阅读说明：本技术 软弱围岩大断面隧道开挖施工方法 (Excavation construction method for weak surrounding rock large-section tunnel ) 是由 谭忠盛 赵金鹏 高俊鹏 周振梁 李宗林 于 2021-07-06 设计创作，主要内容包括：本申请公开了一种软弱围岩大断面隧道开挖施工方法,该软弱围岩大断面隧道开挖施工方法包括如下步骤：拱部超前支护；上台阶环形开挖,并留置上台阶核心土；上拱部初期支护；上台阶核心土开挖；下台阶中部倒梯形开挖；下台阶两侧开挖；下台阶初期支护,并与上拱部初期支护封闭成环。本申请实现了提升施工过程中的安全性的同时,加快施工效率,缩短工期从而降低工程投入的技术效果,进而解决了相关技术中的软弱围岩隧道施工方法存在开挖支护技术步骤繁琐,施工效率较低,安全性差,不能及时封闭成环的问题。(The application discloses a weak surrounding rock large-section tunnel excavation construction method, which comprises the following steps: supporting arch part in advance; annularly excavating the upper step, and keeping the core soil of the upper step; primary support of an upper arch part; excavating upper step core soil; excavating the middle part of the lower step in an inverted trapezoid manner; excavating two sides of the lower step; the lower step primary support and the upper arch primary support are sealed to form a ring. According to the construction method, the construction efficiency is accelerated while the safety in the construction process is improved, the technical effect of reducing the project investment is achieved by shortening the construction period, and the problems that the excavation supporting technology steps are complicated, the construction efficiency is low, the safety is poor and the ring cannot be closed in time in the weak surrounding rock tunnel construction method in the related technology are solved.)

1. A construction method for excavating a weak surrounding rock large-section tunnel is characterized by comprising the following steps:

supporting arch part in advance;

annularly excavating the upper step, and keeping the core soil of the upper step;

primary support of an upper arch part;

excavating upper step core soil;

excavating the middle part of the lower step in an inverted trapezoid manner;

excavating two sides of the lower step;

the lower step primary support and the upper arch primary support are sealed to form a ring.

2. The weak surrounding rock large-section tunnel excavation construction method of claim 1, wherein the arch portion advance support specifically comprises: and an advanced large pipe shed is adopted for supporting at the opening of the hole, and an advanced small pipe or an advanced anchor rod is adopted for supporting in the hole.

3. The weak surrounding rock large-section tunnel excavation construction method of claim 2, wherein in the arch portion advance support construction process, holes are arranged according to technical requirements, an advance external insertion angle is mastered, and the external insertion angle is adjusted according to actual conditions on site;

the overlapping length of adjacent sections is required to meet the design and specification requirements, the support tail is required to be firmly welded with the steel support, grouting construction is required to be carried out strictly according to the design mixing proportion, and grouting pressure is well controlled.

4. The weak surrounding rock large-section tunnel excavation construction method of claim 3, wherein the upper step core soil section area occupies 50% of the upper step section area.

5. The weak surrounding rock large-section tunnel excavation construction method of claim 4, wherein the distance between the upper end face of the upper step core soil and the arch crown of the tunnel is 1.3-1.7 m.

6. The weak surrounding rock large-section tunnel excavation construction method according to any one of claims 1 to 5, characterized in that the preliminary bracing of the upper arch part is specifically as follows: primarily spraying concrete; setting a system anchor rod; hanging a net; erecting a steel arch frame; arranging a foot-locking anchor rod or anchor pipe; and spraying the concrete again to the designed thickness.

7. The weak surrounding rock large-section tunnel excavation construction method of claim 6, wherein the steel arch frame of the erection steel arch frame is erected according to a designed size, joints are fixedly connected through bolts, and welding connection is performed when necessary;

the space and welding of the longitudinal connecting steel bars are strictly carried out according to the design and specification requirements so as to ensure the integrity of primary support, and in a particularly soft stratum, the arch wall foot can be provided with a profile steel joist so as to enhance the integrity and avoid cracking or overlarge deformation of the primary support caused by uneven settlement.

8. The excavation construction method for the weak surrounding rock large-section tunnel according to claim 7, wherein the section of the core soil of the upper step is in a regular trapezoid shape, and the bottom edge of the core soil of the upper step is the top edge of the inverted trapezoid section in the middle of the lower step.

9. The excavation construction method of the weak surrounding rock large-section tunnel according to claim 8, wherein the width of the lower portion of the lower step is 2.5-3.0 m, the width of the upper portion of the lower step is 4.0-5.0 m, and the distance between the upper step and the core soil is 5.0-6.0 m.

10. The excavation construction method of the weak surrounding rock large-section tunnel according to claim 9, wherein the excavation on both sides of the lower step is staggered from the inverted trapezoidal excavation part in the middle of the lower step by a distance of 3.0-5.0 m.

Technical Field

The application relates to the technical field of tunnel excavation construction, in particular to a weak surrounding rock large-section tunnel excavation construction method.

Background

China is a country with wide breadth, complex terrain and variable geology. With the further development of economy, the requirements of China on tunnel construction are greatly increased. Correspondingly, under the condition of weak surrounding rock, the problem that how to safely and efficiently realize the excavation process of the large-section tunnel is intuitively faced by the engineering interface is solved.

When the tunnel passes through the weak surrounding rock section, the tunnel has the characteristics of low overall strength and poor self-stability, so that great troubles are caused to the excavation support of engineering construction and the safety problems of workers. In the construction process of the tunnel at the weak surrounding rock section, the improper excavation and supporting measures can cause overlarge deformation of surrounding rocks around the tunnel face, invade lining clearance, even cause local block falling and even collapse of the tunnel face, thereby influencing the construction safety, prolonging the construction period and increasing the engineering investment. The existing weak surrounding rock tunnel construction method has the problems of complicated excavation supporting technical steps, low construction efficiency, poor safety and incapability of being sealed in time to form a ring.

Disclosure of Invention

The main purpose of the application is to provide a weak surrounding rock large-section tunnel excavation construction method, and the method is used for solving the problems that excavation supporting technology steps are complex, construction efficiency is low, safety is poor, and ring formation cannot be closed in time in a weak surrounding rock tunnel construction method in the related technology.

In order to achieve the purpose, the application provides a soft surrounding rock large-section tunnel excavation construction method, which comprises the following steps: supporting arch part in advance; annularly excavating the upper step, and keeping the core soil of the upper step; primary support of an upper arch part; excavating upper step core soil; excavating the middle part of the lower step in an inverted trapezoid manner; excavating two sides of the lower step; the lower step primary support and the upper arch primary support are sealed to form a ring.

Further, the arch part advance support specifically comprises: and an advanced large pipe shed is adopted for supporting at the opening of the hole, and an advanced small pipe or an advanced anchor rod is adopted for supporting in the hole.

Furthermore, during the construction process of the arch part advance support, arranging holes according to the technical requirements, mastering the advanced extrapolation angle, and adjusting the extrapolation angle according to the actual field condition;

the overlapping length of adjacent sections is required to meet the design and specification requirements, the support tail is required to be firmly welded with the steel support, grouting construction is required to be carried out strictly according to the design mixing proportion, and grouting pressure is well controlled.

Further, the section area of the core soil of the upper step occupies 50% of the section area of the upper step.

Furthermore, the distance between the upper end surface of the upper step core soil and the arch crown of the tunnel is 1.3-1.7 m.

Further, the preliminary bracing of the upper arch part is specifically as follows: primarily spraying concrete; setting a system anchor rod; hanging a net; erecting a steel arch frame; arranging a foot-locking anchor rod or anchor pipe; and spraying the concrete again to the designed thickness.

Furthermore, the steel arch frame in the erection steel arch frame is erected according to the designed size, the joints are connected and fixed by bolts and are welded when necessary;

the space and welding of the longitudinal connecting steel bars are strictly carried out according to the design and specification requirements so as to ensure the integrity of primary support, and in a particularly soft stratum, the arch wall foot can be provided with a profile steel joist so as to enhance the integrity and avoid cracking or overlarge deformation of the primary support caused by uneven settlement.

Furthermore, the section of the upper step core soil is in a regular trapezoid shape, and the bottom edge of the upper step core soil is the top edge of the inverted trapezoid section in the middle of the lower step.

Furthermore, the width of the lower part of the lower step is 2.5-3.0 m, the width of the upper part of the lower step is 4.0-5.0 m, and the distance between the lower part and the upper step is 5.0-6.0 m.

Furthermore, when two sides of the lower step are excavated, the lower step is staggered with the inverted trapezoidal excavated part in the middle of the lower step, and the staggered distance is 3.0-5.0 m.

In the embodiment of the application, the arch part is arranged for forepoling; annularly excavating the upper step, and keeping the core soil of the upper step; excavating core soil of an upper step of the primary support of the upper arch part; excavating the middle part of the lower step in an inverted trapezoid manner; excavating two sides of the lower step; the lower step primary support and the upper arch portion primary support are sealed to form a ring, so that the safety in the construction process is improved, the construction efficiency is accelerated, the construction period is shortened, the technical effect of engineering investment is reduced, and the problems that the excavation supporting technology steps are complex, the construction efficiency is low, the safety is poor, and the ring cannot be sealed in time in the weak surrounding rock tunnel construction method in the related technology are solved.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, serve to provide a further understanding of the application and to enable other features, objects, and advantages of the application to be more apparent. The drawings and their description illustrate the embodiments of the invention and do not limit it. In the drawings:

FIG. 1 is a schematic structural diagram according to an embodiment of the present application;

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

the method comprises the following steps of 1 arch part advanced support, 2 upper step annular excavation, 3 upper step core soil excavation, 4 lower step two-side excavation, 5 lower step preliminary support, 6 lower step middle inverted trapezoid excavation and 7 upper arch part preliminary support.

Detailed Description

In order to make the technical solutions better understood by those skilled in the art, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only partial embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

It should be noted that the terms "first," "second," and the like in the description and claims of this application and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It should be understood that the data so used may be interchanged under appropriate circumstances such that embodiments of the application described herein may be used.

In this application, the terms "upper", "lower", "inside", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings. These terms are used primarily to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to a particular orientation or to be constructed and operated in a particular orientation.

Moreover, some of the above terms may be used to indicate other meanings besides the orientation or positional relationship, for example, the term "on" may also be used to indicate some kind of attachment or connection relationship in some cases. The specific meaning of these terms in this application will be understood by those of ordinary skill in the art as appropriate.

Furthermore, the terms "disposed," "provided," "connected," "secured," and the like are to be construed broadly. For example, "connected" may be a fixed connection, a detachable connection, or a unitary construction; can be a mechanical connection, or an electrical connection; may be directly connected, or indirectly connected through intervening media, or may be in internal communication between two devices, elements or components. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.

In addition, the term "plurality" shall mean two as well as more than two.

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.

As shown in fig. 1 to 2, an embodiment of the present application provides a soft surrounding rock large-section tunnel excavation construction method, including the following steps: supporting arch part in advance; annularly excavating the upper step, and keeping the core soil of the upper step; primary support of an upper arch part; excavating upper step core soil; excavating the middle part of the lower step in an inverted trapezoid manner; excavating two sides of the lower step; the lower step primary support and the upper arch primary support are sealed to form a ring.

In this embodiment, the tunnel face is divided into five parts for excavation, and the tunnel face is integrally divided into an upper part and a lower part, wherein the upper part includes an upper step annular part and an upper step core soil part, and the lower part includes a lower step middle inverted trapezoidal part located at a middle intersection and two lower step parts located at two sides. Because the construction method aims at weak surrounding rocks, advanced support is required between excavation, namely an arch support structure is arranged above the tunnel face of the tunnel. The arch part advance support specifically comprises the following steps: the method comprises the following steps that an advanced large pipe shed is adopted for supporting at a tunnel opening, an advanced small pipe or an advanced anchor rod is adopted for supporting in a tunnel, holes are distributed according to technical requirements in the construction process of the advanced support of the arch part, an advanced external insertion angle is mastered, and the external insertion angle is adjusted according to the actual situation on site; the overlapping length of adjacent sections is required to meet the design and specification requirements, the support tail is required to be firmly welded with the steel support, grouting construction is required to be carried out strictly according to the design mixing proportion, and grouting pressure is well controlled.

After the arch advance support construction is finished, firstly, annular excavation is carried out on the upper step to form an annular excavation area, and as the annular excavation is carried out on the upper step, the core soil of the upper step is kept, so that the stability of the tunnel face can be maintained. The section of the upper step core soil is in a regular trapezoid shape, and the section area of the upper step core soil occupies 50% of the section area of the upper step, so that the operation of a constructor is facilitated. The annular excavation height of the upper step is determined by combining the machining size of the steel arch according to the actual surrounding rock condition, the operation of personnel is convenient, and the annular excavation height is preferably controlled to be 3.5-4.0 m; the excavation circulating footage is preferably controlled according to the spacing of 2 steel arches, and is generally 0.5-1.0 m.

As shown in fig. 1 to 2, the distance between the upper end surface of the upper step core soil and the arch crown of the tunnel is 1.3-1.7m, preferably 1.5m, so that the operation is convenient for constructors to operate.

As shown in fig. 1 to 2, after each excavation, primary support should be performed in time to achieve "early shotcrete anchor", wherein the primary support of the upper arch part specifically includes: primarily spraying concrete; setting a system anchor rod; hanging a net; erecting a steel arch frame; arranging a foot-locking anchor rod or anchor pipe; and spraying the concrete again to the designed thickness. Erecting a steel arch frame in the erecting steel arch frame according to the designed size, connecting and fixing the joints by using bolts, and welding when necessary;

the space and welding of the longitudinal connecting steel bars are strictly carried out according to the design and specification requirements so as to ensure the integrity of primary support, and in a particularly soft stratum, the arch wall foot can be provided with a profile steel joist so as to enhance the integrity and avoid cracking or overlarge deformation of the primary support caused by uneven settlement.

As shown in fig. 1 to 2, the section of the core soil of the upper step is in a regular trapezoid shape, the bottom edge of the core soil of the upper step is the top edge of the inverted trapezoid section at the middle part of the lower step, the width of the lower part of the inverted trapezoid excavated at the middle part of the lower step is 2.5 to 3.0m, the width of the upper part of the inverted trapezoid excavated lower part of the lower step is 4.0 to 5.0m, and the distance from the core soil of the upper step is 5.0 to 6.0 m.

Specifically, the double-side-wall guide pit and CRD construction method adopts an excavation method of excavating two sides, then excavating a middle structure, and the middle soil body left after excavating the soil bodies on the two sides is in a regular trapezoid, square or other structure. In the construction method, the mode that the middle of the lower step is firstly excavated and the two sides of the lower step are excavated is adopted, due to the inverted trapezoidal structure in the middle, the downward excavation is facilitated, the width of the bottom is smaller, soil bodies on the two sides of the lower step can form soil pressure on the bottom, and the bottom uplift can be effectively prevented.

Furthermore, when two sides of the lower step are excavated, the lower step is staggered with the inverted trapezoidal excavated part in the middle of the lower step, the staggered distance is 3.0-5.0m, the length of the single-side excavation is not more than 1.2m, and the control is preferably carried out according to the space between 2 steel arches.

The construction method effectively reduces the construction difficulty, and the construction method has the advantages that the working procedure is simple, the excavation and the primary support of each part are easy to control, and the construction difficulty is reduced. The method has the advantages of simple process, easy control of excavation and initial support of each part and low construction difficulty.

Compared with the construction method of double-side-wall pilot tunnel and CRD, the construction method greatly saves temporary steel frames and temporary sprayed concrete, saves labor and materials; meanwhile, the excavation method is free of temporary support, and the time for dismantling the temporary support is saved, so that the working procedures are easy to convert when surrounding rocks change, and the construction progress is accelerated. In addition, the core soil supports the top working surface, so that the stability is good; excavating is carried out under the protection of a support; short footage and equipment utilization shorten the exposure time of surrounding rocks; the working procedures are less, the distance between the working procedures is short, the primary support can be sealed into a ring as soon as possible, and the support effect is exerted. The construction method can be flexibly applied, and when the construction method is used alone, the height of the staggered platform can be flexibly adjusted according to the actual surrounding rock condition.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.