A multi-arch excavation method for super-large flat tunnel

Abstract

The invention provides a method for excavating a multi-arch of a super-large flat tunnel: the excavation section of the tunnel is divided into six parts, including an upper left pilot tunnel, a lower left pilot tunnel, an upper right pilot tunnel, a lower right pilot tunnel, an upper rock wall, and a lower rock wall; the first support part is the initial support of the left arch and the spray layer on the left side of the upper rock wall; the second support part is the initial support of the left side wall; the third support part is the initial support of the right arch and the spray layer on the right side of the upper rock wall; the fourth support part is the initial support of the right side wall; the fifth support part is the initial support of the arch; the sixth support part is the initial support of the invert arch; and the seventh support part is the secondary lining. The upper rock wall and the lower rock wall are combined into a vertical support structure to achieve the effect of reducing the span of the tunnel; based on the active support concept and using the idea of ​​"using cables instead of support", prestressed anchor cables are applied at the arch crown, arch waist and arch foot of the tunnel for tensioning and locking, so as to control the deformation of the surrounding rock, reduce the construction safety risk brought by excavating the upper rock wall, and play the role of supporting and reducing the span.

Description

Technical Field

[0001] The invention relates to the field of tunnel expansion blasting excavation in tunnels and underground structures, and in particular to a multi-arch excavation method for a super-large flat tunnel. Background Art

[0002] With the rapid development of my country's economy and the rapid advancement of urbanization, the demand for transportation is increasing, and the highway transportation capacity is becoming increasingly saturated. The construction of super-large cross-section highway tunnels is imminent. In the construction of super-large cross-section highway tunnels, there are often problems such as large span, unfavorable stress redistribution, and flattened cross-section. At the same time, the compressive stress at the arch foot of the tunnel is concentrated, which requires high bearing capacity of the foundation, and the overlying rock mass will produce a large loose load. The larger the span and height of the tunnel, the greater the buried depth required to form a collapse arch, and the self-stability of the surrounding rock is poor. Its construction method is often a traditional partial excavation method such as the double side wall pilot method, CD method (middle partition wall method) and CRD method (cross middle partition wall method). Its process is complicated, the construction efficiency is low, and the economic cost is high. Therefore, it is particularly important to seek an economical and efficient construction method under the premise of ensuring construction safety. Summary of the invention

[0003] The purpose of the present invention is to overcome the defects of the prior art and provide a method for excavating a super-large flat tunnel with multiple arches, which greatly ensures the safety of construction, speeds up the construction progress, and has obvious economic benefits. The present invention at least solves some of the problems in the prior art.

[0004] The present invention is achieved in that:

[0005] The present invention provides a multi-arch excavation method for a super-large flat tunnel: the excavation section of the tunnel is divided into six parts, including a left upper pilot tunnel as a first excavation part, a left lower pilot tunnel as a second excavation part, a right upper pilot tunnel as a third excavation part, a right lower pilot tunnel as a fourth excavation part, an upper rock wall as a fifth excavation part, and a lower rock wall as a sixth excavation part; the first excavation part, the second excavation part, the third excavation part, the fourth excavation part, the fifth excavation part, and the sixth excavation part are excavated in sequence; the support system of the tunnel includes a first support part, a second support part, a third support part, a fourth support part, and a fifth support part. The first supporting section is the initial support for the left arch corresponding to the first excavation section and the sprayed layer on the left side of the upper rock wall. The second supporting section is the initial support for the left side wall corresponding to the second excavation section. The third supporting section is the initial support for the right arch corresponding to the third excavation section and the sprayed layer on the right side of the upper rock wall. The fourth supporting section is the initial support for the right side wall corresponding to the fourth excavation section. The fifth supporting section is the initial support for the arch top corresponding to the fifth excavation section. The sixth supporting section is the initial support for the invert corresponding to the sixth excavation section. The seventh supporting section is the secondary lining.

[0006] Furthermore, the multi-arch excavation method of the super-large flat tunnel specifically includes the following steps:

[0007] S1. Excavate the first excavation part, then perform initial support on the first support part and perform spraying on the left side of the upper rock wall;

[0008] S2. Prestressed anchor cables are installed at the arch crown, left arch waist and left arch foot;

[0009] S3, excavating the second excavation part, and then performing initial support on the second support part;

[0010] S4, excavate the third excavation part, then perform initial support on the third support part and perform spraying on the right side of the upper rock wall;

[0011] S5. Apply prestressed anchor cables at the right arch waist and right arch foot;

[0012] S6, excavating the fourth excavation part, and then performing initial support on the fourth support part. At this time, the fifth excavation part and the sixth excavation part are combined to form an integral vertical support structure;

[0013] S7, excavating the fifth excavation part, and then performing initial support on the fifth support part;

[0014] S8, excavating the sixth excavation part, and then performing initial support on the sixth support part;

[0015] S9. When the time and conditions for the construction of the secondary lining are met, the seventh support section shall be supported, that is, the waterproof layer shall be laid on the entire section and the secondary lining of the tunnel shall be constructed, and the invert filling layer shall be constructed above the bottom of the secondary lining.

[0016] Furthermore, before tunnel excavation in step S1, geological survey and advanced geological forecast are first carried out to determine whether to carry out advanced support according to the surrounding rock conditions.

[0017] Furthermore, the advance support adopts an advance large pipe rack or an advance grouting small pipe.

[0018] Furthermore, after the completion of steps S1 to S8, support inspection and monitoring measurement are carried out. If the deformation value meets the construction requirements, the next cycle of excavation and support construction is carried out.

[0019] Furthermore, smooth blasting, pre-splitting blasting or micro-seismic blasting is used during excavation.

[0020] Furthermore, the length of the prestressed anchor cables at the arch top is greater than the length of the prestressed anchor cables at other locations.

[0021] Furthermore, the ratio of the excavation areas of the first excavation part, the second excavation part, the third excavation part, the fourth excavation part, the fifth excavation part and the sixth excavation part is 2.8:1:2.8:1:0.8:3.0.

[0022] Furthermore, during the entire excavation process, the second excavation part lags behind the first excavation part, the third excavation part lags behind the second excavation part, the fourth excavation part lags behind the third excavation part, the fifth excavation part lags behind the fourth excavation part, and the sixth excavation part lags behind the fifth excavation part.

[0023] Further, the second excavation portion lags behind the first excavation portion by 10 m, the third excavation portion lags behind the second excavation portion by 2 m, the fourth excavation portion lags behind the third excavation portion by 10 m, the fifth excavation portion lags behind the fourth excavation portion by 4 m, and the sixth excavation portion lags behind the fifth excavation portion by 4 m.

[0024] The present invention has the following beneficial effects:

[0025] The present invention provides a method for excavating a multi-arch tunnel of an ultra-large flat tunnel, which makes full use of the bearing capacity of the hard rock mass. The upper rock wall and the lower rock wall are combined into a vertical support structure to achieve the effect of reducing the tunnel span, greatly reducing the excavation process and the construction and removal of temporary supports in traditional partial excavation construction. At the same time, based on the concept of active support and utilizing the idea of ​​"using cables instead of supports", prestressed anchor cables are applied at the arch crown, arch waist and arch foot of the tunnel for tensioning and locking, so as to control the deformation of the surrounding rock, reduce the construction safety risk brought by the excavation of the upper rock wall, and play the role of support and span reduction.

[0026] During the entire excavation process, the second excavation part is kept lagging behind the first excavation part, the third excavation part is kept lagging behind the second excavation part, the fourth excavation part is kept lagging behind the third excavation part, the fifth excavation part is kept lagging behind the fourth excavation part, and the sixth excavation part is kept lagging behind the fifth excavation part. The present invention provides an effective construction method for a super-large flat tunnel, greatly ensures the safety of construction, speeds up the construction progress, and has obvious economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 A front view of the excavation construction provided by the embodiment of the present invention;

[0029] Figure 2 A side view of excavation construction provided by an embodiment of the present invention;

[0030] Figure 3 A plan view of excavation construction provided by an embodiment of the present invention;

[0031] Figure 4 A flow chart of excavation construction provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] like Figure 1-Figure 4 The embodiment of the present invention provides a method for excavating a continuous arch of an ultra-large flat tunnel, in which an upper rock wall (i.e., the fifth excavation part 5) and a lower rock wall (i.e., the sixth excavation part 6) at the middle position of the tunnel are combined into an integral vertical support structure to achieve the purpose of reducing the tunnel excavation span. Based on the active support concept, prestressed anchor cables 7 are applied at the arch crown, arch waist and arch foot positions for tensioning and locking to control the deformation of the surrounding rock and reduce the construction safety risk caused by excavating the upper rock wall. The method is particularly suitable for the construction of ultra-large flat tunnels, greatly reduces the construction risk, reduces the application and removal of temporary supports, speeds up the construction progress, reduces the project investment, and has obvious economic benefits.

[0034] A method for excavating a super-large flat tunnel with multiple arches, specifically comprising the following steps:

[0035] Step 1: Figure 1 , the excavation section of the tunnel is set as follows: the upper left pilot tunnel is the first excavation part 1, the lower left pilot tunnel is the second excavation part 2, and the upper left pilot tunnel and the lower left pilot tunnel constitute the left excavation part; the upper right pilot tunnel is the third excavation part 3, the lower right pilot tunnel is the fourth excavation part 4, the upper right pilot tunnel and the lower right pilot tunnel constitute the right excavation part, the upper rock wall is the fifth excavation part 5, and the lower rock wall is the sixth excavation part 6;

[0036] The support system of the tunnel includes a first support part 101, a second support part 102, a third support part 103, a fourth support part 104, a fifth support part 105, a sixth support part 106, and a seventh support part 107, wherein the first support part 101 is the initial support 8 of the left arch corresponding to the first excavation part 1 and the spray layer 12 on the left side of the upper rock wall, the second support part 102 is the initial support 8 of the left side wall corresponding to the second excavation part 2, the third support part 103 is the initial support 8 of the right arch corresponding to the third excavation part 3 and the spray layer 13 on the right side of the upper rock wall, the fourth support part 104 is the initial support 8 of the right side wall corresponding to the fourth excavation part 4, the fifth support part 105 is the initial support 8 of the arch corresponding to the fifth excavation part 5, the sixth support part 106 is the initial support 8 of the invert corresponding to the sixth excavation part 6, and the seventh support part 107 is the secondary lining;

[0037] Step 2: excavate the first excavation part 1, and then perform initial support 8 on the first support part 101 and apply the left spraying layer 12 of the upper rock wall;

[0038] Step 3: Apply prestressed anchor cables 7 at the arch crown, left arch waist and left arch foot;

[0039] Step 4: excavating the second excavation portion 2, and then performing initial support 8 on the second support portion 102;

[0040] Step 5: excavate the third excavation part 3, and then perform initial support 8 on the third support part 103 and apply the spray layer 13 on the right side of the upper rock wall;

[0041] Step 6: Apply prestressed anchor cables 7 at the right arch waist and right arch foot;

[0042] Step 7: excavate the fourth excavation part 4, and then perform initial support 8 on the fourth support part 104. At this time, the fifth excavation part 5 and the sixth excavation part 6 are combined to form an integral vertical support structure to achieve the effect of reducing the span, so as to control the deformation of the surrounding rock and ensure the safety of construction;

[0043] Step 8: excavating the fifth excavation portion 5, and then performing initial support 8 on the fifth support portion;

[0044] Step 9: excavating the sixth excavation portion 6, and then performing initial support 8 on the sixth support portion;

[0045] Step 10: When the time and conditions for secondary lining construction are met, the seventh support section 107 is supported, i.e., the waterproof layer and the secondary lining of the tunnel are laid on the entire section, and the invert filling layer 10 is constructed above the bottom of the secondary lining 9. The waterproof layer is provided between the initial support 8 and the secondary lining 9, and the initial support 8, the waterproof layer, and the secondary lining 9 are all laid on the entire section.

[0046] The initial support 8 adopts a double-layer structure, including a first layer of initial support, a second layer of initial support, and also includes a system anchor rod arranged in the arch wall of the tunnel. The first layer of initial support includes a steel frame and a steel mesh, and the second layer of initial support includes a grating steel frame and a steel mesh. The steel frame, grating steel frame and steel mesh are all arranged in the shotcrete. The first layer of initial support and the second layer of initial support both provide full-section support for the tunnel. Along the longitudinal direction of the tunnel, two adjacent steel frames are fastened together by multiple longitudinal connecting steel bars.

[0047] The tunnel support system also includes the left arch foot locking anchor pipe and the right arch foot locking anchor pipe, both of which are 3 to 5 meters higher than the top of the tunnel invert filling layer.

[0048] During the entire excavation process, the second excavation part 2 lags behind the first excavation part 1, the third excavation part 3 lags behind the second excavation part 2, the fourth excavation part 4 lags behind the third excavation part 3, the fifth excavation part 5 lags behind the fourth excavation part 4, and the sixth excavation part 6 lags behind the fifth excavation part 5.

[0049] Furthermore, in this embodiment, the second excavation portion lags behind the first excavation portion by 10 m, the third excavation portion lags behind the second excavation portion by 2 m, the fourth excavation portion lags behind the third excavation portion by 10 m, the fifth excavation portion lags behind the fourth excavation portion by 4 m, and the sixth excavation portion lags behind the fifth excavation portion by 4 m.

[0050] Further, such as Figure 1 The width of the vertical rock column in the upper rock wall is 2.0m.

[0051] Furthermore, based on the concept of active support and using the idea of ​​"using cables instead of supports", prestressed anchor cables 7 are installed at the tunnel arch crown, arch waist and arch foot for tensioning and locking to control the deformation of the surrounding rock, while reducing the construction safety risks brought by the excavation of the upper rock wall, thereby achieving the functions of support and span reduction.

[0052] Furthermore, the excavation section and the longitudinal spacing of each excavation part should be maintained, the excavation contour line should be smooth, and stress concentration should be avoided. Controlled blasting technology should be adopted, such as smooth blasting, pre-splitting blasting or micro-seismic blasting.

[0053] Furthermore, the length of the prestressed anchor cable 7 at the arch top is 12 m, and the length of the prestressed anchor cables 7 at other locations is 10 m, and the prestressing values ​​are all 1000 kN.

[0054] Furthermore, the construction steps of the prestressed anchor cable are initial tensioning, secondary compensating tensioning and locking, and sealing grouting.

[0055] Furthermore, according to the surrounding rock conditions, advance support can be carried out before tunnel excavation. Advance support can choose technologies such as advance large pipe shed or advance grouting.

[0056] Furthermore, the ratio of the excavation areas of the first to sixth excavation parts is approximately 2.8:1:2.8:1:0.8:3.0.

[0057] Furthermore, the multi-arch excavation method for a super-large flat tunnel provided by the present invention is suitable for excavating flat tunnels with a larger cross-section, and the surrounding rock is grade III or IV hard rock.

[0058] The present invention is used for the excavation and construction of super-large flat tunnels in tunnels and underground structures. First, geological surveys and advanced geological forecasts are carried out. Whether to carry out advanced support is determined according to the surrounding rock conditions. Then, excavation and support are carried out in sequence. The upper rock wall and the lower rock wall are combined into an integral vertical support structure in the middle position of the tunnel to achieve the effect of reducing the span. Based on the active support concept and the idea of ​​"using cables instead of supports", prestressed anchor cables are applied at the arch crown, arch waist and arch foot for tensioning and locking, so as to control the deformation of the surrounding rock and reduce the construction safety risks brought by excavating the upper rock wall.

[0059] Implementation method:

[0060] 1) If Figure 1 As shown, the cross section of the tunnel is divided into 6 parts, which are described as Part 1 - upper left pilot tunnel (first excavation part 1), Part 2 - lower left pilot tunnel (second excavation part 2), Part 3 - upper right pilot tunnel (third excavation part 3), Part 4 - lower right pilot tunnel (fourth excavation part 4), Part 5 - upper rock wall (fifth excavation part 5), and Part 6 - lower rock wall (sixth excavation part 6), which are excavated in numerical order.

[0061] 2) If Figure 1 As shown, corresponding to the excavated sections, the initial support is divided into Section I (first supporting section 101), Section II (second supporting section 102), Section III (third supporting section 103), Section IV (fourth supporting section 104), Section V (fifth supporting section 105), and Section VI (sixth supporting section 106), and the secondary lining is Section VII (seventh supporting section 107).

[0062] Figure 3 In the embodiment, a plurality of trestles 11 are arranged between the invert filling layer 10 and the cross section of the sixth excavation part 6 .

[0063] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for excavating a multi-arch of a super-large flat tunnel, characterized in that: The excavation section of the tunnel is divided into six parts, including the upper left pilot tunnel as the first excavation part, the lower left pilot tunnel as the second excavation part, the upper right pilot tunnel as the third excavation part, the lower right pilot tunnel as the fourth excavation part, the upper rock wall as the fifth excavation part, and the lower rock wall as the sixth excavation part. The first excavation part, the second excavation part, the third excavation part, the fourth excavation part, the fifth excavation part, and the sixth excavation part are excavated in sequence. The support system of the tunnel includes the first support part, the second support part, the third support part, the fourth support part, the fifth support part, and the sixth support part. The first supporting part is the initial support of the left arch corresponding to the first excavation part and the sprayed layer on the left side of the upper rock wall, the second supporting part is the initial support of the left side wall corresponding to the second excavation part, the third supporting part is the initial support of the right arch corresponding to the third excavation part and the sprayed layer on the right side of the upper rock wall, the fourth supporting part is the initial support of the right side wall corresponding to the fourth excavation part, the fifth supporting part is the initial support of the arch corresponding to the fifth excavation part, the sixth supporting part is the initial support of the inverted arch corresponding to the sixth excavation part, and the seventh supporting part is the secondary lining; The multi-arch excavation method of a super-large flat tunnel includes the following steps: S1. Excavate the first excavation part, then perform initial support on the first support part and perform spraying on the left side of the upper rock wall; S2. Prestressed anchor cables are installed at the arch crown, left arch waist and left arch foot; S3, excavating the second excavation part, and then performing initial support on the second support part; S4, excavate the third excavation part, then perform initial support on the third support part and perform spraying on the right side of the upper rock wall; S5. Apply prestressed anchor cables at the right arch waist and right arch foot; S6, excavating the fourth excavation part, and then performing initial support on the fourth support part. At this time, the fifth excavation part and the sixth excavation part are combined to form an integral vertical support structure to achieve the effect of reducing the span, so as to control the deformation of the surrounding rock and ensure the safety of construction; S7, excavating the fifth excavation part, and then performing initial support on the fifth support part; S8, excavating the sixth excavation part, and then performing initial support on the sixth support part; S9. When the time and conditions for secondary lining construction are met, the seventh support section is supported, i.e. the waterproof layer is laid on the entire section and the secondary lining of the tunnel is constructed, and the invert filling layer is constructed above the bottom of the secondary lining; During the entire excavation process, the second excavation portion is kept lagging behind the first excavation portion, the third excavation portion is kept lagging behind the second excavation portion, the fourth excavation portion is kept lagging behind the third excavation portion, the fifth excavation portion is kept lagging behind the fourth excavation portion, and the sixth excavation portion is kept lagging behind the fifth excavation portion; The multi-arch excavation method of the super-large flat tunnel combines the fifth excavation part and the sixth excavation part at the middle position of the tunnel into an integral vertical support structure to achieve the purpose of reducing the tunnel excavation span.

2. The method for excavating a super-large flat tunnel by multiple arches according to claim 1, characterized in that: In step S1, before tunnel excavation, geological survey and advanced geological forecast are first carried out to determine whether to carry out advanced support according to the surrounding rock conditions.

3. The method for excavating a super-large flat tunnel by multiple arches according to claim 2, characterized in that: Advance support uses advance large pipe racks or advance grouting small pipes.

4. The method for excavating a super-large flat tunnel by multiple arches according to claim 1, characterized in that: After the completion of steps S1 to S8, support inspection and monitoring measurement are carried out. If the deformation value meets the construction requirements, the next cycle of excavation and support construction is carried out.

5. The method for excavating a super-large flat tunnel with multiple arches according to claim 1, characterized in that: Smooth blasting, pre-splitting blasting or micro-seismic blasting are used during excavation.

6. The multi-arch excavation method for a super-large flat tunnel according to claim 1, characterized in that: The length of the prestressed anchor cables at the arch top is greater than that at other locations.

7. The multi-arch excavation method for a super-large flat tunnel according to claim 1, characterized in that: The ratio of the excavation areas of the first excavation part, the second excavation part, the third excavation part, the fourth excavation part, the fifth excavation part and the sixth excavation part is 2.8:1:2.8:1:0.8:3.

0.

8. The multi-arch excavation method for a super-large flat tunnel according to claim 1, characterized in that: The second excavation part lags behind the first excavation part by 10 m, the third excavation part lags behind the second excavation part by 2 m, the fourth excavation part lags behind the third excavation part by 10 m, the fifth excavation part lags behind the fourth excavation part by 4 m, and the sixth excavation part lags behind the fifth excavation part by 4 m.

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