A method for tunneling and excavation in underground mines with weak interlayers

Abstract

This invention discloses a method for excavating underground mine roadways containing weak interlayers, relating to the field of underground mine roadway construction technology. A horizontal grouting hole is drilled at the arch of the roadway for single-hole grouting of the surrounding rock. In the middle of the roadway, trench excavation is carried out to create a support trench. Wooden pillars are used to temporarily support the support trench, and hydraulic equipment is used to apply prestress to the roadway roof. The left half of the roadway is excavated, and after construction on one side, support work is carried out on that side. Then, the right half is excavated, and after construction on one side, support work is carried out on that side. After both sides are excavated and supported, the wooden pillars supporting the middle section are removed, and the surrounding rock of the roadway roof is maintained. Single-hole grouting reinforces the top surrounding rock; the use of wooden pillars to support the support trench, and the unilateral construction and support during roadway excavation, minimize the exposed area of ​​the surrounding rock during construction, preventing continuous rockfall.

Description

Technical Field

[0001] This invention relates to the field of underground mine tunnel construction technology, specifically to a method for tunneling and excavation in underground mines containing weak interlayers. Background Technology

[0002] During the excavation of underground mine tunnels, weak and fractured zones are often encountered. These soft rock strata are generally characterized by low strength and poor stability. Their failure characteristics include spalling, rockfall, or collapse. The rock strata are poorly cemented and easily affected by blasting vibrations. They disintegrate or expand when exposed to water, which has a great impact on tunnel construction. In severe cases, it can bring the tunneling and support work to a standstill, affecting the normal construction progress and posing a high safety risk.

[0003] Traditional construction methods for tunnels in complex geological sections often employ full-section grouting, advanced small-diameter pipe grouting, steel arch supports, and pipe roof supports. These methods involve complex construction procedures, and due to the large exposed area of ​​the roof during prolonged periods, roof collapses frequently occur at the working face. The active pressure from the roof and surrounding rock often causes deformation of the steel arch supports, making subsequent maintenance difficult and frequently requiring secondary support.

[0004] CN109184742A discloses a pre-grouting method for high-pressure, water-rich, soft surrounding rock mountain tunnels, with the following specific steps: S1: Excavate and support the upper left section of the tunnel pilot tunnel; S2: Excavate and support the lower left section of the tunnel pilot tunnel; S3: Backfill with rubble concrete, and pour the invert lining after support; S4: Excavate the tunnel arch and provide initial support; S5: Construct a grout stop wall and fix it to the tunnel wall with a steel mesh; S6: Install a borehole pipe in the borehole and fix it with a steel mesh; S7: Grout the excavation outline using a small guide pipe at an angle forward; S8: Design the grouting pressure and select the grouting cement slurry. The method of first supporting and then grouting with advanced small guide pipes is complex. For grouting construction in water-rich tunnels, the cement grout setting time is not easy to adjust and the initial setting time is long. Although the cemented body has high compressive strength, the shrinkage rate of the solid body is large and the water blocking efficiency is poor. Since most tunnels involve infrastructure projects, mainly the excavation of mountains, the cross-sectional area is large and the pressure is mainly concentrated in the tunnel shoulder and top. Compared with the small section excavation of underground mines, the support requirements are high, the cycle is long, the construction is cumbersome, and the applicability is poor.

[0005] CN109826632A discloses a method for controlling large deformation in a single-line tunnel in weak, fractured carbonaceous shale. Based on the three-stage excavation method, it employs small-diameter pipe grouting to reinforce the surrounding rock at the arch as pre-support; long anchor bolts are installed at the arch foot and sidewalls with a certain pre-tightening force to control the tunnel's horizontal convergence; three I-beams connected end-to-end are used as longitudinal connectors between adjacent steel arch frames to improve their overall integrity; and anchor pipes are welded to the steel arch frames via positioning rings. The bench method used in tunnel cross-section excavation has a working area comparable to that of an underground mine roadway, and requires strict support, making it only suitable for large-section tunnel excavation. Summary of the Invention

[0006] The purpose of this invention is to provide a method for tunneling in underground mines with weak interlayers, which solves the problems of complex construction procedures and the risk of collapse in existing technologies.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for tunneling and excavation in underground mines containing weak interlayers, characterized by the following construction steps:

[0008] S1. Drill a horizontal grouting hole at the arch of the tunnel and perform single-hole grouting on the surrounding rock;

[0009] S2. Conduct trenching in the middle of the tunnel to excavate support trenches;

[0010] S3. Use wooden pillars to temporarily support the support trench and use hydraulic equipment to apply prestress to the roadway roof;

[0011] S4. Excavate the left half of the tunnel. After the construction on one side is completed, carry out support work on that side. Then excavate the right half of the tunnel. After the construction on one side is completed, carry out support work on that side.

[0012] S5. After the excavation and support on both sides are completed, remove the wooden pillars of the central support and maintain the surrounding rock of the tunnel roof;

[0013] S6. Repeat steps S1 to S5 until the tunnel excavation is completed.

[0014] A further technical solution is that in step S1, the grouting hole is located at the highest point of the roadway top, with its direction parallel to the roadway excavation direction, and the length of the grouting hole is twice the advance of a single cycle.

[0015] A further technical solution is that in step S1, the single-hole grouting volume Q = πr 2 hnα(1+β), where r is the penetration radius; h is the grouting thickness; n is the porosity of the soil and rock mass; α is the filling rate; and β is the grout loss coefficient, which takes a value of 0.1 to 0.2.

[0016] A further technical solution is that the width of the support groove in step S2 is 30-40cm.

[0017] A further technical solution is that in step S3, the diameter of the wooden column is 15-20cm, the interval between adjacent wooden columns is 50-70cm, a top plate pad is provided on the top of the wooden column, a support base is provided at the bottom of the wooden column, and a hydraulic support rod is provided below the support base.

[0018] A further technical solution is that the single-sided construction in step S4 extends from the middle of the tunnel to both sides, using a cantilever tunneling machine.

[0019] A further technical solution is to arrange steel mesh for the support operation, fix it with anchor bolts, and then spray grout onto the surface.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: the top surrounding rock is reinforced by single-hole grouting; the support trench is then supported by wooden columns, so that the stress at the top plate is transferred to the tunnel floor through the wooden columns, avoiding large-scale rockfall and spalling; during the tunnel construction and excavation process, the exposed area of ​​the surrounding rock is minimized by unilateral regional construction and support, effectively preventing deformation and damage of the support structure, further preventing continuous rockfall, resulting in high construction efficiency and high safety. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of the present invention.

[0022] Figure 2 This is a construction diagram of the present invention.

[0023] Figure 3 This is a schematic diagram of the wooden column support in this invention.

[0024] Figure 4 This is a schematic diagram of the tunnel support in this invention.

[0025] In the diagram: 1. Grouting hole; 2. Top plate pad; 3. Right half; 4. Support groove; 5. Support base; 6. Wooden column; 7. Left half; 8. Support base; 9. Hydraulic support rod; 10. Hydraulic pipe; 11. Manual operating lever. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0027] Figure 1A method for tunneling in underground mines with weak interlayers is shown, and the construction steps are as follows:

[0028] A horizontal grouting hole is drilled at the arch of the tunnel, located at the highest point of the tunnel roof, parallel to the tunnel excavation direction. The length of the grouting hole is twice the advance length of a single cycle, which is 3 meters. Single-hole grouting of the surrounding rock ensures that the grouting material has fully solidified by the next advance, resulting in good strength of the roof and surrounding rock. Prior to grouting, advanced geological forecasting is necessary to analyze the specific properties of the surrounding rock, providing support for controlling the grouting parameters. The single-hole grouting volume Q = πr 2 hnα(1+β), where r is the penetration radius; h is the grouting thickness; n is the porosity of the soil and rock mass; α is the filling rate; and β is the grout loss coefficient, which takes a value of 0.1 to 0.2.

[0029] The grouting of the arch of underground mine tunnels uses the chemical grout Marisan E. Marisan E is a high-molecular-weight polyurethane product synthesized from two components. It has good permeability and is often used for stratum reinforcement and water sealing. It has excellent adhesion and can form a high bond with the stratum (the compressive strength of the consolidated body is 15.35 MPa, which is about twice that of cement grout). It has good flexibility and reacts with water to further expand and foam, forming a multi-element network of closed elastomers. It can generate secondary osmotic pressure (expansion ratio of 20 times), better sealing cracks to achieve the purpose of stopping leakage.

[0030] The location in the middle of the tunnel is selected, and the specific excavation range is marked during the actual construction process. A support trench is excavated using a cantilever tunneling machine. Compared with blasting, mechanical drilling has a smaller surrounding rock disturbance coefficient and is more efficient. The width of the support trench is designed to be between 30cm and 40cm, and the height of the support trench reaches the top of the tunnel.

[0031] like Figure 2 As shown, wooden pillars are used for temporary support of the support trench. The diameter of the wooden pillars is 15-20cm, and the tunnel advance is about 3m at a time. The interval between two wooden pillars is controlled at 50-70cm, and the specific interval is adjusted according to the type of surrounding rock. During the support process, there are roof pads corresponding to the wooden pillars on the tunnel roof. To facilitate the installation of the wooden pillars, there is a hydraulic structure at the bottom of the wooden pillars, which can be manually used to apply prestress to the tunnel roof, effectively preventing pressure from the surrounding rock. The prestress provided is generally calculated based on the burial depth and the unit weight of the overlying strata, combined with on-site monitoring (usually between 15-50KN).

[0032] like Figure 3As shown, the wooden column is equipped with a support base, which is specifically a circular iron support plate. The hydraulic support rod under the support base can be raised and lowered freely under the action of the hydraulic system. The raising and lowering of the hydraulic support rod extends to the outside of the working face through hydraulic pipes and is adjusted by a manual operating lever.

[0033] The top plate of the wooden column is made of wood and can be a single plate for a single column or a single plate shared by multiple columns. When finally removing the column, the hydraulic structure at the bottom of the column is first depressurized.

[0034] After installing the central wooden support column, single-sided excavation begins. The cantilever tunneling machine expands from the center outwards to both sides. After single-sided excavation is completed, support work on one side should be carried out quickly to prevent instability caused by prolonged exposure of the roof rock. Specifically, the left half of the tunnel is excavated, and support work is carried out on that side after single-sided excavation; then the right half is excavated, and support work is carried out on that side after single-sided excavation. The support work involves arranging steel mesh, fixing it with anchor bolts, and then applying shotcrete to the surface. Figure 4 As shown, the resin anchor spacing is 800mm, the row spacing is 1000mm, and the steel mesh spacing is 150mm×150mm.

[0035] After the excavation and support on both sides are completed, the wooden pillars of the central support are removed, and the surrounding rock of the tunnel roof is maintained; shotcrete and anchor support are used.

[0036] Repeat the above steps until the tunnel excavation is completed.

[0037] In actual construction, taking the main roadway excavation of Kunyang Phosphate Mine No. 2 as an example, mechanical excavation was used on site. The roadway was 4500mm wide, 3800mm high, and 110m deep. Multiple 3500mm long support logs with a compressive strength greater than 3MPa were prepared. During construction, fractured zones and weak interlayers with an average thickness of 800mm were encountered, and significant water inflow, mainly fissure water, was observed. Before roadway excavation, the roof was reinforced with Marisan E grouting at a pressure of 8.5MPa for approximately 20 minutes. After installing the support columns, excavation proceeded along the surrounding rock of both sides of the roadway, expanding from the center outwards. After one side was excavated, rapid support was implemented, primarily using anchor bolts, steel mesh, and shotcrete. Then, excavation proceeded along the other side. After the support on both sides was completed, the roof support was installed, thus completing one cycle of excavation. No rockfalls or spalling occurred during the process, and the support was effective.

[0038] Although the invention has been described herein with reference to several illustrative embodiments, it should be understood that many other modifications and implementations can be devised by those skilled in the art, which will fall within the scope and limits of this disclosure. More specifically, various modifications and improvements can be made to the components or layouts within the scope of this disclosure, the drawings, and the claims. Besides modifications and improvements to the components or layouts, other uses will be apparent to those skilled in the art.

Claims

1. A method for tunneling and excavating underground mine roadways containing weak interlayers, characterized in that... The construction steps are as follows: S1. Drill a horizontal grouting hole at the arch of the tunnel and perform single-hole grouting on the surrounding rock; S2. Conduct trenching in the middle of the tunnel to excavate support trenches; S3. Use wooden pillars to temporarily support the support trench and use hydraulic equipment to apply prestress to the roadway roof; S4. Excavate the left half of the tunnel. After the construction on one side is completed, carry out support work on that side. Then excavate the right half of the tunnel. After the construction on one side is completed, carry out support work on that side. S5. After the excavation and support on both sides are completed, remove the wooden pillars of the central support and maintain the surrounding rock of the tunnel roof; S6. Repeat steps S1 to S5 until the tunnel excavation operation is completed; In step S1, the grouting hole is located at the highest point of the roadway top, and its direction is parallel to the roadway excavation direction. The length of the grouting hole is twice the advance of a single cycle. The single-hole grouting volume in step S1 ,in The penetration radius; This refers to the grouting thickness; Porosity of the soil and rock mass; For fill rate, The slurry loss coefficient is 0.1 to 0.

2. In step S2, the width of the support groove is 30-40cm.

2. The method for tunneling and excavation in underground mines with weak interlayers according to claim 1, characterized in that: In step S3, the diameter of the wooden column is 15-20cm, the interval between adjacent wooden columns is 50-70cm, the top of the wooden column is provided with a top plate pad, the bottom of the wooden column is provided with a support base, and a hydraulic support rod is provided below the support base.

3. The method for tunneling and excavation in underground mines with weak interlayers according to claim 1, characterized in that: In step S4, the single-sided construction extends from the middle of the tunnel to both sides, using a cantilever tunneling machine.

4. The method for tunneling and excavation in underground mines with weak interlayers according to claim 1, characterized in that: The support operation involves laying a steel mesh, fixing it with anchor bolts, and then spraying grout onto the surface.

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