CN114382520B

CN114382520B - NPR anchor rod active supporting method suitable for hard rock tunnel

Info

Publication number: CN114382520B
Application number: CN202210298198.0A
Authority: CN
Inventors: 陶志刚; 毛亚东; 明伟; 王志领; 王翔; 郭爱鹏; 杨晓杰; 何满潮
Original assignee: China University of Mining and Technology Beijing CUMTB
Current assignee: China University of Mining and Technology Beijing CUMTB
Priority date: 2022-03-25
Filing date: 2022-03-25
Publication date: 2022-06-17
Anticipated expiration: 2042-03-25
Also published as: CN114382520A

Abstract

The invention belongs to the technical field of tunnel support, and particularly relates to an NPR anchor rod active support method suitable for a hard rock tunnel; the tunnel is excavated by adopting a three-step method, and the first step, the second step and the third step are all supported by adopting an active supporting method, wherein the active supporting method comprises the following steps: step 1, firstly, excavating steps and temporarily supporting a tunnel face; step 2, spraying concrete on the surface of the excavated part; step 3, determining the driving position of the NPR anchor rod on the vault or the side wall of the excavation face, drilling and cleaning the hole; step 4, anchoring an NPR anchor rod in the drilled hole; step 5, paving a flexible net on the vault or the side wall of the excavation surface, and installing a steel belt on the end part of the NPR anchor rod on the same annular surface; and 6, placing an anchor rod supporting plate at the end part of the NPR anchor rod and installing an anchor. According to the active supporting method, the grid steel frame is omitted, the construction speed is improved, and the supporting cost is reduced. Moreover, the construction efficiency can be improved, and the construction period can be shortened.

Description

NPR anchor rod active supporting method suitable for hard rock tunnel

Technical Field

The invention belongs to the technical field of tunnel support, and particularly relates to an NPR anchor rod active support method suitable for a hard rock tunnel.

Background

With the continuous promotion of the urbanization process in China, tunnel engineering is increasing day by day, and the problem of tunnel support from the tunnel engineering is also coming to the end. At present, in stable rock strata such as hard rocks and harder rocks which are shallow or not deeply buried, a large-span (more than 12 m) tunnel is supported passively by adopting a grid steel frame and anchor spraying design, and anchor rods in the existing design scheme are densely arranged, so that the number of drilled holes is too large, and the integrity of surrounding rocks is seriously influenced; the arching effect of the hollow grouting anchor rod is not obvious, the space between grid steel frames is small, and the required quantity is large. The tunnel construction propelling speed is slow, the construction efficiency is low, the construction period is long, the economic benefit is not ideal, and the popularization is not facilitated.

Therefore, there is a need to provide an improved solution to the above-mentioned deficiencies of the prior art.

Disclosure of Invention

The invention aims to provide an NPR anchor rod active supporting method suitable for a hard rock tunnel, and at least solves the problems of low construction efficiency, long construction period and the like of the existing supporting scheme.

In order to achieve the above purpose, the invention provides the following technical scheme:

an NPR anchor rod active supporting method suitable for a hard rock tunnel is characterized in that the tunnel is excavated by a three-step method, a first step, a second step and a third step are all supported by the active supporting method, the excavation direction of the tunnel is taken as the longitudinal direction, and the direction perpendicular to the longitudinal direction is taken as the circumferential direction; the active supporting method comprises the following steps:

step 1, firstly, excavating steps and temporarily supporting a tunnel face;

step 2, spraying concrete on the surface of the excavated part;

step 3, determining the driving position of the NPR anchor rod on the vault or the side wall of the excavation face, drilling and cleaning the hole;

step 4, anchoring an NPR anchor rod in the drilled hole;

step 5, paving a flexible net on the vault or the side wall of the excavation surface, installing steel belts on the end parts of the NPR anchor rods on the same annular surface, and connecting the NPR anchor rods on the same annular surface in series through the annularly extending steel belts;

and 6, placing an anchor rod supporting plate at the end part of the NPR anchor rod and installing an anchor.

In the active bracing method described above, preferably, the anchor rods adjacent in the longitudinal direction are arranged offset from each other.

In the active bracing method, preferably, in step 5, after the installation of the circumferentially extending steel strips is completed, the longitudinally extending steel strips are installed at the end parts of the bolts, and the longitudinally extending steel strips are used for connecting the NPR bolts in series on the same axis; the steel belt network in a shape like a Chinese character jing is formed by the steel belt extending in the circumferential direction and the steel belt extending in the longitudinal direction.

In the active bracing method described above, preferably at least one NPR bolt is spaced between adjacent longitudinally extending steel strips.

In the active supporting method, preferably, after the anchor rod supporting plate and the anchor are installed, a tensioning machine is used for applying pretightening force to the NPR anchor rod, so that the NPR anchor rod and the surrounding rock are coupled.

In the active bracing method described above, the NPR bolts on the tunnel vault are preferably longer than the NPR bolts on the side walls.

In the active bracing method described above, preferably, the steel strip is a W steel strip.

In the active supporting method, preferably, the steel strip is a reinforced strip, the reinforced strip includes a steel strip and a plurality of steel bars, the plurality of steel bars are arranged on the steel strip in parallel, the steel strip and the steel bars extend in the same direction, and a preformed hole is formed in the steel strip at a position where the anchor rod is installed, so as to facilitate installation of the reinforced strip.

In the active bracing method as described above, preferably, in step 4, a resin anchoring agent is charged into the bottom of the borehole, and then an NPR bolt is charged, and the NPR bolt is rotated to anchor the NPR bolt in the borehole.

In the active supporting method, preferably, in step 6, after the NPR anchor rod applies the pre-tightening force, the early-strength concrete is sprayed again, so that the NPR anchor rod is combined with the steel belt and the flexible net into a whole.

Has the advantages that: according to the active supporting method, a grid steel frame is omitted, NPR anchor rods and W steel bands (or reinforced bands) are arranged along the circumferential direction of the tunnel, longitudinal connection of flexible nets is assisted, and NPR anchor rod rib arches formed after concrete is sprayed are used for remarkably improving the integrity and circumferential tensile strength of a sprayed layer, improving the construction rate and reducing the supporting cost. Moreover, the construction efficiency can be improved, and the construction period can be shortened.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. Wherein:

FIG. 1 is a schematic view illustrating the construction of a first step according to an embodiment of the present invention;

FIG. 2 is a schematic view illustrating the construction of a second step according to an embodiment of the present invention;

FIG. 3 is a schematic view illustrating the construction of a third step according to an embodiment of the present invention;

FIG. 4 is a schematic view of a W-steel belt or a ribbed belt on a tunnel crown according to an embodiment of the invention;

fig. 5 is a schematic diagram of a W-steel belt or a ribbed belt on a tunnel side wall in an embodiment of the invention.

In the figure: 1. an NPR anchor rod; 2. a steel belt; 21. w steel band; 22. and (4) reinforcing the rib belt.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments that can be derived by one of ordinary skill in the art from the embodiments given herein are intended to be within the scope of the present invention.

In the description of the present invention, the terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are for convenience of description of the present invention only and do not require that the present invention must be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. The terms "connected" and "connected" used herein should be interpreted broadly, and may include, for example, a fixed connection or a detachable connection; they may be directly connected or indirectly connected through intermediate members, and specific meanings of the above terms will be understood by those skilled in the art as appropriate.

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

According to the specific embodiment of the invention, as shown in fig. 1-5, the invention provides an NPR anchor rod active supporting method suitable for a hard rock tunnel, wherein the tunnel is excavated by a three-step method, the first step, the second step and the third step are all supported by the active supporting method, the excavation direction of the tunnel is longitudinal, and the direction perpendicular to the longitudinal direction is circumferential; the active supporting method comprises the following steps:

step 1, firstly digging steps and temporarily supporting a tunnel face.

And 2, spraying concrete on the surface of the excavated part.

And 3, determining the driving position of the NPR anchor rod 1 on the vault or the side wall of the excavation surface, drilling and cleaning the hole.

Step 4, anchoring the NPR anchor rod 1 in the drilled hole; the anchor rods are installed in the drilled holes, and the adjacent anchor rods in the longitudinal direction are arranged in a staggered mode. That is, two bolts adjacent in the longitudinal direction do not overlap each other, and bolts spaced apart from each other in the longitudinal direction overlap each other in the longitudinal direction, that is, the bolts are arranged obliquely at 45 ° in the longitudinal direction.

In this embodiment, the length of the NPR bolt 1 on the tunnel vault is greater than the NPR bolt 1 on the sidewall. In the embodiment, the vault and the side wall are designed by NPR anchor rods 1 with unequal lengths, so that the function of the anchor rods in primary support is fully exerted, and the support pressure of the secondary lining is reduced.

In step 4, resin anchoring agent is charged into the bottom of the borehole, then the NPR bolt 1 is charged, and the NPR bolt 1 is rotated to anchor the NPR bolt 1 in the borehole.

The resin anchoring agent can realize quick anchoring, and a tensioning machine is used for quickly applying high pre-tightening force (150-200 kN) after the resin anchoring, so that the NPR anchor rod 1 can timely act on surrounding rocks, the surrounding rock pressure is borne as soon as possible, and the expansion of a collapse arch is avoided.

And 5, paving a flexible net on the vault or the side wall of the excavation surface, installing steel belts 2 on the end parts of the NPR anchor rods 1 on the same circumferential surface, and connecting the NPR anchor rods 1 on the same circumferential surface in series through the circumferentially extending steel belts 2.

In the embodiment, after the installation of the steel band 2 which extends circumferentially is finished, the steel band 2 which extends along the longitudinal direction is installed at the end part of the anchor rod, and the NPR anchor rods 1 which are on the same axis are connected in series through the steel band 2 which extends along the longitudinal direction; the steel strips 2 extending in the circumferential direction and the steel strips 2 extending in the longitudinal direction form a well-shaped steel strip 2 net. Thereby can be with the better connection one-piece of all stock, and then can carry out better strutting to the tunnel. Adjacent longitudinally extending steel strips 2 are spaced apart by at least one anchor rod. On the basis of forming the steel strip 2 net, the using amount of the steel strips 2 is reduced as much as possible, so that the supporting cost is saved as much as possible.

In the present embodiment, the steel strip 2 uses a W steel strip 21 or a ribbed strip 22. The W steel belt 21 has high structural strength and low cost and is convenient to construct. Add muscle area 22 and include billet and a plurality of reinforcing bars, a plurality of reinforcing bars set up on the billet side by side, and the billet is unanimous with the extending direction of reinforcing bar, is provided with the preformed hole with the place of stock installation on the billet to add the installation of muscle area 22.

And 6, placing an anchor rod supporting plate at the end part of the NPR anchor rod 1, installing an anchor, and applying pretightening force to the NPR anchor rod 1 by using a tensioning machine. After the NPR anchor rod 1 applies pretightening force, the early-strength concrete is sprayed again, so that the NPR anchor rod 1, the steel belt 2 and the flexible net are combined into a whole.

Compared with the traditional anchor rod, the NPR (Negative Poisson's ratio) anchor rod proposed by the design of the flood tide academician has the extraordinary mechanical characteristics of Negative Poisson ratio effect, high constant resistance, large deformation, energy absorption, continuous repeated impact and the like. Therefore, the method is applied to tunnel support, and an NPR anchor rod rib arch method without a grid steel frame is provided. The NPR anchor rods are connected and combined with the steel belts and the flexible nets to form ribs, and the tunnel annular reinforced support structure body formed by spraying concrete can further reinforce the support of the tunnel; the NPR anchor rods are anchored in surrounding rocks and coupled with the surrounding rocks to form a combined arch, so that the integrity and the circumferential tensile strength of a sprayed layer are obviously improved, the boundary constraint strength of a sprayed layer thin plate between the NPR anchor rods is enhanced, the full coverage of tunnel excavation surface support is realized, and the anchor net spraying support effect is better exerted.

In conclusion, in the technical scheme of the NPR anchor rod active supporting method applicable to the hard rock tunnel, the grid steel frame is omitted, the NPR anchor rods and the W steel band (or the reinforced band) are arranged in the circumferential direction of the tunnel, the flexible net is longitudinally connected, and the NPR anchor rod rib arches formed after concrete is sprayed can obviously improve the integrity and the circumferential tensile strength of a sprayed layer and realize the full coverage of the tunnel excavation surface support, so that the grid steel frame can be omitted, the construction rate is improved, and the support cost is reduced. And the support density is optimized, and the longitudinal spacing of anchor rod rings is optimized by applying high pretightening force to the NPR anchor rod, so that the using amount of the anchor rod is reduced.

And the construction period can be saved, the resin anchoring agent can be quickly solidified, the number of anchor rods can be reduced after the anchor rod supporting density is optimized, the active supporting construction time is shortened, and the construction steps can be optimized by canceling the grid steel frame, so that the construction efficiency is improved, and the construction period is shortened.

It should be understood that the above description is only exemplary, and the embodiments of the present application do not limit the present invention.

The above description is intended to be illustrative of the preferred embodiment of the present invention and should not be taken as limiting the invention, but rather, the invention is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

Claims

1. An NPR anchor rod active supporting method suitable for a hard rock tunnel is characterized in that the tunnel is excavated by a three-step method, and a first step, a second step and a third step are all supported by an active supporting method, wherein the excavation direction of the tunnel is taken as the longitudinal direction, and the direction perpendicular to the longitudinal direction is taken as the circumferential direction; the active supporting method comprises the following steps:

step 1, firstly, excavating steps and temporarily supporting a tunnel face;

step 2, spraying concrete on the surface of the excavated part;

step 4, anchoring an NPR anchor rod in the drilled hole;

step 5, paving a flexible net on the vault or the side wall of the excavated surface, installing steel belts on the end parts of the NPR anchor rods on the same annular surface, and connecting the NPR anchor rods on the same annular surface in series through the steel belts extending in the annular direction;

step 6, placing an anchor rod supporting plate at the end part of the NPR anchor rod and installing an anchor;

the adjacent anchor rods are arranged in a staggered manner along the longitudinal direction;

in step 5, after the installation of the hoop-extending steel belts is completed, installing longitudinally-extending steel belts at the end parts of the anchor rods, wherein the longitudinally-extending steel belts are used for connecting the NPR anchor rods on the same axis in series; forming a # -shaped steel belt net by the circumferentially extending steel belt and the longitudinally extending steel belt;

adjacent longitudinally extending steel strips are spaced apart by at least one NPR anchor.

2. The active support method of claim 1, wherein after the anchor supporting plate and the anchor are installed, a tensioning machine is used for applying pre-tightening force to the NPR anchor rod, so that the NPR anchor rod and the surrounding rock are coupled.

3. The active support method of claim 1, wherein the length of the NPR bolts on the tunnel vault is greater than the NPR bolts on the sidewall.

4. The active support method of claim 1, wherein the steel strip is a W-steel strip.

5. The active support method according to claim 1, wherein the steel strip is a reinforced strip, the reinforced strip comprises a steel strip and a plurality of steel bars, the plurality of steel bars are arranged on the steel strip side by side, the steel strip and the steel bars extend in the same direction, and a reserved hole is formed in the steel strip where the anchor rod is installed so as to facilitate installation of the reinforced strip.

6. The active bracing method according to any one of claims 1 to 4, wherein in step 4, resin anchoring agent is charged into the bottom of the borehole, and then NPR bolt is charged, and the NPR bolt is rotated to anchor the NPR bolt in the borehole.

7. The active support method of any one of claims 1 to 4, wherein in step 6, after the NPR anchor rods apply the pretightening force, the early strength concrete is sprayed again, so that the NPR anchor rods are combined with the steel belts and the flexible nets into a whole.