A double-sided wall pilot tunnel excavation method that is conducive to large-scale mechanized construction

Abstract

The present invention relates to a double-sided drift method for excavation that is conducive to large-scale mechanized construction. By adjusting the excavation sequence of the left, middle, and right drifts, the drifts can be advanced synchronously and orderly under the condition of meeting the longitudinal staggering distance, significantly improving the daily excavation footage of the overall tunnel section and shortening the cycle of the initial support closure of the ultra-large-span tunnel section.

Description

Technical Field

[0001] This invention belongs to the field of tunnel engineering construction technology, specifically relating to a double-sided wall pilot tunnel excavation method that is conducive to large-scale mechanized construction. Background Technology

[0002] Currently, ultra-large span tunnels are increasingly emerging in highway tunnel construction. To ensure construction safety, the sectional excavation method is almost universally adopted. Among these methods, the double-side-wall pilot tunnel method is widely used in shallow-buried sections and complex geological conditions. The double-side-wall pilot tunnel method is a construction technique that involves excavation and support simultaneously. Its principle is to use two central partition walls to divide the entire tunnel cross-section into three smaller sections (left, middle, and right). The left and right pilot tunnels are constructed first, followed closely by the middle section. After the initial support of the invert arch is formed, the temporary supports of the two pilot tunnels are removed to form the full cross-section. Both pilot tunnels are inverted oval in shape, which helps control the settlement of the arch crown. This method is mainly suitable for strata such as cohesive soil, sand, and gravel layers.

[0003] Although the double-sided wall pilot tunnel method involves multiple excavation sections, significant disturbance, and a long initial support closure time, each section closes immediately after excavation. Therefore, deformation hardly develops during construction. While the double-sided wall pilot tunnel method is safe to construct, it has disadvantages such as slow speed, high cost, numerous procedures, frequent step changes, high requirements for manpower and equipment resources, and low construction efficiency. Summary of the Invention

[0004] The present invention addresses the aforementioned problems by providing a double-sided wall pilot tunnel excavation method that facilitates large-scale mechanized construction, thereby solving the issues of slow construction progress and numerous step transitions in the existing double-sided wall pilot tunnel method.

[0005] This invention is achieved through the following measures:

[0006] A double-sided pilot tunnel excavation method that facilitates large-scale mechanized construction includes:

[0007] Step 1: Construction preparation: surveying and setting out and advanced geological forecasting.

[0008] Step 2: First, perform advance support and excavation of the side wall pilot tunnel upper step.

[0009] Step 3: Initial support for the upper step of the right-hand guide tunnel, and advanced support for the upper step of the left-hand guide tunnel.

[0010] Step 4: Excavate the upper and middle steps of the right-hand pilot tunnel simultaneously, while excavating the upper step of the left-hand pilot tunnel at the same time.

[0011] Step 5: Initial support is provided simultaneously on the upper and middle steps of the right-hand pilot tunnel, initial support is provided on the upper step of the left-hand pilot tunnel, and advance support is provided for the middle pilot tunnel.

[0012] Step 6: Excavate the three steps of the right-hand pilot tunnel simultaneously, excavate the upper and middle steps of the left-hand pilot tunnel simultaneously, and excavate the upper step of the middle pilot tunnel.

[0013] Step 7: Initial support of the three steps of the right-hand pilot tunnel is performed simultaneously; initial support of the upper and middle steps of the left-hand pilot tunnel is performed simultaneously; initial support of the upper step of the middle pilot tunnel is performed.

[0014] Step 8: Excavate the right-hand pilot tunnel in three stages simultaneously, excavate the left-hand pilot tunnel in three stages simultaneously, and excavate the upper and middle stages of the middle pilot tunnel simultaneously.

[0015] Step 9: Synchronous initial support of the three steps in the right-hand pilot tunnel, synchronous initial support of the three steps in the left-hand pilot tunnel, and synchronous initial support of the upper and middle steps in the middle pilot tunnel.

[0016] Step 10: Excavate the right-hand pilot tunnel in three stages simultaneously, the left-hand pilot tunnel in three stages simultaneously, and the middle pilot tunnel in three stages simultaneously.

[0017] Step 11: Initial support and closure into a ring.

[0018] Step 12, Monitoring and Measurement: This includes monitoring and measurement of the surrounding rock and observation of surface subsidence.

[0019] Step 13: Remove the temporary supports for the central partition wall.

[0020] Step Fourteen: Casting the invert arch and backfilling with concrete.

[0021] Step 15: Waterproofing construction and arch wall lining.

[0022] Furthermore, each pilot tunnel must be pre-supported before each excavation. Pre-support generally uses φ42×3.5mm seamless small pipes, with the outer insertion angle of the small pipes controlled at 5-10°, and 1:1 cement grout is injected.

[0023] Furthermore, in step four, after the right pilot tunnel face is excavated for 8m, the upper and middle steps are excavated simultaneously. When the longitudinal distance between the left and right pilot tunnels is 8m, the pilot tunnels on both sides can be excavated at the same time.

[0024] Furthermore, the condition for the simultaneous excavation of the three steps of the pilot tunnel in step six is ​​that after the middle step is excavated forward by 8m, the longitudinal distance between the middle pilot tunnel and the left pilot tunnel must be 8m before the upper step of the middle pilot tunnel is excavated.

[0025] Furthermore, the upper steps of the left and right pilot tunnels are 7.5m high and 8m long, the middle steps are 2.3m high, and the lower steps are 2.3m high (with an inverted arch of 3.9m); the upper steps of the middle pilot tunnel are 6.2m high and no more than 8m long, the middle steps are 4.1m high and no more than 12m long, and the lower steps with an inverted arch are 4.1m high.

[0026] Furthermore, the maximum length of temporary support to be removed at one time shall not exceed 12m.

[0027] Furthermore, the working face is excavated using an excavator, and weak blasting is used when the surrounding rock is relatively hard.

[0028] Furthermore, when the left, middle, and right pilot tunnels are excavated simultaneously in three stages, the cross-sectional area of ​​the pilot tunnels on both sides is increased, and the cross-sectional area of ​​the middle pilot tunnel meets the minimum equipment construction space requirements.

[0029] Furthermore, high-powered excavators, loaders, wet spraying robots, and other construction machinery are used during the construction of the side guide pit to achieve mechanized construction and improve construction efficiency.

[0030] The beneficial effects of this invention are:

[0031] 1. This invention optimizes the excavation cross-section by adjusting the construction sequence, simplifies the process, and allows each pilot tunnel to be excavated and supported simultaneously;

[0032] 2. Under the condition that each pilot tunnel meets the longitudinal staggered distance, it can be advanced synchronously and orderly, which significantly improves the average daily excavation progress of the overall tunnel cross section and shortens the cycle of initial support closure of ultra-large span tunnel cross section.

[0033] 3. Each pilot tunnel has sufficient construction space to meet the requirements of mechanized construction. Attached Figure Description

[0034] Figure 1 This is a top-view construction flowchart of the left-middle-right pilot tunnel of the present invention;

[0035] Figure 2 This is a schematic diagram of the AA-section excavation cross-section of the present invention;

[0036] Figure 3 This is a schematic diagram of the BB cross-section excavation section of the present invention;

[0037] Figure 4 This is a schematic diagram of the CC section excavation cross-section of the present invention. Detailed Implementation

[0038] 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. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0039] The components of the embodiments of the invention described and illustrated herein can typically be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention. Specific Implementation Example 1

[0041] A double-sided wall pilot tunnel excavation method that facilitates large-scale mechanized construction is characterized by the following steps:

[0042] Step 1: Construction Preparation: Surveying and Setting Out and Advanced Geological Prediction;

[0043] Step 2: Advance support and excavation of the upper bench of the right-hand pilot tunnel;

[0044] Step 3: Initial support for the upper step of the right-hand pilot tunnel, and advanced support for the upper step of the left-hand pilot tunnel;

[0045] Step 4: The upper and middle steps of the right pilot tunnel are excavated simultaneously, while the upper step of the left pilot tunnel is excavated at the same time. After the steps on the working face of the right pilot tunnel are excavated for 8m, the upper and middle steps are excavated forward at the same time. When the longitudinal distance between the left and right pilot tunnels is 8m, the two pilot tunnels can be excavated at the same time.

[0046] Step 5: Initial support is provided simultaneously on the upper and middle steps of the right-hand pilot tunnel, initial support is provided on the upper step of the left-hand pilot tunnel, and advance support is provided for the middle pilot tunnel.

[0047] Step 6: Excavate the three steps of the right-hand pilot tunnel simultaneously, excavate the upper and middle steps of the left-hand pilot tunnel simultaneously, and excavate the upper step of the middle pilot tunnel. The condition for the simultaneous excavation of the three steps of the right-hand pilot tunnel is that after the middle step is excavated forward by 8m, the longitudinal distance between the middle pilot tunnel and the left-hand pilot tunnel is 8m before the upper step of the middle pilot tunnel is excavated.

[0048] The upper steps of the left and right pilot tunnels are 7.5m high and 8m long, the middle steps are 2.3m high, and the lower steps are 2.3m high; the upper steps of the middle pilot tunnel are 6.2m high and no more than 8m long, the middle steps are 4.1m high and no more than 12m long, and the lower steps with the invert arch are 4.1m high.

[0049] Step 7: Synchronous initial support of the three steps of the right-hand pilot tunnel, synchronous initial support of the upper and middle steps of the left-hand pilot tunnel, and initial support of the upper step of the middle pilot tunnel.

[0050] Step 8: Excavate the right-hand pilot tunnel in three stages simultaneously, excavate the left-hand pilot tunnel in three stages simultaneously, and excavate the upper and middle stages of the middle pilot tunnel simultaneously.

[0051] Step 9: Synchronous initial support of the three steps in the right-hand pilot tunnel, synchronous initial support of the three steps in the left-hand pilot tunnel, and synchronous initial support of the upper and middle steps in the middle pilot tunnel.

[0052] Step 10: Excavate the right-hand pilot tunnel in three stages simultaneously, the left-hand pilot tunnel in three stages simultaneously, and the middle pilot tunnel in three stages simultaneously.

[0053] Step 11: Initial support and closure into a ring;

[0054] Step 12, Monitoring and Measurement: This includes monitoring and measurement of the surrounding rock and observation of surface subsidence;

[0055] Step 13: Remove the temporary supports of the partition wall; the maximum length of temporary supports to be removed at one time shall not exceed 12m.

[0056] Step Fourteen: Casting the invert arch and backfilling with concrete;

[0057] Step 15: Waterproofing construction and arch wall lining.

[0058] Before each excavation, each pilot tunnel must be pre-supported. Seamless guide pipes are used for pre-support, with the outer insertion angle of the guide pipes controlled at 5-10°, and 1:1 cement grout is injected.

[0059] The working face is excavated using an excavator, and weak blasting is used when the surrounding rock is relatively hard. Specific Implementation Example 2

[0061] Based on Example 1, a specific temporary support structure was added. When forming the tunnel cross-section, a permanent steel frame was set on the surrounding rock walls inside the tunnel. The permanent steel frame was composed of multiple steel frame segments, and each segment was connected by a permanent steel frame connecting member. Temporary steel frames were symmetrically installed on the upper and lower permanent steel frames along the tunnel centerline. Each set of temporary steel frames could be a single steel frame or composed of multiple steel frame segments. The temporary steel frames composed of multiple steel frame segments were connected by temporary steel frame connecting members. Movable steel frames were also connected to the temporary steel frame connecting members at both ends of the temporary steel frame. The two movable steel frames were then connected to the permanent steel frame through the temporary steel frame connecting members.

[0062] Temporary steel frames are reusable steel frames, while movable steel frames are non-reusable steel frames. Both temporary and movable steel frames are made of I-beams. Specific Implementation Example 3

[0064] Based on Example 1, another temporary support structure is added to carry out the initial support construction and tunnel temporary support structure in steps eleven and thirteen. Specifically, the following method is adopted: During the initial excavation of the tunnel, the initial support construction is carried out from back to front along the longitudinal extension direction of the tunnel, and the initial installation frame of multiple initial support steel frames is installed. The initial installation frames of multiple initial support steel frames are fastened together by multiple longitudinal connectors arranged along the longitudinal extension direction of the tunnel. At the same time, a tunnel temporary support structure is installed in the initial installation frame of each initial support steel frame. Each tunnel temporary support structure is fastened together with the initial installation frame located on its outer side. Each tunnel temporary support structure and the initial installation frame located on its outer side are arranged on the same tunnel section of the tunnel being constructed.

[0065] The temporary support structure inside the tunnel includes two symmetrical side support frames supported on the left and right sides of the subsequent excavation area, an upper support frame supported on the upper part of the subsequent excavation area, an upper support structure supported above the upper support frame and between the preliminary installation frame, and two side support structures supported between the two side support frames and the preliminary installation frame, respectively. The two side support structures are located in the left wall guide tunnel and the right wall guide tunnel, respectively, and the upper support structure is located in the arch guide tunnel. The upper support frame and the two side support frames form the inner support frame. The inner support frame, the upper support structure, and the two side support structures are all arranged on the same vertical plane. Specific Implementation Example 4

[0067] Based on Example 3, the arch wall lining in step fifteen is constructed using a mobile full-span scaffolding. The specific construction is as follows: The tunnel is constructed in multiple segments from back to front along its longitudinal extension direction, with each segment employing the same construction method. Each segment of the tunnel includes a left-side guide tunnel, a right-side guide tunnel, an upper core soil area guide tunnel, and a lower bench excavation guide tunnel located directly below the upper core soil area guide tunnel. The left-side and right-side guide tunnels are symmetrically arranged. The upper core soil area guide tunnel and the lower bench excavation guide tunnel are both located between the left-side and right-side guide tunnels. The upper core soil area guide tunnel is divided into an arch guide tunnel and a middle guide tunnel located directly below the arch guide tunnel. The secondary lining structure of the tunnel is a concrete lining that provides full-section support for the tunnel. The secondary lining structure includes an arch wall lining that supports the tunnel's arch wall and a tunnel bottom support structure that supports the tunnel's bottom. The tunnel consists of an arch lining and two arch foot linings connected between the arch wall lining and the tunnel bottom invert lining, respectively. The two arch foot linings are symmetrically arranged on the left and right sides of the tunnel bottom invert lining. The arch foot lining includes the bottom lining of the side wall located at the bottom of the arch wall lining and the arch foot section of the invert lining located outside the tunnel bottom invert lining. The initial support structure of the tunnel includes multiple initial support steel frames arranged from back to front along the longitudinal extension direction of the tunnel and providing full-section support for the tunnel. The initial support steel frame is a supporting steel frame that provides full-section support for the tunnel. The initial support steel frame includes a steel arch frame located inside the arch wall lining and supporting the arch wall of the tunnel, a bottom connecting frame located below the invert lining and supporting the bottom of the tunnel, and two arch foot steel frames connected between the steel arch frame and the bottom connecting frame, respectively. The two arch foot steel frames are symmetrically arranged on the left and right sides of the bottom connecting frame. The steel arch frame and the two arch foot steel frames constitute the initial installation frame of the initial support steel frame. Specific Implementation Example 5

[0069] In addition to the above embodiments, high-powered excavators, loaders, wet spraying robots and other construction machinery are used during the construction of the side guide pit to achieve mechanized construction and improve construction efficiency.

[0070] Preferably, a mobile rock or concrete milling equipment is used, including an excavator body, a milling mechanism, and a connecting platform.

[0071] The equipment also includes tracks, a boom, and hydraulic cylinders. The boom of the excavator body is hinged to the base via a connecting platform; the boom is connected to the first hydraulic cylinder, and the boom is connected to the second hydraulic cylinder. The first and second hydraulic cylinders are connected to the operator's cab via a hydraulic control system. The excavator body is moved to the working area by the tracks, and the milling mechanism is extended to the working face by the hydraulic cylinders controlling the boom and boom; the rotation and stopping of the cutter head are controlled by the hydraulic motor via two-way valve handles on the operator's cab control panel.

[0072] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of this application. It should not be construed that the specific embodiments of this application are limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of this application, and all such modifications and substitutions should be considered within the scope of protection of this application.

Claims

1. A double-sided wall pilot tunnel excavation method that facilitates large-scale mechanized construction, characterized in that, Includes the following steps: Step 1: Construction Preparation: Surveying and Setting Out and Advanced Geological Prediction; Step 2: Advance support and excavation of the upper bench of the right-hand pilot tunnel; Step 3: Initial support for the upper step of the right-hand pilot tunnel, and advanced support for the upper step of the left-hand pilot tunnel; Step 4: Excavate the upper and middle steps of the right-hand pilot tunnel simultaneously, while excavating the upper step of the left-hand pilot tunnel at the same time; Step 5: Initial support is provided simultaneously on the upper and middle steps of the right-hand pilot tunnel, initial support is provided on the upper step of the left-hand pilot tunnel, and advance support is provided for the middle pilot tunnel. Step 6: Excavate the three steps of the right-hand pilot tunnel simultaneously, excavate the upper and middle steps of the left-hand pilot tunnel simultaneously, and excavate the upper step of the middle pilot tunnel. Step 7: Synchronous initial support of the three steps of the right-hand pilot tunnel, synchronous initial support of the upper and middle steps of the left-hand pilot tunnel, and initial support of the upper step of the middle pilot tunnel. Step 8: Excavate the right-hand pilot tunnel in three stages simultaneously, excavate the left-hand pilot tunnel in three stages simultaneously, and excavate the upper and middle stages of the middle pilot tunnel simultaneously. Step 9: Synchronous initial support of the three steps in the right-hand pilot tunnel, synchronous initial support of the three steps in the left-hand pilot tunnel, and synchronous initial support of the upper and middle steps in the middle pilot tunnel. Step 10: Excavate the right-hand pilot tunnel in three stages simultaneously, the left-hand pilot tunnel in three stages simultaneously, and the middle pilot tunnel in three stages simultaneously. Step 11: Initial support and closure into a ring; Step 12, Monitoring and Measurement: This includes monitoring and measurement of the surrounding rock and observation of surface subsidence; Step 13: Remove the temporary supports for the central partition wall; Step Fourteen: Casting the invert arch and backfilling with concrete; Step 15: Waterproofing construction and arch wall lining.

2. The construction method according to claim 1, characterized in that: Before each excavation, each pilot tunnel must be pre-supported. Seamless guide pipes are used for pre-support, with the outer insertion angle of the guide pipes controlled at 5-10°, and 1:1 cement grout is injected.

3. The construction method according to claim 1, characterized in that: In step four, the steps on the working face of the right pilot tunnel are first excavated for 8m, and then the upper and middle steps are excavated simultaneously. When the longitudinal distance between the left and right pilot tunnels is 8m, the pilot tunnels on both sides can be excavated at the same time.

4. The construction method according to claim 1, characterized in that: In step six, the simultaneous excavation of the three steps of the right-hand guide tunnel must meet the following conditions: after the middle step is excavated forward by 8m, the longitudinal distance between the middle guide tunnel and the left-hand guide tunnel must be 8m before the upper step of the middle guide tunnel is excavated.

5. The construction method according to claim 1, characterized in that: When the left, middle and right pilot tunnels are excavated simultaneously in three stages, the cross-sectional area of ​​the pilot tunnels on both sides should be increased, and the cross-sectional area of ​​the middle pilot tunnel should meet the minimum equipment construction space requirements.

6. The construction method according to claim 1, characterized in that: The maximum length of temporary support for the partition wall to be removed at one time shall not exceed 12m.

7. The construction method according to claim 3, characterized in that: The working face is excavated using an excavator, and weak blasting is used when the surrounding rock is relatively hard.

8. The construction method according to claim 1, characterized in that: The support adopts a temporary support structure. When forming the tunnel cross section, a permanent steel frame is set on the surrounding rock wall inside the tunnel. The permanent steel frame is composed of multiple steel frames. Each permanent steel frame is connected by a permanent steel frame connecting component. Temporary steel frames are symmetrically installed on the upper and lower permanent steel frames along the tunnel centerline. Each set of temporary steel frames is composed of one or more steel frames.

9. The construction method according to claim 8, characterized in that: A temporary steel frame is constructed using multiple steel frame sections. Each section of the temporary steel frame is connected to the other sections by temporary steel frame connecting members. Movable steel frames are also connected to the temporary steel frame connecting members at both ends of the temporary steel frame. The two movable steel frames are then connected to the permanent steel frame by the temporary steel frame connecting members.

10. The construction method according to claim 9, characterized in that: The temporary steel frame is a reusable steel frame, while the movable steel frame is a non-reusable steel frame. Both the temporary and movable steel frames are made of I-beams.

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