JP7257086B2 - Comprehensive Construction Method for Low Overburden Sections of Tunnels - Google Patents

Description

TECHNICAL FIELD The present invention relates to the field of construction technology for tunnel construction, and more particularly to a comprehensive construction method for low-overburden sections of tunnels .

At present, during the construction of tunnel construction in our country, the process, technology and construction methods are all mature and perfect. Due to the uncertainty and unpredictability of various factors such as stratum lithology, geological structure, and groundwater distribution during tunnel construction, there is no construction experience that can be referred to when encountering special geology and topography during the construction process.

In particular, during the construction process of the low overburden section, the actual minimum overburden at the site is shallow, the surrounding rock is strongly weathered tuff, the design is evaluated as V grade surrounding rock, and the surface layer is silty mixed with crushed stone with a thickness of 3 to 4 m. Due to the clay covering layer and relatively abundant surface water during the rainy season, problems such as rock collapses were likely to occur, and the safety of construction work in the low overburden section of the tunnel could not be guaranteed.

An object of the present invention is to overcome the above-mentioned problems in the prior art, and to provide a method suitable for tunnel construction in low-overburden sections with abundant surface water and poor surrounding rock properties. .

The present invention presents the following technical means in order to achieve the above object.

This is a comprehensive construction method for the low overburden section of the tunnel , in which grout is injected to the ground surface in the low overburden section of the tunnel. is laid, concrete is placed on the surface of the water stop plate to block the infiltration of surface water, step S1, in the ground where the tunnel is drilled according to the design drawing, a plurality of marked coordinates are formed in an arch shape surrounding the tunnel Marking is performed so as to line up , and drilling is performed by a drill machine so as to gradually separate from the outer peripheral surface of the tunnel as it goes in the drilling direction of the tunnel at the plurality of marking coordinates, and after completion of drilling, the inside of the hole is cleaned. Step S2 of pushing the pipe roof into the drilled hole, attaching a grout stop valve to the pipe roof, closing the cracks in the drilled hole and its surroundings with a fixing agent, grouting the pipe roof through a grout injector , and extending the length of the pipe roof is made in one cycle for 10 m, the length of the pipe roof joint in one cycle is 3 m or more, and the end of each section steel pipe used for the pipe roof is pre-cut to a length of 50 mm, and the connecting steel pipe uses seamless steel pipes with a length of 300 mm and an outer diameter of 95 mm, a step S3 in which threads are cut within the entire length of the connecting steel pipe, and the upper level is excavated. After spraying, centering is installed as a support, and after the shoring is completed, spraying is carried out again to the thickness specified in the design. Install a temporary steel frame at the excavation site, connect adjacent steel frames with reinforcing bars, excavate the middle stage, excavate one side of the tunnel cross section, and proceed with excavation while keeping a certain distance , Immediately after the excavation on either side is completed, the centering is added to the legs of the upper centering. Concrete is sprayed again, and after the erection of the legs on both sides is completed, a temporary steel frame is installed on the excavated site as a temporary invert. excavate one side of the tunnel section, keep a certain distance on both sides of the tunnel cross section during excavation, and after excavation on either side is completed, immediately add centering to the centering leg, and The tunnel will be excavated using a 3-stage bench cut method with temporary inverts, including placing anchor bolts after the erection is complete and concrete will be sprayed again to the design thickness, and the primary support will be installed for the excavation. A comprehensive construction method for a low-overburden section of a tunnel, including step S4.

Regarding the tunnel's low overburden, alternating layers of crushed rock around it, and abundant surface water, the underground excavation of the tunnel uses a three-step bench cut method with a temporary invert, which greatly guarantees the safety of excavation and Through pipe roof support and pre-grout excavation auxiliary construction method, we realize safe excavation, improve quality and efficiency, solve construction safety hazards in the low overburden section of the tunnel, and prevent tunnel collapse accidents. reduce the chances.

By using the 3-step bench cut method with temporary invert during the excavation process, the disturbance of the surrounding rock mass is greatly reduced, and the whole shoring system is connected through the temporary invert shoring structure, making it more stable. do.

It is a front layout drawing of a pipe roof. 1 is a schematic diagram showing a pipe roof casting; FIG. It is a vertical cross-sectional view of the construction order of the three-stage bench cut construction method with temporary invert. It is a cross-sectional view of the construction order of the three-step bench cut construction method with temporary invert. It is a centering development view. FIG. 10 is a schematic diagram showing centering replenishment;

The purpose of the present invention is to provide a comprehensive construction method for the low overburden section of a tunnel by the regional railway mining method in order to guarantee the safety of the construction process. It is used in the construction of the overburden section tunnel 1 and greatly reduces the disturbance to the surrounding rock during the construction process.

1 to 6, the construction method provided by the present invention includes the following steps.

Step S1: Inject grout to the ground surface in the low overburden section of Tunnel 1, and reinforce the ground surface by the ground grout injection method. , the ground surface is gradually reinforced on both sides according to the cross-sectional width range of the tunnel 1.

Step S2: Marking according to the design drawing, drilling according to the marking coordinates with a drill machine, cleaning the hole after drilling is completed, and pushing the pipe roof into the drilled hole; After the construction of the pipe roof 2, the surveyor marks according to the design drawing and numbers each empty space. Clean any residue in the holes. The diameter of the drilling hole is 3-5mm larger than the diameter of the steel pipe, and a total of 46 holes are drilled in the pipe roof 2, the pipe interval in the circumferential direction is 40cm, and the outer angle of the drilling inclination angle is 12° or less. Specifically, it can be adjusted according to the actual situation. Construction error of steel pipes: 20 cm or less in the radial direction and 10 cm or less in the circumferential direction between adjacent steel pipes. After the drilled hole has been cleaned, it is pushed in with a hammer or down-the-hole drill, and the length of pushing is more than 95% of the length of the steel pipe, and the gravel inside the steel pipe is blown off with a high-pressure air hose.

Step S3: Install a grout stop valve on the pipe roof 2, close the drilled hole and the cracks around it with a fixing agent, grout the pipe roof 2 through a grouting machine, install the pipe roof 2, and then install the fixing agent. close the cracks in the hole mouth and surroundings, spray concrete near the pipe roof 2 and the face as necessary to prevent face collapse, install a grout stop valve, and ensure the smoothness of the grout stop valve.

Step S4: The tunnel 1 is excavated using a three-step bench cut construction method with a temporary invert, and primary support is constructed for the excavated portion.

In another alternative embodiment of the present application, in step S4, the triple bench cut construction method with temporary inversion includes the following steps.

The upper stage 1.1 is excavated, and after the excavation of the upper stage 1.1 is completed, concrete is first sprayed on the surrounding rock surface of the excavated portion, and the centering 3 is erected as a support. After the excavation of the bench is completed, the primary support is immediately applied to the pit corresponding to the upper level 1.1, and the primary shotcrete is sprayed with c25 concrete on the surrounding rock surface after excavation. A concrete layer 5 was formed, the thickness of the spraying was 4 cm, and after the completion of the shoring, it was sprayed again to the thickness specified in the design, and the spraying method was the wet spraying method. The centering 3 is erected, and the centering 3 uses I18 type rigid steel frame as a support, and the distance between the centerings 3 is 0.6m. As shown in FIGS. 3 to 5, the installation arrangement of the centering 3 uses seamless steel pipes of φ42 mm and L = 4.0 m on each side of the centering 3 as locking anchor pipes, and two centering pipes on each side. 3, after driving the anchor pipe, the reinforcing bar 9 is welded tightly to the centering 3, the model number of the reinforcing bar is Φ22U type screw thread, and the adjacent steel frames are connected with the reinforcing bar 9, and the rigid steel frame is 4 cm thick. 25 Concrete is erected after primary spraying, and after erection, concrete is sprayed again to the design thickness to form a secondary sprayed concrete layer 4 . The arch portion of the surrounding bedrock is fixed by anchor bolts 6, which are hollow anchor bolts of 4 m in length and Φ22. For the side walls, Φ22 mortar anchor bolts with a length of 4 m are used, and the interval between the anchor bolts 6 is 1.2 m × 1.0 m in the vertical direction of the outer circumference. A steel frame is installed as a temporary invert, and after the installation is completed, c25 concrete with a thickness of 10 cm is sprayed on the bottom to close it.

Excavate the middle section 1.2, excavate one side of the tunnel 1 cross section, proceed with excavation with a certain distance on both sides of the tunnel 1 section when excavating, and immediately after excavation on either side is completed, the upper section 1.2. The centering is added to the centering leg of 1 by the centering adder 3.1, and after the erection of the leg is completed, anchor bolts 6 are driven in, and concrete is sprayed again to the design thickness on both sides of the excavated part. After the erection of the legs on both sides is completed, a temporary steel frame is installed on the excavated site as a temporary invert, and after the installation is completed, concrete is sprayed and closed. Here, the excavation distance on both sides is 2 to 3 m apart, and immediately after the excavation on one side is completed, the leg of the upper stage 1.1 is added to the centering by the centering extension part 3.1, and the centering 3 on both sides is completed. After that, I16 temporary steel frames with an interval of 0.6m are installed as temporary inverts on the excavation site, and the temporary steel frames are connected to the main body of the centering 3. Spray c25 concrete to block.

Excavate the lower stage 1.3, excavate one side of the tunnel 1 cross section, keep a certain distance on both sides of the tunnel 1 cross section when excavating, and immediately after the excavation of either side is completed, the centering 3 The legs are centered by means of a centering joint 3.1, and after the erection of the legs is completed, the anchor bolts are driven in and the concrete is sprayed again to the design thickness.

The excavation distance on both sides is 2 to 3m, and immediately after the excavation on one side is completed, the leg of the upper stage 1.1 is added to the centering by the centering addition part 3.1, and the joint part is two pieces of 16mm thickness. The steel plates are butted against each other, a 3mm-thick rubber floor plate is sandwiched between the steel plates, the steel plates are joined with M27 bolts and nuts, and the rigid steel frame is fully welded to the steel plates. After erecting the steel frame, anchor bolts 6 are placed, and shotcrete of c25 concrete is shot again to the design thickness.

In this example, the spacing of the shorings of the excavation length per excavation cycle of the upper stage 1.1 should not exceed the spacing of one centering 3. The spacing of the shoring of the excavation length per excavation cycle of the middle stage 1.2 should not exceed the spacing of the two centerings 3. The spacing of the shoring of the excavation length per excavation cycle of the lower stage 1.3 should not exceed the spacing of the two centerings 3. The distance between each centering 3 is 0.6 m.

In another alternative embodiment of the present application, the joint where the leg is centered by the centering joint 3.1 consists of two 16 mm thick steel plates butted together, the steel plates being joined with an M27 bolt nut set. Then, the centering 3 is fully welded to the steel plates, and a 3 mm thick rubber floor plate is sandwiched between the steel plates. It is connected with the centering 3 via steel plates, and at the same time uses rubber soles for cushioning, reducing disturbance to the surrounding rock during the excavation process.

In another alternative embodiment of the present application, locking anchor pipes 7 are provided on both sides of the centering 3, two or more on each side approaching the centering 3, and the rebars 9 are tightly attached to the centering 3 after driving the locking anchor pipes. The centerings 3 are welded to each other, and the adjacent centerings 3 are connected by longitudinal rebars 9, which are spaced 1.0 m apart in the circumferential direction.

In another alternative embodiment of the present application, in step S2, the hole locations are numbered when marking is applied, where steel flower tubes are pressed into the odd-numbered holes to form the pipe roof 2, and the even-numbered holes are A pipe roof 2 is formed by pushing a seamless steel pipe into the hole.

A hot-rolled seamless steel pipe having an outer diameter of 89 mm and a wall thickness of 5 mm was used for the pipe roof 2 . A 150 mm long thread is cut in advance on the outside of the end of each section steel pipe used for the pipe roof 2, a seamless steel pipe with a length of 300 mm and an outer diameter of 95 mm is used for the connecting steel pipe, and threads are cut within the entire length of the connecting steel pipe, The number of joints within the same section shall not exceed 50% of the total number of steel pipes. 150mm spacing, 10-16mm hole diameter, arranged in the shape of a plum blossom, are drilled with grouting material injection holes on the steel flower tube, leaving a 150mm long non-perforated grout stop section at the tail, pipe roof 2 The length is made in one cycle every 10m, the length of one cycle of pipe roof 2 joining is 3m or more, the odd-numbered holes use steel flower tubes, and the even-numbered holes use seamless steel pipes.

During construction, the steel flower tube is first cast to inject grout material, and then the seamless steel pipe is cast into the corresponding drilling hole. Inspect the quality of steel tube grout accordingly.

The pipe roof 2 is grouted through the following steps, i.e.
1) The grouting material of the pipe roof 2 uses cement slurry with a water-cement ratio of 1:1 (weight ratio);
2) The grouting pressure is 1.0 MPa, adjusted according to the actual situation;
3) Steel flower tubes are used for odd-numbered holes, and seamless steel tubes are used for even-numbered holes. and then cast a seamless steel pipe;
4) Before grouting, perform a water push test to check whether the mechanical equipment is in order and whether the hose connection is correct;
5) Cement slurry is blended with a stirring bucket to prevent contamination of foreign matter when blending cement slurry, and the stirred slurry can be filtered before use;
6) the blended slurry should be poured to completion within the specified time and used immediately upon blending;
7) The order of grouting is from bottom to top, the amount of grouting is large first and then small, and the grouting pressure is from low to high;
8) grouting can be terminated when the grouting volume reaches the design volume or when the grouting pressure reaches the design final pressure;
9) During the grouting process, constantly observe changes in the grouting pressure and grouting pump discharge rate, analyze the grouting situation, and prevent pipe clogging, grout escape, and grout leakage. and making a grouting record to analyze grouting effectiveness;
10) When grouting occurs, if grout pressure rises sharply by filling multiple holes with a slurry separator or filling one injection hole with a slurry separator and grouting holes, stop the machine and investigate the cause. If the cement slurry injection volume is large and the pressure is unchanged, the slurry concentration and blending ratio should be adjusted to shorten the solidification time, and low flow rate and low pressure grouting or intermittent grouting should be used.

In another alternative embodiment of the present application, in step S1, a grouting point is located within an allotted grouting area on the ground surface and injected with a grouting tube. The grouting points are arranged in the shape of a plum blossom at intervals of 1 meter within the grouting range allocated on the ground surface, and the grouting material is cement slurry (1: 1) is used and the grout pressure is 0.8 MPa. After the grouting to the ground surface is completed, an EVA waterstop is laid within the grouting area, and C20 concrete with a thickness of 10 cm is placed on the surface of the waterstop to block the infiltration of surface water. The pipe roof 2 is produced in one cycle for 10 m, and the length of the pipe roof 2 joining in one cycle is 3 m or more. It should be understood that the above description is merely illustrative and that the examples of the present application are not limiting.

Summarizing the above, the present invention provides a comprehensive construction method for the low overburden section of the tunnel by the regional railway mining method, and grouting the tunnel 1 through the pipe roof 2, thereby reducing the surrounding rock mass of the tunnel 1. enhance character. In addition, the grouting points were arranged in the shape of a plum blossom at intervals of 1 meter within the grouting area allocated on the ground surface of Tunnel 1. After completion, water stop treatment will reduce surface water infiltration and improve construction safety. Based on our experience, the present invention reduces disturbance to the surrounding bedrock during the construction process and ensures the safety of the construction process when constructing a tunnel in a low overburden section where the surface water is abundant and the surrounding bedrock is of poor quality. Proven.

1 tunnel 1.1 upper stage 1.2 middle stage 1.3 lower stage 2 pipe roof 3 centering 3.1 extension of centering 4 secondary shotcrete layer 5 primary shotcrete layer 6 anchor bolt 7 locking anchor pipe 8 invert 9 rebar

Claims (9)

A comprehensive construction method for a low overburden section of a tunnel ,
After grouting to the ground surface in the low overburden section of the tunnel, and completing the grouting to the ground surface, an EVA waterstop is laid within the grouting area, and concrete is poured into the surface of the waterstop. a step S1 of occlusion to block surface water infiltration;
According to the design drawing, marking is performed on the ground where the tunnel is to be drilled so that a plurality of marking coordinates are arranged in an arch shape surrounding the tunnel, and the tunnel is drilled in the drilling direction of the tunnel at the plurality of marking coordinates by a drill machine. a step S2 in which the pipe roof is drilled so as to gradually separate from the outer peripheral surface of the pipe roof , the inside of the hole is cleaned after the drilling is completed, and the pipe roof is pushed into the drilled hole;
A step S3 of attaching a grout stop valve to the pipe roof, closing the drill hole and cracks around it with a fixing agent, and grouting the pipe roof via a grout injector,
The length of the pipe roof is made in one cycle in 10m, the length of the pipe roof joint in one cycle is not less than 3m, and the end of each section steel pipe used for the pipe roof is preliminarily lengthened. 150 mm threads are cut, connecting steel pipes are seamless steel pipes having a length of 300 mm and an outer diameter of 95 mm, and threads are cut within the entire length of the connecting steel pipes;
A step S4 of excavating the tunnel using a three-stage bench cut construction method with temporary invert and constructing primary support for the excavated portion,
The three-stage bench cut method with the temporary invert is
After excavating the upper level and completing the excavation of the upper level, concrete is first sprayed on the surrounding rock surface of the excavated part, the centering is erected as support, and after the completion of the shoring, the concrete is sprayed again to the thickness specified in the design. , The arch part of the surrounding bedrock is fixed with anchor bolts, and after erecting the steel frames on both sides, a temporary steel frame is installed at the excavated site as a temporary invert, and the adjacent steel frames are connected with reinforcing bars;
Excavate the middle section, excavate one side of the tunnel section, keep a certain distance between both sides of the tunnel section when excavating, and immediately after the excavation of one side is completed, the centering leg of the upper section After the centering is added, the anchor bolts are driven after the erection of the legs is completed, concrete is sprayed again to the design thickness on both sides of the excavated part, and after the erection of the legs on both sides is completed, Installing a temporary steel frame as a temporary invert on the excavated site, and after the installation is completed, spraying concrete to block it;
Excavate the lower stage, excavate one side of the tunnel section, keep a certain distance on both sides of the tunnel section when excavating, and immediately after excavation on either side is completed, immediately place the centering leg. After the centering is added, the anchor bolts are placed after the leg construction is completed, and concrete is sprayed again to the design thickness.
A comprehensive construction method for a low overburden section of a tunnel, characterized by: The interval of the shoring of the excavation length per excavation cycle of the upper stage does not exceed one centering interval,
The interval between the shorings of the excavation length per cycle of excavation in the middle stage does not exceed the interval between the two centerings 3,
The distance between the shorings of the excavation length per excavation cycle of the lower stage does not exceed the distance between the two centerings 3,
The comprehensive construction method for the low overburden section of the tunnel according to claim 1, characterized in that: The integrated construction method for low overburden sections of tunnels according to claim 2, characterized in that the distance between each centering is 0.6m. The joint part of the extension of the centering on the leg is made by butting two steel plates together, joining the steel plates with a bolt and nut set, fully welding the centering to the steel plate, and inserting a 3mm thick rubber bottom plate between the steel plates. The comprehensive construction method for the low overburden section of the tunnel according to claim 3, characterized in that it sandwiches. Locking anchor pipes are provided on both sides of the centering, and two or more on each side approach the centering. The overall construction method for a low overburden section of a tunnel according to claim 4, characterized in that the direction is connected by the reinforcing bars, and the circumferential spacing of the reinforcing bars is 1.0m. In the step S2, when marking, the positions of the holes are numbered, where steel flower tubes are pressed into the odd-numbered holes to form the pipe roof, and seamless steel tubes are pressed into the even-numbered holes to form the pipe roof. The comprehensive construction method for the low overburden section of the tunnel according to claim 1, characterized in that: During construction, the steel flower tube is first cast to inject the grout material, and then the seamless steel pipe is cast into the corresponding drilled hole. The overall construction method for tunnel low overburden section according to claim 6, characterized in that the quality of the grout of the steel flower tube is inspected according to . In the step S1, the grouting point is arranged within the grouting range assigned on the ground surface, and the grouting pipe is used to inject;
The grouting points are arranged in a plum blossom shape at 1 meter intervals.
The comprehensive construction method for the low overburden section of the tunnel according to claim 1, characterized in that: The tunnel according to any one of claims 1 to 8, wherein the pipe roof is manufactured in one cycle for 10 m, and the length of the pipe roof joint in one cycle is 3 m or more. Comprehensive construction method for low overburden sections.

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