Deformation control structure for small-clearance intersecting tunnels in upper-hard and lower-soft stratum

Abstract

The utility model discloses a kind of small clear distance intersection tunnel deformation control structures of hard over-soft stratum, including hard rock layer and soft soil layer, hard rock layer and soft soil layer are horizontal or near horizontal sedimentary rock layer, hard rock layer is covered on the top of soft soil layer;Upper tunnel is set in hard rock layer, lower tunnel is set in soft soil layer, upper tunnel and lower tunnel are cross laid, and the intersection position of upper tunnel and lower tunnel is overlap area;The vault of lower tunnel distance upper and lower two tunnel overlap area 3-5 m position is grouting area, grouting modification is grouted in grouting area, and grouting area is vault ±120 ° sector area;Radial anchor rod of radial distribution is constructed in overlap area, and a plurality of vertical prestressed anchor cables are also constructed in overlap area, the vault of lower tunnel is connected at the lower end of prestressed anchor cable, the upper end of prestressed anchor cable extends to upper tunnel, load transmission plate is constructed in the arch bottom of upper tunnel, and the upper end of prestressed anchor cable is fixed on load transmission plate.

Description

Technical Field

[0001] This utility model belongs to the field of tunnel construction technology, specifically relating to a deformation control structure for a small-clearance intersection tunnel in hard upper and soft lower strata. Background Technology

[0002] During urbanization, urban transportation systems are gradually developing towards spatial three-dimensionality and multi-layered structures. Due to limitations in construction sites and route planning requirements, tunnel intersections are unavoidable. Underpasses with small clearances exhibit significant characteristics such as high risk of near-intersection, significant coupling of multiple effects, superimposed environmental effects, and difficulties in deformation and stability control. These factors pose a significant challenge to the deformation control of the surrounding rock of the lower tunnel. Traditional support measures primarily rely on anchor bolts combined with thickened linings, but this structural form is mostly suitable for hard or relatively hard rock strata and not for underpasses located in soft rock or soil layers. Furthermore, traditional support measures result in the lower tunnel primarily bearing passive stress, leading to excessive bending moments at the tunnel roof and difficulties in controlling deformation. Therefore, developing appropriate surrounding rock deformation control measures based on the characteristics of hard upper and soft lower strata to ensure the safety of underpass construction with small clearances and prevent tunnel roof collapse has become a critical problem that urgently needs to be solved in design and construction. Utility Model Content

[0003] This invention addresses the challenge of controlling the deformation of a tunnel located in hard rock strata and a lower tunnel located in soft rock strata. It proposes a deformation control structure suitable for tunnels with small clearances in hard-rock upper and soft-rock lower strata. By using prestressed anchor cables to connect the lower tunnel in the soft soil layer to the upper tunnel in the hard rock layer, the characteristics of the upper hard rock strata are fully utilized to reduce the soil load on the lining arch of the lower tunnel. This results in a comprehensive control technology and construction method combining "advanced grouting modification + anchor support force adjustment," effectively controlling the deformation during the construction of the lower tunnel.

[0004] Therefore, the present invention adopts the following technical solution: A deformation control structure for a small-clearance tunnel with hard upper and soft lower strata includes a hard rock layer and a soft soil layer. The hard rock layer and the soft soil layer are horizontal or near-horizontal sedimentary rock layers, with the hard rock layer covering the soft soil layer. An upper tunnel is constructed within the hard rock layer, and a lower tunnel is constructed within the soft soil layer. The upper and lower tunnels are intersected, and the intersection of the upper and lower tunnels is called the overlap zone. The arch of the lower tunnel, located 3-5 m away from the overlap zone of the upper and lower tunnels, is the grouting zone. Grouting is injected into the grouting zone to modify the structure. The grouting zone is a fan-shaped area of ​​±120° from the arch. Radial anchor bolts are installed in the overlapping area, and several vertical prestressed anchor cables are also installed in the overlapping area. The lower end of the prestressed anchor cable is connected to the arch of the lower tunnel, and the upper end of the prestressed anchor cable extends into the upper tunnel. A load transfer plate is installed at the bottom of the upper tunnel arch, and the upper end of the prestressed anchor cable is fixed to the load transfer plate.

[0005] Furthermore, the prestressed anchor cable includes a sheath, steel strands, a lower anchor plate, a lower clamp, an upper anchor plate, and an upper clamp. The lower anchor plate and the lower clamp are fixed to the arch of the lower tunnel, and the upper anchor plate and the upper clamp are fixed to the load transfer plate.

[0006] Furthermore, the intersection angle between the upper tunnel and the lower tunnel is 0° to 90°.

[0007] Furthermore, the radial anchor bolt holes are evenly distributed in a fan shape at ±120° of the arch crown, arch waist, and sidewalls, with a hole inclination of 5°-15°, a circumferential spacing of approximately 0.6-1.0 m, and an axial step distance of 0.5-1.0 m.

[0008] The design principle of this utility model is as follows: It fully utilizes the strength advantage of the upper tunnel in hard rock strata, connecting the lower tunnel lining, constructed in soft soil, to the upper tunnel using prestressed anchor cables. This reduces the soil load on the lower tunnel arch, saving on project costs compared to the traditional construction scheme of anchor bolts combined with thickened lining. Furthermore, it possesses high construction feasibility, good durability, and low-carbon environmental friendliness. Based on this, a combined "advanced grouting modification + anchor bolt support force adjustment" scheme is used to reinforce and strengthen the surrounding rock of the lower tunnel arch, forming a deformation control structure for small-clearance intersecting tunnels in hard upper and soft lower strata.

[0009] The beneficial effects of this utility model are as follows: 1. This utility model connects the lower tunnel in the soft soil layer to the upper tunnel in the hard rock layer through prestressed anchor cables, making full use of the strength advantage of the hard rock layer to treat the surrounding rock of the soft soil layer and reduce the soil load borne by the arch of the lower tunnel lining.

[0010] 2. This utility model involves pre-grouting the soft soil surrounding rock before tunnel construction, which binds the soft soil layer in the tunnel overlap area into a whole, actively enhancing the strength and self-stability of the surrounding rock, and reducing the deteriorating effects of the lower tunnel construction on the upper tunnel structure, such as additional stress and superimposed deformation.

[0011] 3. This utility model applies pre-grouting reinforcement to soft soil layers and then applies anchor bolt support and force adjustment to the lower tunnel, forming a comprehensive control technology and construction method of "pre-grouting modification + anchor bolt support and force adjustment", which effectively improves the stress state of the lining.

[0012] 4. This utility model has a simple principle and is feasible to operate. Compared with the traditional construction scheme of anchor bolts combined with thickened lining, it can save project costs and reduce the amount of concrete used, and has significant economic and low-carbon benefits. Attached Figure Description

[0013] Figure 1 This is a three-dimensional schematic diagram of tunnel construction according to this utility model; Figure 2 This is a schematic diagram of the cross-sectional structure for tunnel construction according to this utility model; Figure 3 This is a structural schematic diagram of the prestressed anchor cable of this utility model; In the diagram: 1-Hard rock layer, 2-Soft soil layer, 3-Upper tunnel, 4-Lower tunnel, 5-Prestressed anchor cable, 51-Steel strand, 52-Sheath, 53-Upper anchor plate, 54-Upper clamp, 55-Lower anchor plate, 56-Lower clamp, 6-Load transfer plate, 7-Anchor bolt, 8-Grouting area. Detailed Implementation

[0014] The present invention will be further described below with reference to the accompanying drawings and specific embodiments: like Figure 1-3 As shown, a deformation control structure for a small-clearance intersecting tunnel in hard-lower-soft strata includes a hard rock layer 1 and a soft soil layer 2. The hard rock layer 1 and the soft soil layer 2 are horizontal or near-horizontal sedimentary rock layers, with the hard rock layer 1 covering the soft soil layer 2. An upper tunnel 3 is constructed within the hard rock layer 1, and a lower tunnel 4 is constructed within the soft soil layer 2. The upper tunnel 3 and the lower tunnel 4 are intersected, with an intersection angle of 0° to 90°. The intersection of the upper tunnel 3 and the lower tunnel 4 is the overlapping area. The arch of the lower tunnel 4, located 3-5 m away from the overlapping area of ​​the upper and lower tunnels, is the grouting zone 8. Grouting is injected into the grouting zone 8 for modification. The grouting zone 8 is a fan-shaped area of ​​±120° from the arch.

[0015] Radial anchor bolts 7 are installed in the overlapping area, and several vertical prestressed anchor cables 5 are also installed in the overlapping area. The lower end of the prestressed anchor cable 5 is connected to the arch of the lower tunnel 4, and the upper end of the prestressed anchor cable 5 extends into the upper tunnel 3. A load transfer plate 6 is installed at the bottom of the arch of the upper tunnel 3, and the upper end of the prestressed anchor cable 5 is fixed to the load transfer plate 6. The prestressed anchor cable 5 includes a sheath 52, a steel strand 51, a lower anchor plate 55, a lower clamp 56, an upper anchor plate 53, and an upper clamp 54. The lower anchor plate 55 and the lower clamp 56 are fixed to the arch of the lower tunnel 4, and the upper anchor plate 53 and the upper clamp 54 are fixed to the load transfer plate 6.

[0016] The holes of the radial anchor bolts 7 are evenly distributed in a fan shape at ±120° of the arch crown, arch waist, and side walls, with a hole inclination of 5°-15°, a circumferential spacing of about 0.6-1.0 m, and an axial step distance of 0.5-1.0 m.

[0017] It should be noted that this utility model discloses the case where the prestressed anchor cable 5 is a steel strand 51. Those skilled in the art can also use other prestressed tendons such as steel wire or prestressed precision-rolled threaded steel. The angle between the axes of the lower tunnel 4 and the upper tunnel 3 in this utility model can be any angle from 0 to 90°. This utility model is applicable to tunnels with various cross-sectional shapes, such as double-circular tunnels, near-rectangular tunnels, elliptical tunnels, and rectangular tunnels, and is not limited to these types. Figure 2The shape of the tunnel shown in the image.

[0018] In addition, this scheme can be used when both the upper and lower tunnels are newly built, or when the upper tunnel 3 is an existing line and the lower tunnel 4 is a newly built line. When constructing for an existing line, it is necessary to excavate at the invert of the existing tunnel, install the load transfer plate 6, the upper anchor plate 53 and the upper clamp 54 at the excavation location, and after completing the prestressing operation, rebuild the invert at the excavation location and restore the normal operation of the existing tunnel.

Claims

1. A deformation control structure for a small-clearance intersecting tunnel in hard-lower-soft strata, comprising a hard rock layer (1) and a soft soil layer (2), wherein the hard rock layer (1) and the soft soil layer (2) are horizontal or near-horizontal sedimentary rock layers, and the hard rock layer (1) overlies the soft soil layer (2); an upper tunnel (3) is formed within the hard rock layer (1), and a lower tunnel (4) is formed within the soft soil layer (2), wherein the upper tunnel (3) and the lower tunnel (4) are intersected, and the intersection of the upper tunnel (3) and the lower tunnel (4) is an overlapping area; characterized in that: The arch of the lower tunnel (4) is located 3-5 m away from the overlapping area of ​​the upper and lower tunnels. The arch is a grouting area (8). Grouting is performed in the grouting area (8). The grouting area (8) is a fan-shaped area of ​​±120° of the arch. Radial anchors (7) are installed in the overlapping area. Several vertical prestressed anchors (5) are also installed in the overlapping area. The lower end of the prestressed anchor (5) is connected to the arch of the lower tunnel (4). The upper end of the prestressed anchor (5) extends into the upper tunnel (3). A load transfer plate (6) is installed at the bottom of the arch of the upper tunnel (3). The upper end of the prestressed anchor (5) is fixed on the load transfer plate (6).

2. The deformation control structure for small-clearance intersecting tunnels in hard-over-soft strata according to claim 1, characterized in that, The prestressed anchor cable (5) includes a sheath (52), a steel strand (51), a lower anchor plate (55), a lower clamp (56), an upper anchor plate (53), and an upper clamp (54). The lower anchor plate (55) and the lower clamp (56) are fixed to the arch of the lower tunnel (4), and the upper anchor plate (53) and the upper clamp (54) are fixed to the load transfer plate (6).

3. The deformation control structure for small-clearance tunnels in hard-over-soft strata according to claim 1, characterized in that, The intersection angle between the upper tunnel (3) and the lower tunnel (4) is 0° to 90°.

4. The deformation control structure for small-clearance tunnels in hard-over-soft strata according to claim 1, characterized in that, The radial anchor bolts (7) are evenly distributed in a fan shape at ±120° of the arch top, arch waist, and side walls, with a hole inclination of 5°-15°, a circumferential spacing of about 0.6-1.0 m, and an axial step distance of 0.5-1.0 m.

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