A mechanical excavation method for hard rock tunnel

Abstract

The present invention provides a mechanical excavation method for a hard rock tunnel, and belongs to the technical field of tunnel engineering excavation. The existing hard rock tunnel excavation method has a great impact on the surrounding environment, and is inefficient and costly. The present invention adopts a face partition design, and drills holes in the corresponding partitions to reduce the hardness of the rock mass, and uses mechanical equipment for excavation and excavation, which reduces the impact on the surrounding environment, reduces construction costs, and improves construction efficiency.

Description

Technical Field

[0001] The invention relates to a mechanical excavation method for a hard rock tunnel, belonging to the technical field of tunnel engineering excavation. Background Art

[0002] Generally, the drilling and blasting method is used to excavate hard rock tunnels, but the drilling and blasting method has large vibrations and noises, which have a great impact on the surrounding environment. For areas with high requirements for vibration and noise, when the drilling and blasting method cannot be used, non-blasting mechanical methods are often used to excavate tunnels.

[0003] At present, the commonly used mechanical excavation technologies include expansion cracking, impact crushing, cutting, cutting, and tunnel boring machine methods. The expansion cracking method requires excavation of the open face, and the open face excavation often uses methods such as drilling and coring, which are inefficient and have small space, affecting the subsequent hydraulic expansion cracking effect; the impact crushing method includes two methods: manual pneumatic pick crushing and hydraulic impact hammer crushing, which produce certain impact vibrations, high construction noise, low efficiency, and low excavation surface smoothness; the cutting method is mostly used in stone mining, with high technical requirements and extremely low efficiency, and is not suitable for tunnel construction; the cutting method uses mechanical cutting teeth to break rocks, which is generally used when the rock strength is less than 60MPa, with high rock breaking efficiency. When the rock strength is too high, the cutting teeth are consumed a lot, the economy is poor, and even the rock cannot be broken; the tunnel boring machine method can efficiently break hard rock, but its cross-section is single and the construction cost is high. It is generally used in long and large tunnels with circular cross-sections. Summary of the invention

[0004] The object of the present invention is to provide a mechanical excavation method for a hard rock tunnel, so as to solve the problems of high cost and low efficiency in excavating a hard rock tunnel.

[0005] In order to achieve the above object, the present invention provides a hard rock tunnel mechanical excavation method, comprising the following steps:

[0006] 1) Zoning: Divide the face of the hard rock tunnel to be excavated into:

[0007] A contour modification area, which is arranged along the contour edge of the tunnel face to be excavated and is used to form a structural contour of the tunnel face to be excavated;

[0008] A cutting zone, which is arranged at the structural center of the face to be excavated or at a position close to the structural center, and is used for cutting operations by a mechanical cutting device to form a cutting excavation space, and the cutting excavation space creates an open surface for subsequent fracturing operations, and the cutting zone is rectangular; the cutting zone is arranged as a single one and is located at the spatial center of the face; or at least two cutting zones are arranged at the face to be excavated and are arranged symmetrically or evenly; there are cutting drill holes in the cutting zone; a fracturing zone, which is located in the structural area between the contour modification zone and the cutting zone, and fracturing holes are arranged in the horizontal and vertical directions around the cutting zone for fracturing operations of the face to be excavated; the fracturing zone also includes supplementary holes, and the supplementary holes are arranged by a hard rock drilling device;

[0009] 2) drilling holes, evenly distributing drill holes in the modification area, cutting area and fracturing area by means of a hard rock drilling device, wherein the drilling spacing of the fracturing area drill holes is less than the minimum fracturing resistance line; the modification area drill holes are drilled along the excavation contour line, forming an external insertion angle with the excavation contour line, and the depth of the modification area drill holes is greater than the depth of the fracturing area drill holes;

[0010] 3) Rock cutting: using mechanical cutting devices to cut the rock in the cutting area to form cutting excavation space;

[0011] 4) Rock mass fracturing: the fracturing device is used to perform fracturing in layers on the boreholes in the fracturing zone from the cutting zone toward the contour modification zone, so as to perform fracturing operations on the rock mass in the fracturing zone until the excavation of the rock mass in the fracturing zone is completed;

[0012] 5) Contour correction: the modified area borehole is expanded and fractured by the expansion device, and then the modified area after the expansion and fracture operation is cut by the mechanical cutting device to form a smooth excavation contour surface structure;

[0013] 6) Carry out support work on the hard rock tunnel after excavation;

[0014] 7) Repeat the above steps 2) to 6) to perform cyclic operations on the face of the hard rock tunnel to be excavated until the excavation of the entire hard rock tunnel to be excavated is completed.

[0015] The beneficial effects of the present invention are as follows: a mechanical excavation method for a hard rock tunnel, which performs a zoning design on the face of a hard rock tunnel, sets corresponding boreholes on the cutting area to reduce the hardness of the rock mass, facilitates the cutting of the area into subsequent excavation driving excavation space, sets multiple layers of expansion and fracturing boreholes around the cutting area, and fractures and peels off the rock mass in the expansion and fracturing area layer by layer, continuously expands the excavation space, drills and sets modification boreholes in the contour modification area to perform expansion and fracturing, and performs cutting and modification on uneven positions, so that the air surface is smooth for subsequent support construction, and supports the excavated hard rock tunnel to meet the excavation design strength requirements. The cutting area on the small-section face is designed on the center line to facilitate the operation of the drilling equipment and the cutting equipment, and the cutting area on the large-section face is designed to be distributed on both sides of the center line, and can be operated by two drilling equipment or cutting equipment at the same time, thereby improving the tunnel excavation efficiency. The excavation method of the present invention can achieve rapid excavation of hard rock tunnels, improve tunnel excavation efficiency, and reduce construction costs and the impact on the surrounding environment of construction.

[0016] Furthermore, the hard rock drilling device includes a geological drill and a rock drilling rig; the fracturing device includes a wedge splitter, a rock fracturing device, and a hydraulic fracturing device. Furthermore, in the above method, the mechanical cutting device includes:

[0017] The equipment body is the bearing base of the mechanical cutting device;

[0018] The cutting part is arranged at the front end of the equipment body, adopts carbide cutters or high-pressure water jets to break rocks, and is used for cutting operations of hard rocks.

[0019] Furthermore, in the above method, the device body comprises:

[0020] A walking part, which is arranged at the bottom of the equipment body and provides power for the free movement of the mechanical cutting device;

[0021] A dust removal part, which is arranged on the equipment body and is used to clean the dust generated during the hard rock cutting process;

[0022] The slag transportation part is arranged on the equipment body and is used for cleaning and transporting the slag after cutting the hard rock.

[0023] The beneficial effects of this are: drilling through hard rock drilling devices such as geological drills and rock drilling rigs, and fracturing the drilled holes through fracturing devices such as wedge splitters, rock splitters, and hydraulic splitters, and when cutting through mechanical cutting devices, free movement is achieved through the walking part on the equipment body, rock cutting is performed through the cutting part, dust generated during the cutting process is cleaned through the dust removal part, and the slag generated by cutting is cleaned and transported through the slag transportation part, thereby achieving efficient and safe excavation of hard rock tunnels to be excavated.

[0024] Furthermore, in the above method, the fracturing zone drilled holes and the supplementary holes constitute a fracturing hole system combination, and the fracturing hole system combination is arranged in a matrix structure or arranged at equal intervals.

[0025] The beneficial effect of this is that supplementary holes are added in the fracturing zone, and the supplementary holes and the fracturing zone drill holes form a fracturing hole system combination, which can be drilled by a hard rock drilling device to improve the fracturing efficiency of the fracturing zone drill holes. Furthermore, in the above method, the cutting zone drill holes are arranged in rows or columns in the cutting zone, and the cutting zone drill holes in two adjacent rows or columns are arranged in a staggered manner.

[0026] The beneficial effect of this is that the cutting drilling is to reduce the hardness of the rock mass in the cutting area, and the staggered arrangement helps to further reduce the hardness of the rock mass in the cutting area, facilitates excavation of cutting equipment with low hardness requirements, and reduces construction costs.

[0027] Furthermore, in the above method, the external interpolation angle α formed by the drill hole in the modified area and the excavation contour line is 3°-5°.

[0028] Furthermore, in the above method, the depth L′ of the drilling holes in the cutting area and the expansion area is n times the excavation footage L, n=1, 2, 3, 4,...; the drilling depth L" of the modification area satisfies the following conditions: n*L / cosα≤L"≤n*L / cosα+0.5, where n=1, 2, 3, 4,..., and α is 3°-5°.

[0029] The beneficial effects of this are: drilling holes of a certain depth according to the excavation progress of the construction, and the holes are orthogonal to the heading face, which can reduce the problem of reduced efficiency caused by the intersection of holes inside the rock mass. The holes are modified to be drilled at a certain angle to the excavation contour line, which can minimize the construction losses caused by under-excavation and ensure construction efficiency.

[0030] A body to be excavated, the boundary line of the excavation face of which is a contour line, including a cutting area, a contour modification area and a fracturing area, wherein the cutting area is located at or near the middle of the excavation face in the horizontal direction and is connected to the ground, the contour modification area is located in an area on the excavation face within a set distance from the contour line, and the fracturing area is an area on the excavation face excluding the cutting area and the contour modification area;

[0031] Cutting drill holes are evenly arranged in the cutting area, modifying drill holes are arranged along the contour line in the contour modification area, and one or more rows of fracturing drill holes are arranged around the cutting area in the fracturing area. The hole spacing between the fracturing drill holes and the modifying drill holes is smaller than the minimum fracturing resistance line.

[0032] The beneficial effects of the present invention are as follows: a body to be excavated, i.e., a construction object during excavation of a hard rock tunnel, is divided into zones on the excavation surface, and corresponding boreholes are arranged on the cutting area to reduce the hardness of the hard rock, so as to facilitate cutting of the area for subsequent fracturing to create an air-facing surface, and further, multiple layers of fracturing boreholes are arranged around the cutting area to facilitate sequential fracturing of the fracturing boreholes and then peeling to achieve expansion of the excavation space, and modification boreholes are arranged in the contour modification area to prevent under-excavation, and after fracturing, the uneven positions are modified to make the air-facing surface smooth. The body to be excavated of the present invention is easy to excavate, can improve the rock breaking efficiency during excavation, and reduce the cost of tunnel construction.

[0033] Furthermore, in the above-mentioned body to be excavated, when the excavation face width is less than or equal to 8m and the height is less than or equal to 6.5m, the cutting area is located on the center line of the excavation face; when the excavation face width is greater than 8m and the height is greater than 6.5m, a cutting area is set on each side of the left and right sides of the center line of the excavation face.

[0034] Furthermore, in the above-mentioned body to be excavated, the width of the cutting area is 1m-2.5m, and the height is 2m-4.5m.

[0035] The beneficial effect of this is that the number and position of the cutting areas are adjusted according to the width and height of the body to be excavated, and their width and height are adjusted, which can provide a cost-saving and efficiency-enhancing excavation object for hard rock tunnel excavation.

[0036] Furthermore, in the above-mentioned body to be excavated, the fracturing zone also includes supplementary holes, which are located between the cutting zone and a row of fracturing boreholes adjacent to the cutting zone or between any two rows of fracturing boreholes or between the contour modification zone and a row of fracturing boreholes adjacent to the contour modification zone.

[0037] The beneficial effect of this is: supplementary holes are set in the middle area of ​​the fracturing zone where the spacing between the fracturing holes is larger, which facilitates fracturing and prevents the spacing between the fracturing holes from being too large, making it difficult to achieve effective fracturing in one go. This can further reduce the difficulty of fracturing in the fracturing zone and facilitate excavation.

[0038] Furthermore, in the above-mentioned body to be excavated, the cutting drill holes are arranged in rows or columns in the cutting area, and the cutting drill holes in two adjacent rows or columns are arranged in a staggered manner.

[0039] The beneficial effect of this is that the staggered arrangement is set up to reduce the hardness of the rock mass in the cutting area during cutting and drilling, and the hardness of the rock mass in the cutting area can be further reduced, making it convenient to use cutting equipment with low hardness requirements for excavation, thereby reducing construction costs.

[0040] Furthermore, in the above-mentioned body to be excavated, when multiple rows of fracturing drill holes are set in the fracturing zone, the row spacing between two adjacent rows of fracturing drill holes is 50cm-100cm.

[0041] Furthermore, in the above-mentioned body to be excavated, the diameters of the cutting boreholes, modification boreholes, expansion boreholes and supplementary boreholes are 42mm-140mm.

[0042] Furthermore, in the above-mentioned body to be excavated, the hole spacing of the cutting drill holes is 50mm-100mm, the hole spacing of the modification drill holes is 100mm, the hole spacing of the expansion drill holes is 100mm-300mm, and the hole spacing of the supplementary holes is 50mm-100mm.

[0043] Furthermore, in the above-mentioned body to be excavated, the cutting borehole, the modification borehole and the fracturing borehole are orthogonal to the excavation surface of the body to be excavated, and the modification borehole is arranged along the contour line, and the external interpolation angle formed with the contour line is 3°-5°.

[0044] Furthermore, in the above-mentioned body to be excavated, the depths of the cutting borehole, the fracturing borehole and the supplementary hole are consistent, and the depth of the modification borehole is greater than the depth of the cutting borehole.

[0045] The beneficial effects of this are: the drilling depth can be set freely according to construction requirements, but it is necessary to ensure that the cutting drill holes, expansion drill holes and supplementary holes are orthogonal to the excavation surface so that they will not form intersections inside the excavation body; the modification drill holes are set along the contour line to form a certain angle to ensure the excavation efficiency of the excavation body during the excavation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 A process flow chart of the mechanical excavation method for a hard rock tunnel according to the present invention;

[0047] Figure 2 It is a schematic diagram of the tunnel face partitioning of the present invention;

[0048] Figure 3 It is a schematic diagram of the division and drilling of the tunnel face of a small and medium-section tunnel of the present invention;

[0049] Figure 4 It is a schematic diagram of the division of the tunnel face and drilling of a large-section tunnel in the present invention. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0051] Method Example 1:

[0052] Take the face of a small-section hard rock tunnel as an example. The width of the face of a small-section hard rock tunnel is ≤8.0m and the height is ≤6.5m. Figure 1 The process flow of the excavation method of the present invention shown in the figure includes the following steps:

[0053] 1) Design the tunnel excavation face in different zones, such as Figure 2 As shown, it includes a drilling cutting area 1, a contour modification area 2 and a drilling expansion area 3. After the excavation of the tunnel face is completed using the excavation method of the present invention, the excavation section composed of the sum of the partitions includes the original designed excavation contour line 5.

[0054] Specifically, according to the size of the tunnel face, the drilling cutting zone can be designed as single or multiple. The single drilling cutting zone of the tunnel face with a small cross-section is located in the central area of ​​the tunnel face, that is, the area where the vertical center line of the tunnel perpendicular to the ground is located. Multiple drilling cutting zones can be arranged on the tunnel face with a large cross-section. The drilling cutting zone is as far away from the left and right edges of the tunnel face as possible. The contour modification zone is distributed along the excavation contour line of the tunnel face, and its formation area includes the excavation contour line of the tunnel face. Excluding the drilling cutting zone and the contour modification zone, the other areas of the tunnel face are all drilling expansion zones.

[0055] The above-mentioned borehole cutting zone 1, contour modification zone 2 and borehole expansion and fracturing zone 3 are all designed with boreholes. The borehole cutting zone is designed with evenly distributed cutting boreholes. After drilling, the strength of the rock mass is weakened, which is suitable for cutting equipment to cut the rock mass. The modified boreholes in the contour modification zone are arranged along the tunnel excavation contour line. The borehole expansion and fracturing zone is designed with multiple rows of expansion and fracturing holes (i.e., expansion and fracturing boreholes) and supplementary holes according to a certain arrangement rule. The boreholes of a single row of expansion and fracturing holes are arranged at equal intervals, and the hole spacing is less than the minimum expansion and fracturing resistance line. The supplementary holes are mainly used to improve the expansion and fracturing efficiency of the expansion and fracturing holes, and are mainly arranged between the borehole cutting zone and the innermost expansion and fracturing holes, between two adjacent rows of expansion and fracturing holes, and between the outermost expansion and fracturing holes and the excavation contour line.

[0056] Referring to the above-mentioned zoning method and drilling layout standards, carry out zoning design and drilling design for the planned excavation face, and determine the location and number of drilling holes.

[0057] like Figure 3 The diagram shows the face division and drilling design of the small-section hard rock tunnel of this embodiment, including the drilling cutting area 11 located in the center area of ​​the face (i.e., the area where the center line is located) or near the center area, the contour modification area and the drilling expansion area 3 set along the excavation contour line 5. The center line of the face refers to the midline that bisects the face perpendicular to the ground. The cutting area 11 is used as a basis for expanding the excavation space formed by the cutting area by expanding the expansion holes layer by layer during excavation. Considering the construction efficiency and cost, the width of the drilling cutting area 11 is set to 1.0-1.5m and the height is set to 2.0-3.5m.

[0058] The three zones are drilled in accordance with the drilling layout standard. The drilling cutting zone 11 is designed with cutting holes arranged in a plum blossom shape, that is, the holes in the drilling cutting zone are arranged in rows from the ground upward, and the holes between two adjacent rows are staggered. Multiple columns can also be arranged in the left and right directions in the cutting zone, and the holes in two adjacent columns are staggered, which can effectively reduce the hardness of the rock mass in the cutting zone and facilitate the use of cutting equipment with low hardness requirements.

[0059] The hole spacing of the multiple rows or columns of cutting holes drilled in the cutting area 11 is 50mm-100mm. In order to prevent the cutting holes from intersecting inside the excavation body and affecting the progress of the cyclic excavation during the subsequent construction, the cutting holes should be orthogonal to the face.

[0060] The fracturing drill holes are arranged in the fracturing zone 3 surrounding the drilling cutting zone 11. The four layers of fracturing drill holes arranged from the inside to the outside along the cutting zone 11 are fracturing drill holes 31, 32, 33 and 34, respectively. The row spacing between any two adjacent rows of fracturing drill holes is 50 cm to 100 cm. Specifically, Figure 3 The distance between each column of the expansion drill holes in the 31st and 32nd layers in the vertical direction is 50cm, and the distance between each row in the horizontal direction is 100cm. The net spacing between two adjacent expansion drill holes in each row or column is 100mm-300mm. Each expansion drill hole is orthogonal to the face to prevent intersection inside the rock mass to be excavated.

[0061] In addition, considering the uneven spacing between the expansion holes in different layers, such as Figure 3 As shown, a number of supplementary holes 41 are also arranged between the rows of fracturing boreholes with larger spacing in the upper row of the fracturing zone 3, which are used to achieve reliable stripping of the fracturing zone. The supplementary holes 41 are arranged between the cutting zone 11 and the row of the fracturing borehole 31 layer, the wider area between the fracturing borehole 31 layer and the fracturing borehole 32 layer, the fracturing borehole 32 layer and the fracturing borehole 33 layer, the fracturing borehole 33 layer and the fracturing borehole 34 layer, and the fracturing borehole 34 layer and the modified borehole 21. The supplementary holes 41 are flexibly arranged according to needs. It is necessary to arrange as many supplementary holes as possible to effectively reduce the hardness of the rock mass and ensure that the corresponding layer of fracturing boreholes can be effectively stripped. The construction cost and efficiency must also be considered. In this embodiment, the net spacing of the supplementary holes is set to 50mm-100mm, and is orthogonal to the face, and does not intersect with any other boreholes inside the rock mass to be excavated.

[0062] In order to prevent under-excavation and ensure the flatness of the free surface of the tunnel after excavation, a contour modification area is also set up. The contour modification area is set along the excavation contour line 5. Usually, in the actual excavation process, it appears as an annular area including the excavation contour line 5. At least one layer of modified drill holes must be set in the contour modification area, so the width of the contour modification area is greater than the aperture of the modified drill holes.

[0063] The modified boreholes 21 on the contour modification area are arranged along the excavation contour line 5, and the external interpolation angle with the excavation contour line 5 is 3°-5°, that is, the modified boreholes 21 on the contour modification area are arranged along the excavation contour line 5 in a direction away from the center of the face (i.e., the intersection of the center line of the face and the ground), and form an angle of 3°-5° with the axis of the tunnel (i.e., the vector line along the tunnel excavation direction). In order to set as many modified boreholes as possible, while taking into account the construction cost and efficiency, the net spacing of the modified boreholes 21 is set to 100mm. After the modified boreholes 21 are fractured, the free surface after the fracture is smoothed and modified. Specifically, the rock protrusions protruding from the free surface to a set height can be cut and corrected by cutting equipment to ensure the flatness.

[0064] The diameter of the borehole is determined according to the drill bit diameter of the drilling equipment. The diameter of the cut borehole, modification borehole, expansion borehole and supplementary borehole is generally 42mm-140mm. In order to improve the process connection and construction efficiency, the diameter of all the boreholes set on the face mentioned in this embodiment is 89mm.

[0065] The depths of the cutting borehole, expansion borehole and supplementary hole are consistent and are generally set freely according to the construction progress. The depth of the modification borehole is greater than the depth of the cutting borehole.

[0066] 2) Drilling: Complete all designed drilling holes in sequence according to the convenience of equipment operation. After drilling the holes in the drilling expansion zone and the contour modification zone to the designed depth, clean the rock debris to ensure the cleanliness of the hole. The drilling holes in the drilling cutting zone do not need to be cleaned. The drilling holes in the drilling cutting zone and the drilling expansion zone are orthogonal to the excavation face, and the drilling holes in the contour modification zone are inserted at an angle of 3°-5° with the excavation contour line.

[0067] The borehole diameter can be one or multiple, and the borehole diameter is 42-140mm. In order to improve the drilling efficiency, the borehole diameter of all boreholes is 89mm. The drilling depth of the drilling cutting area and the drilling expansion area is consistent, and the depth L' is n times the cyclic excavation footage L (n = 1, 2, 3, 4, 5, ...). The drilling depth L" in the contour modification area meets the conditions: n*L / cosα≤L"≤n*L / cosα+0.5 (α is the external insertion angle, generally 3°-5°). In this embodiment, the depth of the cutting borehole is 5m, and the depth of the modified borehole is 5.1m-5.3m.

[0068] In this embodiment, technologically mature hard rock drilling equipment, such as geological drills, rock drilling rigs, etc., are used to drill the boreholes designed in step 1). The drilling equipment enters the construction area to facilitate the working principle of the equipment drilling, and completes the drilling work of all designed boreholes in sequence. After the boreholes in the borehole expansion zone 3 and the contour modification zone are drilled to the designed depth, the rock debris is cleaned to ensure the cleanliness of the hole. The boreholes in the borehole cutting zone 11 are not cleaned of rock debris. The boreholes in the borehole cutting zone 11 and the borehole expansion zone 3 are orthogonal to the excavation face, and the modified borehole 21 has an extrapolated angle of 3°-5° with the excavation contour line. After the drilling is completed, the drilling equipment withdraws from the construction site.

[0069] 3) Rock cutting: The cutting equipment cuts and drills the rock in the cutting area according to the cyclic excavation footage L to form an excavation space of a certain depth. The cutting surface cannot be less than the designed drilling cutting area area to create an open surface for subsequent fracturing operations and improve the fracturing efficiency. The designed drilling depth L' on the drilling cutting area is n times the cyclic excavation footage L. The cutting depth of each drilling cutting area is consistent with the cyclic excavation footage L. The face can be re-divided and drilled after n cutting operations. During or after the cutting operation, the rock debris should be cleaned and transported according to the on-site conditions to keep the face operation area flat and open.

[0070] In this embodiment, a non-explosive excavation construction equipment for hard rock tunnels is used to perform cutting construction on the drilling cutting area. After the equipment is in place and started, the equipment cutting head is used to rotate at high speed to cut the rock mass in the drilling cutting area 11, forming an excavation space with a depth of 1.0m, a width of 1.0-1.5m, and a height of 2.0-3.5m. After the cutting operation is completed, the cutting equipment is retreated to an unaffected area. During or after the cutting operation, the rock slag is cleaned and transported according to the on-site conditions to keep the face operation area flat and open.

[0071] 4) Rock mass fracturing: hydraulic fracturing equipment is used to fracture the rock mass in the fracturing area of ​​the drilled hole. The fracturing sequence is from inside to outside, and the single-layer fracturing sequence is bilaterally symmetrical and excavated hole by hole from bottom to top. After the front row of holes is fractured, the supplementary holes between the next row of holes are fractured, and the fracturing sequence of the supplementary holes is from inside to outside. The fracturing operation uses mature hydraulic fracturing tools, such as wedge splitters, rock fracturing tools, hydraulic fracturing tubes, etc.

[0072] The drilling cycle fracturing depth in the drilling fracturing zone is consistent with the cyclic excavation footage. According to the fracturing principle, the fracturing operation can be carried out hole by hole, or in batches of multiple holes simultaneously.

[0073] In this embodiment, hydraulic fracturing equipment is used to perform fracturing operation on the borehole fracturing zone 3. The fracturing sequence is from inside to outside, that is, the fracturing is carried out in layers in the order of 31st layer → 32nd layer → 33rd layer → 34th layer. The fracturing sequence of a single layer is bilaterally symmetrical and excavated hole by hole from bottom to top. After the front row of holes is fractured, the supplementary holes 41 between the next row of holes are fractured. The fracturing sequence of the supplementary holes 41 is from inside to outside. 5-10 holes are drilled for fracturing each time. During the fracturing operation, the rock slag is cleaned and transported according to the on-site conditions to facilitate the on-site fracturing operation.

[0074] 5) Excavation profile correction: The hydraulic fracturing equipment fracturifies the rock mass in the excavation profile modification area. The fracturing sequence is bilaterally symmetrical and sequentially excavated hole by hole. The fracturing depth of the drilling cycle in the profile modification area is consistent with the cycle footage. According to the fracturing principle, the fracturing operation can be performed hole by hole or in batches of multiple holes at the same time. After the fracturing is completed, the cutting equipment cuts the rock mass that invades the tunnel design excavation contour line to form a smooth excavation contour surface.

[0075] In this embodiment, hydraulic fracturing equipment is used to fracture the rock mass in the excavation contour modification area, and the fracturing sequence is left-right symmetrical and hole-by-hole excavation. After the fracturing operation is completed, the fracturing equipment is withdrawn and the cutting equipment is brought in. The high-speed rotating cutting head of the cutting equipment is used to cut the rock mass in the contour modification area that intrudes the designed excavation contour line 5 to form a smooth excavation contour surface. Then the cutting equipment is withdrawn, the rock slag is cleaned and transported, and construction conditions are created for the support operation.

[0076] 6) Support: Support operations are carried out on the excavation space formed including the designed excavation contour line, including erecting steel frames, laying steel frame mesh, spraying concrete, installing anchor rods, etc.

[0077] During the excavation of a small-section hard rock tunnel, the face can be cycled 4-5 times according to steps 3-6, and then the holes can be drilled again according to step 2) according to the zoning and drilling design described in step 1), and excavation can be carried out according to steps 3-6 until the tunnel is excavated to the designed mileage. During the construction of steps 2-6, the rock debris should be cleaned according to the on-site conditions.

[0078] The mechanical excavation method of the small-section tunnel face of the present invention is adopted. A cutting area and a contour modification area are set on the face, and other areas of the face are used as expansion and fracturing areas. Drill holes are set in the corresponding areas to reduce the hardness of the rock mass. The cutting area is first cut and crushed, and the free surface is continuously expanded by crushing the expansion and fracturing area. In the contour modification area, expansion and fracturing modification holes are first made, and then cutting and modification are performed along the excavation contour line to form a smoother excavation contour surface, thereby ensuring construction efficiency, reducing construction costs, and facilitating the orderly progress of subsequent tunnel support and other projects.

[0079] Method Example 2:

[0080] Take the face of a large-section hard rock tunnel as an example. The width of the face of a large-section hard rock tunnel is greater than 8.0m and the height is greater than 6.5m. Figure 1 The process flow of the excavation method of the present invention shown in the figure includes the following steps:

[0081] 1) The tunnel excavation face is zoned and designed, including a drilling cutting area, a contour modification area and a drilling expansion area. After the tunnel face is excavated using the excavation method of the present invention, the excavation section composed of the sum of the zones contains the original designed excavation contour line.

[0082] Specifically, according to the size of the tunnel face, the drilling cutting zone can be designed as single or multiple. The single drilling cutting zone of the tunnel face of a small cross-section tunnel is located in the central area of ​​the tunnel face, and multiple drilling cutting zones can be arranged on the tunnel face of a large cross-section tunnel. The drilling cutting zone is as far away from the left and right edges of the tunnel face as possible. The contour modification zone is distributed along the excavation contour line of the tunnel face, and its formation area includes the excavation contour line of the tunnel face. Excluding the drilling cutting zone and the contour modification zone, the other areas of the tunnel face are all drilling expansion zones.

[0083] The above-mentioned drilling cutting area, contour modification area and drilling expansion and fracturing area are all designed with drill holes. The drilling cutting area is designed with evenly distributed drill holes. After drilling, the strength of the rock mass is weakened, which is suitable for cutting equipment to cut the rock mass. The drill holes in the contour modification area are arranged along the tunnel excavation contour line. The drilling expansion and fracturing area is designed with multiple rows of expansion and fracturing holes and supplementary holes according to a certain arrangement rule. The drill holes of a single row of expansion and fracturing holes are arranged at equal intervals, and the hole spacing is less than the minimum expansion and fracturing resistance line. The supplementary holes are mainly used to improve the expansion and fracturing efficiency of the expansion and fracturing holes. They are mainly set between the drilling cutting area and the innermost expansion and fracturing holes, between two adjacent rows of expansion and fracturing holes, and between the outermost expansion and fracturing holes and the excavation contour line.

[0084] Referring to the above-mentioned zoning method and drilling layout standards, carry out zoning design and drilling design for the planned excavation face, and determine the location and number of drilling holes.

[0085] like Figure 4 The diagram shows the face division and drilling design of the large-section hard rock tunnel of this embodiment, including a cutting area on each side of the center line of the face, the center line of the face refers to the midline perpendicular to the ground that divides the face into two halves, a cutting area 121 is set on the right side of the center line of the face, and a cutting area 122 is set on the left side of the center line of the face. When excavating, the excavation space formed by the cutting area is continuously expanded by extruding the extrusion holes layer by layer based on the extrusion areas 121 and 122. Considering the construction efficiency and cost, the width of the cutting area 121 and the cutting area 122 is set to 1m-2.5m, and the height is set to 2m-4.5m.

[0086] According to the drilling layout standard, the above three partitions are drilled and arranged. Multiple rows or columns of cutting drill holes are set on the cutting area 121 and the cutting area 122. In order to reduce the hardness of the hard rock, the cutting drill holes of two adjacent rows or columns are staggered, and the net spacing between adjacent cutting drill holes is 50mm-100mm. In order to prevent the cutting drill holes from crossing inside the excavation body and affecting the progress of the cyclic excavation during the subsequent construction, the cutting drill holes should be orthogonal to the face.

[0087] The fracturing boreholes are arranged in the fracturing zone 3 surrounding the cutting zone 121 and the cutting zone 122. Four layers of fracturing boreholes are arranged on the fracturing zone from the center to the outside along the cutting zone 121 and the cutting zone 122. The fracturing boreholes arranged outward from the cutting zone 121 are 351 layers, 361 layers, 371 layers and 381 layers respectively. The fracturing boreholes arranged outward from the cutting zone 122 are 352 layers, 362 layers, 372 layers and 382 layers respectively. The fracturing boreholes of the 381 layer and the 382 layer overlap at the center line of the face. The row spacing between any two adjacent rows of fracturing boreholes is 50cm-100cm, and the net spacing between each row of fracturing boreholes is 100mm-300mm. Each fracturing borehole is orthogonal to the face to prevent intersection inside the excavation body and affect subsequent excavation and advancement.

[0088] In addition, considering the uneven spacing between the expansion holes in different layers, such as Figure 4 In the fracturing zone 3, a number of supplementary holes 42 are also arranged on the fracturing zone 3. The supplementary holes 42 are arranged in the areas between the cutting zone 121 and the fracturing borehole 351 layer, the cutting zone 122 and the fracturing borehole 352 layer, the 351 layer and the 361 layer, the 361 layer and the 371 layer, the 371 layer and the 381 layer, the 352 layer and the 362 layer, the 362 layer and the 372 layer, the 372 layer and the 382 layer, the 381 layer and the modified borehole 22, and the 382 layer and the modified borehole 22. The supplementary holes 42 are flexibly arranged. It is necessary to arrange as many supplementary holes as possible to effectively reduce the hardness of the rock mass, and the construction cost and efficiency must also be considered. The net spacing of the supplementary holes is set to 50mm-100mm, and is orthogonal to the face, and does not intersect with any other boreholes in the excavation body.

[0089] In order to prevent under-digging and ensure the flatness of the free face of the tunnel after excavation, a contour modification area is also set. The contour modification area is set along the contour line 5. Usually, in the actual construction process, it is a ring area including the contour line 5. The contour modification area must be set with at least one layer of modified boreholes, so the width of the contour modification area is greater than the aperture of the modified boreholes. After the modified boreholes 42 are expanded and fractured, the free face after expansion and fracture is flattened and modified. Specifically, the rock protrusions that protrude from the free face to a set value can be ground and corrected by cutting equipment to ensure flatness.

[0090] The modified boreholes 22 on the contour modification area are arranged along the excavation contour line 5, and the external interpolation angle with the excavation contour line 5 is 3°-5°, that is, the modified boreholes 22 on the contour modification area are arranged along the excavation contour line 5 in a direction away from the center of the tunnel face (i.e., the intersection of the center line of the tunnel face and the ground), and form an angle of 3°-5° with the axis of the tunnel (i.e., the vector line along the tunnel excavation direction). In order to set as many modified boreholes as possible, while taking into account the construction cost and efficiency, the net spacing of the modified boreholes 22 is set to 100mm.

[0091] The diameter of the borehole is determined according to the drill bit diameter of the drilling equipment. The diameter of the cut borehole, modification borehole, expansion borehole and supplementary borehole is generally 42mm-140mm. In order to improve the process connection and construction efficiency, the diameter of all the boreholes set on the face mentioned in this embodiment is 102mm.

[0092] The depths of the cutting borehole, expansion borehole and supplementary hole are consistent and are generally set freely according to the construction progress. The depth of the modification borehole is greater than the depth of the cutting borehole.

[0093] 2) Drilling: Complete all designed drilling holes in sequence according to the convenience of equipment operation. After drilling the holes in the drilling expansion zone and the contour modification zone to the designed depth, clean the rock debris to ensure the cleanliness of the hole. The drilling holes in the drilling cutting zone do not need to be cleaned. The drilling holes in the drilling cutting zone and the drilling expansion zone are orthogonal to the excavation face, and the drilling holes in the contour modification zone are inserted at an angle of 3°-5° with the excavation contour line.

[0094] The borehole diameter can be one or multiple, and the borehole diameter is 42-140mm. In order to improve the drilling efficiency, the borehole diameter of all boreholes is 102mm. The drilling depth of the drilling cutting area and the drilling expansion area is consistent, and the depth L' is n times the cyclic excavation footage L (n = 1, 2, 3, 4, 5, ...). The drilling depth L" in the contour modification area meets the condition: n*L / cosα≤L"≤n*L / cosα+0.5 (α is the external insertion angle, generally 3°-5°). The depth of the cutting borehole in this embodiment is 3m, and the depth of the modified borehole is 3.1m-3.2m.

[0095] In this embodiment, technologically mature hard rock drilling equipment, such as geological drills, rock drilling rigs, etc., are used to drill the boreholes designed in step 1). In order to improve the working efficiency, two drilling equipments are used to work simultaneously. The drilling equipment enters the construction area to facilitate the working principle of the equipment drilling, and completes the drilling work of all designed boreholes in sequence. After the boreholes in the borehole expansion zone 3 and the contour modification zone 22 are drilled to the designed depth, the rock debris is cleaned to ensure the cleanliness of the hole. The boreholes in the borehole cutting zone 1 are not cleaned of rock debris. The boreholes in the borehole cutting zone 121, the borehole cutting zone 122 and the borehole expansion zone 3 are orthogonal to the excavation face, and the borehole in the contour modification zone 22 has an external angle of 3°-5° with the excavation contour line 5. After the drilling is completed, the drilling equipment withdraws from the construction site.

[0096] 3) Rock cutting: The cutting equipment cuts and drills the rock in the cutting area according to the cyclic excavation footage L to form an excavation space of a certain depth. The cutting surface cannot be less than the designed drilling cutting area area to create an open surface for subsequent fracturing operations and improve the fracturing efficiency. The designed drilling depth L' on the drilling cutting area is n times the cyclic excavation footage L. The cutting depth of each drilling cutting area is consistent with the cyclic excavation footage L. The face can be re-divided and drilled after n cutting operations. During or after the cutting operation, the rock debris should be cleaned and transported according to the on-site conditions to keep the face operation area flat and open.

[0097] In this embodiment, a special or modified milling and excavation equipment, such as a cantilever tunneling machine, is used to cut rocks with a cutting head device to carry out cutting construction on the drilling cutting area. After the milling and excavation equipment is in place and started, the equipment cutting head is used to rotate at high speed to cut the rock mass in the drilling cutting area 121 and the drilling cutting area 122 to form two excavation spaces with a depth of 1.0m, a width of 1.0-2.5m, and a height of 2.0-4.5m. After the cutting operation is completed, the cutting equipment is retreated to an unaffected area. During or after the cutting operation, the rock slag is cleaned and transported according to the on-site conditions to keep the face operation area flat and open.

[0098] 4) Rock mass fracturing: hydraulic fracturing equipment is used to fracture the rock mass in the fracturing area of ​​the drilled hole. The fracturing sequence is from inside to outside, and the single-layer fracturing sequence is bilaterally symmetrical and excavated hole by hole from bottom to top. After the front row of holes is fractured, the supplementary holes between the next row of holes are fractured, and the fracturing sequence of the supplementary holes is from inside to outside. The fracturing operation uses mature hydraulic fracturing tools, such as wedge splitters, rock fracturing tools, hydraulic fracturing tubes, etc.

[0099] The drilling cycle fracturing depth in the drilling fracturing zone is consistent with the cyclic excavation footage. According to the fracturing principle, the fracturing operation can be carried out hole by hole, or in batches of multiple holes simultaneously.

[0100] In this embodiment, 2-4 sets of hydraulic fracturing equipment are used to carry out fracturing operations with the drilling cutting areas on both sides as the center. The fracturing sequence is step-by-step excavation from the inside to the outside, i.e., 351 layers → 361 layers → 371 layers → 381 layers and 352 layers → 362 layers → 372 layers → 382 layers. The single-layer fracturing sequence is bilaterally symmetrical and excavated hole by hole from bottom to top. After the front row of holes is fractured, the supplementary holes 42 between the next row of holes are fractured, and the fracturing sequence of the supplementary holes 42 is from the inside to the outside. The stripping of the rock strata in the drilling fracturing area is achieved by fracturing a layer of fracturing boreholes adjacent to the drilling cutting area, and the excavation space is continuously expanded until the drilling fracturing area is completely excavated. Each set of fracturing equipment fracturies 5-10 boreholes each time. During the fracturing operation, the rock debris is cleaned and transported according to the on-site conditions to facilitate on-site fracturing operations.

[0101] 5) Excavation profile correction: The hydraulic fracturing equipment fracturifies the rock mass in the excavation profile modification area. The fracturing sequence is bilaterally symmetrical and sequentially excavated hole by hole. The fracturing depth of the drilling cycle in the profile modification area is consistent with the cycle footage. According to the fracturing principle, the fracturing operation can be performed hole by hole or in batches of multiple holes at the same time. After the fracturing is completed, the cutting equipment cuts the rock mass that invades the tunnel design excavation contour line to form a smooth excavation contour surface.

[0102] In this embodiment, hydraulic fracturing equipment is used to fracture the rock mass in the excavation contour modification area 22, and the fracturing sequence is left-right symmetrical and hole-by-hole excavation. After the fracturing operation is completed, the fracturing equipment is withdrawn and the cutting equipment is brought in. The cutting head of the cutting equipment is used to cut the rock mass in the contour modification area 22 that intrudes the designed excavation contour line 5 to form a smooth excavation contour surface. Then the cutting equipment is withdrawn, the rock slag is cleaned and transported, and construction conditions are created for the support operation.

[0103] 6) Support: Support operations are carried out on the excavation space formed including the designed excavation contour line, including erecting steel frames, laying steel frame mesh, spraying concrete, installing anchor rods, etc.

[0104] During the excavation of a large-section hard rock tunnel, the face can be cycled 2-3 times according to steps 3-6, and then the holes can be drilled again according to step 2) according to the zoning and drilling design described in step 1), and excavation can be carried out according to steps 3-6 until the tunnel is excavated to the designed mileage. During the construction of steps 2-6, the rock debris should be cleaned according to the on-site conditions.

[0105] The mechanical excavation method of the large-section tunnel face adopts the method, two cutting areas are set on both sides of the center line of the face, and a contour modification area is also set, and other areas of the face are used as expansion and fracturing areas. Drill holes are set in the corresponding areas to reduce the hardness of the rock mass. First, the cutting area is cut and crushed, and the free surface is continuously expanded by crushing the expansion and fracturing area. In the contour modification area, the expansion and fracturing modification drill holes are first made, and then cutting and modification are performed along the excavation contour line to form a smoother excavation contour surface, thereby ensuring construction efficiency, reducing construction costs, and facilitating the orderly progress of subsequent tunnel support and other projects.

[0106] Example 1 of the body to be excavated:

[0107] According to Figure 2 The tunnel face partition diagram shown in FIG. 1 is used to illustrate the body to be excavated in this embodiment, that is, the excavation face of the body to be excavated is divided into the following sections: Figure 2 The tunnel face is divided into sections, including cutting area 1, contour modification area 2, expansion and fracturing area 3 and contour line 5. The side where the excavation body is to be excavated is the excavation face, and the boundary line of the excavation face is the contour line, that is, the minimum design excavation contour line when the tunnel is excavated. The cutting area 1 is located at the center or close to the center of the excavation face, and should be far away from the left and right edges of the excavation face, and connected to the intersection line of the ground and the excavation face, so that when the excavation body is to be excavated, the excavation space after the excavation of the cutting area 1 can be taken as the center, and when the excavation is performed to other areas on the excavation face, the left and right sides and the upper area of ​​the excavation body can be operated at the same time, which can improve the construction efficiency; the contour modification area 2 is distributed along the contour line 5, and its formation area includes the contour line 5. When the contour modification area 2 is excavated and cut, the probability of under-excavation can be reduced, saving construction time and manpower; the other areas on the excavation face except the cutting area 1 and the contour modification area 2 are the expansion and fracturing areas 3.

[0108] Specifically, according to Figure 3 The small-section tunnel face partition and drilling schematic diagram shown in FIG. 1 is used to explain the body to be excavated in this embodiment as follows. The excavation face mentioned in this embodiment is Figure 3 The tunnel face in the tunnel: When the width of the tunnel face of the excavated body is not more than 8m and the height is not more than 6m, a cutting area 11 is set at the position of the center line of the tunnel face. The center line of the tunnel face refers to the midline that divides the tunnel face perpendicular to the ground. The cutting area 11 is used as a basis for excavation and excavation. The excavation space formed by the cutting area is continuously expanded by excavating the excavation holes layer by layer. Considering the construction efficiency and cost, the width of the cutting area 11 is set to 1m-1.5m and the height is set to 2m-3.5m.

[0109] Multiple rows or columns of cutting holes are drilled on the cutting area 11. To reduce the hardness of the hard rock (the body to be excavated), the cutting holes in two adjacent rows or columns are arranged alternately, and the net spacing of the cutting holes is 50mm-100mm. In order to prevent the cutting holes from crossing inside the excavation body and affecting the progress of the cyclic excavation during subsequent construction, the cutting holes should be orthogonal to the excavation surface.

[0110] The cutting area with cutting holes can be cut by milling equipment. The cutting head of the milling equipment breaks the cutting area with cutting holes to form an excavation space with a certain depth. The excavation space formed after cutting has a certain free surface. In the subsequent rock excavation, the adjacent holes of the excavation space are expanded and cracked to make it continuously expand, which can effectively improve the excavation efficiency.

[0111] The expansion drilling holes are arranged in the expansion zone 3 surrounding the cutting zone 11. The four layers of expansion drilling holes arranged from the inside to the outside along the cutting zone 11 on the expansion zone 3 are respectively the expansion drilling holes 31 layer, 32 layer, 33 layer and 34 layer. The row spacing between any two adjacent rows of expansion drilling holes is 50cm-100cm. Specifically, as Figure 3 The distance between each column of the fracturing drill holes in the 31st and 32nd layers in the vertical direction is 50cm, and the distance between each row in the horizontal direction is 100cm. The net spacing between two adjacent fracturing drill holes in each row or column is 100mm-300mm. Each fracturing drill hole is orthogonal to the excavation face to prevent intersection inside the excavation body.

[0112] In the fracturing zone 3, after the cutting zone 11 is hollowed out to form an excavation space, the fracturing borehole (31) of the layer closest to the cutting zone in the fracturing zone 3 is fractured. Since the hole spacing of the fracturing boreholes is less than the minimum fracturing resistance line, the hard rock of the excavation body after fracturing is cracked along the fracturing boreholes to form fracturing cracks, and the hard rock between the fracturing cracks of the 31st layer of fracturing boreholes and the free surface of the cutting zone 11 is peeled off, and then the hard rock between each layer of the fracturing boreholes and the excavation space is peeled off in turn.

[0113] In addition, considering the uneven spacing between the expansion holes in different layers, such as Figure 3As shown, a number of supplementary holes 41 are also arranged between the rows of fracturing boreholes with larger spacing in the upper row of the fracturing zone 3, which are used to achieve reliable stripping of the fracturing zone. The supplementary holes 41 are arranged between the cutting zone 11 and the row of the fracturing borehole 31 layer, the wider area between the fracturing borehole 31 layer and the fracturing borehole 32 layer, the fracturing borehole 32 layer and the fracturing borehole 33 layer, the fracturing borehole 33 layer and the fracturing borehole 34 layer, and the fracturing borehole 34 layer and the modified borehole 21. The supplementary holes 41 are flexibly arranged according to needs. It is necessary to arrange as many supplementary holes as possible to effectively reduce the hardness of the rock mass and ensure that the corresponding layer of fracturing boreholes can be effectively stripped. The construction cost and efficiency must also be considered. In this embodiment, the net spacing of the supplementary holes is set to 50mm-100mm, and is orthogonal to the excavation face and does not intersect with any other boreholes inside the excavation body.

[0114] In order to prevent under-excavation and ensure the flatness of the free surface of the tunnel after excavation, a contour modification area is also set up. The contour modification area is set along the contour line 5. Usually, in the actual excavation process, it appears as an annular area including the contour line 5. At least one layer of modified drill holes must be set in the contour modification area, so the width of the contour modification area is greater than the aperture of the modified drill holes.

[0115] The modified boreholes 21 on the contour modification area are arranged along the contour line 5, and the external interpolation angle with the contour line 5 is 3°-5°, that is, the modified boreholes 21 on the contour modification area are arranged along the contour line 5 in a direction away from the center of the excavation face (i.e., the intersection of the center line of the excavation face and the ground), and form an angle of 3°-5° with the axis of the body to be excavated (i.e., the vector line along the tunnel excavation direction). In order to set as many modified boreholes as possible, while taking into account the construction cost and efficiency, the net spacing of the modified boreholes 21 is set to 100mm. After the modified boreholes 21 are fractured, the free surface after the fracture is smoothed and modified. Specifically, the rock protrusions protruding from the free surface to a set height can be cut and corrected by cutting equipment to ensure the flatness.

[0116] The diameter of the drill hole is determined according to the drill bit diameter of the drilling equipment. The diameter of the cutting drill hole, modification drill hole, expansion drill hole and supplementary hole is generally 42mm-140mm. In order to improve the process connection and construction efficiency, the diameter of all the drill holes set on the excavation body mentioned in this embodiment is 89mm.

[0117] The depths of the cutting borehole, expansion borehole and supplementary hole are consistent, generally equal to the thickness of the body to be excavated. The depth of the modification borehole is greater than the depth of the cutting borehole. For example, the depth of the cutting borehole is 5m, and the depth of the modification borehole is 5.1m-5.3m.

[0118] Example 2 of the body to be excavated:

[0119] According to Figure 2The tunnel face partition diagram shown in FIG. 1 is used to illustrate the body to be excavated in this embodiment, that is, the excavation face of the body to be excavated is divided into the following sections: Figure 2 The tunnel face partition is designed in the following way. When the width of the excavation face of the excavated body is greater than 8m and the height is greater than 6.5m, it is set as follows.

[0120] Specifically, according to Figure 4 The large-section tunnel face division and drilling schematic diagram shown in FIG. 1 is used to explain the body to be excavated in this embodiment as follows. The excavation face mentioned in this embodiment is Figure 4 The tunnel face in: A cutting area is set on each side of the center line of the excavation face. The center line of the excavation face refers to the midline perpendicular to the ground that divides the excavation face into two halves. A cutting area 121 is set on the right side of the center line of the excavation face, and a cutting area 122 is set on the left side of the center line of the excavation face. When excavating, the excavation space formed by the cutting area is continuously expanded by excavating the excavation holes layer by layer based on the excavation area 121 and the excavation area 122. Considering the construction efficiency and cost, it is best to set the width of the cutting area 121 and the cutting area 122 to 1m-2.5m and the height to 2m-4.5m.

[0121] Multiple rows or columns of cutting drill holes are arranged on the cutting area 121 and the cutting area 122. To reduce the hardness of the hard rock (the body to be excavated), the cutting drill holes of two adjacent rows or columns are arranged alternately, and the net spacing between adjacent cutting drill holes is 50mm-100mm. In order to prevent the cutting drill holes from crossing inside the excavation body and affecting the progress of the cyclic excavation during the subsequent construction, the cutting drill holes should be orthogonal to the excavation surface.

[0122] The cutting areas 121 and 122 provided with cutting holes can be cut by milling equipment, and the cutting head of the milling equipment breaks the cutting area provided with cutting holes to form an excavation space with a certain depth. The excavation space formed after cutting has a certain free surface, and the boreholes adjacent to the excavation space are expanded and cracked during subsequent rock excavation to make it continuously expand, which can effectively improve the excavation efficiency.

[0123] The fracturing boreholes are arranged in the fracturing zone 3 surrounding the cutting zone 121 and the cutting zone 122. Four layers of fracturing boreholes are arranged on the fracturing zone from the center to the outside along the cutting zone 121 and the cutting zone 122. The fracturing boreholes arranged outward from the cutting zone 121 are 351 layers, 361 layers, 371 layers and 381 layers of fracturing boreholes respectively. The fracturing boreholes arranged outward from the cutting zone 122 are 352 layers, 362 layers, 372 layers and 382 layers of fracturing boreholes respectively. The 381-layer fracturing boreholes and the 382-layer fracturing boreholes overlap at the center line of the excavation face. The row spacing between any two adjacent rows of fracturing boreholes is 50cm-100cm, and the net spacing between each row of fracturing boreholes is 100mm-300mm. Each fracturing borehole is orthogonal to the excavation face to prevent intersection inside the excavation body and affect subsequent excavation and advancement.

[0124] In the fracturing zone 3, after the cutting zones 121 and 122 are hollowed out to form a fracturing free surface, the fracturing boreholes (351, 352) in the fracturing zone 3 that are closest to the cutting zone are fractured. Since the hole spacing of the fracturing boreholes is less than the minimum fracturing resistance line, the hard rock of the excavation body after fracturing extends along the fracturing boreholes to form fracturing cracks, and the hard rock between the fracturing cracks of the fracturing borehole 351 and the free surface of the cutting zone 121 is peeled off, and the hard rock between the fracturing cracks of the fracturing borehole 352 and the free surface of the cutting zone 122 is peeled off, and then the hard rock between each layer of the fracturing boreholes and the free surface is peeled off in turn.

[0125] In addition, considering the uneven spacing between the expansion holes in different layers, such as Figure 4 In the area where the row spacing between two rows of fracturing boreholes is large, in order to reliably fractur e and realize the stripping of hard rock in the fracturing zone, a number of supplementary holes 42 are further provided on the fracturing zone 3. The supplementary holes 42 are arranged in the wider area between the cutting zone 121 and the fracturing borehole 351 layer, the cutting zone 122 and the fracturing borehole 352 layer, the 351 layer and the 361 layer, the 361 layer and the 371 layer, the 371 layer and the 381 layer, the 352 layer and the 362 layer, the 362 layer and the 372 layer, the 372 layer and the 382 layer, the 381 layer and the modified borehole 22, and the 382 layer and the modified borehole 22. The supplementary holes 42 are flexibly arranged as needed. It is necessary to arrange as many supplementary holes as possible to ensure that the corresponding layer of fracturing boreholes can be effectively fractur e and stripped, and the construction cost and efficiency must also be considered. In this embodiment, the net spacing of the supplementary holes 42 is set to 50mm-100mm, and is orthogonal to the excavation face, and does not intersect with any other boreholes in the excavation body.

[0126] In order to prevent under-digging and ensure the flatness of the free face of the tunnel after excavation, a contour modification area is also set. The contour modification area is set along the contour line 5. Usually, in the actual construction process, it is a ring area including the contour line 5. The contour modification area must be set with at least one layer of modified boreholes, so the width of the contour modification area is greater than the aperture of the modified boreholes. After the modified boreholes 42 are expanded and fractured, the free face after expansion and fracture is flattened and modified. Specifically, the rock protrusions that protrude from the free face to a set value can be ground and corrected by cutting equipment to ensure flatness.

[0127] The modified boreholes 22 on the contour modification area are arranged along the contour line 5, and the external interpolation angle with the contour line 5 is 3°-5°, that is, the modified boreholes 22 on the contour modification area are arranged along the contour line 5 in a direction away from the center of the excavation face (i.e., the intersection of the center line of the excavation face and the ground), and form an angle of 3°-5° with the axis of the body to be excavated (i.e., the vector line along the tunnel excavation direction). In order to arrange as many modified boreholes as possible, while taking into account the construction cost and efficiency, the net spacing of the modified boreholes 22 is set to 100mm.

[0128] The diameter of the drill hole is determined according to the drill bit diameter of the drilling equipment. The diameter of the cutting drill hole, modification drill hole, expansion drill hole and supplementary hole is generally 42mm-140mm. In order to improve the process connection and construction efficiency, the diameter of all the drill holes set on the excavation body mentioned in this embodiment is 102mm.

[0129] The depths of the cutting borehole, expansion borehole and supplementary hole are consistent, generally equal to the thickness of the body to be excavated. The depth of the modification borehole is greater than the depth of the cutting borehole. For example, the depth of the cutting borehole is 5m, and the depth of the modification borehole is 5.1m-5.3m.

[0130] The present invention is used for excavation and advancement in hard rock tunnels. The use of the object to be excavated in the above embodiment can effectively reduce the hardness of the rock mass to be excavated, and equipment that can cut or drill holes in rock mass with lower hardness can be used for excavation and advancement, thereby reducing construction costs. At the same time, the diameters of the holes on the object to be excavated can be adjusted according to the drilling equipment, and the optimal number of holes can be further determined, thereby improving construction efficiency.

Claims

1. A mechanical excavation method for a hard rock tunnel, characterized in that: The steps include: 1) Zoning: Divide the face of the hard rock tunnel to be excavated into: A contour modification area, which is arranged along the contour edge of the tunnel face to be excavated and is used to form a structural contour of the tunnel face to be excavated; A cutting zone, which is arranged at the structural center of the face to be excavated or at a position close to the structural center, and is used to form a cutting excavation space by cutting operations through a mechanical cutting device, and the cutting excavation space creates an open surface for subsequent expansion and fracturing operations, and the cutting zone is rectangular; the cutting zone is arranged as a single one and is located at the spatial center of the face; or at least two cutting zones are arranged on the face to be excavated and are arranged symmetrically or evenly; there are cutting drill holes in the cutting zone; An expansion and fracturing zone, wherein the expansion and fracturing zone is located in a structural area between the contour modification zone and the cutting zone, and expansion and fracturing holes are arranged in the horizontal and vertical directions around the cutting zone for the expansion and fracturing operation of the tunnel face to be excavated; the expansion and fracturing zone also includes supplementary holes, which are arranged by a hard rock drilling device; 2) drilling holes, evenly distributing drill holes in the modification area, cutting area and fracturing area by means of a hard rock drilling device, wherein the drill hole spacing of the fracturing area drill holes is less than the minimum fracturing resistance line; the drill holes in the cutting area and the fracturing area are orthogonal to the face to be excavated, the drill holes in the modification area are drilled along the excavation contour line, forming an external insertion angle with the excavation contour line, and the depth of the drill holes in the modification area is greater than the depth of the drill holes in the fracturing area; 3) Rock cutting: using mechanical cutting devices to cut the rock in the cutting area to form cutting excavation space; 4) Rock mass fracturing: the fracturing device is used to perform fracturing in layers on the boreholes in the fracturing zone from the cutting zone toward the contour modification zone, so as to perform fracturing operations on the rock mass in the fracturing zone until the excavation of the rock mass in the fracturing zone is completed; 5) Contour correction: the modified area borehole is expanded and fractured by the expansion device, and then the modified area after the expansion and fracture operation is cut by the mechanical cutting device to form a smooth excavation contour surface structure; 6) Carry out support work on the hard rock tunnel after excavation; 7) Repeat the above steps 2) to 6) to perform cyclic operations on the face of the hard rock tunnel to be excavated until the excavation of the entire hard rock tunnel to be excavated is completed.

2. The mechanical excavation method for a hard rock tunnel according to claim 1, characterized in that: The hard rock drilling device includes a geological drill and a rock drilling rig; the fracturing device includes a wedge splitter, a rock fracturing device, and a hydraulic fracturing device.

3. The mechanical excavation method for a hard rock tunnel according to claim 1, characterized in that: The mechanical cutting device comprises: The equipment body is the bearing base of the mechanical cutting device; The cutting part is arranged at the front end of the equipment body, adopts carbide cutters or high-pressure water jets to break rocks, and is used for cutting operations of hard rocks.

4. The mechanical excavation method for a hard rock tunnel according to claim 3, characterized in that: The device body comprises: A walking part, which is arranged at the bottom of the equipment body and provides power for the free movement of the mechanical cutting device; A dust removal part, which is arranged on the equipment body and is used to clean the dust generated during the hard rock cutting process; The slag transportation part is arranged on the equipment body and is used for cleaning and transporting the slag after cutting the hard rock.

5. The mechanical excavation method for a hard rock tunnel according to any one of claims 1 to 4, characterized in that: The fracturing zone drill holes and the supplementary holes form a fracturing hole system combination, and the fracturing hole system combination is arranged in a matrix structure or arranged at equal intervals.

6. The mechanical excavation method for a hard rock tunnel according to claim 1, characterized in that: The cutting area drill holes are arranged in rows or columns in the cutting area, and the cutting area drill holes in two adjacent rows or columns are arranged in a staggered manner.

7. The mechanical excavation method for a hard rock tunnel according to claim 1, characterized in that: The external interpolation angle α formed by the drill hole in the modified area and the excavation contour line is 3°-5°.

8. The mechanical excavation method for a hard rock tunnel according to claim 7, characterized in that: The depth L′ of the drilling holes in the cutting area and the expansion area is n times the excavation footage L, n=1, 2, 3, 4,...; the drilling depth L" in the modification area satisfies the following conditions: n*L / cosα≤L"≤n*L / cosα+0.5, where n=1, 2, 3, 4,..., and α is 3°-5°.

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