CN114086563B - Construction method for improving bearing capacity of soil body right above shallow tunnel - Google Patents

Abstract

A construction method for improving the bearing capacity of soil body right above a shallow tunnel belongs to the technical field of tunnel construction. The method comprises the following steps: constructing an inclined self-supporting steel sheet pile foundation pit supporting structure, and excavating and cleaning soil in the inclined self-supporting steel sheet pile foundation pit supporting structure until the integral structure of the existing shallow tunnel is exposed; and (3) carrying out the construction of the mixed reinforcement ground beam structure in the soil body below the existing shallow tunnel, constructing a reinforcing structure outside the existing shallow tunnel, backfilling the soil body between the inclined self-supporting steel sheet pile foundation pit supporting structures, removing the inclined self-supporting steel sheet pile foundation pit supporting structures, and recovering the site. The invention saves materials and labor, is economical in construction and shortens the construction period; the slope laying width is reduced, the construction site is saved, and the construction can be performed in a narrow construction site; the waterproof property and the supporting rigidity of the steel sheet pile are improved, and the steel sheet pile is not easy to deform; the bearing capacity above and below the existing shallow tunnel is improved, and the requirement of future development planning of cities is met.

Description

Construction method for improving bearing capacity of soil body right above shallow tunnel

Technical Field

The invention relates to a construction method for improving the bearing capacity of soil body right above a shallow tunnel, and belongs to the technical field of tunnel construction.

Background

With the powerful pushing of urban construction, urban land is utilized more efficiently, and some urban underground shallow tunnels can be fully utilized according to urban planning, so that more forms of infrastructure or buildings with more abundant functions are built. Therefore, a higher requirement is placed on the upper bearing capacity of the existing shallow tunnel.

The foundation construction of China has been carried out for years, the initial design of shallow tunnels built in early stages does not consider the upper bearing capacity, and after the construction is aged for years, the upper bearing capacity can not meet the urban development requirement, and the upper land resources can not be reused.

For the situation, some plans choose to directly dismantle the existing shallow tunnel, but some existing shallow tunnels have high initial cost, the structure is well preserved, and the direct dismantling clearly wastes the residual value. Therefore, the method is particularly important for the lifting work of the bearing capacity above the existing shallow tunnel.

The existing shallow tunnel is generally used for a long time, the surrounding of the tunnel is usually prosperous along with the development of time, the buildings are more, the construction sites are very limited, and the construction is a challenge; secondly, after the structure is built, the stress field around the stratum of the structure tends to be stable, a secondary stress field and an initial stress field generated by construction on the existing structure are overlapped, and how to ensure the safety of the structure and the existing surrounding buildings under the condition of complex stress becomes a problem which needs to be solved in the process of improving the bearing capacity above the existing shallow tunnel.

Disclosure of Invention

In order to solve the problems in the background technology, the invention provides a construction method for improving the bearing capacity of the soil body right above a shallow tunnel.

The invention adopts the following technical scheme: a construction method for improving the bearing capacity of soil body right above a shallow tunnel comprises the following steps:

s1: constructing a foundation pit supporting structure of the inclined self-supporting steel sheet pile;

s2: excavating and cleaning soil bodies among the foundation pit supporting structures of the inclined self-supporting steel sheet piles until the integral structure of the existing shallow tunnel is exposed;

s3: carrying out mixed reinforcement construction of a ground beam structure in soil below an existing shallow tunnel;

s4: constructing a reinforcing structure outside the existing shallow tunnel;

s5: filling soil back between foundation pit supporting structures of the inclined self-supporting steel sheet piles;

s6: and removing the foundation pit supporting structure of the inclined self-supporting steel sheet pile, recovering the site, and completing the carrying capacity lifting engineering of the area right above the existing shallow tunnel.

Compared with the prior art, the invention has the beneficial effects that:

1. under the condition of the field permission, the self-supporting capacity of the soil is utilized, the steel sheet pile with a certain inclination is adopted to support the excavated foundation pit, compared with the vertical support, the anchor rod can be reduced, the materials and the labor are saved, the construction is economical, and the construction period can be shortened; compared with the common slope, the width of the slope is reduced, the construction site is saved, and the construction can be performed in a narrower construction site;

2. the invention utilizes the I-shaped steel sheet pile with the G-shaped connector, the connector increases the seepage path of water, and the waterproofness of the steel sheet pile is improved; the I-shaped structure increases the section moment of inertia, improves the supporting rigidity of the steel sheet pile, and is not easy to deform;

3. the invention adopts the mixed reinforcement ground beam structure below the existing shallow tunnel with the concrete ground beams and the grouting reinforcement soil beams alternately arranged one by one, obviously improves the bearing capacity of the foundation below the existing shallow tunnel without affecting the structure of the existing shallow tunnel, and creates conditions for reconstruction and expansion engineering above the existing shallow tunnel;

4. the invention uses the reinforcing frame to reinforce the existing shallow tunnel structure, can realize the reutilization of the existing shallow tunnel, and avoids the waste of the existing shallow tunnel with residual value. The use of the reinforcing frame can protect the old structure of the existing shallow tunnel from being damaged, and meanwhile, the bearing capacity above the existing shallow tunnel is improved, and the requirement of future development planning of cities is met.

Drawings

FIG. 1 is a schematic diagram of the structure of the present invention after S4 is completed;

FIG. 2 is a cross-sectional view of FIG. 1;

FIG. 3 is a schematic view of the structure of a steel sheet pile;

fig. 4 is a top view of fig. 3.

Detailed Description

The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the invention, but not all embodiments, and all other embodiments obtained by those skilled in the art without making creative efforts based on the embodiments of the present invention are all within the protection scope of the present invention.

A construction method for improving the bearing capacity of soil body right above a shallow tunnel comprises the following steps:

s1: constructing an inclined self-supporting steel sheet pile foundation pit supporting structure, and pressing an I-shaped steel sheet pile 2 with a G-shaped connector;

s101: the construction position is determined by paying off of GPS total stations along two sides of the existing shallow tunnel 5 in the field 1, the error is less than 5cm, the setting position and the setting sequence of the steel sheet pile 2 are determined by positioning paying off, and the gray line can be sprayed for indication;

s102: pressing a single steel sheet pile 2 which is inclined from top to bottom by 0 to 20 degrees into the construction position according to a design angle by using a matched steel sheet pile pressing machine until the lower end part of the steel sheet pile 2 reaches the pile bottom design elevation;

the single steel sheet pile 2 comprises at least one steel sheet pile 2, and when the number of the steel sheet piles 2 is greater than one, the steel sheet piles 2 are sequentially connected along the axial direction thereof and adjacent end portions are welded and connected.

If one steel sheet pile 2 cannot reach the pile bottom design elevation, carrying out a reinforcing welding procedure with the next steel sheet pile when the upper part of the steel sheet pile is about 1.5 m away from the ground, and adopting diamond steel plate welding, wherein the procedures all accord with the corresponding steel welding technical specifications; after the steel sheet piles are connected in a butt joint mode, the welding joints are required to be staggered up and down during construction, the risk that the whole stress is on the joint at the same position is reduced, and then the pressing operation is carried out.

The steel sheet pile 2 is an I-shaped steel sheet pile with a G-shaped connector, the upper flange of the steel sheet pile is 500mm long, the lower flange of the steel sheet pile is 300mm long, the thickness of the steel sheet pile is 20mm, the web is 500mm high, and the thickness of the steel sheet pile is 14mm. G-shaped convolution interfaces for splicing adjacent steel sheet piles are arranged on two sides of the upper flange;

the form and the inclination of the steel sheet pile are measured and monitored at any time during the process of pressing the steel sheet pile, the error between the form and the inclination and the design inclination is not more than 1 percent, and when the deviation is too large, the steel sheet pile is lifted and pressed in again;

s103: one side of the existing shallow tunnel 5 is pressed into a steel sheet pile row group formed by connecting a plurality of steel sheet piles 2 in parallel along the length direction of the existing shallow tunnel 5, and the adjacent steel sheet piles 2 are connected through G-shaped interfaces;

when the adjacent steel sheet piles are pressed in, the positions of the steel sheet piles are confirmed to be accurate, when the adjacent steel sheet piles are pressed in, the G-shaped connectors are connected, then the angles are confirmed to be connected, and then the steel sheet piles are pressed in;

s104: and a group of steel sheet pile row groups are pressed into the other side of the existing shallow buried tunnel 5 along the length direction of the existing shallow buried tunnel 5, and adjacent steel sheet piles 2 are connected through G-shaped interfaces to form an inclined self-supporting steel sheet pile foundation pit supporting structure.

S2: after the inclined self-supporting steel sheet pile foundation pit supporting structures are formed, excavating and cleaning soil bodies among the inclined self-supporting steel sheet pile foundation pit supporting structures in the S1 above the existing shallow-buried tunnel 5, and completely cleaning the soil bodies around the existing shallow-buried tunnel 5 until the integral structure of the existing shallow-buried tunnel 5 is exposed;

s201: cleaning the soil body above the top plate of the existing shallow tunnel 5;

s202: and cleaning soil bodies at two sides of the existing shallow tunnel 5, wherein a symmetrical layering construction method is adopted in the construction process, and the height difference of the soil bodies at two sides is not more than 2.0m.

S3: carrying out mixed reinforcement construction of a ground beam structure in soil below the existing shallow tunnel 5;

s301: a small tunnel penetrating the width direction of the existing shallow tunnel 5 is excavated in the soil body below the existing shallow tunnel 5 at equal intervals by using a small excavating machine;

the length of the small tunnel is consistent with the width of the existing shallow buried tunnel, the height and the width are determined according to the actual size of the existing shallow buried tunnel, and the width of the spacing soil body is the same as the width of the small tunnel; when a small tunnel is excavated, the existing shallow tunnel structure is monitored at any time;

s302: s301, supporting a formwork in the small tunnel, erecting a steel bracket, binding steel bars and pouring concrete to form a concrete land beam 6 for supporting the existing shallow tunnel 5;

s303: grouting is carried out in soil between every two adjacent concrete ground beams 6, the soil strength is improved, grouting reinforced soil beams 7 are formed, and the concrete ground beams 6 and the grouting reinforced soil beams 7 are alternately arranged one by one to form a mixed reinforced ground beam structure below the existing shallow tunnel 5.

Grouting is sequentially performed according to a hole-jumping interval grouting mode, and a grouting construction method of firstly surrounding and then in the middle is adopted. The grouting material is pure cement slurry, the cement is ordinary silicate cement, the water-cement ratio is 1:1, and the grouting pressure is determined according to the foundation treatment standard and the actual situation.

S4: constructing a reinforcing structure outside the existing shallow tunnel 5;

s401: the method comprises the steps of constructing a reinforcing frame 3 outside an existing shallow tunnel 5, wherein the main construction content is to newly construct high-strength side walls and top plate structures on two sides and the upper part of the existing shallow tunnel, roughening the outer wall of the existing shallow tunnel before construction, and preparing for filling mortar, wherein a 10cm gap is reserved between the reinforcing frame 3 and the outer wall of the existing shallow tunnel 5, so that the existing shallow tunnel is prevented from bearing the load transmitted by the reinforcing frame;

s402: and (3) injecting M20 masonry mortar 4 into the gap in S401 to prevent the gap from causing the destruction of the concrete structure in the later development period of time.

S5: after the reinforced structure reaches the design strength, orderly withdrawing equipment and personnel, and filling soil bodies back between foundation pit supporting structures of the inclined self-supporting steel sheet piles, wherein the symmetrical layering construction method is adopted during backfilling, and the height difference of the soil bodies at two sides is not more than 2.0m;

s6: when the inclined self-supporting steel sheet pile foundation pit supporting structure is pulled out, the selection of a pile pulling starting point and a pile pulling sequence is determined according to actual engineering conditions, and the pile pulling sequence is opposite to the pressing sequence; and after pile pulling is completed, filling the pile holes, recovering the site, and completing the carrying capacity improvement project of the area right above the existing shallow tunnel.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Furthermore, it should be understood that although the present disclosure describes embodiments, not every embodiment is provided with a separate embodiment, and that this description is provided for clarity only, and that the disclosure is not limited to the embodiments described in detail below, and that the embodiments described in the examples may be combined as appropriate to form other embodiments that will be apparent to those skilled in the art.

Claims (1)

1. A construction method for improving the bearing capacity of soil body right above a shallow tunnel is characterized by comprising the following steps: the method comprises the following steps:

s1: constructing a foundation pit supporting structure of the inclined self-supporting steel sheet pile;

s101: determining construction positions at two sides of an existing shallow tunnel (5);

s102: pressing a single steel sheet pile (2) which is obliquely arranged from top to bottom into the construction position S101 according to a design angle until the lower end part of the steel sheet pile (2) reaches the pile bottom design elevation;

the single steel sheet pile (2) comprises at least one steel sheet pile (2), and when the number of the steel sheet piles (2) is greater than one, the steel sheet piles (2) are sequentially connected along the axial direction of the steel sheet piles, and adjacent end parts are welded and connected;

s103: pressing a group of steel sheet pile row groups formed by parallel connection of a plurality of steel sheet piles (2) into one side of an existing shallow tunnel (5);

s104: pressing a group of steel sheet pile row groups into the other side of the existing shallow buried tunnel (5) to form an inclined self-supporting steel sheet pile foundation pit supporting structure;

s2: digging and cleaning soil bodies among foundation pit supporting structures of the inclined self-supporting steel sheet piles in the step S1 until the integral structure of the existing shallow tunnel (5) is exposed;

s201: cleaning the soil body above the top plate of the existing shallow tunnel (5);

s202: cleaning soil bodies at two sides of an existing shallow buried tunnel (5), wherein a symmetrical layering construction method is adopted in the construction process, and the height difference of the soil bodies at two sides is not more than 2.0m;

s3: carrying out mixed reinforcement construction of a ground beam structure in soil below an existing shallow tunnel (5);

s301: excavating small tunnels penetrating the existing shallow-buried tunnel (5) in the width direction at equal intervals in the soil body below the existing shallow-buried tunnel (5);

s302: s301, supporting a formwork in the small tunnel, erecting a steel bracket, binding steel bars and pouring concrete to form a concrete land beam (6) for supporting the existing shallow tunnel (5);

s303: grouting is carried out in soil between every two adjacent concrete ground beams (6) to form grouting reinforced soil beams (7), and the concrete ground beams (6) and the grouting reinforced soil beams (7) are alternately arranged one by one to form a mixed reinforced ground beam structure below the existing shallow tunnel (5);

s4: constructing a reinforcing structure outside the existing shallow tunnel (5);

s401: constructing a reinforcing frame (3) outside the existing shallow tunnel (5), wherein a gap is reserved between the reinforcing frame (3) and the outer wall of the existing shallow tunnel (5);

s402: injecting mortar (4) into the gap in S401;

s5: filling soil back between foundation pit supporting structures of the inclined self-supporting steel sheet piles;

s6: and removing the foundation pit supporting structure of the inclined self-supporting steel sheet pile, recovering the site, and completing the carrying capacity lifting engineering of the area right above the existing shallow tunnel.

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