Surrounding rock steel arch support construction method

Abstract

The invention relates to the technical field of railway tunnels, in particular to a surrounding rock steel arch support construction method, after a tunnel is excavated, a steel arch is annularly spliced and installed along the section of the tunnel, primary support is carried out, the steel arch is formed by splicing and connecting steel arch sections, and each steel arch section is composed of a profile steel arch section and a flexible expansion pipe; the section steel arch frame sections are circular-arc-shaped section steel arch frame sections with openings in the upper portions, the flexible expansion pipes are embedded in the circular-arc-shaped steel arch frame sections, the flexible expansion pipes are filled with filling materials, and the flexible expansion pipes are extruded through the filling materials till the flexible expansion pipes are tightly attached to the inner walls of the circular-arc-shaped section steel arch frame sections. A first buffer layer is further arranged between the flexible expansion pipe and the arc-shaped steel arch frame section, and the first buffer layer is an elastic rubber plate arranged on the inner side of the arc-shaped steel arch frame section. According to the method, the primary support is more stable and firmer, the supporting force is higher, certain toughness and buffering force are achieved, and on the basis that the supporting strength is guaranteed, the support is not prone to breakage.

Description

Technical Field

[0001] The invention relates to the technical field of railway tunnels, and in particular to a surrounding rock steel arch support construction method. Background Art

[0002] In the process of tunnel construction, it is inevitable to encounter a large number of soft rock formations, which have the characteristics of low rock strength, broken rock mass, and poor surrounding rock environment. At the same time, with the continuous expansion of my country's construction scale, the construction of three-lane and four-lane tunnels has become more extensive, and the tunnel excavation section has continued to expand. Some ultra-large section tunnels pass through soft rock formations, which require high initial support strength, bringing great challenges to the design and construction of tunnel support structure systems. Domestic and foreign countries are also actively exploring new initial support systems to meet the requirements of the bearing capacity of the support structure for ultra-large section tunnel construction under soft rock formation conditions; steel tube concrete has the advantages of high bearing capacity, good plasticity and toughness, and good economic benefits.

[0003] At present, the initial support system of ultra-large-section tunnels under the condition of large deformation of soft rock has the following problems: Under the condition of large deformation of soft rock, the initial support of the tunnel needs to be implemented in time, but the current construction process of the initial support of the tunnel is relatively cumbersome, and the timing of support is greatly affected by the construction capacity of the construction unit. It is necessary to provide a rapid construction method for large deformation of soft rock to ensure the timeliness of support. At present, steel tube concrete is widely used in port projects, bridges, and high-rise buildings, and the structural verification is relatively mature. However, in the application of tunnels, its structural verification lacks normative support, especially for the verification of this combined support structure, there is no relevant technical support.

[0004] The tunnel section of Xigu Tunnel of Lanzhou-Hefei Railway passes through a fault fracture zone, with a tunnel depth of 400m and a fracture zone width of 100-130m. The fracture zone is mainly composed of crushed rock. The construction of this section is affected by the depth of burial and the fracture fracture zone. The stress between underground rock and soil layers is large, the stability of the tunnel surrounding rock is poor, and the water inflow is large. During the construction and operation, geological disasters such as tunnel collapse, water inrush, and mud inrush are prone to occur. Therefore, it is more necessary to consider the stability of the support to ensure safety and avoid collapse accidents. Summary of the invention

[0005] In order to solve the problems and shortcomings existing in the prior art, the present invention provides a surrounding rock steel arch support construction method, which makes the initial support more stable and firm, has stronger supporting force, and has a certain toughness and a certain buffering force. On the basis of ensuring the supporting strength, it is not easy to break.

[0006] Specifically, the present invention provides a surrounding rock steel arch support construction method, comprising: after tunnel excavation, circumferentially splicing and installing steel arches along the tunnel section for initial support, the steel arches are formed by assembling and connecting steel arch segments, the steel arch segments are composed of profiled steel arch segments and flexible expansion tubes, the profiled steel arch segments are arc-shaped profiled steel arch segments with upper openings, the flexible expansion tubes are embedded in the arc-shaped steel arch segments, the flexible expansion tubes are filled with filling materials, the flexible expansion tubes are squeezed by the filling materials to make them close to the inner wall of the arc-shaped profiled steel arch segments, and a first buffer layer is also provided between the flexible expansion tube and the arc-shaped profiled steel arch segments, the first buffer layer is an elastic rubber plate provided on the inner side of the arc-shaped profiled steel arch segments; The support construction method steps are as follows: Step 1: excavate the current step; Step 2: Splice and install the steel arch frame segment, the flexible expansion tube and the first buffer layer corresponding to the current step to form a steel arch frame segment, and then fix the steel arch frame segment; Step 3: Inject filling material into the expansion hose.

[0007] Preferably, the flexible expansion tubes in adjacent steel arch segments are bonded together by adhesive, and a clamp connector is sleeved at each connection point of adjacent flexible expansion tubes.

[0008] Preferably, the initial support also includes spraying concrete on the tunnel surrounding rock after tunnel excavation, and then laying a steel mesh, with the steel mesh close to the concrete spraying surface. After the steel mesh is laid, re-spraying concrete, and then installing a steel arch frame, which is located on the side of the steel mesh away from the surrounding rock surface.

[0009] Preferably, the steel arch frame segments are assembled by bolt connection to form a steel arch frame.

[0010] Preferably, before tunnel excavation, advance geological prediction is carried out, the geological prediction results are analyzed, the locations where faults may occur are speculated, and the sections where faults may occur are verified.

[0011] Preferably, advance support is carried out after advanced geological forecast.

[0012] Preferably, after the advance support, excavation and initial support are carried out, and the tunnel excavation is carried out using the step method.

[0013] Preferably, a second buffer layer is laid under the steel arch frame.

[0014] Preferably, the second buffer layer is a high-density closed-cell rubber-plastic sponge board.

[0015] Preferably, after the second buffer layer is laid, secondary lining is carried out.

[0016] Compared with the prior art, the beneficial effect of the present invention is that after tunnel excavation, the steel arch frame is spliced ​​and installed along the tunnel section in an annular direction for initial support. The steel arch frame is assembled and connected by steel arch frame segments. Before installation, it is easy to transport and saves transportation costs. At the same time, a flexible expansion tube is embedded inside the steel arch frame segment, and the flexible expansion tube is filled with filling material. The flexible expansion tube is squeezed by the filling material to make it close to the inner wall of the arc-shaped steel arch frame segment. The overall quality of the structure can be lighter, further effectively improving transportation efficiency and reducing the labor intensity of workers. When in use, filler material is injected into the flexible expansion tube to improve the overall strength and pressure resistance and maintain the initial support stability; further, a first buffer layer is provided between the flexible expansion tube and the arc-shaped steel arch frame segment. The first buffer layer is an elastic rubber plate arranged on the inner side of the arc-shaped steel arch frame segment, which has certain strength and toughness. When the surrounding rock pressure is too large, it provides a certain buffer for the deformation of the steel arch frame, releases the surrounding rock pressure, and reduces the support pressure on the steel arch frame, so as to avoid the deformation and even fracture of the steel arch frame due to excessive pressure, and ensure the overall stability of the initial support. The support provided by the present invention has a greater bearing capacity and a safer and more reliable structure.

[0017] The surrounding rock steel arch support construction method of the present invention has simple construction technology and safer construction process. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Hereinafter, some specific embodiments of the present invention will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings: Figure 1 is a schematic diagram of the steel arch structure in Example 1 of the present invention; Figure 2 is a schematic diagram of the overall structure of a tunnel support according to Embodiment 1 of the present invention; Figure 3 Schematic diagram of the initial support structure according to Example 1 of the present invention.

[0019] In the figure: 1-initial support, 2-secondary lining, 3-middle pipe shed, 4-small guide tube, 5-primary sprayed concrete, 6-steel mesh, 7-re-sprayed concrete, 8-steel arch frame, 9-steel arch frame segment, 10-first buffer layer, 11-flexible expansion tube. DETAILED DESCRIPTION

[0020] Refer to the following Figure 1 to Figure 2To describe a surrounding rock steel arch support construction method of an embodiment of the present invention. In the description of this embodiment, it should be understood that the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features, that is, include one or more of the features. In the description of the present invention, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. When a feature "includes or contains" one or some of the features it covers, unless otherwise specifically described, this indicates that other features are not excluded and may further include other features.

[0021] In the description of the present embodiment, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0022] Figure 1 Schematic diagram of the internal structure of a steel arch frame according to an embodiment 1 of the present invention. Figure 1 As shown, combined with Figures 2 to 3 The present invention provides a surrounding rock steel arch support construction method, wherein after tunnel excavation, a steel arch is installed along the tunnel section in a circumferential direction for initial support 1, the steel arch is formed by assembling and connecting steel arch segments, the steel arch segments are composed of profiled steel arch segments 9 and flexible expansion tubes 11, the profiled steel arch segments are arc-shaped profiled steel arch segments with an upper opening, the flexible expansion tube is embedded in the arc-shaped steel arch, the flexible expansion tube is filled with filling material, the flexible expansion tube is squeezed by the filling material to make it close to the inner wall of the arc-shaped profiled steel arch segment, and a first buffer layer 10 is also provided between the flexible expansion tube and the arc-shaped profiled steel arch segment, the first buffer layer is an elastic rubber plate arranged on the inner side of the arc-shaped profiled steel arch segment.

[0023] The specific steps include: Step a: Since many faults in the earth's crust do not extend to the surface or are covered by the overburden, the number of faults revealed during tunnel excavation is often greater than the number found on the surface. Therefore, before tunnel excavation, geological surveys and geological sketches are used to determine the approximate mileage of the wide faults found in the survey stage, conduct advanced geological forecasts, analyze the geological forecast results, speculate the possible locations of faults, and verify the sections where faults may occur. There are six types of advanced geological forecasts: geological sketches, TSP, geological radar, transient electromagnetic, advanced impact drilling, and deepening blastholes. Detect the strength, integrity, and water-richness of the surrounding rock in front of the face, then observe the changes in the tunnel surrounding rock based on the face sketch, count the number of joint groups and their morphology, speculate the possible locations of faults in front, conduct horizontal drilling verification on the sections where faults may occur, and formulate corresponding treatment measures. Step b, after the advance geological forecast, advance support is carried out, and the advance support is carried out by the advance middle pipe shed 3 and the advance small guide tube 4; the pipe shed steel pipe adopts hot-rolled seamless steel pipe, and the steel pipe is divided into 6-meter and 3-meter sections. Both ends of each section of the steel pipe are pre-processed into external threaded buckles, and the pipe shed connecting steel pipe is processed into internal threaded buckles for mutual connection. The thread length is 15cm, and the direction is parallel to the line direction. The construction error of the steel pipe deviating from the design position is required to be no more than 20cm, and the number of joints in the same cross section along the longitudinal direction of the tunnel is no more than 50%, and adjacent joints should be staggered; In order to improve the bending resistance of the steel pipe, a steel cage is set inside the steel pipe. The steel cage consists of 4 main bars and a fixed ring. The diameter of the main bar is Φ18. The fixed ring uses short pipe sections with a length of 3 to 5 cm. It is welded to the main bar and set at a spacing of 1.5 m. In order to improve the rigidity, grouting is performed in the steel pipe of the pipe shed; the advance small conduit uses a hot-rolled seamless steel pipe with an outer diameter of Φ42 mm and a wall thickness of 3.5 mm. The front end of the steel pipe is made into a pointed cone shape, and a Φ6 reinforced hoop is welded at the tail to prevent the end from cracking and deformation when the small conduit is installed. A grouting stop section of no less than 100 cm is reserved at the tail as a non-drilled section; a drilling machine (drill bit diameter 6 to 8 mm) is used to drill 3 rows of grouting holes around the pipe wall, with a hole spacing of 10 to 20 cm, arranged in a plum blossom shape; the advance The tail end of the small conduit is sealed with a 6mm thick steel plate and welded with a Φ20mm galvanized pipe with a threaded end for connection with the joint valve. To ensure the safety of tunnel construction through the broken zone, a double-layer small conduit is used and grouting is used for advance support. The parameters are as follows: the arch is supported by a double-layer Φ42 small conduit. The length of the first layer of the small conduit is L=3.5m, the length of the second layer is L=4.0m, the circumferential spacing is 30cm, and the external insertion angles are staggered at 10~15° and 40° respectively. Step c, after the advance support, excavation and initial support are carried out. The tunnel excavation is carried out by the step method, and the specific steps are: upper step excavation → upper step arch initial support → lower step excavation → lower step side wall initial support → invert arch excavation and initial support; the specific process of the initial support is as follows: Step 1: excavate the upper step. The excavation depth of the arch section of the upper step is 1 steel arch frame; Step 2: spray concrete 5 on the surrounding rock surface of the arch in time after blasting, apply mortar anchor rods, and then lay steel mesh 6, the steel mesh is close to the concrete spraying surface 7, and then spray concrete again to reach the designed thickness; Step 3, splicing and installing the steel arch frame segment, the flexible expansion tube and the first buffer layer corresponding to the current step to form a steel arch frame segment, and then fixing and connecting the steel arch frame segment with bolts, and sealing and connecting the flexible expansion tube with an adhesive to form a steel arch frame 8; Step 3: inject filling material into the expansion hose to complete the initial support; Step d, after the initial support is completed, a second buffer layer is laid in the direction of the steel arch frame close to the road surface. The second buffer layer is a high-density closed-cell rubber-plastic sponge board; PF-HD200 high-density closed-cell rubber-plastic sponge board (PF-HD200 high-viscoelastic flexible board) has the three effects of buffering, heat preservation and waterproofing. It is mainly used in tunnels with low surrounding rock strength stress, initial support deformation and secondary lining cracking under strong structural extrusion. It can reduce the indirect contact pressure between the secondary lining and the primary support, make the secondary lining evenly stressed, prevent stress concentration, and protect the secondary lining structure from cracking; it also has the effects of heat preservation and waterproofing. At minus 20 degrees, the thermal conductivity is 0.0453w / mk, so in high-cold areas, it has a good heat preservation effect between the tunnel secondary lining and the support; Step e: After the second buffer layer is laid, secondary lining 2 is performed. Example

[0024] In this embodiment, the flexible expansion tubes in each two adjacent steel arch frame segments are bonded by adhesive to ensure the sealing effect. At the same time, a clamp connector is also provided at the connection of each adjacent flexible expansion tube to further ensure that the flexible expansion tube is tightly and firmly connected.

[0025] Example 1 The construction method is applied to the Xigu Tunnel of Lanzhou-Hefei Expressway, located in the Xigu to Liujiaxia section of Lanzhou City, Gansu Province. It is a double-hole single-track tunnel. The left and right line tunnels are repaired separately. The left line starts and ends at DK3+995~DK17+428, with a length of 13433m, and the right line starts and ends at DYK4+206~DYK17+255, with a length of 13049m; there are 4 inclined shafts in this section, of which No. 1 inclined shaft is 1539.09m with a slope of 10.47%; No. 2 inclined shaft is 1870.85m with a slope of 8.86%; No. 3 inclined shaft is 2971.25m with a slope of 9.68%; No. 4 inclined shaft is 3400.91m with a slope of 9.34%. The tunnel body crosses the fault obliquely in the line mileage DK4+465~DK4+595 (DYK4+625~DYK4+755) section. The broken belt of the fault is about 100~130m wide, and the material of the fault belt is mainly crushed rock. It is a high-angle normal fault. The strike is N65°W, the dip angle is 80°, the dip is north, and the extension length is more than 6km. The fault mainly occurs in the strata of the Lower Cretaceous System. According to the field geological survey of the seismic department, artificial shallow seismic exploration and the identification of age samples: the fault has shown signs of activity since the Holocene. It is a left-lateral strike-slip active fault with a length of 115km. According to the "Earthquake Safety Evaluation Report" of Lanhe Railway, the horizontal slip rate of the fault is 1.4~1.72mm / a. It is predicted that there may be sudden events in the next 100 years. The sudden dislocation amount H:2.6m and V:0.5m in the next 100 years is predicted.

[0026] The surrounding rock steel arch support construction method of Example 1 optimizes the construction process and organizes the construction reasonably, so that the deep mountain tunnel can quickly and safely pass through the broken zone strata. It adopts the excavation scheme of "advanced prediction, advanced support, step-by-step excavation, enhanced support, protection as excavation, intelligent information, and enhanced monitoring". The construction process is relatively safe, which can effectively reduce the settlement of the tunnel through the broken zone strata and better control the deformation of the surrounding rock. At the same time, it speeds up the construction progress and ensures the realization of the construction period goals. Compared with other construction methods, the method of this embodiment can save 2.2 months of construction time and 2 million yuan in costs. The steel arch segments are used for splicing, which saves transportation costs, facilitates transportation, and saves transportation costs. At the same time, a flexible expansion tube is embedded in the steel arch segment, and the flexible expansion tube is filled with filling material. The overall quality of the structure can be lighter, which can further effectively improve the transportation efficiency and reduce the labor intensity of workers. The first buffer layer is designed to provide a certain buffer for the deformation of the steel arch frame when the surrounding rock pressure is too large, release the surrounding rock pressure, reduce the support pressure on the steel arch frame, avoid the steel arch frame from deformation and even fracture due to excessive pressure, and ensure the overall stability of the initial support.

[0027] It can be seen that the surrounding rock steel arch support construction method provided by the present invention has obvious deformation control effect on deep buried tunnels passing through broken zones, and has good economic and social benefits.

[0028] At this point, those skilled in the art should recognize that, although the exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications that conform to the principles of the present invention can still be directly determined or derived based on the content disclosed in the present invention without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should be understood and identified as covering all these other variations or modifications.

Claims

1. A surrounding rock steel arch support construction method, characterized in that: After tunnel excavation, a steel arch frame is installed along the tunnel section in a circumferential direction for initial support. The steel arch frame is formed by assembling and connecting steel arch frame segments. The steel arch frame segments are composed of profiled steel arch frame segments and flexible expansion tubes. The profiled steel arch frame segments are arc-shaped profiled steel arch frame segments with an upper opening. The flexible expansion tube is embedded in the arc-shaped steel arch frame. The flexible expansion tube is filled with a filling material. The flexible expansion tube is squeezed by the filling material until it is in close contact with the inner wall of the arc-shaped profiled steel arch frame segment. A first buffer layer is also provided between the flexible expansion tube and the arc-shaped profiled steel arch frame segment. The first buffer layer is an elastic rubber plate provided on the inner side of the arc-shaped profiled steel arch frame segment. The support construction method steps are as follows: Step 1: excavate the current step; Step 2: Splice and install the steel arch frame segment, the flexible expansion tube and the first buffer layer corresponding to the current step to form a steel arch frame segment, and then fix the steel arch frame segment; Step 3: Inject filling material into the expansion hose.

2. The surrounding rock steel arch support construction method according to claim 1 is characterized in that: The flexible expansion tubes in adjacent steel arch frame segments are bonded together by adhesive, and a clamp connector is sleeved at each adjacent flexible expansion tube connection.

3. The surrounding rock steel arch support construction method according to claim 1 is characterized in that: The initial support also includes spraying concrete on the tunnel surrounding rock after tunnel excavation, and then laying a steel mesh, with the steel mesh close to the concrete spraying surface. After the steel mesh is laid, re-spraying concrete is carried out, and then a steel arch frame is installed. The steel arch frame is located on the side of the steel mesh away from the surrounding rock surface.

4. The surrounding rock steel arch support construction method according to claim 1 is characterized in that: The steel arch frame segments are connected and assembled by bolts to form a steel arch frame.

5. The surrounding rock steel arch support construction method according to claim 1 is characterized in that: Before tunnel excavation, advanced geological forecasting is carried out, the geological forecast results are analyzed, the locations where faults may occur are speculated, and the sections where faults may occur are verified.

6. The surrounding rock steel arch support construction method according to claim 5 is characterized in that: After advanced geological forecast, advance support is carried out.

7. The surrounding rock steel arch support construction method according to claim 6 is characterized in that: After advance support, excavation and initial support are carried out, and tunnel excavation is carried out using the step method.

8. The surrounding rock steel arch support construction method according to claim 1 is characterized in that: A second buffer layer is laid under the steel arch.

9. The surrounding rock steel arch support construction method according to claim 8, characterized in that: The second buffer layer is a high-density closed-cell rubber-plastic sponge board.

10. The surrounding rock steel arch support construction method according to claim 8, characterized in that: After the second buffer layer is laid, the secondary lining is carried out.

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