Subway slope section hard rock tunnel core soil reserved excavation construction method

Abstract

The invention relates to a subway slope section hard rock tunnel core soil reserved excavation construction method which is particularly used for tunnel construction under complex geological conditions. According to the method, the section of a slope section is divided into an upper step, a middle step, a lower step and core soil, and reserved core soil blasting and excavation supporting are sequentially conducted according to the steps. Firstly, reserved excavation of core soil of the upper step is conducted, then excavation of the middle step and the lower step is conducted, and core soil is formed to serve as a working platform. The process comprises the steps of danger elimination, blast hole measurement and lofting, blast hole punching, charging, detonation, supporting and the like. Digital electronic detonators are adopted for phase dislocation delay detonation, low-vibration-velocity control is achieved through technologies such as straight-hole slotting and vibration reduction holes, and core soil is reserved to serve as an operation platform so as to improve construction safety and efficiency. According to the construction method, the high-altitude operation risk is reduced, the support erecting link is reduced, the tunnel supporting progress is accelerated, and the construction method is suitable for hard rock tunnel construction of III-level and IV-level surrounding rocks.

Description

Technical Field

[0001] The invention belongs to the technical field of subway tunnel construction, and relates to a core soil reserved excavation construction method for a hard rock tunnel in a subway slope section. Background Art

[0002] In recent years, urban subways have become one of the important development directions of public transportation in major cities due to their advantages such as speed and punctuality. Underground transportation lines can solve the problem of insufficient ground space in cities, effectively alleviate urban traffic congestion, and play an important role in optimizing urban spatial structure and driving urban economic development.

[0003] With the development of urban underground space, the buried depth of subway stations has gradually become deeper. In addition, the urban ground environment is complex and the choice of entrance and exit locations is limited, resulting in some stations with large entrances and exits designed with large slopes and many corners. For the construction of hard rock tunnels in subway slope sections, conventional methods generally use machinery or ordinary blasting to excavate dark tunnels. For hard rock formations, mechanical excavation efficiency is very slow, and the operating space of large equipment is limited, making mechanical excavation construction extremely difficult. In conventional blasting construction, a disc / ordinary scaffolding pipe operating platform is set up on the slope surface, which is difficult to set up, inefficient, and personnel are exposed under the rock mass in the unsupported section, posing a high safety risk in construction.

[0004] In the construction of subway slope section hard rock tunnel, large machinery or ordinary blasting is generally used for dark tunnel excavation according to conventional construction methods, including:

[0005] Conventional backhoe boring machines dig from the ground to the bottom. When the entrance and exit of the subway station is in the central area of ​​the city, the ground location of the entrance and exit is limited, there is no backhoe boring machine operation site, and the tunnel curve radius is small (the minimum curve radius R = 120), which does not meet the operating conditions of the backhoe boring machine. Due to the limited ground conditions, most of the entrance and exit dark excavation sections are excavated from the inside of the station to the ground (from bottom to top). The excavation width of the entrance and exit section is 7.2~9.4m, and the excavation height is 8.4~9.6m. The central axis of the tunnel has many corners, and conventional large-scale breakers, cantilever rock drills and other large equipment cannot dig at the corners. In addition, the angle between the slope section and the horizontal line is 30°. When large breakers and cantilever rock drills are digging in the slope section, they have to slide to the lower part of the slope surface, which is difficult to operate and has a high safety risk. In addition, the tunnel geology is mainly sandstone (natural compressive strength 26~42Mpa), which makes mechanical excavation difficult.

[0006] The drilling and blasting excavation process requires an operating platform. The conventional method is to use a support trolley. Since the angle between the slope section and the horizontal line is 30°, the support trolley is easy to slide down on the slope section and cannot be fixed. Another method is to set up a buckle / ordinary scaffolding pipe operating platform on the slope surface. This method is difficult to set up and inefficient, and personnel are exposed under the rock mass of the unsupported section. The construction safety risk is relatively large, and each cycle support installation and removal takes about 5 to 6 hours, which is time-consuming. At the same time, because the slope section steel operating trolley is not available for use, the stone "core soil" needs to be used as a stone operating platform for workers. However, for hard rock tunnels excavated by conventional blasting, wedge-shaped grooves must be used for groove excavation. The "core soil" part is blasted first, and the center of the face is used as the air-facing surface for blasting construction, resulting in the inability to preserve the reserved "core soil". Summary of the invention

[0007] In view of this, the purpose of the present invention is to solve the above-mentioned problem and to propose a construction method for core soil reservation excavation of a hard rock tunnel in a subway slope section.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] A construction method for reserved excavation of core soil in a hard rock tunnel of a subway slope section, which divides the slope section into an upper step, a middle step and a lower step according to a one-time excavation height, the core soil is located at the upper step, and hard rock core soil reserved blasting is performed on the area outside the core soil, and the excavation adopts the method of reserved excavation of core soil of the upper step first, and the two sides of the middle step are staggered successively, and the early stage is divided into three steps, and the short step method is adopted for excavation and support, and the lower step excavation and support is performed after the upper step and the middle step are connected; the specific process flow is: first danger elimination of the heading face → blasting hole position measurement and layout → blast hole setting → charging → blasting network connection → evacuation and warning → inspection and detonation → ventilation in the tunnel → second danger elimination of the heading face → blasting effect inspection and dynamic correction of blasting parameters → upper step support → upper step core soil and left middle step excavation and support → right middle step excavation and support → left lower step excavation and support after the upper step and the middle step are connected → right lower step excavation and support.

[0010] Furthermore, the reserved blasting construction of hard rock core soil is a shaped controlled blasting, which adopts digital electronic detonators to realize staggered delayed detonation, adopts short advance and weak blasting, and is supplemented by straight-eye grooving technology and vibration reduction hole technology. Straight-eye grooving, vibration reduction expansion holes, auxiliary holes, peripheral holes, and bottom plate holes are set in the blasting network. Straight-eye grooving and vibration reduction expansion holes are used to form 4 air-facing surfaces on the periphery of the core soil, and the rock layers are peeled off layer by layer to the surrounding areas, so that the core soil is reserved for forming as an operating platform.

[0011] Furthermore, no explosives or detonators are placed in the vibration-damping and expanded slot holes. The detonation sequence is: straight-eye slot → auxiliary hole → peripheral hole → bottom plate hole. The blasting cycle footage is 1.5m, the designed blasting hole depth is 1.7m, and the blasting vibration velocity of sensitive structures is controlled to be no more than 0.3cm / s.

[0012] Furthermore, the detonation network adopts a digital electronic detonator detonation system. The delay time difference of the straight-eye trench is set to 8ms, and the delay time difference of the auxiliary holes, peripheral holes, and bottom plate holes are all set to 18ms, using micro-difference detonation for each hole.

[0013] Furthermore, in the upper step support step, the stone core soil is used as an operating platform to carry out the upper step steel frame, steel mesh installation, locking anchor rod installation and concrete spraying operations to ensure the convenience and safety of the construction.

[0014] Furthermore, in the excavation and support steps of the core soil of the upper step and the left middle step, the height of the left middle step is 3m, the longitudinal length of the step is 3 to 5m, the excavation depth is 1.5m each time, and support is carried out immediately after excavation.

[0015] Furthermore, after the excavation and support of the upper step is completed, the core soil of the previous cycle is removed, and then the middle step is excavated and supported, and then the reserved core soil of the upper step is excavated and supported, and the operations are repeated in sequence.

[0016] Furthermore, in the excavation and support steps of the right middle step, the right middle step lags behind the left middle step by 3 to 5 meters to prevent arch excavation on both sides from causing safety hazards. The height of the right middle step is 3m, the longitudinal length of the step is 3 to 5m, the excavation advance is 1.5m each time, and support is carried out immediately after excavation.

[0017] Furthermore, in the excavation and support steps of the lower step, after the upper step and the middle step are connected, the lower left step is blasted and excavated, and support is carried out immediately after excavation; the excavation on both sides of the lower step is staggered by 3 to 5 meters to prevent arch excavation and cause safety hazards. The height of the lower step is 3m, the longitudinal length of the step is 3 to 5m, the excavation advance is 1.5m each time, and support is carried out immediately after excavation.

[0018] The beneficial effects of the present invention are:

[0019] 1. The present invention divides the one-time excavation height of the slope section into three steps + core soil reserved for a total of 4 steps, which reduces the risk factor of personnel working at high altitudes and reduces the number of scaffolding steps. Since the scaffolding is set up close to the excavation face, there is a risk of falling blocks on the face arch and bare rock surface, so there is a great safety risk during the scaffolding operation period. The construction method can avoid high-risk operations here, speed up the entry of the face into the support process, complete the excavation and support process as soon as possible, achieve the principle of early closure of the support, and better ensure the safety of tunnel construction.

[0020] 2. The present invention realizes the reserved core rock platform and low-vibration blasting on the dark tunnel through shaped controlled blasting, solves the problems of large longitudinal slope support construction operation platform and large blasting vibration speed; reduces the construction and dismantling links of the working platform, speeds up the construction progress, and achieves obvious social and economic benefits.

[0021] 3. The present invention is applicable to the construction of hard rock tunnels in slope sections, and the construction geological conditions are applicable to hard rock (III and IV grade surrounding rock) tunnels.

[0022] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0024] Figure 1 It is a schematic diagram of the step division section of the core soil reserved excavation construction method of the hard rock tunnel in the slope section of the subway in the present invention.

[0025] Figure 2 It is a schematic diagram of the blasting network in the present invention.

[0026] Figure 3 Schematic diagram of the reserved stone core soil operating platform.

[0027] Figure 4 It is a longitudinal section schematic diagram of the core soil reserved excavation construction method of the hard rock tunnel in the slope section of the subway in the present invention.

[0028] Figure 5 Schematic diagram of the excavation support process.

[0029] Figure numerals: 1-straight eye groove; 2-vibration reduction expansion hole; 3-auxiliary hole; 4-auxiliary hole; 5-peripheral hole. DETAILED DESCRIPTION

[0030] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and the features in the embodiments can be combined with each other without conflict.

[0031] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0032] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0033] See also Figures 1 to 5 It is a construction method for reserving core soil for hard rock tunnel in the slope section of subway. The slope section is divided into upper step, middle step and lower step according to the one-time excavation height. The core soil is located in the upper step. The area outside the core soil is subjected to hard rock core soil reserving blasting. The excavation adopts the method of reserving core soil for the upper step first, and the two sides of the middle step are staggered successively. In the early stage, it is divided into three steps, and the short step method (3-5m) is adopted for excavation and support. After the upper step and the middle step are connected, the lower step excavation and support are carried out.

[0034] The specific process flow is: primary hazard elimination of the face → measurement and layout of blasting hole positions → blasting hole drilling → charging → blasting network connection → evacuation and warning → inspection and detonation → ventilation in the tunnel → secondary hazard elimination of the face → blasting effect inspection and dynamic correction of blasting parameters → upper step support → upper step core soil and left middle step excavation and support → right middle step excavation and support → left lower step excavation and support after the upper step and middle step are connected → right lower step excavation and support.

[0035] Among them, the reserved blasting construction of hard rock core soil is a shaped controlled blasting, which adopts digital electronic detonator to realize staggered delayed detonation, adopts short advance and weak blasting, supplemented by straight-eye grooving technology and vibration reduction hole technology. Straight-eye grooving 1 (T1~T20), vibration reduction expansion grooving hole 2, auxiliary hole 3 (F1~F10), auxiliary hole 4 (F11~F24), peripheral hole 5 (Z1~Z26), bottom plate hole (D1~D8) are set in the blasting network, as shown in the figure; straight-eye grooving and vibration reduction expansion grooving holes are used to form 4 free surfaces on the periphery of the core soil to peel off the rock layer layer by layer to realize the reserved shaping of the core soil as an operating platform.

[0036] No explosives or detonators are placed in the vibration reduction expansion slot hole. The detonation sequence is: straight-eye slot → auxiliary hole (F1-F10) → auxiliary hole (F11-F24) → peripheral hole → bottom plate hole. The blasting cycle footage is 1.5m, the blasting design hole depth is 1.7m, and the blasting vibration speed of sensitive structures is controlled at no more than 0.3cm / s. The detonation network adopts a digital electronic detonator detonation system. The delay time difference of the straight-eye slot is set to 8ms, and the delay time difference of the auxiliary hole, peripheral hole, and bottom plate hole is set to 18ms. Micro-difference detonation is adopted for each hole.

[0037] Among them, in the upper step support step, the stone core soil is used as an operating platform to carry out the upper step steel frame, steel mesh installation, locking anchor rod installation and concrete spraying operations to ensure the convenience and safety of construction.

[0038] Among them, in the excavation and support steps of the core soil of the upper step and the left middle step, the height of the left middle step is 3m, the longitudinal length of the step is 3~5m, the excavation advance is 1.5m each time, and support is carried out immediately after excavation.

[0039] Among them, after the excavation and support of the upper step is completed, the core soil of the previous cycle is removed, and then the middle step is excavated and supported, and then the excavation and support of the reserved core soil of the upper step are carried out, and the operations are repeated in sequence.

[0040] Among them, in the excavation and support steps of the right middle step, the right middle step lags behind the left middle step by 3 to 5 meters to prevent arch excavation on both sides and cause safety hazards. The height of the right middle step is 3m, the longitudinal length of the step is 3 to 5m, the excavation advance is 1.5m each time, and support is carried out immediately after excavation.

[0041] Among them, in the excavation and support steps of the lower step, after the upper step and the middle step are connected, the lower left step is blasted and excavated, and support is carried out immediately after excavation; the excavation on both sides of the lower step is staggered, with a stagger of 3 to 5m to prevent arch excavation and cause safety hazards. The height of the lower step is about 3m, the longitudinal length of the step is 3 to 5m, the excavation advance is 1.5m each time, and support is carried out immediately after excavation.

[0042] The initial support of the dark excavation tunnel adopts steel arch frame + spray anchor support. Before support, check whether the excavation section is under-excavated to ensure the smooth installation of the arch frame. The steel arch frame is measured to assist in positioning. Each upper step arch frame consists of 3 units, and the arch frame is spliced ​​and installed from bottom to top.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A construction method for core soil reservation excavation of a hard rock tunnel in a subway slope section, characterized in that: The slope section is divided into upper step, middle step and lower step according to the one-time excavation height. The core soil is located in the upper step, and the hard rock core soil is reserved for blasting in the area outside the core soil. The excavation adopts the method of reserving the core soil of the upper step first, and the two sides of the middle step are staggered in sequence. The early stage is divided into three steps, and the short step method is used for excavation and support. After the upper step and the middle step are connected, the lower step excavation and support are carried out. The specific process flow is: first danger elimination of the heading face → blasting hole position measurement and layout → blasting hole setting → charging → blasting network connection → evacuation and warning → inspection and detonation → ventilation in the tunnel → secondary danger elimination of the heading face → blasting effect inspection and dynamic correction of blasting parameters → upper step support → upper step core soil and left middle step excavation and support → right middle step excavation and support → left lower step excavation and support after the upper step and the middle step are connected → right lower step excavation and support.

2. The core soil reserved excavation construction method for a hard rock tunnel in a subway slope section according to claim 1 is characterized by: The reserved blasting construction of hard rock core soil is a shaped controlled blasting, which adopts digital electronic detonators to realize staggered delayed detonation, adopts short advance and weak blasting, supplemented by straight-eye grooving technology and vibration reduction hole technology. Straight-eye grooving, vibration reduction expansion holes, auxiliary holes, peripheral holes and bottom plate holes are set in the blasting network. Straight-eye grooving and vibration reduction expansion holes are used to form 4 free surfaces on the periphery of the core soil, and the rock layers are peeled off layer by layer to the surrounding areas, so that the core soil is reserved as an operating platform.

3. The core soil reserved excavation construction method for a hard rock tunnel in a subway slope section according to claim 2 is characterized in that: No explosives or detonators are placed in the vibration-damping expansion slot hole. The detonation sequence is: straight-eye slot → auxiliary hole → peripheral hole → bottom plate hole. The blasting cycle footage is 1.5m, the designed blasting hole depth is 1.7m, and the blasting vibration speed of sensitive structures is controlled at no more than 0.3cm / s.

4. The core soil reserved excavation construction method for a hard rock tunnel in a subway slope section according to claim 2 is characterized in that: The blasting network adopts a digital electronic detonator blasting system. The delay time difference of the straight-eye trench is set at 8ms, and the delay time difference of the auxiliary holes, peripheral holes, and bottom plate holes are all set at 18ms. Micro-difference blasting is adopted for each hole.

5. The core soil reserved excavation construction method for a hard rock tunnel in a subway slope section according to claim 2 is characterized by: In the upper step support step, the stone core soil is used as an operating platform to carry out the upper step steel frame, steel mesh installation, locking anchor rod installation and concrete spraying operations to ensure the convenience and safety of construction.

6. The core soil reserved excavation construction method for a hard rock tunnel in a subway slope section according to claim 2 is characterized by: In the excavation and support steps of the core soil of the upper step and the left middle step, the height of the left middle step is 3m, the longitudinal length of the step is 3 to 5m, the excavation depth is 1.5m each time, and support is carried out immediately after excavation.

7. The core soil reserved excavation construction method for a hard rock tunnel in a subway slope section according to claim 6 is characterized by: After the excavation and support of the upper step is completed, the core soil of the previous cycle is removed, and then the middle step is excavated and supported, and then the reserved core soil of the upper step is excavated and supported, and the operations are repeated in sequence.

8. The core soil reserved excavation construction method for a hard rock tunnel in a subway slope section according to claim 6 is characterized by: During the excavation and support steps of the right middle step, the right middle step lags behind the left middle step by 3 to 5 meters to prevent arch excavation on both sides from causing safety hazards. The height of the right middle step is 3m, the longitudinal length of the step is 3 to 5m, the excavation advance is 1.5m each time, and support is carried out immediately after excavation.

9. The core soil reserved excavation construction method for a hard rock tunnel in a subway slope section according to claim 7 is characterized by: In the excavation and support steps of the lower step, after the upper and middle steps are connected, the lower left step is blasted and excavated, and support is carried out immediately after excavation; the excavation on both sides of the lower step is staggered by 3 to 5m to prevent arch excavation and cause safety hazards. The height of the lower step is 3m, the longitudinal length of the step is 3 to 5m, the excavation advance is 1.5m each time, and support is carried out immediately after excavation.

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