CN112761161A

CN112761161A - Deep foundation pit excavation combined supporting structure suitable for aeolian sand stratum

Info

Publication number: CN112761161A
Application number: CN202110012399.5A
Authority: CN
Inventors: 张俊儒; 赵生杰; 孔超; 严俊; 杨志君; 马凯蒙; 郑宗溪; 杨瞻梦
Original assignee: Southwest Jiaotong University; China Railway Eryuan Engineering Group Co Ltd CREEC; China State Railway Group Co Ltd
Current assignee: Southwest Jiaotong University; China Railway Eryuan Engineering Group Co Ltd CREEC; China State Railway Group Co Ltd
Priority date: 2021-01-06
Filing date: 2021-01-06
Publication date: 2021-05-07

Abstract

The invention discloses a deep foundation pit excavation combined supporting structure suitable for a wind-blown sand stratum, wherein the upper half part of the deep foundation pit excavation combined supporting structure is an open-cut side slope, and a plurality of side slope anchor rods are driven into the side slope; the lower half part inwards sets gradually from the toe position of side slope and spouts stake and drilling bored concrete pile formation fender pile soon, and fender pile inboard is the foundation ditch, and the foundation ditch bottom spouts the stake soon for the base, and the concrete of base is on the base spouts the stake soon, is the tunnel lining in the foundation ditch, backfills on the tunnel lining. The deep foundation pit excavation combined supporting structure is more reasonable in design, lower in cost and safer and more efficient in construction.

Description

Deep foundation pit excavation combined supporting structure suitable for aeolian sand stratum

Technical Field

The invention belongs to the field of supporting structures for railway tunnel construction, and particularly relates to a deep foundation pit excavation combined supporting structure suitable for a wind-blown sand stratum.

Background

Aeolian sand is a deposit formed by wind power transportation, is widely distributed in China, and mainly exists in northwest areas (mainly inner Mongolia, Gansu, Xinjiang and the like) and partial Tibet areas. The structure of the tunnel is loose, the shear strength is poor, and after the tunnel is excavated, if the support is not timely, the surrounding rock is deformed greatly. The traditional construction generally adopts a mode of subsection excavation and advanced support to build a tunnel, the construction process is complicated, and after the method is adopted for excavation, the tunnel face has poor stability, and the conditions of vault collapse, roof collapse and the like (the roof collapse is shown in that the vault collapses and extends all the way to the ground surface to form a pit on the ground surface) are easy to occur, thereby causing great troubles to the safe and efficient construction of the tunnel.

In the Tibet area of China, the aeolian sand also has the characteristic of shallow buried depth, generally not exceeding about 40m and is positioned at the inlet and outlet positions of a tunnel. When the tunnel passes through the stratum, the vault can even have the roof fall, for example, the tunnel of the Sichuan-Tibet line Lhasa-Linzhi segge Deji has the situation, so that the safety of constructors is threatened, meanwhile, due to the roof fall, the roof fall area needs to be buried in the later period, and the construction cost is increased.

Disclosure of Invention

The invention provides a deep foundation pit excavation combined supporting structure suitable for a wind-blown sand stratum, and aims to solve the problem of railway tunnel construction in a shallow-buried wind-blown sand stratum.

The invention relates to a deep foundation pit excavation combined supporting structure suitable for a wind-blown sand stratum, wherein the upper half part is an open-cut side slope, and a plurality of side slope anchor rods are driven into the side slope; the lower half part inwards sets gradually from the toe position of side slope and spouts stake and drilling bored concrete pile formation fender pile soon, and fender pile inboard is the foundation ditch, and the foundation ditch bottom spouts the stake soon for the base, and the concrete of base is on the base spouts the stake soon, is the tunnel lining in the foundation ditch, backfills on the tunnel lining.

Further, transverse supports are arranged between the fender piles of the foundation pit.

Further, the slope of the side slope and the distribution of the anchor rods of the side slope are determined according to the shear strength of the aeolian sand.

Further, the cast-in-situ bored pile extends to below the inverted arch.

Furthermore, the inverted arch position of the foundation pit is filled with aeolian sand with a certain thickness for ensuring the bearing capacity of the foundation.

The beneficial technical effects of the invention are as follows:

1. the upper half part of the tunnel is excavated by slope-making open cut, the slope toe is positioned at a certain position above the tunnel instead of directly placing the slope toe to the bottom of the inverted arch, the excavation amount is relatively small, and the construction cost is saved.

2. The foundation pit adopts fender pile (by the drilling bored concrete pile with spout the stake soon and constitute), and the drilling bored concrete pile is used for foundation pit antidumping, spouts the stake soon and is used for ending husky, its condition that can not appear leaking husky.

3. The fender pile sets up horizontal stull, has hindered the horizontal displacement of country rock, guarantees that country rock horizontal displacement is less. And due to the action of the cross braces, the bending moment of the fender pile generated by the soil pressure is redistributed, so that the bending moment is smaller than that of the fender pile without the cross braces, and the bending resistance of the fender pile is enhanced.

4. Because a larger space is formed after the foundation pit is excavated, the tunnel lining can be constructed at one time, and the construction efficiency is high.

Drawings

Fig. 1 is a sectional view of the combined supporting structure of the invention.

Fig. 2 is a plan view of the combined supporting structure of the invention.

Fig. 3 is a schematic view of a slope anchor arrangement.

In the drawings, the numbers are explained as follows: 1-a ground line; 2-side slope; 3-central axis of tunnel; 4-side slope anchor rod; 5-jet grouting pile; 6-transverse supporting; 7-tunnel lining; 8-base jet grouting pile; 9-drilling a cast-in-place pile; 10-base concrete; 11-palm surface; 12-toe position.

Detailed Description

The invention is described in further detail below with reference to the figures and the detailed description.

The invention discloses a deep foundation pit excavation combined supporting structure suitable for a wind-blown sand stratum, which is shown in a figure 1 and a figure 2, wherein the upper half part is an open-cut side slope 2, and a plurality of side slope anchor rods 4 are driven into the side slope 2; the lower half part is inwards provided with a jet grouting pile 5 (a jet grouting pile is used for stopping sand) and a cast-in-situ bored pile 9 in sequence from a toe position 12 of the side slope 2 to form a fender post, the inner side of the fender post is provided with a foundation pit, the bottom of the foundation pit is provided with a base jet grouting pile 8, base concrete 10 is arranged on the base jet grouting pile 8, a tunnel lining 7 is arranged in the foundation pit, and the tunnel lining 7 is backfilled.

Further, transverse supports 6 are arranged among the fender piles of the foundation pit according to different burial depths.

Further, the slope of the side slope 2 and the distribution of the side slope anchors 4 (an example of the distribution of the side slope anchors is shown in fig. 3) are determined according to the shear strength of the aeolian sand.

Further, the bored pile 9 extends below the inverted arch, ensuring sufficient resistance to overturning.

The embodiment of the deep foundation pit excavation combined supporting structure provided by the invention comprises the following steps:

1. before construction, slope 2 is firstly put, slope anchor rods 4 are arranged on the slope, the slope is determined according to the shear strength of aeolian sand, and slope feet 12 are located above the tunnel.

2. And (5) constructing the jet grouting pile 5 and the cast-in-situ bored pile 9 after slope putting is finished.

3. When the fender pile reaches the design strength, a foundation pit is excavated from top to bottom, and the rotary jet grouting pile 5 is constructed while the foundation pit is excavated.

4. And after the foundation pit is excavated to the designed depth, constructing a foundation rotary jet grouting pile 8 and foundation concrete 10.

5. And when the base jet grouting pile 8 and the base concrete 10 reach the designed strength, constructing the tunnel lining 7.

6. The tunnel lining 7 reaches the design strength and backfills the foundation pit.

Claims

1. A deep foundation pit excavation combined supporting structure suitable for a wind-blown sand stratum is characterized in that the upper half part is an open-cut side slope (2), and a plurality of side slope anchor rods (4) are driven into the side slope (2); the lower half inwards sets gradually from toe position (12) of side slope (2) and spouts stake (5) and drilling bored concrete pile (9) formation fender post soon, and fender post inboard is the foundation ditch, and the foundation ditch bottom spouts stake (8) soon for the base, for base concrete (10) on base spout stake (8), is tunnel lining (7) in the foundation ditch, backfills on tunnel lining (7).

2. The combined supporting structure for deep foundation pit excavation suitable for aeolian sand formation according to claim 1, characterized in that transverse supports (6) are arranged between fender piles of said foundation pit.

3. The deep foundation pit excavation combined supporting structure suitable for the wind-blown sand formation is characterized in that the slope of the side slope (2) and the distribution of the side slope anchor rods (4) are determined according to the shear strength of the wind-blown sand.

4. The combined supporting structure for deep foundation pit excavation suitable for aeolian sand formation according to claim 1, characterized in that said bored pile (9) extends below the inverted arch.

5. The combined supporting structure for the excavation of the deep foundation pit suitable for the aeolian sand stratum as claimed in claim 1, wherein an inverted arch position of the foundation pit is filled with aeolian sand with a certain thickness for ensuring the bearing capacity of the foundation.