阅读说明：本技术 一种软岩大跨和变截面隧道的施工方法 (Construction method of soft rock large-span and variable-section tunnel ) 是由 杨志威 龙东宏 李志华 蔡颖 肖志国 于 2021-07-22 设计创作，主要内容包括：本发明公开了一种软岩大跨和变截面隧道的施工方法,包括施工开挖时进行超前地质预测,进行单线/双线正洞并建立支护体系,开挖侧导洞贯通单线/双线正洞,在侧导洞中预埋支护钢架,设置监测点,根据监测点的监测结果动态设计施工方案,仰拱和二衬紧跟开挖支护体系施工,整体一次性浇筑。(The invention discloses a construction method of a soft rock large-span and variable-section tunnel, which comprises the steps of carrying out advanced geological prediction during construction and excavation, carrying out single-line/double-line main tunnel and establishing a supporting system, excavating a side guide tunnel to penetrate through the single-line/double-line main tunnel, embedding a supporting steel frame in the side guide tunnel, setting a monitoring point, dynamically designing a construction scheme according to a monitoring result of the monitoring point, constructing an inverted arch and a secondary lining following the excavation supporting system, and integrally pouring at one time.)

1. A construction method of a soft rock large-span and variable cross-section tunnel is characterized by comprising the following steps:

s1, performing advanced geological prediction according to surrounding rocks and strata during tunnel construction excavation, observing and analyzing lithological change of an excavation working face, judging and analyzing the approximate condition of the front surrounding rocks according to the difficulty degree and mucking condition of drilling by adopting advanced horizontal drilling, and performing emergency preparation for timely changing a construction scheme;

s2, single-line/double-line main tunnel construction is carried out, a support system comprising a primary support and an advance support is built at the surrounding rock of the construction section, and the primary support and the advance support are strengthened according to the actual excavation geological conditions of the construction section;

s3, after the single-line/double-line main tunnel construction is carried out to the split repair transition section, the split repair transition section carries out side pilot tunnel excavation on side walls on two sides of the large span section by adopting a double-side-wall pilot tunnel method according to variable cross-section construction mileage until the side walls are communicated with the double-line/single-line main tunnel; constructing two side wall foundations and an upper side wall of the large span section, and pre-embedding the primary support steel frame of the side wall foundations and the side wall part of the large span section;

s4, embedding monitoring points in the tunnel split-repair transition section, wherein the monitoring points with the same section are embedded with the same mileage;

and S5, performing inverted arch and second-lining construction after the construction of the excavation supporting system, wherein the inverted arch and the inverted arch are filled with concrete by using a trestle platform, the inverted arch is integrally cast and formed in one step, the second lining is integrally cast at one step by adopting an integral lining form trolley arch wall, and concrete is pumped.

2. The construction method of the soft rock large-span and variable-section tunnel according to claim 1, wherein step S2 is implemented by respectively adopting a step method plus temporary inverted arch excavation method or a double-side wall pilot tunnel excavation method for the case that the split and repair transition section is affected by high ground stress and the split and repair transition double-line and large-span sections are adopted according to actual situations.

3. The construction method of the soft rock large-span and variable-section tunnel according to claim 2, characterized in that phi 42 small-conduit advance support + HW175 steel frame + anchor net-blasting combined support is adopted during the step method and the temporary inverted arch excavation; and when the double-side-wall pilot tunnel method is used for excavation, a double-layer advanced support, a HW200 steel frame and an anchor net spraying combined support are adopted.

4. The construction method of the soft rock large-span and variable-section tunnel according to claim 1, wherein in step S3, a novel tunnel lining supporting structure is adopted in the split-repairing transition section.

5. The method of claim 1, wherein in step S4, the monitoring items of the monitoring points include surrounding rock pressure, steel frame internal force, shotcrete strain, anchor shaft force, tunnel clearance convergence and secondary lining internal force.

6. The construction method of the soft rock large-span and variable-section tunnel according to claim 1, wherein in the step S3, the side guide tunnels are supported by steel frame double layers within 8 meters, and temporary cross braces are arranged at the bottoms of the steel frames.

7. The construction method of the soft rock large-span and variable-section tunnel according to claim 1, wherein the step S4 further comprises constructing a side guide tunnel side wall foundation, and the method for constructing the side guide tunnel side wall foundation comprises the following steps:

s71, reversely arranging trusses on the finished side guide holes;

s72, welding the longitudinal truss pieces by using connecting steel bars;

and S73, after the side wall truss of the side guide hole is finished, utilizing the side wall truss vertical mold to pour the side wall foundation, and pouring section by section.

Technical Field

The invention relates to the field of tunnel construction, in particular to a construction method of a soft rock large-span and variable cross-section tunnel.

Background

At present, with the leap development of economy, the design and construction of large-span tunnels are widely adopted at home and abroad, but at present, the large-span tunnels are generally used in strata with stable surrounding rocks, the tunnels are not common in soft rocks in earthquake active fracture zones, and the large-span tunnels are not constructed in the soft rocks.

Disclosure of Invention

Aiming at the problems, the invention provides a construction method of a soft rock large-span and variable cross-section tunnel, which monitors and measures the tunnel construction to bring the design and construction operation of the tunnel into scientific dynamic management, so that the project is always in a good operation state, the safety of the tunnel construction and the project construction quality are ensured, and the tunnel project achieves the purposes of economy, reasonableness and reliability.

The technical scheme of the invention is as follows:

a construction method of a soft rock large-span and variable cross-section tunnel comprises the following steps:

s1, performing advanced geological prediction according to surrounding rocks and strata during tunnel construction excavation, observing and analyzing lithological change of an excavation working face, judging and analyzing the approximate condition of the front surrounding rocks according to the difficulty degree and mucking condition of drilling by adopting advanced horizontal drilling, and performing emergency preparation for timely changing a construction scheme;

s2, single-line/double-line main tunnel construction is carried out, a support system comprising a primary support and an advance support is built at the surrounding rock of the construction section, and the primary support and the advance support are strengthened according to the actual excavation geological conditions of the construction section;

s3, after the single-line/double-line main tunnel construction is carried out to the split repair transition section, the split repair transition section carries out side pilot tunnel excavation on side walls on two sides of the large span section by adopting a double-side-wall pilot tunnel method according to variable cross-section construction mileage until the side walls are communicated with the double-line/single-line main tunnel; constructing two side wall foundations and an upper side wall of the large span section, and pre-embedding the primary support steel frame of the side wall foundations and the side wall part of the large span section;

s4, embedding monitoring points in the tunnel split-repair transition section, wherein the monitoring points with the same section are embedded with the same mileage;

and S5, performing inverted arch and second-lining construction after the construction of the excavation supporting system, wherein the inverted arch and the inverted arch are filled with concrete by using a trestle platform, the inverted arch is integrally cast and formed in one step, the second lining is integrally cast at one step by adopting an integral lining form trolley arch wall, and concrete is pumped.

The working principle of the technical scheme is as follows:

by a reasonable construction method, the construction strictly follows the structure construction of a new Austrian method in the construction, construction technical measures of 'short footage, weak blasting, less disturbance, early shotcrete, duty measurement and early sealing' are adopted, the measurement result is monitored and controlled by combining advanced geological prediction and monitoring points, support parameters are dynamically designed and dynamically adjusted, a support system is built and strengthened according to geology in the construction process, the construction safety is ensured, an inverted arch and a secondary lining closely follow the support system, the inverted arch and the secondary lining are respectively integrally poured and formed once, the construction period is shortened, and feasible conditions are provided for the adoption of a large-span tunnel on a railway and a highway.

In a further technical scheme, in step S2, for the case where the split and repair transition section is affected by high ground stress and is a split and repair transition double line and a long span, the step method and the temporary inverted arch excavation or the double-side-wall pilot tunnel excavation are respectively adopted according to actual conditions. Different construction methods are adopted according to different geological conditions, so that the construction efficiency is improved.

In a further technical scheme, a phi 42 small guide pipe advance support, a HW175 steel frame and an anchor net spraying combined support are adopted during the step method and the temporary inverted arch excavation; and when the double-side-wall pilot tunnel method is used for excavation, a double-layer advanced support, a HW200 steel frame and an anchor net spraying combined support are adopted. Different supporting structures are respectively constructed aiming at different construction methods, so that the safety in the construction tunnel is ensured.

In a further technical scheme, in step S3, the split-combined maintenance transition section adopts a novel tunnel lining supporting structure. The procedure conversion risk of the twin-line combined repair span construction is reduced.

In a further technical scheme, in step S4, the monitoring items of the monitoring points include surrounding rock pressure, steel frame internal force, sprayed concrete strain, anchor rod axial force, tunnel clearance convergence and secondary lining internal force. And (4) observing the stress deformation conditions of surrounding rocks, steel arch frames and sprayed concrete, and providing data support for the dynamic design and construction of the tunnel.

In a further technical scheme, in step S3, a steel frame double-layer support is adopted for the side guide tunnel within 8 meters of the tunnel, and a temporary cross brace is arranged at the bottom of the steel frame. The construction safety of the side guide hole is ensured.

In a further technical solution, step S4 further includes constructing a side guide tunnel side wall foundation, where the method for constructing the side guide tunnel side wall foundation is as follows:

s71, reversely arranging trusses on the finished side guide holes;

s72, welding the longitudinal truss pieces by using connecting steel bars;

and S73, after the side wall truss of the side guide hole is finished, utilizing the side wall truss vertical mold to pour the side wall foundation, and pouring section by section.

And the side guide hole side wall foundation is quickly constructed, so that the construction period is shortened, and the side guide hole is quickly reinforced.

The invention has the beneficial effects that:

1. by a reasonable construction method, the construction strictly follows the structure construction of a new Austrian method in the construction, construction technical measures of 'short footage, weak blasting, less disturbance, early shotcrete, duty measurement and early sealing' are adopted, the measurement result is monitored and controlled by combining advanced geological prediction and monitoring points, support parameters are dynamically designed and dynamically adjusted, a support system is built and strengthened according to geology in the construction process, the construction safety is ensured, an inverted arch and a secondary lining closely follow the support system, the inverted arch and the secondary lining are respectively integrally poured and formed once, the construction period is shortened, and feasible conditions are provided for the adoption of a large-span tunnel on a railway and a highway;

2. different construction methods are adopted according to different geological conditions, so that the construction efficiency is improved;

3. different supporting structures are respectively constructed aiming at different construction methods, so that the safety in the construction tunnel is ensured;

4. reducing the procedure conversion risk of the construction of the double-line combined repair span;

5. the monitoring points are helpful for observing the stress deformation conditions of surrounding rocks, steel arch frames and sprayed concrete, and provide data support for the dynamic design and construction of the tunnel.

6. The construction period is short, and the construction is safe.

Drawings

Fig. 1 is a schematic flow chart of a construction method of a soft rock large-span and variable cross-section tunnel according to an embodiment of the invention.

Detailed Description

The embodiments of the present invention will be further described with reference to the accompanying drawings.

Example (b):

as shown in fig. 1, a construction method of a soft rock large-span and variable cross-section tunnel includes the following steps:

s1, performing advanced geological prediction according to surrounding rocks and strata during tunnel construction excavation, observing and analyzing lithological change of an excavation working face, judging and analyzing the approximate condition of the surrounding rocks in front according to the difficulty degree and mucking condition of drilling by adopting advanced horizontal drilling, making emergency preparation for timely changing a construction scheme, continuing construction if the surrounding rocks in front accord with the current construction scheme, and changing the construction scheme if the surrounding rocks in front do not accord with the current construction scheme;

s2, single-line/double-line main tunnel construction is carried out, a support system comprising a primary support and an advance support is built at the surrounding rock of the construction section, and the primary support or the advance support is strengthened according to the actual excavation geological conditions of the construction section;

s3, after the single-line/double-line main tunnel construction is carried out to the split repair transition section, the split repair transition section carries out side pilot tunnel excavation on side walls on two sides of the large span section by adopting a double-side-wall pilot tunnel method according to variable cross-section construction mileage until the side walls are communicated with the double-line/single-line main tunnel; constructing two side wall foundations and an upper side wall of the large span section, and pre-embedding the primary support steel frame of the side wall foundations and the side wall part of the large span section;

s4, burying monitoring points in the tunnel split-repair transition section, mainly monitoring vault settlement and surrounding rock convergence projects, uniformly burying the monitoring points with the same cross section at equal intervals, adjusting a scheme according to monitoring results and constructing;

s5, constructing an inverted arch and a secondary lining following the excavation supporting system, wherein the inverted arch and the inverted arch are filled with concrete by using a trestle platform, the inverted arch is integrally cast and formed in one step, the secondary lining is integrally cast at one step by adopting an integral lining form trolley arch wall, and the concrete is pumped.

The working principle of the technical scheme is as follows:

by a reasonable construction method, the construction strictly follows the structure construction of a new Austrian method in the construction, construction technical measures of 'short footage, weak blasting, less disturbance, early shotcrete, duty measurement and early sealing' are adopted, the measurement result is monitored and controlled by combining advanced geological prediction and monitoring points, support parameters are dynamically designed and dynamically adjusted, a support system is built and strengthened according to geology in the construction process, the construction safety is ensured, an inverted arch and a secondary lining closely follow the support system, the inverted arch and the secondary lining are respectively integrally poured and formed once, the construction period is shortened, and feasible conditions are provided for the adoption of a large-span tunnel on a railway and a highway.

In another embodiment, in step S2, for the case where the split-repair transition section is affected by high ground stress and is a split-repair transition double line and a long span, the step method plus temporary inverted arch excavation or double-side-wall pilot tunnel excavation is respectively adopted according to actual situations. Different construction methods are adopted according to different geological conditions, so that the construction efficiency is improved.

In another embodiment, a phi 42 small conduit advance support, a HW175 steel frame and an anchor net spraying combined support are adopted during the step method and the temporary inverted arch excavation; and when the double-side-wall pilot tunnel method is used for excavation, a double-layer advanced support, a HW200 steel frame and an anchor net spraying combined support are adopted, wherein the double-layer advanced support comprises a phi 76 middle pipe shed and a phi 42 small pipe. Different supporting structures are respectively constructed aiming at different construction methods, so that the safety in the construction tunnel is ensured.

In another embodiment, in step S3, if the geological and ground stress conditions of the split-combined repair transition section are changed greatly from those of the construction drawing, the bell-mouth large-span support structure is combined and repaired, and the construction method and the process need to be designed specifically; meanwhile, based on geological conditions, the construction of the large span is combined and repaired by two lines, the process conversion risk is extremely high, the deformation control difficulty of surrounding rocks is extremely high, and a novel tunnel lining supporting structure is adopted in the combining and repairing transition section. The construction difficulty is reduced, and the process conversion risk of the twin-line combined repair span construction is reduced.

In another embodiment, in step S4, the monitoring items of the monitoring points include surrounding rock pressure, steel frame internal force, sprayed concrete strain, anchor rod axial force, tunnel clearance convergence and secondary lining internal force. And (4) observing the stress deformation conditions of surrounding rocks, steel arch frames and sprayed concrete, and providing data support for the dynamic design and construction of the tunnel.

In another embodiment, in step S3, the side guide tunnels are supported by HW175 steel frame double-layer supports within 8 meters of the tunnel, the longitudinal distance is 0.8 meters, the bottom of the steel frame is provided with temporary crossbars, and the crossbars are constructed by I18 temporary crossbars to reinforce the supports. The construction safety of the side guide hole is ensured.

In another embodiment, step S4 further includes constructing a side guide hole side wall foundation, where the method of constructing the side guide hole side wall foundation includes:

s71, reversely arranging trusses on the finished side guide holes;

s72, welding the longitudinal truss pieces by using connecting steel bars;

s73, after the side wall truss of the side guide hole is finished, the side wall truss is used for erecting a mold to cast a side wall foundation, a casting end is formed every 12 meters, and the section-by-section casting is carried out, wherein the C20 concrete is adopted for the casting.

In the embodiment, the truss is composed of I18 and HW200 steel frames, the connecting steel bars are phi 22 connecting steel bars, and the circumferential arrangement distance of the connecting steel bars is 1 m;

and the side guide hole side wall foundation is quickly constructed, so that the construction period is shortened, and the side guide hole is quickly reinforced.

In another embodiment, the side tunnel support also comprises 17 leading small ducts per ring, wherein each leading small duct is 4.5 meters long, and the longitudinal distance is 3.2 meters; 20 b-shaped steel frames of the side guide tunnel arch wall steel frame workers are arranged at intervals of 0.8 m/steel frame, phi 22 longitudinal connecting steel bars are arranged among the steel frames, and the circumferential arrangement interval of the connecting steel bars is 1 m; the locking feet adopt phi 22 mortar anchor rods, each truss is 8 in number and 4 m in length; the meshes are phi 8 reinforcing meshes, and the grid spacing is 20cm and 20 cm; the inside side wall anchor rods are 3 meters long and phi 22 glass fiber anchor rods, the longitudinal distance between the rings is 1.2 x 1.0m, the outside side wall anchor rods are 10 meters long and phi 32 self-advancing anchor rods, and the longitudinal distance between the rings is 0.8 x 1.0 m; the concrete sprayed on the side pilot tunnel adopts C30 sprayed concrete, and the sprayed concrete thickness is 25 cm.

The above-mentioned embodiments only express the specific embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.