Extrusion surrounding rock shallow tunnel initial support structure and construction method

Abstract

An initial support structure of a shallow-buried tunnel of squeezing surrounding rock and a construction method, to resist large deformation of the tunnel of expansive soil surrounding rock, and to realize fast excavation, fast support and fast loop of soft surrounding rock tunnel. The initial support structure comprises a steel frame, a steel pipe concrete pile and an outer arch frame of an arch. The steel pipe concrete piles are arranged in rows outside the lateral sides of the tunnel excavation contour line, the top ends of the steel pipe concrete piles on the same side are fixed to the crown beam, and the upper step corbels and the middle step corbels are respectively welded on the steel pipe concrete piles at positions corresponding to the upper step and the middle step bottom surfaces. The outer arch frame of the arch is arranged outside the upper step surrounding rock, and the lower end of the outer arch frame is fixedly connected to the upper step corbels on the two sides. The initial support steel frame is composed of the upper step initial support steel frame, the middle step initial support steel frame, the lower step initial support steel frame and the inverted arch initial support steel frame connected into a loop, and the lower end of the middle step initial support steel frame and the upper end of the lower step initial support steel frame are fixedly connected to the middle step corbel.

Description

Technical Field

[0001] This invention relates to mountain tunnel construction technology, specifically to an initial support structure and construction method for shallow-buried tunnels in extrusive surrounding rock. Background Technology

[0002] The Jakarta-Bandung High-Speed ​​Railway (HSR) section DK74+020 to DIK114+500, spanning 40.5 km, includes 12 mountain tunnels with a total length of 14,788 m. The surrounding rock is of poor quality, with Class V and VI rock accounting for 76.1%; the lithology is also poor, with clay, cohesive soil, and mudstone exhibiting expansive properties; the tunnels are shallow, with 11 of the 12 tunnels having a depth of less than 100 m; rainfall is high, as the area along the line experiences a tropical rainforest climate, characterized by year-round heat and humidity, with an average of 223 rainy days and an average annual rainfall of 2415.8 mm.

[0003] Expansive soil, due to its water absorption and expansion characteristics and water loss and shrinkage, exhibits significant deformation during tunnel construction under wet-dry cycles. This can lead to issues such as arch crown settlement, sidewall convergence, invert arch bulging, and even lining cracking. These problems are characterized by large deformation volumes, long durations, and high deformation rates. Unconverged deformation of the surrounding rock and initial support, along with large deformations necessitating the replacement of the arch support, further exacerbates the situation during the rainy season by allowing surface water to seep through deformation joints. This significantly reduces the rock's strength, resulting in a larger plastic range and even greater deformation, severely threatening construction safety and making it difficult to guarantee the project schedule. Adhering to the principles of appropriate stress release and proactive rock reinforcement, controlling tunnel deformation requires addressing the issue of large deformation caused by arch support instability at the maximum span during mid-bench excavation. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an initial support structure for shallow buried tunnels in squeezing surrounding rock, so as to lock the initial support that has not yet formed a ring in the tunnel, resist large deformation of tunnels in expansive soil surrounding rock, ensure construction safety, and realize a virtuous cycle of rapid excavation, rapid support and rapid ring formation in tunnels in weak surrounding rock.

[0005] The technical solution adopted by this invention to solve its technical problem is as follows:

[0006] This invention discloses an initial support structure for shallow-buried tunnels in compressional surrounding rock, comprising an initial support steel frame, characterized in that it further comprises steel-concrete composite piles and an outer arch frame; the steel-concrete composite piles are arranged in rows on both sides of the tunnel excavation outline, extending vertically downwards from the ground to a certain elevation below the excavation outline, with the top of each steel-concrete composite pile on the same side fixed to a cap beam, and upper step corbels and middle step corbels respectively welded to the bottom of each steel-concrete composite pile at locations corresponding to the bottom of the upper and middle steps; the outer arch frame... The frame is set outside the surrounding rock of the upper step, and its lower end is fixedly connected to the corbels of the upper step on both sides. The initial support steel frame is composed of the initial support steel frame of the upper step, the initial support steel frame of the middle step, the initial support steel frame of the lower step, and the initial support steel frame of the invert arch connected in a ring. The lower end of the initial support steel frame of the middle step and the upper end of the initial support steel frame of the lower step are fixedly connected to the corbels of the middle step. Temporary cross braces of the upper step that provide support to the lower ends of the two sides of the initial support steel frame are fixedly installed, as well as temporary cross braces of the middle step that provide support to the lower ends of the two sides of the initial support steel frame.

[0007] Another technical problem to be solved by the present invention is to provide a construction method for the above-mentioned initial support structure of a shallow-buried tunnel in confined surrounding rock. The construction method includes the following steps:

[0008] ① After positioning and testing, the steel pipe of the steel pipe concrete cast-in-place pile is driven in, and C30 micro-expansion underwater concrete is used to pour the steel pipe to form a steel pipe concrete cast-in-place pile.

[0009] ② Excavate the upper step, and after the excavation is completed, spray the excavated surface with initial concrete, and then install the outer arch frame of the outer arch.

[0010] ③ Remove the surface concrete of the steel pipe concrete cast-in-place pile, weld the upper step corbel to the steel pipe concrete cast-in-place pile and the outer arch frame of the arch, and then spray concrete again.

[0011] ④ Install the initial support steel frame for the inner upper step, excavate the middle step, and after the excavation is completed, install temporary cross bracing for the upper step.

[0012] ⑤ The initial support steel frame of the middle step is connected to the steel pipe concrete cast-in-place pile through the corbel of the middle step. After completion, temporary cross bracing of the middle step is installed.

[0013] ⑥ Excavate the lower bench. After the excavation is completed, the initial support steel frame for the lower bench is placed on the ground, and adjacent steel frames are longitudinally connected by I-beams.

[0014] ⑦ Carry out the invert arch construction.

[0015] The beneficial effects of this invention are as follows: It employs steel-concrete composite piles to lock the initial support within the tunnel before it forms a ring, solving the problem of arch frame instability and resisting large deformations in expansive soil surrounding rock tunnels, thus ensuring construction safety; the composite lining structure design can resist the full rock and soil pressure of the overburden layer, effectively solving the problems of reduced bearing capacity of the extrusive surrounding rock foundation and overall arch frame settlement, achieving a virtuous cycle of rapid excavation, rapid support, and rapid ring formation in soft surrounding rock tunnels; it effectively overcomes the challenges of shallow tunnel burial, biased pressure, expansive surrounding rock, extremely high ground stress, and large deformation, ensuring project progress. Attached Figure Description

[0016] This instruction manual includes the following eight figures:

[0017] Figure 1 This is a cross-sectional view of an initial support structure for a shallow-buried tunnel in extrusive surrounding rock according to the present invention.

[0018] Figure 2 This is a cross-sectional view (enlarged) of the initial support structure for a shallow-buried tunnel in extrusive surrounding rock according to the present invention;

[0019] Figure 3 yes Figure 2 A magnified view of part A in the middle;

[0020] Figure 4 This is a front view of the upper step corbel in the initial support structure of a shallow buried tunnel in extrusive surrounding rock according to the present invention.

[0021] Figure 5 This is a top view of the upper step corbel in the initial support structure of a shallow buried tunnel in extrusive surrounding rock according to the present invention.

[0022] Figure 6 yes Figure 2 A magnified view of part B in the middle;

[0023] Figure 7 This is a front view of the intermediate step corbel in the initial support structure of a shallow buried tunnel in extrusive surrounding rock according to the present invention.

[0024] Figure 8 This is a top view of the middle step corbel in the initial support structure of a shallow buried tunnel in extrusive surrounding rock according to the present invention.

[0025] The diagram shows the components and their corresponding markings: ground D, upper step D1, middle step D2, lower step D3, invert D4, steel-concrete composite pile 10, cap beam 11, upper step corbel 12, I-beam corbel support plate 121, rib plate 122, middle step corbel 13, corbel support plate 131, corbel rib plate 132, through groove 133, outer arch frame 20, enlarged arch foot 21, initial support steel frame 30, upper step initial support steel frame 31, middle step initial support steel frame 32, middle step steel frame connecting steel plate 321, lower step initial support steel frame 33, lower step steel frame connecting steel plate 331, invert initial support steel frame 34, upper step temporary cross brace 35, middle step temporary cross brace 36, secondary lining 40. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0027] Reference Figure 1 and Figure 2 The present invention discloses an initial support structure for shallow-buried tunnels in extrusive surrounding rock, comprising an initial support steel frame 30, steel-concrete composite piles 10, and an outer arch frame 20. The steel-concrete composite piles 10 are arranged in rows on both sides of the tunnel excavation outline, extending vertically downward from the ground surface D to a certain elevation below the excavation outline. The top of each steel-concrete composite pile 10 on the same side is fixed to the capping beam 11. Upper step corbels 12 and middle step corbels 13 are welded to each steel-concrete composite pile 10 at locations corresponding to the bottom surfaces of the upper step D1 and middle step D2, respectively. The outer arch frame 20 of the arch is set outside the surrounding rock of the upper step D1, and its lower end is fixedly connected to the upper step corbels 12 on both sides; the initial support steel frame 30 is composed of the upper step initial support steel frame 31, the middle step initial support steel frame 32, the lower step initial support steel frame 33 and the invert arch initial support steel frame 34 connected in a ring. The lower end of the middle step initial support steel frame 32 and the upper end of the lower step initial support steel frame 33 are fixedly connected to the middle step corbels 13, and the upper step temporary cross braces 35 that support the lower ends of the two sides of the initial support steel frame 31 and the middle step temporary cross braces 36 that support the lower ends of the two sides of the middle step initial support steel frame 32 are fixedly installed.

[0028] Reference Figure 1By using the steel-concrete composite piles 10 initially installed close to the tunnel excavation edge, the strata are anchored and a firm anchor is provided for the initial support steel frame 30. During the construction of the middle bench D2, the initial support steel frame arch is fixedly connected to the steel-concrete composite piles 10, forming a portal arch support system. This system is simple in structure, clearly defined in its stress distribution, and provides active support, effectively curbing large deformations of the surrounding rock. With the construction of the lower bench D3 and the invert arch D4, the initial support system forms a ring, and the steel-concrete composite piles 10 and the initial support arch form a double "K"-shaped support, seamlessly integrating with the surrounding rock. The deformation of the surrounding rock and the initial support steel frame stabilizes, allowing for immediate construction of the secondary lining, thus stabilizing the disturbed surrounding rock early and significantly improving deformation control.

[0029] Reference Figure 3 , Figure 4 and Figure 5 The upper step bracket 12 is composed of an I-beam bracket support plate 121 and ribs 122 welded together. The I-beam bracket support plate 121 is formed by welding two parallel I-beam components, and the ribs 122 are laterally spaced below the I-beam bracket support plate 121. Enlarged arch feet 21 are welded to both ends of the outer arch frame 20 of the arch section, and these enlarged arch feet 21 are welded to the I-beam bracket support plate 121. The upper step bracket 12 is stacked under the enlarged arch feet 21 of the outer arch frame 20 of the arch section. Adjustment is achieved by moving the welded positions of the enlarged arch feet 21 and the I-beam bracket support plate 121 laterally along the tunnel.

[0030] Reference Figure 6 , Figure 7 and Figure 8 The middle step corbel 13 is composed of a corbel support plate 131 and a corbel rib plate 132 welded together. The corbel rib plates 132 are laterally spaced below the corbel support plate 131. Through grooves 133 extending laterally along the tunnel are spaced apart on the surface of the corbel support plate 131, allowing the steel frame connecting steel plate to be bolted laterally along the corbel support plate 131. The lower end of the middle step initial support steel frame 32 is welded with a middle step steel frame connecting steel plate 331, and the upper end of the lower step initial support steel frame 33 is welded with a lower step steel frame connecting steel plate 331. The middle step initial support steel frame 32, the lower step initial support steel frame 33, and the middle step corbel 13 are fixedly connected by bolts passing through the middle step steel frame connecting steel plate 331, the through grooves 133, and the lower step steel frame connecting steel plate 331.

[0031] Reference Figures 1 to 3 The present invention discloses a construction method for the initial support structure of a shallow-buried tunnel in a squashed surrounding rock, comprising the following steps:

[0032] ① After positioning and testing, steel pipe concrete pile 10 was installed and C30 micro-expansion underwater concrete was used to pour into the steel pipe to form steel pipe concrete pile 10.

[0033] ② Excavate the upper step D1. After the excavation is completed, spray the excavated surface with initial concrete and then install the outer arch frame 20 of the outer arch.

[0034] ③ Remove the surface concrete of the steel pipe concrete cast-in-place pile 10, weld the upper step corbel 12 to the steel pipe concrete cast-in-place pile 10 and the outer arch frame 20 of the arch, and spray concrete again.

[0035] ④ Install the initial support steel frame 31 for the inner layer of the upper step, excavate the middle step D2, and after the excavation is completed, install the temporary cross bracing 35 for the upper step.

[0036] ⑤ The initial support steel frame 32 of the middle step is welded to the steel pipe concrete cast-in-place pile 10 through the middle step corbel 13. After completion, the temporary cross bracing 36 of the middle step is installed.

[0037] ⑥ Excavate the lower bench D3. After the excavation is completed, the initial support steel frame 33 of the lower bench is placed on the ground. Adjacent steel frames are connected longitudinally by I-beams, using I18 I-beams with a circumferential spacing of 1m.

[0038] ⑦ Carry out the construction of the invert arch 34.

[0039] The above description is merely an illustration of some principles of the initial support structure and construction method for shallow buried tunnels in compressional surrounding rock according to the present invention. It is not intended to limit the present invention to the specific structures and applicable scope shown and described. Therefore, all possible modifications and equivalents are within the scope of the patent application of the present invention.

[0040] The scope of the patent application.

Claims

1. An initial support structure for shallow-buried tunnels in compressional surrounding rock, comprising an initial support steel frame (30), characterized in that: It also includes steel-concrete composite piles (10) and an outer arch frame (20); the steel-concrete composite piles (10) are arranged in rows on both sides of the tunnel excavation outline, extending vertically downward from the ground (D) to a certain elevation below the excavation outline. The top of each steel-concrete composite pile (10) on the same side is fixed to the cap beam (11). On each steel-concrete composite pile (10), the upper step corbel (12) and the middle step corbel (13) are welded to the bottom of the upper step (D1) and the middle step (D2) respectively. The outer arch frame (20) is set outside the surrounding rock of the upper step (D1), and its lower end is connected to the upper steps on both sides. The corbel (12) forms a fixed connection; the initial support steel frame (30) is composed of an upper step initial support steel frame (31), a middle step initial support steel frame (32), a lower step initial support steel frame (33) and an invert arch initial support steel frame (34) connected in a ring. The lower end of the middle step initial support steel frame (32) and the upper end of the lower step initial support steel frame (33) are fixedly connected to the middle step corbel (13), and the upper step temporary cross brace (35) which provides support to the lower ends of both sides of the initial support steel frame (31) and the middle step temporary cross brace (36) which provides support to the lower ends of both sides of the middle step initial support steel frame (32) are fixedly installed.

2. The initial support structure for shallow-buried tunnels in compressional surrounding rock as described in claim 1, characterized in that: The upper step bracket (12) is composed of an I-beam bracket support plate (121) and a rib plate (122) welded together. The I-beam bracket support plate (121) is welded together from two parallel I-beam components, and the rib plate (122) is arranged horizontally at intervals below the I-beam bracket support plate (121).

3. The initial support structure for shallow-buried tunnels in compressive surrounding rock as described in claim 2, characterized in that: The outer arch frame (20) of the arch section is welded to both ends with enlarged arch feet (21), and the enlarged arch feet (21) are welded to I-beam bracket plates (121).

4. The initial support structure for shallow-buried tunnels in compressional surrounding rock as described in claim 1, characterized in that: The middle step corbel (13) is composed of a corbel support plate (131) and a corbel rib plate (132) welded together. The corbel rib plates (132) are arranged horizontally at intervals below the corbel support plate (131). Through grooves (133) extending horizontally along the tunnel are arranged at intervals on the surface of the corbel support plate (131).

5. The initial support structure for shallow-buried tunnels in compressive surrounding rock as described in claim 2, characterized in that: The lower end of the initial support steel frame (32) of the middle step is welded with the connecting steel plate (331) of the middle step steel frame, and the upper end of the initial support steel frame (33) of the lower step steel frame is welded with the connecting steel plate (331) of the lower step steel frame. The initial support steel frame (32) of the middle step, the initial support steel frame (33) of the lower step steel frame, and the corbel (13) of the middle step are fixedly connected by bolts passing through the connecting steel plate (331) of the middle step steel frame, the through groove (133) and the connecting steel plate (331) of the lower step steel frame.

6. A construction method for an initial support structure for a shallow-buried tunnel in compressive surrounding rock as described in any one of claims 1 to 5, comprising the following steps: ① After positioning and testing, the steel pipe of the concrete-filled steel pipe pile (10) is installed, and C30 micro-expansion underwater concrete is used to fill the steel pipe to form a concrete-filled steel pipe pile (10). ② Excavate the upper step (D1), and after the excavation is completed, spray concrete on the excavated surface, and then install the outer arch frame (20) of the outer arch. ③ Remove the concrete from the surface of the steel pipe concrete cast-in-place pile (10), weld the upper step corbel (12) to the steel pipe concrete cast-in-place pile (10) and the outer arch frame (20) of the arch, and spray concrete again; ④ Install the initial support steel frame (31) of the inner layer of the upper step, excavate the middle step (D2), and after the excavation is completed, lay the temporary cross bracing (35) of the upper step; ⑤ The initial support steel frame (32) of the middle step is welded to the steel pipe concrete cast-in-place pile (10) through the middle step corbel (13). After completion, the temporary cross bracing (36) of the middle step is installed. ⑥ Excavate the lower bench (D3). After the excavation is completed, the initial support steel frame (33) of the lower bench is placed on the ground, and the adjacent steel frames are longitudinally connected by I-beams. ⑦ Carry out the construction of the invert arch (34).

Images