Soft rock tunnel rapid roof-lifting construction method

Abstract

The invention discloses a soft rock tunnel rapid top-lifting construction method, which relates to the technical field of tunnel construction, and comprises the steps of construction preparation, advanced geological forecast, measurement and line drawing, tunnel body excavation, primary support, reinforced steel frame erection and top-lifting construction. The method has the beneficial effects that micro-step blasting construction is adopted, the method has the advantages of being high in construction efficiency, small in disturbance to surrounding rock, good in construction quality and the like, is suitable for tunnel construction under various soft rock geological conditions and in a certain section size and length range, and an efficient, safe and stable solution is provided for rapid top-lifting construction of the soft rock tunnel.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel construction, and in particular to a method for quickly top-lifting a soft rock tunnel. Background Art

[0002] In tunnel construction, it is often necessary to expand the tunnel section due to different construction stages or design changes, that is, to carry out top-lifting operations. Soft rock tunnels face many challenges in top-lifting construction due to their low rock strength, developed joints and fissures, and poor self-stabilization ability. Traditional top-lifting methods for soft rock tunnels often have problems such as low construction efficiency, high safety risks, and large disturbance to the surrounding rock. For example, some conventional methods are prone to cause surrounding rock collapse when removing the original support structure and excavating the upper rock mass, which in turn affects the construction progress and endangers the safety of construction workers. At the same time, due to the characteristics of soft rock, it is difficult to effectively coordinate the installation of the support structure after excavation with the control of surrounding rock deformation, resulting in a prolonged construction period. Therefore, it is of great practical significance to develop a rapid top-lifting technology suitable for soft rock tunnels. Summary of the invention

[0003] The purpose of the present invention is to provide a method for rapid roof construction of soft rock tunnels in order to solve the above-mentioned problems. The method has the advantages of high construction efficiency, little disturbance to the surrounding rock, and good construction quality. It is suitable for tunnel construction in a variety of soft rock geological conditions, a certain cross-sectional size and a certain length range.

[0004] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0005] A method for rapid top-lifting construction of a soft rock tunnel comprises the following steps:

[0006] (1) Construction preparation: Carry out technical preparation work, provide technical and safety technical briefing training to operators; prepare and inspect the required materials, including advance small guide tubes, steel frames, anchor rods, steel mesh and concrete, etc.;

[0007] (2) Advanced geological prediction: Use geological sketches, elastic wave reflection method TSP, and electromagnetic wave reflection method (geological radar) to predict the geological conditions ahead, and guide the excavation support measures of the top section according to the prediction results;

[0008] (3) Surveying and drawing: Determine the tunnel excavation contour line according to the design drawings, and mark the tunnel center line, arch center position, excavation contour line, bottom plate elevation, etc. on the excavation face;

[0009] (4) Tunnel excavation: The micro-step method is used for construction. The advance per cycle is not more than 1.0 m. The excavation advance of the upper step is not more than the spacing of one steel frame, and the excavation advance of the lower step is not more than the spacing of two steel frames. The locking foot anchor pipe is installed before the excavation of the invert arch. The excavation advance per cycle of the invert arch is not more than the spacing of three steel frames. During the excavation process, the transition section at the intersection of the cross tunnel and the main tunnel is excavated first, and then the excavation is gradually expanded to the main tunnel to form a working surface.

[0010] (5) Initial support: After excavation is completed, initial support for the tunnel structure is carried out, including initial shotcrete, shotcrete anchor net system support, erection of tunnel structure steel frame, installation of locking anchor rods and re-shotcrete to the designed thickness;

[0011] (6) Erection of reinforced steel frame: Erection of reinforced steel frame at the intersection of the cross tunnel and the main tunnel, erection of the main tunnel steel frame, removal of temporary support, and formation of the working surface;

[0012] (7) Top-lift construction: According to the above steps, the top-lift construction of the left and right lines of the main tunnel is completed respectively, including the excavation and support of the upper and lower steps, until the top-lift construction is completed.

[0013] Preferably, the length of the excavation step by the micro-step method is controlled within 3 to 5 m, the initial support is promptly closed into a ring after tunnel excavation, and the distance between the initial support of the invert and the foremost heading face shall not be greater than 35 m.

[0014] Preferably: in the construction preparation steps, 20 meters before entering the main tunnel top, the advanced geological forecast data is analyzed, and the top active support parameters, advanced reinforcement measures, auxiliary tunnels and initial support reinforcement sections of active intersections are dynamically confirmed.

[0015] Preferably, during the excavation process, the excavation is gradually expanded to an uphill excavation and forward excavation, so that support is provided while excavation is carried out, and the excavation section and the cross-hole section form an upper step section, and the upper step height is 5.2m to 7.5m.

[0016] Preferably, in the initial support step, the thickness of the initial sprayed concrete is 4 cm, and the re-sprayed concrete reaches the designed thickness.

[0017] Preferably, the reinforcing steel frame adopts a double-jointed reinforcing ring steel frame, and the main tunnel steel frame is connected to the reinforcing ring steel frame at the intersection by welding.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: the rapid top-lift construction method for soft rock tunnels of the present invention effectively improves construction efficiency, reduces safety risks, and reduces disturbance to surrounding rocks through measures such as micro-step construction, strengthening geological prediction, accurate measurement and marking, strict control of excavation advance, and timely closure of initial support, thereby providing an efficient, safe, and stable solution for rapid top-lift construction of soft rock tunnels. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 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 labor.

[0020] Figure 1 It is a schematic diagram of the construction process flow of the present invention.

[0021] Figure 2 It is a plan layout diagram and a steel frame schematic diagram of the transition section from the transverse tunnel to the main tunnel described in the present invention.

[0022] Figure 3 This is a schematic diagram of the gradual expansion of steps on the left line of the main tunnel of Shiheng 4 according to the present invention.

[0023] Figure 4 It is a schematic diagram of the erection of the right line steel frame of the main tunnel described in the present invention.

[0024] Figure 5 It is a schematic diagram of the erection of the left line steel frame of the main tunnel described in the present invention.

[0025] Figure 6 It is a schematic diagram of the gradual expansion and excavation of the transverse tunnel into the main tunnel described in the present invention.

[0026] Figure 7 It is a schematic diagram of the gradual expansion of the left line of Shiheng 4 entering the main tunnel according to the present invention. DETAILED DESCRIPTION

[0027] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0028] The present invention will be further described below in conjunction with the accompanying drawings:

[0029] Example 1

[0030] like Figure 1-Figure 7 As shown, a method for rapid top-lifting construction of a soft rock tunnel comprises:

[0031] 1. Construction preparation:

[0032] (1) 20 meters before entering the main tunnel, notify the Luolong Project Department to organize all parties to conduct on-site surveys, analyze the advanced geological forecast data, and dynamically confirm the parameters of the active support for the top, advanced reinforcement measures, auxiliary tunnels, and primary support reinforcement sections of active intersections;

[0033] (2) When the distance between the auxiliary tunnel excavation and the main tunnel is less than 10m and after entering the main tunnel, the principle of "pre-reinforcement first, then excavation, one frame for one support" shall be strictly followed for the weak surrounding rock of grade IV and V and the unfavorable geological sections, and no more than one frame shall be excavated in each cycle;

[0034] (3) After the strengthening support measures within 3-5m of the main tunnel are completed, the Luolong Project Department will organize the acceptance of the conditions for the top-lift construction according to the tunnel entry acceptance procedure. Only after passing the acceptance can the top-lift construction begin;

[0035] 2. Specific construction steps:

[0036] (1) When the normal excavation and support construction of the No. 5 cross tunnel reaches the transition section, the transition section is reinforced with 10 I18 steel frames, and a closed ring steel frame is added in the bottom plate;

[0037] (2) When the last steel frame of the transverse tunnel is installed, the temporary support of the right main tunnel is gradually climbed upwards. After the construction reaches the arch of the main tunnel, the temporary support of the right main tunnel is gradually lowered to the 4th horizontal tunnel. The 1st steel frame is installed to form an upper step operation platform; each steel frame climbs (lowers) 41cm; the micro-step method is used for excavation, and the advance per cycle is 1.0m; the excavation elevation is 25cm outside the excavation contour line of the main tunnel (excluding the reserved deformation) to facilitate the erection of the initial support steel frame at the intersection of the main tunnel. Considering that the deformation of the surrounding rock may be large, the actual excavation size is 10-12cm higher than the designed arch elevation; during construction, the excavation is gradually expanded to excavate forward uphill, so as to achieve support while excavating. The excavation section forms an upper step section with the cross tunnel section, and the upper step height is 5.2m-7.5m;

[0038] (3) After the temporary support of the upper step of the right-line main tunnel is completed, the temporary support of the lower step of the right-line main tunnel will be started. The left and right sides will be staggered, and the excavation advance shall not be greater than the distance between 2 steel frames. After excavating to Shiheng 4, the work will be carried out synchronously and parallel to the upper step of Shiheng 4.

[0039] (4) After the lower step of the right line of the main tunnel is constructed to form a micro step with the excavation support of the upper step of Shiheng 4, the temporary support of the lower step of the right line main tunnel and the upper step of Shiheng 4 are carried out simultaneously until the normal construction of Shiheng 4 begins; the cross section adopts the cross section during temporary support, the initial support steel frame adopts I18 steel frame, the spacing of the transition section is 0.8m, and the normal section is 1m; the step height is 5.7m for the upper step and 2m for the lower step;

[0040] (5) When constructing the last steel frame of horizontal 4, gradually climb upward to expand the excavation to construct the temporary support of the upper steps of the left main tunnel. After constructing to the arch of the main tunnel, gradually lower and continue to construct the temporary support of the left main tunnel to the left side wall. Each steel frame climbs (lowers) 41cm; micro-step method excavation, each cycle of advance is 1.0m;

[0041] (6) After the temporary support of the upper step of the left main tunnel is completed, the temporary support of the lower step of the left main tunnel will be started. The left and right sides will be staggered, and the excavation depth shall not exceed the distance between two steel frames; the height of the lower step is 2.5m;

[0042] (7) After the excavation and support of the lower step of the left line of the main tunnel is completed, a double reinforced ring steel frame is erected at the intersection of Shiheng 4 and the left line of the main tunnel, and the main tunnel arch frame is erected. The main tunnel steel frame is connected to the reinforced ring steel frame at the intersection of Shiheng 4 and the left line by welding, and the other end is directly dropped to the bottom; after the erection is completed, the primary support concrete of the main tunnel is sprayed in time;

[0043] (8) Remove the temporary support steel frames on both sides of the left line of the main tunnel, and excavate and support the upper steps in staggered manner towards the large and small miles. After the upper steps on both sides are excavated to a length of 10 meters, close the heading face and carry out the excavation and support of the lower steps. After the micro steps are formed, enter the normal process of excavation and construction, and the left line top is completed;

[0044] (9) After the left line is topped off, a reinforcement ring steel frame is erected at the intersection of Shiheng 4 and the right line, and at the intersection of No. 5 transverse tunnel and the right line, and then the primary support steel frame of the right line main tunnel of the intersection section is constructed; the main tunnel steel frame is connected to the reinforcement ring steel frame at the intersection by welding; after the steel frame is constructed, the primary support concrete of the main tunnel is sprayed in time;

[0045] (10) The temporary supporting steel frames on both sides of the right line of the main tunnel are removed, and the upper steps are excavated and supported in staggered manner towards the large and small mileages. After the upper steps on both sides are excavated to a length of 10 meters, the heading face is closed and the lower steps are excavated and supported. After the micro steps are formed, the normal excavation construction process is started, and the right line is completed.

[0046] Through the above specific implementation methods, the soft rock tunnel rapid top-lifting technology of the present invention can efficiently and safely complete the tunnel top-lifting construction task under soft rock geological conditions, effectively solve the problems of low construction efficiency, high safety risks, and large disturbance to the surrounding rock existing in traditional top-lifting methods, and has significant economic and social benefits, providing a reliable technical solution for soft rock tunnel engineering construction.

[0047] Example 2

[0048] A method for rapid top-lifting construction of a soft rock tunnel comprises the following steps:

[0049] (1) When the normal excavation and support construction of the No. 5 cross tunnel reaches the transition section, the transition section is reinforced with 10 I18 steel frames, and a closed ring steel frame is added in the bottom plate;

[0050] (2) At the last steel frame of the horizontal tunnel, gradually climb upward to expand the excavation to construct the temporary support of the right-line main tunnel until the arch of the main tunnel is reached, and then gradually lower and continue to construct the temporary support of the right-line main tunnel until the first steel frame of the horizontal tunnel 4 is installed to form an upper step operation platform;

[0051] (3) After the temporary support of the upper step of the right-line main tunnel is completed, the temporary support of the lower step of the right-line main tunnel will be started, with the left and right sides staggered;

[0052] (4) After the construction of the lower step of the right line of the main tunnel has formed a micro step with the excavation and support of the upper step of Shiheng 4, the temporary support of the lower step of the right line main tunnel and the upper step of Shiheng 4 are carried out simultaneously;

[0053] (5) At the last steel frame of Shiheng 4, gradually climb upward to expand the excavation to construct the temporary support of the upper steps of the left line main tunnel until the arch of the main tunnel is reached, and then gradually lower and continue to construct the temporary support of the left line main tunnel to the left line side wall;

[0054] (6) After the temporary support of the upper step of the left main tunnel is completed, the temporary support of the lower step of the left main tunnel will be started, with the left and right sides staggered;

[0055] (7) After the excavation and support of the lower step of the left line of the main tunnel is completed, a double reinforced ring steel frame is erected at the intersection of Shiheng 4 and the left line of the main tunnel, and the arch frame of the main tunnel is erected. The main tunnel steel frame is connected to the reinforced ring steel frame at the intersection of Shiheng 4 and the left line by welding;

[0056] (8) Remove the temporary support steel frames on both sides of the left line of the main tunnel, and excavate and support the upper steps in staggered manner towards the large and small miles. After the upper steps on both sides are excavated to a length of 10 meters, close the heading face and carry out excavation and support for the lower steps. After the micro steps are formed, enter the normal excavation process;

[0057] (9) After the left line is topped off, a reinforcement ring steel frame is erected at the intersection of Shiheng 4 and the right line, and at the intersection of No. 5 transverse tunnel and the right line, and then the initial support steel frame of the right line main tunnel of the intersection section is constructed. The main tunnel steel frame is connected to the reinforcement ring steel frame at the intersection by welding;

[0058] (10) Remove the temporary supporting steel frames on both sides of the right line of the main tunnel, and excavate and support the upper steps in staggered manner towards the large and small steps. After the upper steps on both sides are excavated to a length of 10 meters, close the heading face and carry out excavation and support for the lower steps. After the micro steps are formed, enter the normal excavation construction process.

[0059] Example 3

[0060] A method for rapid top-lifting construction of a soft rock tunnel comprises the following steps:

[0061] (1) 20 meters before entering the main tunnel, organize all parties to conduct on-site survey, analyze the advanced geological forecast data, and dynamically confirm the active support parameters of the top, advanced reinforcement measures, auxiliary tunnels and primary support reinforcement sections of active intersections;

[0062] (2) When the distance between the auxiliary tunnel excavation and the main tunnel is less than 10m and after entering the main tunnel, the principle of "pre-reinforcement first, then excavation, and one frame and one support" shall be strictly implemented;

[0063] (3) After the strengthening support measures within 3 to 5 m of the main tunnel are completed, the acceptance of the construction conditions for the top cantilevering shall be carried out in accordance with the tunnel entry acceptance procedures;

[0064] (4) Carry out construction according to steps (2) to (10) in Example 2.

[0065] Among them, in step (2), the excavation distance per cycle shall not be greater than the spacing of one steel frame to ensure construction safety and stability.

[0066] The basic principles, main features and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for illustrating the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for rapid roofing construction of a soft rock tunnel, characterized in that: The following steps are involved: (1) Construction preparation: Carry out technical preparation work, provide technical and safety technical briefing training to operators; prepare and inspect the required materials, including advance small guide tubes, steel frames, anchor rods, steel mesh and concrete, etc.; (2) Advanced geological prediction: Use geological sketches, elastic wave reflection method TSP, and electromagnetic wave reflection method (geological radar) to predict the geological conditions ahead, and guide the excavation support measures of the top section according to the prediction results; (3) Surveying and drawing: Determine the tunnel excavation contour line according to the design drawings, and mark the tunnel center line, arch center position, excavation contour line, bottom plate elevation, etc. on the excavation face; (4) Tunnel excavation: The micro-step method is used for construction. The advance per cycle is not more than 1.0 m. The excavation advance of the upper step is not more than 1 steel frame spacing, and the excavation advance of the lower step is not more than 2 steel frame spacings. The locking foot anchor pipe is installed before the invert excavation. The excavation advance per cycle of the invert is not more than 3 steel frame spacings. During the excavation process, the transition section at the intersection of the cross tunnel and the main tunnel is excavated first, and then gradually expanded to the main tunnel to form a working surface; (5) Initial support: After excavation is completed, initial support for the tunnel structure is carried out, including initial shotcrete, shotcrete anchor net system support, erection of tunnel structure steel frame, installation of locking anchor rods and re-shotcrete to the designed thickness; (6) Erection of reinforced steel frame: Erection of reinforced steel frame at the intersection of the cross tunnel and the main tunnel, erection of the main tunnel steel frame, removal of temporary support, and formation of the working surface; (7) Top-lift construction: According to the above steps, the top-lift construction of the left and right lines of the main tunnel is completed respectively, including the excavation and support of the upper and lower steps, until the top-lift construction is completed.

2. The method for rapid roofing construction of a soft rock tunnel according to claim 1 is characterized in that: The length of the excavation steps of the micro-step method is controlled within 3 to 5 meters. The initial support is promptly closed into a ring after tunnel excavation, and the distance between the initial support of the invert and the front heading face shall not be greater than 35 meters.

3. The method for rapid roofing construction of a soft rock tunnel according to claim 1 is characterized in that: In the construction preparation steps, 20 meters before entering the main tunnel top, the advanced geological forecast data is analyzed, and dynamic confirmation is carried out on the active support parameters of the top, advanced reinforcement measures, auxiliary tunnels and initial support reinforcement sections of active intersections.

4. The method for rapid roofing construction of a soft rock tunnel according to claim 1 is characterized in that: During the excavation process, the excavation is gradually expanded to an upslope forward excavation, and support is provided while excavation is carried out. The excavation section and the cross tunnel section form an upper step section, and the upper step height is 5.2m to 7.5m.

5. The method for rapid roofing construction of a soft rock tunnel according to claim 1 is characterized in that: In the initial support step, the thickness of the initial sprayed concrete is 4 cm, and the re-sprayed concrete reaches the designed thickness.

6. The method for rapid roofing construction of a soft rock tunnel according to claim 1 is characterized in that: The reinforcing steel frame adopts a double-jointed reinforcing ring steel frame, and the main tunnel steel frame is connected to the reinforcing ring steel frame at the intersection by welding.

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