Permanent and temporary combined yielding support construction method suitable for squeezable surrounding rock tunnel

Abstract

The invention belongs to the field of tunnel engineering, and particularly relates to a permanent and temporary combined yielding support construction method suitable for an extrusion surrounding rock tunnel, which comprises the following steps: excavating the extrusion surrounding rock tunnel by adopting a subsection excavation mode, arranging temporary supports at different subsections, realizing ring formation of a support system, adding yielding components on a temporary support structure, and realizing yielding of each subsection. And finally, yielding in the whole process of partial excavation of the extrusion surrounding rock is achieved. The problems of disengagement, cracking and the like caused by deformation incoordination of the primary support and the surrounding rock behind in the yielding deformation process of the yielding component are avoided.

Description

Technical Field

[0001] The present invention belongs to the field of tunnel engineering, and particularly relates to a construction method for permanent-temporary combined yielding support applicable to tunnels in squeezing surrounding rock. Background Art

[0002] The traditional support structure for squeezing surrounding rock has no yielding function. After the invert is closed, the primary support cracks and is severely distorted. For the yielding components (such as yielding steel frames) acting on the primary support structure, when the yielding components deform, the deformation of the primary support is not coordinated with the deformation of the surrounding rock mass, resulting in the separation of the primary support from the rock mass, and then severe wrinkling and distortion. In addition, the traditional yielding support structure can only achieve yielding after the support system is closed into a ring. However, most of the deformation occurs within 20 days at the initial stage of the deformation of squeezing surrounding rock. When constructing using methods such as the bench method and CRD method, it is difficult to close the ring within 20 days. Summary of the Invention

[0003] The purpose of the present invention is to provide a construction method for permanent-temporary combined yielding support applicable to tunnels in squeezing surrounding rock, which is used to solve the problem of high damage rate of the primary support due to the large deformation rate and lack of yielding in the early stage of tunnels in squeezing surrounding rock.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions:

[0005] A construction method for permanent-temporary combined yielding support applicable to tunnels in squeezing surrounding rock. The squeezing surrounding rock tunnel is excavated by a partial excavation method, and temporary supports are set in different parts to realize the closure of the support system into a ring. Yielding components are added to the temporary support structure to achieve yielding in each part, and finally, yielding is realized throughout the whole process of partial excavation of the squeezing surrounding rock.

[0006] Further, the bench method is used for construction, which is divided into three levels: upper, middle, and lower. Specifically, it includes the following steps:

[0007] S1. After the upper bench is excavated, a steel frame and a steel mesh are erected, shotcrete is sprayed, bolts are constructed, and a temporary cross brace or a temporary invert is constructed. One yielding component is set in the middle, and so on and so forth.

[0008] S2. When the distance between the middle bench and the upper bench reaches the designed length and the yielding joint of the upper bench yields to a certain extent, the middle bench is gradually constructed separately on the left and right: one set of temporary support is removed, the left or right side is excavated, a steel frame is erected, shotcrete is sprayed, and bolts are constructed; the other side is excavated, a steel frame is erected, shotcrete is sprayed, bolts are constructed, the temporary cross brace or invert and the yielding component of the middle bench are constructed, the waste slag and gravel are backfilled and leveled.

[0009] S3. Repeat the above steps to construct the lower bench;

[0010] S4. Wait for yielding. After the invert follows up, the invert is constructed, and the support system is closed into a ring.

[0011] Furthermore, when a temporary invert is used in S1, concrete is not sprayed on the compression member.

[0012] Furthermore, when temporary cross braces are used in S1, the cross braces are leveled by backfilling with waste slag and gravel, and each steel frame of the temporary cross braces is arranged at intervals according to the deformation conditions, and the longitudinal connection of the steel frames is strengthened when arranged at intervals.

[0013] Furthermore, the CRD method is used to divide the large section into several caverns, wherein the second cavern is adjacent to the first cavern in the vertical direction, and the third cavern is adjacent to the first cavern in the horizontal direction, specifically including the following steps:

[0014] S1. Excavate the first cavern, erect steel frame and temporary vertical support, spray concrete, construct anchor rods, construct temporary horizontal brace inverts and install pressure joints, and repeat this cycle;

[0015] S2. When the faces of the first and second caverns reach the designed distance, the second cavern is excavated, steel frames and temporary vertical supports are erected, concrete is sprayed, anchors are constructed, temporary horizontal bracing inverts are constructed, and compression joints are installed, and the cycle continues;

[0016] S3. When the first cavern and the second cavern face reach the designed distance, the third cavern is excavated, steel frames are erected, concrete is sprayed, anchor rods are constructed, temporary cross bracing inverts are constructed, and compression joints are installed, and the cycle continues;

[0017] S4. Repeat this process to construct the remaining caverns one by one;

[0018] S5. Wait for the pressure to be released, monitor and measure, and when the deformation is stable or a certain deformation is released and the deformation rate decreases, remove the temporary supports one by one and construct the second layer of initial support or secondary lining.

[0019] The beneficial technical effects of the present invention are as follows: the present invention achieves support yielding during partial excavation by arranging the yielding member on the temporary support, and avoids the voiding and cracking caused by the incoordination between the initial support and the surrounding rock behind during the yielding deformation of the yielding member. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the small section step method;

[0021] Figure 2 Schematic diagram of the large-section CRD method.

[0022] In the figure: 1, 2, 3, 4, 5, 6 are separated cave chambers. DETAILED DESCRIPTION

[0023] The present invention is further described and illustrated below in conjunction with the accompanying drawings and specific embodiments.

[0024] Through the combination of permanent and temporary support, a yielding member is provided on the temporary support to achieve sectional yielding, solving the problem that the initial deformation rate of the squeezing surrounding rock tunnel is large in the early stage and there is no yielding, resulting in a high failure rate of the initial support.

[0025] For the squeezing surrounding rock tunnel, sectional excavation is adopted, and different sections use temporary supports to form a closed loop of the support system. A yielding member is added to the temporary support structure, enabling each section to achieve yielding and realizing yielding throughout the whole process of sectional excavation of the squeezing surrounding rock.

[0026] After the construction of each part of the temporary cross brace, crushed stones are used for paving to increase the lateral support stiffness and meet the on-site transportation requirements.

[0027] Embodiment 1

[0028] As Figure 1 shown, the bench method:

[0029] S1. After the upper bench is excavated, a steel frame and a steel mesh are erected, shotcrete is sprayed, bolts are constructed, and a temporary cross brace or a temporary inverted arch is constructed. One yielding member is arranged in the middle. When a temporary inverted arch is used, no shotcrete is sprayed at the position of the yielding member. When a temporary cross brace is used, the waste slag crushed stones are backfilled and leveled on the cross brace. The upper bench is continuously constructed in this way and advanced in a cycle. The temporary cross brace can be arranged for each steel frame or can be arranged at intervals according to the deformation situation. When arranged at intervals, the longitudinal connection of the steel frames is strengthened.

[0030] S2. When the distance between the middle bench and the upper bench reaches the designed length and the yielding joint of the upper bench yields to a certain extent, the middle bench is successively constructed separately on the left and right: one steel frame of the temporary support is removed, the left (right) side is excavated, a steel frame is erected, shotcrete is sprayed, and bolts are constructed; the other side is excavated, a steel frame is erected, shotcrete is sprayed, bolts are constructed, the temporary cross brace (inverted arch) and the yielding member of the middle bench are constructed, and the waste slag crushed stones are backfilled and leveled.

[0031] S3. Repeat the above steps to construct the lower bench.

[0032] S4. Wait for yielding. After the inverted arch follows up, the inverted arch is constructed, and the support system is closed into a loop.

[0033] Embodiment 2:

[0034] As Figure 2 shown, the CRD or CD method:

[0035] S1. Chamber 1 is excavated, a steel frame and a vertical temporary support are erected, shotcrete is sprayed, bolts are constructed, a temporary cross brace (inverted arch) is constructed and a yielding joint is installed, and so on in a cycle. Chamber 1 is continuously excavated;

[0036] S2. After the faces of adit 1 and adit 2 reach the designed distance, adit 2 is excavated, and steel frames and vertical temporary supports are erected - shotcrete is applied - construction bolts are installed - temporary cross braces (inverted arches) are constructed and yielding joints are installed, and so on in a cycle to continue excavating adit 2;

[0037] S3. After the faces of adit 1 and adit 2 reach the designed distance, adit 3 is excavated, and steel frames are erected - shotcrete is applied - construction bolts are installed - temporary cross braces (inverted arches) are constructed and yielding joints are installed, and so on in a cycle to continue excavating adit 3;

[0038] S4. Repeat the above process to successively construct adit 4, adit 5, and adit 6.

[0039] S5. Wait for yielding, conduct monitoring and measurement. After the deformation is stable or a certain amount of deformation is released and the deformation rate decreases, the temporary supports are removed one by one, and the second layer of primary support or secondary lining is constructed.

[0040] The embodiments described above are only a preferred solution of the present invention, but they are not intended to limit the present invention. Those of ordinary skill in the relevant technical field can also make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all technical solutions obtained by means of equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A permanent and temporary combined pressure-yielding support construction method suitable for a tunnel with extrusive surrounding rock, characterized by: The segmented excavation method is adopted to excavate the tunnel with squeezing surrounding rock. Temporary supports are set up in different segments to realize the ring of the support system. Pressure-yielding components are added to the temporary support structure to achieve pressure-yielding in each segment, and finally achieve pressure-yielding in the whole process of segmented excavation of squeezing surrounding rock.

2. The permanent and temporary combined pressure-yielding support construction method for a squeeze rock tunnel according to claim 1 is characterized in that: The step method is used for construction, which is divided into three steps: upper, middle and lower. The specific steps include: S1. After the upper step is excavated, the steel frame and steel mesh are erected, concrete is sprayed, anchor rods are constructed, and temporary cross braces or temporary inverts are constructed. A pressure relief member is set in the middle, and the process is repeated in this way; S2. When the distance between the middle step and the upper step reaches the designed length, and the upper step pressure relief joint has been relieved to a certain extent, the middle step is constructed in two steps: one temporary support is removed, the left or right side is excavated, a steel frame is erected, concrete is sprayed, and anchor rods are constructed; the other side is excavated, a steel frame is erected, concrete is sprayed, anchor rods are constructed, temporary horizontal braces or backing and pressure relief components of the middle step are constructed, and waste slag and gravel are backfilled and paved; S3. Repeat this process until the next step is completed; S4. Wait for the pressure to be released, and then construct the invert arch after the invert arch is followed up, and the support system is closed into a ring.

3. The permanent and temporary combined pressure-yielding support construction method for a squeeze rock tunnel according to claim 2 is characterized in that When a temporary invert is used in S1, concrete is not sprayed on the compression member.

4. The permanent and temporary combined pressure-yielding support construction method for a squeeze rock tunnel according to claim 2 is characterized in that When temporary cross braces are used in S1, the cross braces are leveled with backfilled slag and gravel. Each steel frame of the temporary cross braces is arranged at intervals according to the deformation conditions, and the longitudinal connection of the steel frames is strengthened when arranged at intervals.

5. The permanent and temporary combined yielding support construction method applicable to a squeezing surrounding rock tunnel according to claim 1 is characterized in that: The CRD method is used to divide the large section into several caverns, where the second cavern is adjacent to the first cavern in the vertical direction and the third cavern is adjacent to the first cavern in the horizontal direction. The specific steps include: S1. Excavate the first cavern, erect steel frame and temporary vertical support, spray concrete, construct anchor rods, construct temporary horizontal brace inverts and install pressure joints, and repeat this cycle; S2. When the faces of the first and second caverns reach the designed distance, the second cavern is excavated, steel frames and temporary vertical supports are erected, concrete is sprayed, anchors are constructed, temporary horizontal bracing inverts are constructed, and compression joints are installed, and the cycle continues; S3. When the first cavern and the second cavern face reach the designed distance, the third cavern is excavated, steel frames are erected, concrete is sprayed, anchor rods are constructed, temporary cross bracing inverts are constructed, and compression joints are installed, and the cycle continues; S4. Repeat this process to construct the remaining caverns one by one; S5. Wait for the pressure to be released, monitor and measure, and when the deformation is stable or a certain deformation is released and the deformation rate decreases, remove the temporary supports one by one and construct the second layer of initial support or secondary lining.

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