130mm-150mm;

[0068] t3, the outer pipe roof guide pipe is made of steel pipe with a diameter of 150-180mm, and the end inserted into the slope of the opening is tapered;

[0069] The inner pipe roof guide pipe uses steel pipes with a diameter of 80-110mm, and the end inserted into the slope at the opening is tapered;

[0070] The grouting material used is pure cement mortar.

[0071] In S4,

[0072] t1, the spacing between adjacent transverse I-beams is 70-90cm, the longitudinal connectors are I-beams with a spacing of 1m, the transverse connectors are cross-laid steel bars, and the ends of the steel bars are connected to the connection points of the transverse I-beams and the longitudinal connectors.

[0073] The above-mentioned construction methods for shallow-buried, bias-pressure tunnels made of completely weathered granite also include S5, which uses the CD method for tunnel excavation, selecting initial support and secondary lining based on the degree of water immersion, moisture content, and overburden thickness of the completely weathered granite.

[0074] When the completely weathered granite is kept dry throughout the year, with a cover thickness of more than 20m and a moisture content of less than 6%, no initial support is required.

[0075] When the completely weathered granite is in a non-waterlogged state throughout the year, with a cover thickness greater than 20m and a moisture content of 6% to 18%, or when the cover thickness is less than 20m and the moisture content is 6% to 18%, the surrounding rock pressure of the shallow buried biased tunnel of completely weathered granite is calculated, and the construction parameters of the initial support and secondary lining are determined based on the calculation results.

[0076] When the completely weathered granite is in a state of phased water immersion, during the rainy season, the surrounding rock pressure of the shallow buried biased tunnel of the completely weathered granite is calculated, and the construction parameters of the initial support and secondary lining are determined by increasing the calculation results by 20%.

[0077] When the completely weathered granite is submerged in water all year round, the surrounding rock pressure of the shallow buried biased tunnel of the completely weathered granite is calculated, and the construction parameters of the initial support and secondary lining are determined by increasing the calculation results by 25%.

[0078] The present invention has the following beneficial effects.

[0079] 1. For shallow-buried biased tunnels of completely weathered granite, this method takes into account the degree of water soaking and moisture content of the completely weathered granite, the thickness of the overburden, and the influence of groundwater. Based on these characteristics, the method selects tunnel advance support, initial support, secondary lining, etc., which has the characteristics of strong guidance and high support reliability.

[0080] 2. When the height of the slope is higher than 5m, the slope should be gradually lowered and cleared to reduce the load, and then composite shotcrete and anchor support should be carried out layer by layer from bottom to top, which can effectively control the deformation of the slope.

[0081] 3. Driving double-row jet grouting piles on the deep-buried side and single-row jet grouting piles on the shallow-buried side of the shallow-buried tunnel of completely weathered granite can effectively increase the foundation strength and improve the physical and mechanical properties of the completely weathered granite.

[0082] 4. Arranging the aperture and spacing (density) of dewatering wells according to the degree of water immersion of the completely weathered granite, whether it is the rainy season, and the characteristics of the groundwater level can effectively reduce the groundwater level and the degree of water immersion of the completely weathered granite.

[0083] 5. In the slope protection of the tunnel entrance, flexible steel wire mesh was selected based on the characteristics of the completely weathered granite, and a special flexible steel wire mesh fixing device was designed to prevent the flexible steel wire mesh from falling off; the designed composite shotcrete support structure can effectively improve the support performance, and the installed drainage pipe can effectively drain the water in the slope to ensure that the water content in the slope is at a low level.

[0084] 6. During anchor bolt construction, seepage holes are pre-drilled in the grouting holes and grouting pipes located on the slope of the tunnel entrance. This allows the grout injected later to seep smoothly into the area around the anchor bolt, forming a solidified body with a certain strength in the axial direction of the anchor bolt. This improves the pull-out resistance of the anchor bolt and also increases the bearing capacity of the slope.

[0085] 7. Portal support and protection: A semi-open-cut tunnel structure is set up in the biased section of the tunnel. This structure can significantly reduce the influence of biased pressure on the tunnel and provide a good excavation environment for the biased section. A waterproof layer is set on the top of the tunnel structure to prevent surface water and rainwater from seeping into the interior of the structure.

[0086] 8. Determining the anchorage length of the anchor bolts in the opening support protection: First, the potential sliding surface is determined by numerical simulation. The anchorage length is the length from the outside of the deep-buried anti-slide pile to the potential sliding surface and the length inserted into the sliding bed. The length inserted into the sliding bed is 7-8m, which can make the anchor bolts more stable and reliable.

[0087] 9. The tunnel pre-support is connected with the portal retaining protection. The pipe roof sleeve is inserted into the filled semi-open-cut shed. Considering the influence of eccentric pressure, the spacing of the pipe roof sleeve is increased on the eccentric side, which specifically improves the bearing capacity of the eccentric side. Attached Figure Description

[0088] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0089] Figure 1 A flowchart for the construction method of shallow-buried bias-pressure tunnel in completely weathered granite;

[0090] Figure 2 A schematic diagram of the overall spatial structure of the retaining system constructed for the tunnel entry construction method of shallow buried bias-pressure tunnel of completely weathered granite;

[0091] Figure 3 for Figure 2 Cross-sectional view;

[0092] Figure 4 for Figure 3 Enlarged view of the slope protection at the entrance of the tunnel;

[0093] Figure 5 for Figure 3 Enlarged view of the support and protection structure at the tunnel entrance;

[0094] Figure 6 This is a schematic diagram of the flexible steel wire mesh fixing device;

[0095] Figure 7 This is a schematic diagram of grouting for the anchor bolts on the slope.

[0096] Figure 8 This is a schematic diagram of the anchorage of the anchor bolt at the opening;

[0097] Figure 9 This is a diagram showing the arrangement of the pipe roof casing on the arch frame.

[0098] Figure 10 This is a structural diagram of a truss frame.

[0099] In the diagram: 1-Slope protection platform; 2-Interception ditch; 3-Drainage ditch; 4-Flexible wire mesh; 5-Flexible wire mesh fixing device; 5.1-Anti-detachment steel insert; 5.2-Anti-detachment barb; 5.3-Anti-detachment barb hinge; 5.4-Anti-detachment steel insert washer; 5.5-Anti-detachment steel insert lock; 6-Drainage pipe; 7-First layer of concrete; 8-Grouting hole; 9-Grouting pre-reserved hole; 10-Side slope anchor; 11-Anchor support component; 12-Anchor locking component; 13-Consolidated body formed by grouting; 14-Rigid 15-Second layer of concrete; 16-Deeply buried side anti-slide pile; 17-Shallowly buried side anti-slide pile; 18-Shallowly buried side baffle; 19-Guide pipe; 20-Sealing rubber gasket; 21-Grouting pipe; 22-Opening anchor; 23-Filling structure; 24-Waterproof layer; 25-Arch frame; 25.1-Transverse I-beam frame; 25.2-Longitudinal connector; 25.3-Transverse connector; 25.4-Connection point; 26-Outer pipe roof sleeve; 27-Inner pipe roof sleeve; 100-Completely weathered granite. Detailed Implementation

[0100] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0101] This embodiment provides a method for constructing a shallow-buried biased tunnel in a completely weathered granite formation, comprising the following steps.

[0102] S0, clear unstable objects from the slope at the entrance of the tunnel and perform preliminary leveling of the slope surface.

[0103] S1, slope and construct drainage system

[0104] The width of the slope grading platform 1 is 1-1.2m. When the height of the side slope is greater than 5m, a stepped slope grading method is adopted, and the height of each step is controlled at 4-6m (depending on geological conditions; in areas with good geological conditions, it can be widened to 6m).

[0105] The drainage system includes the slope drainage system and the slope surface drainage system;

[0106] Slope drainage system: Drainage holes are excavated on the uphill slope at the entrance of the tunnel according to the preset spacing and preset inclination angle. The drainage holes are inclined downwards at an angle of 8-10° and the spacing between adjacent drainage holes is 80-120cm.

[0107] Slope surface drainage system: A water interception ditch 2 is dug inside the slope platform, and a drainage ditch 3 is dug at the toe of the slope next to the opening. The width and height of the water interception ditch 2 and the drainage ditch 3 are 50cm and 60cm, respectively.

[0108] S2 involves constructing slope protection for the tunnel entrance layer by layer from bottom to top, moving laterally in an S-shaped route, specifically including the following steps.

[0109] t1, Flexible steel wire mesh 4 is laid on the slope surface of the opening. Flexible steel wire mesh 4 is made of steel wire rope with a mesh size of 15×15cm. Due to the loose texture of the completely weathered granite slope surface, the slope surface has only been initially leveled, and there are depressions and protrusions in some areas. Flexible steel wire mesh 4 can fit the slope surface better, providing favorable conditions for subsequent shotcreting and avoiding the phenomenon of voids after shotcreting.

[0110] Because the texture of the completely weathered granite slope is loose and it is in a soft plastic state when it contains water, the bearing capacity of the slope surface is low, and there is a risk of the flexible wire mesh 4 slipping. Therefore, the flexible wire mesh fixing device 5 is used to fix the flexible wire mesh 4.

[0111] The flexible wire mesh fixing device 5 includes an anti-detachment steel rod 5.1, an anti-detachment barb 5.2, an anti-detachment barb hinge 5.3, an anti-detachment steel rod washer 5.4, and an anti-detachment steel rod lock 5.5. The anti-detachment steel rod 5.1 is 80-100cm long and passes through the flexible wire mesh 4, being driven into the slope of the opening. The anti-detachment barb 5.2 is connected to the anti-detachment steel rod 5.1 via the anti-detachment barb hinge 5.3, and has a one-way opening and closing function. It closes when the anti-detachment steel rod 5.1 is driven into the slope of the opening, and closes when the anti-detachment steel rod 5.1 is pulled outward. The opening mechanism serves to resist pull-out, with a maximum opening angle of 20°. At the end of the anti-detachment steel insert 5.1 located outside the slope at the opening edge, an anti-detachment steel insert washer 5.4 and an anti-detachment steel insert lock 5.5 are fitted. The anti-detachment steel insert washer 5.4 is a steel sheet with a diameter of 20cm and a thickness of 5mm, primarily serving a locking function to transfer the force of the anti-detachment steel insert 5.1 to the flexible wire mesh 4. The anti-detachment steel insert lock 5.5 tightly abuts the anti-detachment steel insert washer 5.4 against the flexible wire mesh 4, thus securing the anti-detachment steel insert 5.1.

[0112] The flexible wire mesh fixing device 5 can firmly nail the flexible wire mesh 4 to the slope, so that the flexible wire mesh 4 is closely attached to the slope. On the one hand, it prevents the flexible wire mesh 4 from falling off and provides stable conditions for subsequent shotcreting; on the other hand, it provides an internal pressure effect for the completely weathered granite slope surface, improving the stability of the slope surface layer.

[0113] t2, the completely weathered granite is very sensitive to water. After the flexible wire mesh 4 is laid, drainage pipes 6 are laid on the slope. The drainage pipes 6 are made of PVC pipes with a diameter of 5cm. The drainage pipes 6 are inserted into the drainage holes. The top of the drainage pipes 6 is located inside the slope of the opening, and the bottom is located outside the slope of the opening as the drainage end. After the drainage pipes 6 are laid, the drainage end is temporarily sealed to prevent the subsequent concrete mortar from entering and blocking the drainage pipes 6. The water in the drainage pipes 6 is discharged into the intercepting ditch 2 inside the slope platform and the drainage ditch 3 at the foot of the slope of the opening.

[0114] t3, spray the first layer of concrete 7 and cure it. The first layer of concrete 7 is C20 concrete with a thickness of 10-15cm.

[0115] t4, Drill grouting holes 8 at preset intervals. The grouting holes 8 pass through the first layer of concrete 7 and flexible wire mesh 4 and are drilled vertically into the slope of the tunnel entrance. They are set in a staggered position with the drainage pipe 6. The part located in the slope of the tunnel entrance is opened with a grouting pre-reserved hole 9 to prepare for the subsequent grouting liquid to seep into the surrounding rock and soil.

[0116] t5, insert the side slope anchor 10 into the grouting hole 8. The side slope anchor 10 is selected from 6m anchors and 9m anchors. When the water content of the completely weathered granite is less than 18%, the 6m anchor is used, and when it is higher than 18%, the 9m anchor is used. The anchor support component 11 and the anchor locking component 12 are sleeved on the end of the anchor located outside the grouting hole 8.

[0117] The anchor bolt support component 11 is a metal disc with a thickness of 2cm and a diameter of 20cm. It is mainly used to fix the concrete around the anchor bolt, increase the contact area with the concrete layer, and prevent the concrete layer from shearing and breaking due to excessive pressure.

[0118] The anchor bolt locking component 12 is a nut that is threaded to the end of the anchor bolt. The anchor bolt locking component 12 tightly abuts the anchor bolt holding component 11 against the first layer of concrete 7 to seal the grouting hole 8 and applies pressure to the anchor bolt holding component 11.

[0119] The internal pressure provided by the anchor bolt holding component 11 and the anchor bolt locking component 12 helps to improve the stability of the slope.

[0120] Then grouting is performed. The ratio of cement to sand in the grout is 1:1. Ordinary Portland cement is used for the cement, the maximum particle size of the sand is less than 2.5mm, the strength of the cement mortar is not less than 25MPa, and the ratio of water to cement is 0.36:1-0.43:1. The proportion of water is determined by the moisture content of the granite. When the moisture content is high, the proportion of water is small, and when the moisture content is low, the proportion of water is large.

[0121] The grout with the above ratio has a short initial setting time, meets the strength requirements after final setting, and has good fluidity and adhesion. It can smoothly seep into the completely weathered granite strata through the grouting pre-reserved hole, forming a ring of solidified body 13 with a certain strength near the anchor rod, which increases the pull-out force of the anchor rod, improves the slope stability, and improves the stress conditions of the slope.

[0122] t6, a rigid steel mesh 14 is laid on the first layer of concrete 7, with a mesh size of 20×20cm.

[0123] t7, spray a second layer of concrete 15 onto the rigid steel mesh 14 and cure it. The second layer of concrete 15 is made of C20 concrete and has a thickness of 15-20cm. The second layer of concrete 15 seals the anchor rod support component 11 and the anchor rod locking component 12.

[0124] S3, constructing retaining walls and protection at the tunnel entrance, driving jet grouting piles, and lowering the groundwater level. There is no specific order requirement for these three steps; the diagram illustrates the above sequence.

[0125] The opening support and protection is a semi-open-cut tunnel, and the construction process is as follows.

[0126] t1, Install anti-slide piles

[0127] Due to the requirements of the line, there is a section of slope toe excavation between the tunnel entrance and the boundary between the open and closed sections of the tunnel. This section has obvious eccentric pressure. In order to resist the pressure transmitted from the slope and avoid the tunnel structure from being affected by eccentric pressure, deep-buried anti-slide piles 16 are installed on the deep-buried side of the slope toe. The spacing between the deep-buried anti-slide piles 16 is 1.5-2m. The cross-sectional dimensions and internal steel reinforcement ratio need to be determined according to the pressure transmitted from the slope. The pressure of the slope on the anti-slide piles is mainly determined by numerical simulation calculation and field test.

[0128] Shallow anti-slide piles 17 are driven on the shallow buried side of the slope at the entrance of the tunnel. The spacing between the shallow anti-slide piles 17 is 1.5-2m, aligned with the deep anti-slide piles 16, and the spacing is consistent. The cross-sectional dimensions and internal steel reinforcement ratio need to be determined based on numerical simulation calculations and actual site conditions. A single numerical specification does not conform to the actual site conditions.

[0129] Shallow-buried side baffles 18 are constructed between the shallow-buried side anti-slide piles 17, and the thickness of the shallow-buried side baffles 18 is 0.8-1.5m.

[0130] t2, a guide pipe 19 is installed above the tunnel entrance. The guide pipe 19 passes laterally through the shallow buried anti-slide pile 17 and the original slope toe of the tunnel entrance side slope. The first end is sealed to the deep buried anti-slide pile 16 through a sealing rubber gasket 20 to prevent backflow of grout during injection. The second end is flush with the shallow buried anti-slide pile 17.

[0131] t3, pass the grouting pipe 21 through the guide pipe 19 and the deep-buried side anti-slide pile 16, and insert it into the slope of the tunnel entrance. The part located in the slope of the tunnel entrance is opened with a grouting pre-reserved hole 9.

[0132] t4, insert the anchor rod 22 at the opening into the grouting pipe 21, and sleeve the anchor rod holding component 11 and the anchor rod locking component 12 at the end of the anchor rod located outside the grouting pipe 21. The anchor rod locking component 12 is threadedly connected to the end of the anchor rod 22 at the opening. The anchor rod holding component 11 is tightly abutted against the shallow buried anti-slide pile 17 to seal the grouting pipe 21 and the guide pipe 19, and then grouting is performed.

[0133] The length of the anchor bolt 22 at the tunnel entrance is divided into two parts within the slope at the tunnel entrance. The first part is the length from the outside of the deeply buried anti-slide pile 16 to the potential landslide surface, and the second part is the length from the potential landslide surface to the end of the anchor bolt. The potential sliding surface of the slope is obtained by numerical simulation calculation. The anchoring depth of the anchor bolt is determined based on the distance between the potential sliding surface and the deeply buried anti-slide pile 16. The anchoring depth of the anchor bolt at the tunnel entrance is the length from the outside of the deeply buried anti-slide pile 16 to the potential sliding surface plus the length inserted into the sliding bed, which is 7-8m.

[0134] t5, the deep-buried side anti-slide piles 16, the shallow-buried side anti-slide piles 17, the portal anchors 22, and the shallow-buried side baffles 18 constitute the framework for portal support and protection. In order to ensure that the forces on both sides of the tunnel excavated laterally are uniform, it is necessary to fill the gap between the original slope toe of the portal side slope, the shallow-buried side anti-slide piles 17 and the deep-buried side anti-slide piles 16 with a fill material 23. The fill material 23 is plain concrete. After filling, the lower half of the cross section is the original slope toe, and the upper half is plain concrete. A waterproof layer 24 flush with the shallow-buried side anti-slide piles 17 is laid on the top surface of the fill material 23 to prevent rainwater and surface water from seeping into the structure.

[0135] Jet grouting pile installation: Double rows of jet grouting piles are installed on the deep-buried side of the tunnel, and single rows are installed on the shallow-buried side. The double-row jet grouting piles have a diameter of 50cm and a spacing of 50cm, while the single-row jet grouting piles have a diameter of 60cm and a spacing of 40cm. Installing jet grouting piles can effectively increase the foundation strength and improve the physical and mechanical properties of completely weathered granite.

[0136] Forced drainage is achieved by drilling dewatering wells at the bottom of the tunnel entrance to lower the groundwater level. This can be categorized into three situations:

[0137] The completely weathered granite remains unwaterlogged year-round, so no measures to lower groundwater levels are necessary.

[0138] The completely weathered granite is in a state of phased water immersion. During the rainy season, the groundwater level rises and the completely weathered granite is in a state of water immersion. The diameter of the dewatering well is 20cm, the spacing between the dewatering wells is 2m, and the depth of the dewatering well is 1.5m below the tunnel invert.

[0139] The completely weathered granite is submerged in water year-round. As the groundwater level rises, the surrounding rock of the tunnel is subjected to groundwater pressure. The diameter of the dewatering wells is 30cm, the spacing between the dewatering wells is 1.5m, and the depth of the dewatering wells is 1.5m below the tunnel invert.

[0140] S4. Tunnel advance support is selected based on the degree of water soaking, water content and overburden thickness of the completely weathered granite.

[0141] S5, due to the fact that the tunnel is located in completely weathered granite, the stability of the tunnel face is relatively poor. Therefore, the CD method is used to excavate the tunnel. The initial support and secondary lining are selected according to the water content, moisture content and overburden thickness of the completely weathered granite.

[0142] The process of selecting tunnel pre-support and initial support based on the degree of water soaking, moisture content and overburden thickness of completely weathered granite is as follows.

[0143] When completely weathered granite remains unwaterlogged throughout the year, the retaining system is determined based on the different overburden thicknesses (d) and moisture contents (p) of the completely weathered granite:

[0144] 1. When the cover thickness d is greater than 20m and the moisture content p is less than 6%, the influence of bias pressure does not need to be considered, and tunnel advance support and initial support are not required.

[0145] 2. When the cover thickness d is greater than 20m and the moisture content is 6%-18%, the influence of bias pressure needs to be considered. In this case, tunnel advance support should not be carried out, but initial support should be carried out.

[0146] 3. When the cover thickness d is less than 20m and the moisture content is 6%-18%, the influence of bias pressure needs to be considered, and tunnel advance support and initial support should be carried out.

[0147] When completely weathered granite is in a phased water-soaked state (water-soaked during the rainy season and unwater-soaked during the dry season), the retaining system is determined according to the unwater-soaked state during the dry season. During the rainy season, since completely weathered granite exhibits a fluid plastic state after being soaked in water, the retaining system is determined based on different overburden thicknesses d.

[0148] 1. When the cover thickness d is greater than 28m, the influence of bias pressure needs to be considered. In this case, tunnel advance support can be disregarded and initial support can be carried out.

[0149] 2. When the cover thickness d is less than 28m, the influence of bias pressure needs to be considered, and tunnel advance support needs to be considered and initial support needs to be carried out.

[0150] When the completely weathered granite is submerged in water all year round, the groundwater level rises, the groundwater flow increases, and the surrounding rock at the tunnel entrance is subjected to groundwater pressure. Based on the physical and mechanical parameters of the surrounding rock and the groundwater pressure obtained from the in-situ test, the retaining system is determined through three-dimensional numerical simulation calculation.

[0151] The following are some situations where tunnel pre-support needs to be considered:

[0152] 1. When the weathered granite is in a non-waterlogged state throughout the year, with a cover thickness d of less than 20m and a moisture content of 6% to 18%, the weathered granite is in a water-containing state and exhibits a soft plastic state. The tunnel advance support scheme is an advance large pipe roof.

[0153] 2. The completely weathered granite is in a staged water-soaked state. During the rainy season, when the cover thickness d is less than 28m, the completely weathered granite is in a water-soaked state and exhibits a fluid plastic state. The tunnel pre-support needs to fill the cracks and cavities and control the flow of groundwater to achieve the purpose of sealing the water source and reinforcing the surrounding rock. The tunnel pre-support scheme adopts a combination of horizontal jet grouting and pre-support large pipe roof.

[0154] 3. The completely weathered granite is submerged in water all year round. The tunnel advanced support scheme adds pre-lining support to the combination of horizontal jet grouting and advanced large pipe roof. That is, a 30cm thick concrete is used to form a rigid arch shell to control the flow of groundwater into the tunnel and the lower surface layer.

[0155] The construction method for advanced large pipe sheds includes the following steps.

[0156] t1, at the entrance of the tunnel, a casting cavity is formed by bottom formwork, top formwork and end formwork, and an arch frame 25 and pipe roof sleeve are located in the casting cavity;

[0157] The arch frame 25 includes transverse I-beams 25.1, longitudinal connectors 25.2, and transverse connectors 25.3. Multiple transverse I-beams 25.1 are spaced apart. Multiple longitudinal connectors 25.2 are spaced apart perpendicular to the transverse I-beams 25.1, longitudinally connecting the multiple transverse I-beams 25.1. Adjacent longitudinal connectors 25.2 are connected by multiple transverse connectors 25.3. In this embodiment, the spacing between adjacent transverse I-beams 25.1 is 70-90cm, the longitudinal connectors 25.2 are I-beams spaced 1m apart, and the transverse connectors 25.3 are intersecting steel bars, with the ends of the steel bars connected to the connection point 25.4 between the transverse I-beams 25.1 and the longitudinal connectors 25.2.

[0158] The pipe roof casing includes an outer layer pipe roof casing 26 installed on the outside of the arch frame 25 and an inner layer pipe roof casing 27 installed on the inside of the arch frame 25. Since the tunnel is a shallow buried tunnel with bias pressure, considering the influence of bias pressure, the pipe roof casing is densified on the deep buried side (the side subjected to bias pressure). The spacing between pipe roof casings in the densified area is 40cm, and the spacing between pipe roof casings in the non-densified area is 80cm. The range of the densified area is 140° on the deep buried side and 40° on the non-densified area.

[0159] t2, pour arch concrete into the cavity. C25 concrete is used for the arch. The concrete slump is in the range of 130mm-150mm. The concrete needs to be poured slowly and vibrated to ensure compaction and prevent formwork bursting. After curing and demolding, the arch formed by the pouring is connected with the shallow buried side anti-slide pile 17 and the deep buried side anti-slide pile 16 to form an integral whole, improving the safety of the tunnel entrance.

[0160] t3, pass the outer pipe roof guide pipe and the inner pipe roof guide pipe through the outer pipe roof sleeve 26 and the inner pipe roof sleeve 27, and insert them into the slope at the opening, and then grout.

[0161] The outer pipe roof guide pipe uses a steel pipe with a diameter of 150-180mm. The end inserted into the slope at the tunnel entrance is tapered. Grouting is used to reinforce the completely weathered granite near the outer pipe roof guide pipe, improving the stability of the rock and soil mass, providing advanced support for tunnel excavation, and ensuring the safety of subsequent excavation.

[0162] The inner layer of pipe roof duct is made of steel pipe with a diameter of 80-110mm. The end inserted into the slope at the tunnel entrance is conical. Since the excavated slope is completely weathered granite, in order to prevent the tunnel roof from becoming unstable and collapsing, the inner layer of pipe roof duct is laid along the tunnel excavation outline, which is equivalent to an arched skeleton, which can greatly improve the strength and integrity of the tunnel arch.

[0163] The grouting material used is pure cement mortar, and the water-cement ratio of the grout needs to be adjusted according to the on-site grouting effect.

[0164] The following are some situations where initial support needs to be considered:

[0165] 1. When the completely weathered granite is in a non-waterlogged state throughout the year, with a cover thickness d greater than 20m and a moisture content of 6% to 18%, or a cover thickness d less than 20m and a moisture content of 6% to 18%, the initial support includes shotcrete, anchor bolts, steel mesh, and I20 I-beams. The surrounding rock pressure of the shallow buried biased tunnel of completely weathered granite is calculated, and the thickness and strength of shotcrete, the length and spacing of anchor bolts, the density of steel mesh, and the spacing of I20 I-beams are selected based on the calculation results.

[0166] 2. The completely weathered granite is in a state of phased water immersion. During the rainy season, the initial support includes shotcrete, anchor bolts, steel mesh, and I20 I-beams. The surrounding rock pressure of the shallow buried biased tunnel of completely weathered granite is calculated. Since the completely weathered granite is in a state of water immersion and exhibits a fluid plastic state, the stability of the surrounding rock at the tunnel entrance is poor and its self-weight is greater than that in the non-water immersion state. The thickness and strength of shotcrete, the length and spacing of anchor bolts, the density of steel mesh, and the spacing of I20 I-beams are all increased by 20% based on the calculation results.

[0167] 3. The completely weathered granite is submerged in water year-round. Initial support includes shotcrete, anchor bolts, steel mesh, and I20 I-beams. The surrounding rock pressure of the shallow-buried, biased tunnel of the completely weathered granite was calculated. Due to the submerged state of the completely weathered granite, it exhibits a fluid plastic state, which increases the groundwater pressure that the surrounding rock at the tunnel entrance needs to withstand. The stability of the surrounding rock at the tunnel entrance is poor and its self-weight increases significantly. Therefore, the thickness and strength of the shotcrete, the length and spacing of the anchor bolts, the density of the steel mesh, and the spacing of the I20 I-beams are all increased by 25% based on the calculated results.

[0168] The portal of a shallow-buried, bias-pressure tunnel made entirely of weathered granite is more vulnerable than other tunnel portals. Therefore, secondary lining at the portal should be constructed more promptly to ensure that the secondary lining and initial support work together to increase tunnel safety. The reinforcement calculation and verification for the secondary lining should be based on the surrounding rock pressure results obtained from the three scenarios in the initial support, and the selection and construction should be carried out in accordance with the provisions of the "Railway Tunnel Design Code" (TB 10003-2016).

[0169] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for constructing a shallow-buried, bias-pressure tunnel in completely weathered granite, characterized in that, Includes the following steps: S1, slope and construct drainage system The drainage system includes the slope drainage system and the slope surface drainage system; Slope drainage system: Drainage holes are excavated on the uphill slope at the entrance of the tunnel according to the preset spacing and preset inclination angle, and the drainage holes are inclined downwards; Slope surface drainage system: dig a water interception ditch inside the slope platform and a drainage ditch at the toe of the slope next to the opening; S2, Construct slope protection along the tunnel entrance. t1, Lay flexible steel wire mesh on the slope surface at the entrance of the tunnel; t2, Insert the drain pipe into the drain hole, with the top end of the drain pipe inside the slope of the hole and the bottom end outside the slope of the hole as the drain end; t3, spray the first layer of concrete and cure it; t4, Drill grouting holes at preset intervals. The grouting holes are drilled vertically into the slope of the opening through the first layer of concrete and flexible wire mesh, and are staggered with the drainage pipe. The part located in the slope of the opening is opened with a grouting pre-reserved hole. t5, insert the side slope anchor into the grouting hole, and sleeve the anchor holding component and anchor locking component on the end of the anchor outside the grouting hole. The anchor locking component tightly abuts the anchor holding component against the first layer of concrete to seal the grouting hole, and then grout is injected; t6, lay a rigid steel mesh on the first layer of concrete; t7, spray a second layer of concrete onto the rigid steel mesh and cure it; the second layer of concrete seals the anchor bolt support components and anchor bolt locking components. S3, construct retaining walls and protection at the tunnel entrance, install jet grouting piles, and lower the groundwater level. Constructing retaining walls and protective barriers at the tunnel entrance: t1, Install anti-slide piles Shallow-buried anti-slide piles and deep-buried anti-slide piles are installed on the shallow-buried side and the deep-buried side of the slope at the entrance of the tunnel, respectively, and shallow-buried side baffles are built between the shallow-buried anti-slide piles. t2, Install a guide pipe above the tunnel entrance. The guide pipe passes horizontally through the shallow-buried anti-slide pile and the original slope toe of the tunnel entrance side slope. The first end is sealed to the deep-buried anti-slide pile, and the second end is flush with the shallow-buried anti-slide pile. t3, pass the grouting pipe through the guide pipe and the deep-buried side anti-slide pile, insert it into the slope of the tunnel entrance, and open the grouting pre-reserved hole in the part located in the slope of the tunnel entrance; t4, insert the anchor rod at the opening into the grouting pipe, and sleeve the anchor rod holding component and anchor rod locking component at the end of the anchor rod located outside the grouting pipe. The anchor rod locking component tightly abuts the anchor rod holding component against the shallow buried anti-slide pile to seal the grouting pipe and guide pipe, and then grouting is performed; t5, fill the space between the original slope toe, shallow-buried anti-slide piles and deep-buried anti-slide piles on the slope of the tunnel entrance, and lay a waterproof layer on the top surface of the fill that is flush with the shallow-buried anti-slide piles. Jet grouting piles are installed: double rows of jet grouting piles are installed on the deep buried side of the tunnel, and single rows of jet grouting piles are installed on the shallow buried side of the tunnel. The diameter of the double rows of jet grouting piles is 50cm and the spacing is 50cm. The diameter of the single rows of jet grouting piles is 60cm and the spacing is 40cm. Lowering the groundwater level by drilling dewatering wells at the bottom of the tunnel entrance can be categorized into three situations: The completely weathered granite remains unwaterlogged year-round, so no measures to lower groundwater levels are necessary. The completely weathered granite is in a state of phased water immersion. During the rainy season, the diameter of the dewatering well is 20cm, the spacing between the dewatering wells is 2m, and the depth of the dewatering well is 1.5m below the tunnel invert. The completely weathered granite is submerged in water year-round. The diameter of the dewatering wells is 30cm, the spacing between the dewatering wells is 1.5m, and the depth of the dewatering wells is 1.5m below the tunnel invert. S4. Tunnel pre-support is selected based on the degree of water immersion, water content, and overburden thickness of the completely weathered granite. When the completely weathered granite is in a non-waterlogged state throughout the year, with a cover thickness of more than 20m and a moisture content of 6%-18% or less than 6%, tunnel pre-support is not required. When the completely weathered granite is in a non-waterlogged state throughout the year, with a cover thickness of less than 20m and a moisture content of 6%-18%, advanced large pipe roof is used for tunnel advance support. When the completely weathered granite is in a state of phased water immersion, and the cover thickness is less than 28m during the rainy season, the tunnel advance support is carried out by combining horizontal jet grouting and advanced large pipe roof. When the completely weathered granite is soaked in water all year round, the tunnel advance support is carried out by combining horizontal jet grouting, advanced pipe roof, and pre-lining support. The construction method for advanced large pipe sheds includes the following steps: t1, at the tunnel entrance, a casting cavity is constructed by a bottom formwork, a top formwork, and an end formwork, as well as an arch frame and pipe roof sleeve located within the casting cavity. The pipe roof sleeve includes an outer layer pipe roof sleeve installed on the outside of the arch frame and an inner layer pipe roof sleeve installed on the inside of the arch frame. t2, pour arch concrete into the cavity, cure, remove formwork, and the arch formed by the pouring is connected with the shallow and deep anti-slide piles to form an integral whole; t3, pass the outer and inner pipe roof guide pipes through the outer and inner pipe roof sleeves and insert them into the slope at the opening, then grout. S5 tunnel was excavated using the CD method. Initial support and secondary lining were selected based on the water content, moisture content, and overburden thickness of the completely weathered granite. When the completely weathered granite is kept dry throughout the year, with a cover thickness of more than 20m and a moisture content of less than 6%, no initial support is required. When the completely weathered granite is in a non-waterlogged state throughout the year, with a cover thickness greater than 20m and a moisture content of 6%~18%, or when the cover thickness is less than 20m and the moisture content is 6%~18%, the surrounding rock pressure of the shallow buried biased tunnel of completely weathered granite is calculated, and the construction parameters of the initial support and secondary lining are determined based on the calculation results. When the completely weathered granite is in a state of phased water immersion, during the rainy season, the surrounding rock pressure of the shallow buried biased tunnel of the completely weathered granite is calculated, and the construction parameters of the initial support and secondary lining are determined by increasing the calculation results by 20%. When the completely weathered granite is submerged in water all year round, the surrounding rock pressure of the shallow buried biased tunnel of the completely weathered granite is calculated, and the construction parameters of the initial support and secondary lining are determined by increasing the calculation results by 25%.

2. The full-weathered granite shallow-buried bias tunnel construction method according to claim 1, characterized in that, It also includes S0, clearing unstable objects on the slope at the entrance of the tunnel and performing preliminary leveling of the slope surface at the entrance of the tunnel.

3. The full-weathered granite shallow-buried bias tunnel construction method according to claim 1, characterized in that, In S1, the width of the slope platform is 1-1.2m. When the height of the side slope is greater than 5m, a stepped slope is adopted, and the height of each step is controlled at 4-6m. The inclination angle of the drain hole is 8-10°, and the distance between adjacent drain holes is 80-120cm; The intercepting ditch and the drainage ditch are 50cm wide and 60cm high, respectively.

4. The full-weathered granite shallow-buried bias tunnel construction method according to claim 1, characterized in that, In S2, the slope protection of the tunnel entrance is constructed layer by layer from bottom to top, and the tunnel is moved laterally in an S-shaped route. t1, Flexible wire mesh is laid on the slope surface of the opening side using a flexible wire mesh fixing device; The flexible steel wire mesh fixing device includes anti-detachment steel pins, anti-detachment barbs, anti-detachment barb hinges, anti-detachment steel pin washers, and anti-detachment steel pin locks. The anti-detachment steel rod is driven through the flexible steel wire mesh and into the slope at the entrance of the hole; The anti-detachment barb is connected to the anti-detachment steel rod through the anti-detachment barb hinge. It closes when the anti-detachment steel rod is driven into the slope of the hole and opens when the anti-detachment steel rod is pulled outward. An anti-detachment steel plug gasket and an anti-detachment steel plug lock are fitted at the end of the anti-detachment steel plug located outside the slope of the opening. The anti-detachment steel plug lock sleeve tightly abuts the anti-detachment steel plug gasket against the flexible steel wire mesh. t2, After the drainage pipe is laid, the drainage end is temporarily sealed; t3, the first layer of concrete uses C20 concrete, and the concrete thickness is 10-15cm; For t5, 6m and 9m anchor bolts are selected for the slope anchor bolts. When the moisture content of the completely weathered granite is less than 18%, 6m anchor bolts are used, and when it is higher than 18%, 9m anchor bolts are used. The anchor bolt locking component is threaded to the end of the anchor bolt of the slope anchor bolt. The ratio of cement to sand in the grout is 1:

1. Ordinary Portland cement is used for cement. The maximum particle size of sand is less than 2.5mm. The strength of cement mortar is not less than 25Mpa. The ratio of water to cement is 0.36:1-0.43:

1. t7, the second layer of concrete uses C20 concrete, with a thickness of 15-20cm.

5. The full-weathered granite shallow-buried bias tunnel construction method according to claim 1, characterized in that, In S3, t1, the spacing between shallow-buried anti-slide piles is 1.5-2m, the spacing between deep-buried anti-slide piles is 1.5-2m, and the thickness of the shallow-buried baffle is 0.8-1.5m; t2, A sealing rubber gasket is installed between the first end of the guide tube and the deeply buried anti-slide pile; t4, the anchor bolt locking component is threadedly connected to the end of the anchor bolt at the opening. The anchoring depth of the anchor bolt at the opening is the length from the outside of the deep-buried anti-slide pile to the potential sliding surface plus the length inserted into the sliding bed. The length inserted into the sliding bed is 7-8m. t5, the filling material is plain concrete.

6. The full-weathered granite shallow-buried bias tunnel construction method according to claim 1, characterized in that, In S4, t1, the arch frame includes a transverse I-beam frame, longitudinal connectors and transverse connectors; Multiple horizontal I-beam frames are spaced apart; Multiple longitudinal connectors are spaced apart perpendicular to the transverse I-beams, longitudinally connecting multiple transverse I-beams; Adjacent longitudinal connecting parts are connected by multiple transverse connecting parts; The density of pipe roof sleeves on the deep-buried side of the tunnel is several times that on the shallow-buried side of the tunnel. t2, the arch concrete is C25 concrete, and the concrete slump is in the range of 130mm-150mm; t3, the outer pipe roof guide pipe is made of steel pipe with a diameter of 150-180mm, and the end inserted into the slope of the opening is tapered; The inner pipe roof guide pipe uses steel pipes with a diameter of 80-110mm, and the end inserted into the slope at the opening is tapered; The grouting material used is pure cement mortar.

7. The method for constructing a shallow-buried, biased-pressure tunnel in completely weathered granite according to claim 6, characterized in that, In S4, t1, the spacing between adjacent transverse I-beams is 70-90cm, the longitudinal connectors are I-beams with a spacing of 1m, the transverse connectors are cross-laid steel bars, and the ends of the steel bars are connected to the connection points of the transverse I-beams and the longitudinal connectors.

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