High slope entrance support structure of super-large-span tunnel in rock formation and its construction method

Abstract

The present invention discloses a high-slope tunnel entrance support structure for a super-large-span tunnel in a rock formation and a construction method thereof, including: an upslope ground beam, which is an external force-bearing structure of the tunnel entrance support system; an annular upslope anchor cable, which is arranged at the slope of the tunnel entrance, and the unstable blocks formed by the rock cracks and broken zones at the top of the tunnel entrance section structure are fixed to the surrounding stable blocks by the annular upslope anchor cable, or the unstable blocks are connected in series to form a stable block; a vertical high-strength prestressed steel cable, which is arranged in the lowering hole of the upslope ground beam and cross-arranged with the annular upslope anchor cable; an in-tunnel system anchor rod or anchor cable, which is arranged above the top middle hole and above the top side hole. The present invention realizes the rapid and safe construction of the super-large-span underground structure with a high slope in the hard rock formation, forms a self-stabilizing reinforcement body for the tunnel entrance slope, and avoids the risk of the formation of sliding surfaces in the rock mass above the tunnel entrance, the collapse of unstable blocks or the rock wedge-shaped body at the top of the cavern range due to excavation.

Description

Technical Field

[0001] The invention relates to the field of underground engineering, and in particular to a high-slope tunnel entrance support structure of a super-large-span tunnel in a rock formation and a construction method thereof. Background Art

[0002] China is a mountainous country. According to statistics, the area of ​​mountains, hills and plateaus accounts for 69% of the country's total land area. Most of the strata in these areas are rock strata. Rock strata are also widely distributed in the plains of the country. Fine sandstone strata are mainly distributed in the Yangtze River Delta Plain and northern Jiangsu; fine sandstone strata are mainly distributed in the Lixiahe and Taihu areas; sub-sandstone strata are a type of rock strata between sandstone and gravel strata, mainly distributed in the Yangtze River Delta Plain, the Yellow River Flood Area and the coastal areas.

[0003] With the development of the national economy, the development and utilization of underground space has received more and more attention. The development and utilization of underground space can realize the expansion of urban space and improve the efficiency of land use; it can stimulate the technological demand for construction and promote the transformation of underground engineering science and technology industry and technological progress; it can establish a complete underground disaster prevention space system and enhance the country's ability to resist disasters and wars.

[0004] Ultra-large span underground projects in rock strata face problems such as large span and thin cover soil at the entrance section. In addition, the superposition of weak structural zones such as joints and fissures can easily cause cavern collapse during construction. There is little research on how to achieve safe and rapid construction of ultra-large span underground project entrances in rock strata. Summary of the invention

[0005] The purpose of the present invention is to provide a high-slope tunnel entrance support structure for a super-large-span tunnel in a rock stratum and a construction method thereof, so as to realize the rapid and safe tunnel construction of a super-large-span underground structure with a high slope in a hard rock stratum, form a self-stabilizing reinforcement body on the tunnel entrance slope, avoid the risk of formation of sliding surfaces, unstable blocks or wedge-shaped rock blocks at the top of the cavern range collapsing due to excavation in the rock mass above the tunnel entrance, and avoid the problem of tunnel entrance collapse due to improper support of unstable blocks at the top of the excavation range.

[0006] To achieve the above-mentioned purpose, the specific technical scheme of a rock formation ultra-large-span tunnel high-slope portal support structure and its construction method of the present invention is as follows:

[0007] A high-slope tunnel entrance support structure for a super-large-span tunnel in a rock stratum comprises: an upslope ground beam, which is an external force-bearing structure of a tunnel entrance support system; an annular upslope anchor cable, which is arranged at the slope of the tunnel entrance, and through which unstable blocks formed by rock fissures and broken zones at the top of the tunnel entrance section structure are fixed to surrounding stable blocks, or unstable blocks are connected in series to form stable blocks; vertical high-strength prestressed steel cables, which are arranged in lowering holes of the upslope ground beam and cross-arranged with the annular upslope anchor cables; and in-tunnel system anchor rods or anchor cables, which are arranged above the top middle hole and above the top side hole.

[0008] A construction method for a high-slope tunnel entrance support structure of a super-large-span tunnel in a rock formation, comprising:

[0009] Step 1: excavate the original slope in stages;

[0010] Step 2: During the excavation of the tunnel entrance slope, a circular upslope anchor cable is constructed;

[0011] Step 3, drilling holes for vertical high-strength prestressed steel cables on the upward slope;

[0012] Step 4: construct the upslope ground beam and reserve holes for lowering the vertical high-strength prestressed steel cables;

[0013] Step 5: Divide the tunnel opening into the top middle tunnel, the top side tunnel, the temporary supporting rock mass, the soil mass below the side tunnel, and the soil mass below the middle tunnel and the temporary supporting rock mass;

[0014] Step 6, excavating the middle hole at the top of the tunnel entrance section;

[0015] Step 7, excavating the side hole at the top of the tunnel entrance section;

[0016] Step 8: excavate temporary supporting rock mass, and construct system anchor rods and vertical high-strength prestressed steel cables in the tunnel;

[0017] Step nine: excavate the soil below the side tunnel and the soil below the middle tunnel and the temporary supporting rock mass.

[0018] The advantages of the high-slope tunnel entrance support structure of a super-large-span tunnel in a rock formation and the construction method thereof of the present invention are:

[0019] 1) Realize the rapid and safe construction of underground structures with high slopes and large spans in hard rock formations, form a self-stabilizing reinforcement body on the slope of the cave entrance, avoid the risk of the formation of sliding surfaces, unstable blocks or wedge-shaped rock blocks at the top of the cavern range collapsing due to excavation, and avoid the problem of cave entrance collapse caused by improper support of unstable blocks at the top of the excavation range;

[0020] 2) The ground beam, vertical high-strength prestressed steel cable, and circumferential upslope anchor cable can form an overall stress circle for the unstable rock mass above the cave entrance;

[0021] 3) The middle hole and the side hole at the top of the tunnel are constructed in advance to provide conditions for the tensioning of vertical high-strength prestressed steel cables and the anchor rods (cables) of the system in the tunnel;

[0022] 4) By utilizing the self-stabilization and compressive resistance of the rock mass, through skipping construction and phased support, the rock mass on the top of the previously excavated cavern can be supported in time, the stress can be redistributed, and ultimately the safe construction of the high slope entrance section of the ultra-large span underground structure can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is an elevation view of the cave entrance support structure of the present invention;

[0024] Figure 2 It is a longitudinal section view of the cave entrance support structure of the present invention.

[0025] In the figure: 1. Top middle hole; 2. Top side hole; 3. Temporary supporting rock mass; 4. Circumferential upslope anchor cable; 5. Vertical high-strength prestressed strong steel cable; 6. Upslope ground beam; 7. Upslope fixed end of steel cable; 8. Fixed end in the hole; 9. Soil under the side hole; 10. Soil under the middle hole and temporary supporting rock mass; 11. In-hole system anchor rod (in-hole system anchor cable); 12. Slope. DETAILED DESCRIPTION

[0026] In order to better understand the purpose, structure and function of the present invention, the rock formation ultra-large span tunnel high slope portal support structure and its construction method of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0027] like Figure 1 and Figure 2 As shown, the present invention discloses a rock formation super-large-span tunnel high-slope tunnel entrance support structure, which is suitable for super-large-span underground structures with high slopes and small span ratios in hard rock areas. The support structure includes an upslope ground beam 6, an annular upslope anchor cable 4, a vertical high-strength prestressed steel cable 5 and an in-tunnel system anchor rod (in-tunnel system anchor cable) 11. The super-large-span underground engineering tunnel entrance section consists of three parts: a top middle tunnel, a top side tunnel, and a temporary supporting rock mass.

[0028] Furthermore, the back slope beam 6, as the external force-bearing structure of the tunnel entrance support system, bears the point tension transmitted by the vertical high-strength prestressed strong steel cable, and converts the point tension into linear pressure and evenly transmits it to the back slope platform, so as to make the rock mass at the top of the tunnel entrance structure vertically stable. The rock mass between the top middle hole and the top side hole is the temporary support of the tunnel entrance.

[0029] Furthermore, the annular backslope anchor cable 4 is arranged at the side slope of the tunnel entrance, and the unstable blocks formed by the rock cracks and broken zones at the top of the tunnel entrance section structure are fixed to the surrounding stable blocks through the annular backslope anchor cable 4, or the unstable blocks are connected in series to form stable blocks.

[0030] Furthermore, the vertical high-strength prestressed steel cable 5 is arranged in the lowering hole of the upslope ground beam 6 and is cross-arranged with the annular upslope anchor cable 4; the in-tunnel system anchor rod (in-tunnel system anchor cable) 11 and the vertical high-strength prestressed steel cable 5 are arranged above the top middle hole 1 and above the top side hole 2 to maintain the stability of the rock mass above the excavation surface of the middle hole and above the excavation surface of the top side hole 2.

[0031] Furthermore, the in-tunnel system anchor rods 11 (or in-tunnel system anchor cables) and the vertical high-strength prestressed steel cables 5 are arranged at the temporary supporting rock mass 3, that is, the temporary supporting rock mass between the middle hole 1 at the top of the tunnel entrance and the side hole 2 at the top of the tunnel entrance, so as to maintain the stability of the rock mass above the side hole excavation surface.

[0032] Furthermore, the cave entrance includes a middle cave 1 at the top, a side cave 2 at the top, a temporary supporting rock mass 3 (the temporary supporting rock mass is between the middle cave 1 at the top of the cave entrance and the side cave 2 at the top of the cave entrance), soil 9 below the side caves, and soil 10 below the middle cave and the temporary supporting rock mass. The width of each part of the middle cave 1 at the top, the side cave 2 at the top, the temporary supporting rock mass 3, and the soil 9 below the side cave is 12m to 18m, and the width of the soil 10 below the middle cave and the temporary supporting rock mass is the sum of the widths of the middle cave 1 and the temporary supporting rock mass 3 at the top.

[0033] The present invention realizes the formation of an integral stress circle of the unstable rock mass above the cave entrance through the upslope ground beam 6, the vertical high-strength prestressed strong steel cable 5, and the annular upslope anchor cable 4; the middle hole at the top of the cave entrance and the side hole at the top of the cave entrance are constructed in advance to provide conditions for the tensioning of the vertical high-strength prestressed strong steel cable 5 and the system anchor rod 11 (or the system anchor cable in the cave); the self-stabilization and compressive resistance of the rock mass are utilized, and the skipping construction and phased support are carried out, so that the rock mass on the top of the cavern excavated in advance can be supported in time, the stress can be redistributed, and finally the safe construction of the high-slope cave entrance section of the ultra-large-span underground structure is realized.

[0034] The present invention also discloses a construction method for a high-slope tunnel entrance support structure of a super-large-span tunnel in a rock formation, comprising the following steps:

[0035] Step 1: excavate the original slope 12 in stages according to the steepness and construction difficulty, and the width of each platform meets the requirements of the construction of the upslope ground beam 6 and the tensioning of the vertical high-strength prestressed steel cable 7.

[0036] Before constructing the top middle hole, the slope is excavated in grades. The width of each platform is sufficient for laying the ground beam, and the height of each level can be determined according to the steepness of the slope and the difficulty of construction.

[0037] Step 2: During the excavation of the tunnel entrance slope, a circular upslope anchor cable 4 is constructed.

[0038] Step three, drilling holes for the vertical high-strength prestressed steel cables 5 are constructed on the back slope, the drilling depth of which is equal to the excavation surface of the tunnel entrance and meets the installation requirements of the later anchoring end.

[0039] Step 4: construct the upslope ground beam 6 and reserve holes for lowering the vertical high-strength prestressed steel cables 5.

[0040] Step five, divide the cave entrance into five parts, namely, the top middle cave 1, the top side cave 2, the temporary supporting rock mass 3 (the temporary supporting rock mass is between the top middle cave 1 and the top side cave 2), the soil mass 9 below the side cave, and the soil mass 10 below the middle cave and the temporary supporting rock mass.

[0041] The rock mass between the top middle hole and the top side hole is the temporary support for the hole entrance. The width of each part of the top middle hole 1, the top side hole 2, the temporary support rock mass 3, and the soil mass 9 below the side hole is 12m to 18m, and the width of the soil mass 10 below the middle hole and the temporary support rock mass is the sum of the widths of the top middle hole 1 and the temporary support rock mass 3.

[0042] Step six, excavate the middle hole 1 at the top of the tunnel entrance section, construct the in-hole system anchor rod (in-hole system anchor cable) 11 and the vertical high-strength prestressed steel cable 5 above the top middle hole 1 to stabilize the rock mass above the excavation surface of the middle hole.

[0043] Step seven, excavate the top side tunnel 2 of the tunnel entrance section, construct the tunnel system anchor rod (tunnel system anchor cable) 11 and the vertical high-strength prestressed steel cable 5 above the top side tunnel 2, and keep the rock mass above the excavation surface of the top side tunnel 2 stable.

[0044] Step eight, excavate temporary supporting rock mass 3, construct in-tunnel system anchor rods (in-tunnel system anchor cables) 11 and vertical high-strength prestressed steel cables 5, and keep the rock mass above the side tunnel excavation surface stable.

[0045] Step nine, excavate the soil 9 below the side tunnel and the soil 10 below the middle tunnel and the temporary supporting rock mass to complete the construction of the tunnel entrance section.

[0046] The construction sequence in the present invention is back slope 12, annular back slope anchor cable 4, vertical high-strength prestressed strong steel cable 5, back slope ground beam 6, top middle hole, middle hole system anchor rod (cable), top side hole, side hole system anchor rod (cable), temporary supporting rock mass, temporary supporting rock mass upper system anchor rod (cable), and rock mass below the hole entrance.

[0047] The invention discloses a high-slope tunnel entrance support structure for a super-large-span tunnel in a rock formation and a construction method thereof, which can realize the rapid and safe tunnel construction of a super-large-span underground structure with a high slope in a hard rock formation, form a self-stabilizing reinforcement body on the tunnel entrance slope, avoid the risk of the rock mass above the tunnel entrance forming a sliding surface, an unstable block or a wedge-shaped rock block on the top of the cavern range collapsing due to excavation, and avoid the problem of the tunnel entrance collapsing due to improper support of the unstable block at the top of the excavation range; the ground beam, the vertical high-strength prestressed strong steel cable, and the circumferential upslope anchor cable can form an overall stress circle for the unstable rock mass above the tunnel entrance; the middle hole at the top of the tunnel entrance and the side hole at the top of the tunnel entrance are constructed in advance to provide conditions for the tensioning of the vertical high-strength prestressed strong steel cable and the anchor rod (cable) of the system in the tunnel; the self-stabilizing and compressive resistance of the rock mass is utilized, and the rock mass on the top of the cavern excavated in advance is supported in time through the skipping construction and phased support, so that the stress can be redistributed, and finally the safe construction of the high-slope tunnel entrance section of the super-large-span underground structure is realized.

[0048] The present invention is further described above with the aid of specific embodiments. However, it should be understood that the specific description here should not be construed as limiting the essence and scope of the present invention. Various modifications made to the above embodiments by ordinary technicians in the field after reading this specification are all within the scope of protection of the present invention.

Claims

1. A high slope entrance support structure for a large-span tunnel in a rock formation, characterized in that: include: The upslope ground beam (6) is the external force-bearing structure of the tunnel entrance support system; The circumferential upslope anchor cable (4) is arranged at the side slope (12) of the cave entrance. The unstable blocks formed by the rock cracks and fracture zones at the top of the cave entrance structure are fixed to the surrounding stable blocks through the circumferential upslope anchor cable (4), or the unstable blocks are connected in series to form stable blocks. A vertical high-strength prestressed steel cable (5) is arranged in a lowering hole of the upslope ground beam (6) and is arranged crosswise with the annular upslope anchor cable (4); as well as The in-hole system anchor rod or anchor cable (11) is arranged above the top middle hole (1) and above the top side hole (2); The in-hole system anchor rods (11) and the vertical high-strength prestressed steel cables (5) are arranged at the temporary supporting rock mass (3); The cave entrance includes a top middle cave (1), a top side cave (2), a temporary supporting rock mass (3), soil mass (9) below the side cave, and soil mass (10) below the middle cave and the temporary supporting rock mass.

2. The high slope entrance support structure of a large-span tunnel in a rock formation according to claim 1, characterized in that: The widths of the top middle hole (1), the top side hole (2), the temporary supporting rock mass (3), and the soil mass (9) below the side hole are 12m to 18m.

3. The high slope entrance support structure of a super-large-span tunnel in a rock formation according to claim 2, characterized in that: The width of the soil (10) below the middle hole and the temporary supporting rock mass is the sum of the widths of the top middle hole (1) and the temporary supporting rock mass (3).

4. A construction method for a high slope entrance support structure of a super-large-span tunnel in a rock formation according to any one of claims 1 to 3, characterized in that: include: Step 1, excavating the original slope (12) in stages; Step 2: During the excavation of the tunnel entrance slope, a circular upslope anchor cable (4) is constructed; Step 3, drilling holes for vertical high-strength prestressed steel cables (5) on the upward slope; Step 4: construct the upslope ground beam (6) and reserve holes for lowering the vertical high-strength prestressed steel cables (5); Step 5, dividing the cave entrance into a top middle cave (1), a top side cave (2), a temporary supporting rock mass (3), soil mass below the side cave (9), and soil mass below the middle cave and the temporary supporting rock mass (10); Step 6, excavating a middle hole at the top of the tunnel entrance section (1); Step 7, excavating a side hole at the top of the tunnel entrance section (2); Step 8, excavating temporary supporting rock mass (3), constructing system anchor rods and vertical high-strength prestressed steel cables in the tunnel; Step nine, excavating the soil below the side tunnel (9) and the soil below the middle tunnel and the temporary supporting rock mass (10).

5. The construction method according to claim 4, characterized in that: In steps six and seven, in-hole system anchor rods (11) and vertical high-strength prestressed steel cables (5) are constructed above the top middle hole (1) and the top side hole (2) respectively to maintain the stability of the rock mass.

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