Construction method for zero-disturbance excavation and hole entering of tunnel portal

Abstract

The invention relates to a construction method for zero-disturbance excavation and hole entering of a tunnel portal, which comprises the following steps of: adjusting design parameters through measurement and analysis, and optimizing a design construction scheme; then, the light and shade boundary mileage of the entrance is moved towards the outside of the tunnel by a designed distance, the guide wall is constructed along the existing slope, the existing slope is not excavated, and concrete is poured between the guide wall and the slope for sealing after the guide wall and the large pipe shed are constructed; two drilling piles are additionally arranged on each of the left side and the right side of a tunnel portal, top beams are arranged on the tops of the piles and used for supporting an outward-moving guide wall, and zero-upward-slope tunnel entering construction is carried out. Therefore, the tunnel portal can be safely entered after the tunnel portal side upward slope is subjected to less excavation, less disturbance, protection, entry and treatment of the portal soil body, the tunnel portal is prolonged in an environment with complex geological conditions, and the tunnel portal construction safety can be greatly improved by entry under the conditions of less disturbance to the earth surface and zero excavation.

Description

Technical Field

[0001] The present application relates to the technical field of tunnel construction, and in particular to a method for excavating a tunnel entrance with zero disturbance. Background Art

[0002] Tunnels are engineering structures buried in the ground. They are a form of human use of underground space. Tunnels can be divided into railway tunnels, municipal tunnels, military tunnels, etc. Under complex geological conditions, the entrance slope of the tunnel is Quaternary volcanic deposited clay soil. The soil layer is thick, the soil is relatively loose, the water content is high, the porosity is large, and the original soil layer has a certain structural strength. After the soil is exposed to water and disturbed, the properties are significantly deteriorated, which is special. The tunnel entrance section is located on a slope that is severely eroded by surface water and has developed weathering cracks. After excavation, it is difficult for the rock mass to form a bearing system. The slope surface of the tunnel entrance is prone to tensile cracking, and its stability is difficult to guarantee. At the same time, the tunnel entrance is in a hilly area. Due to the limitations of terrain conditions, the location of the tunnel entrance sometimes has to be selected in a high slope section. This "potentially unstable slope" is under the action of engineering unloading. At the same time, during the construction of the tunnel entrance slope protection, continuous heavy rains deteriorate the soil properties, and eventually cause the tunnel entrance to slip.

[0003] Domestic railway tunnels are usually restricted by line selection, and tunnel portal projects inevitably have shallow burial, eccentric pressure, complex geology, and complex surrounding environment. In recent years, with the large-scale construction of domestic tunnels, the back slopes at the portals have tended to collapse, scour, and peel off during construction. Even during operation, the portals are blocked after heavy rainfall, and settlement and cracking of open-cut linings also occur from time to time, seriously affecting operational safety. Summary of the invention

[0004] Based on this, it is necessary to provide a construction method for zero-disturbance excavation of the tunnel entrance to address the problem of low safety in tunnel entrance construction.

[0005] The present application provides a construction method for zero-disturbance excavation of a tunnel entrance, which comprises the following steps:

[0006] Fully understand the geological conditions and environmental conditions before tunnel construction, strengthen the observation of geological conditions and deformation during construction, continuously adjust the design parameters through measurement and analysis, and optimize the design and construction plan;

[0007] Move the entrance light and dark boundary mileage to the outside of the tunnel by the designed distance, and construct the guide wall along the existing slope. No excavation is performed on the existing slope, and only the surface loose soil is cleaned. After the guide wall and the large pipe shed are completed, concrete is poured between the guide wall and the slope to seal it;

[0008] Two bored piles are added on each side of the tunnel entrance, and a cap beam is set on the top of the piles to support the outward-moving guide wall and carry out zero-slope entry construction.

[0009] When this scheme is used for tunnel portal excavation and tunnel construction, it is first necessary to fully understand the geological conditions and environmental conditions before tunnel construction, strengthen the observation of geological conditions and deformation during construction, continuously adjust the design parameters through measurement and analysis, and optimize the design and construction scheme; then move the entrance light and dark boundary mileage to the outside of the tunnel by the designed distance, and construct the guide wall along the existing slope. No excavation is performed on the existing slope, and only the surface loose soil is cleaned. After the large pipe shed is completed, concrete is poured between the guide wall and the slope to seal it; 2 bored piles are added to the left and right arch feet of the guide wall of the tunnel portal, and a crown beam is set on the top of the pile to carry out zero backslope tunnel construction; in this way, less excavation and less disturbance can be formed on the backslope of the tunnel portal, protection is first provided, and then tunnel entry is carried out. Only after the soil at the tunnel portal is properly handled can the tunnel be safely entered. In an environment with complex geological conditions, the extended tunnel portal adopts arch-protected dark excavation to enter the tunnel. Entering the tunnel with less disturbance to the surface and zero excavation can greatly improve the safety of tunnel portal construction.

[0010] The technical solution of this application is further described below:

[0011] In one of the embodiments, when entering the tunnel for construction, it is necessary to clear the surface vegetation within the tunnel excavation range and spray 15 cm thick concrete to seal it.

[0012] In one of the embodiments, when entering the cave, all exposed side slopes on the ground are reinforced by using local materials and installing bamboo anchor rods vertically on the slopes, so that the bamboo anchor rods can be used as glass fiber anchor rods.

[0013] In one of the embodiments, when entering the hole for construction, it is necessary to prevent slippage and protect the slope. For strata prone to slippage, a row of bored cast-in-place piles can be installed at the foot of the slope for protection, and a cap beam can be constructed on the top of the bored cast-in-place piles.

[0014] In one of the embodiments, in order to reduce the impact of tunnel excavation on the existing sliding slope, according to the principle of entering the tunnel early and exiting the tunnel late, the light and dark boundary mileage of the tunnel entrance is extended 10m outside the tunnel.

[0015] In one of the embodiments, the design of the side slope should follow the principle of strong footing, which means that a foot guard should be set for each level of the side slope, and anti-slip piles should be set at the foot of the slope when the stratum at the entrance of the cave is extremely poor.

[0016] In one of the embodiments, the design of the side slope should also follow the principle of waist consolidation, which means increasing the stability of the slope by excavating in reasonable steps and setting reasonable step heights, while also setting reasonable protection measures for the side slope based on geological conditions.

[0017] In one of the embodiments, the design of the side slope should also follow the principle of full protection, which means that full-enclosed protection measures should be taken for the mudstone formation cave entrance to the side slope surface.

[0018] In one embodiment, the tunnel entrance should be arranged along the ridge line as far as possible, and the slope of the side slope should be as slow as possible.

[0019] In one embodiment, the step height of the side slope is set to 4m~8m. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application.

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0022] FIG. 1 is a plan view of the structural layout of a tunnel opening according to an embodiment.

[0023] FIG. 2 is a schematic structural diagram of a longitudinal section of a tunnel entrance.

[0024] Figure 3 The present invention is a flowchart of the steps of a method for zero-disturbance excavation of a tunnel portal according to an embodiment.

[0025] Description of reference numerals:

[0026] 100. Tunnel; 10. Tunnel entrance; 20. Guide wall; 30. Large pipe shed; 40. Spray seeding. DETAILED DESCRIPTION

[0027] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0028] In the description of the present application, it should be understood that if the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. appear, the orientation or position relationship indicated by these terms is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0029] In addition, if the terms "first" or "second" appear, these terms are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, if the term "plurality" appears, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0030] In this application, unless otherwise clearly specified and limited, if the terms "installed", "connected", "connected", "fixed" and the like appear, these terms should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0031] In the present application, unless otherwise clearly specified and limited, if there is a description that a first feature is "above" or "below" a second feature, etc., or similar descriptions appear, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0032] It should be noted that if an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. If an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. If any, the terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in this application are for illustrative purposes only and do not represent the only implementation method.

[0033] See also Figure 3 , a construction method for zero-disturbance excavation of a tunnel entrance 10 is shown in an embodiment of the present application, and includes the following steps:

[0034] S10: Tunnel 100 fully understood the geological conditions and environmental conditions before construction, strengthened observation of geological conditions and deformation during construction, continuously adjusted design parameters through measurement and analysis, and optimized the design and construction plan.

[0035] S20: Move the entrance light-dark boundary mileage toward the outside of the tunnel by a designed distance, and construct the guide wall 20 along the existing slope. No excavation is performed on the existing slope, and only the surface loose soil is cleaned. After the construction of the guide wall 20 and the large pipe shed 30 is completed, concrete is poured between the guide wall 20 and the slope to seal it.

[0036] S30: Add two bored piles on both sides of the tunnel entrance, and set a cap beam on the pile top to support the outward-moving guide wall 20, so as to carry out zero backslope tunnel construction.

[0037] Please refer to Figures 1 and 2. In summary, the implementation of the technical solution of this embodiment will achieve the following beneficial effects: when using this solution to excavate the tunnel entrance 10 and enter the cave, it is necessary to first fully understand the geological conditions and environmental conditions before the construction of the tunnel 100, strengthen the observation of geological conditions and deformation during the construction process, continuously adjust the design parameters through measurement and analysis, and optimize the design and construction plan; then move the entrance light and dark boundary mileage toward the outside of the cave by a designed distance, and construct the guide wall 20 along the existing slope. No excavation is performed on the existing slope, and only the surface loose soil is cleaned. The guide wall After the construction of 20 and the large pipe shed 30 is completed, concrete is poured between the guide wall 20 and the slope to seal it; at the same time, 2 bored piles are added on both sides of the arch foot of the guide wall 20 at the tunnel entrance, and a crown beam is set on the pile top to carry out zero backslope tunnel construction; in this way, less excavation and less disturbance can be formed on the backslope of the tunnel entrance 10, protection is first carried out, and then tunnel entry can be carried out. Only after the soil at the tunnel entrance is properly handled can the tunnel be entered safely. In an environment with complex geological conditions, the tunnel entrance is extended by using a protective arch to enter the tunnel. Entering the tunnel with less disturbance to the surface and zero excavation can greatly improve the construction safety of the tunnel entrance 10.

[0038] It is particularly important to explain that during construction in the rainy season, the exposed soil layer after clearing the surface is soaked by rainfall, and its strength is significantly reduced and its mechanical properties deteriorate. In order to enter the cave safely and smoothly, it is necessary to take measures such as adding pile foundations and arch protection to enter the dark cave in advance (enter the cave with zero backslope), minimize the cutting and excavation of clearing the surface and the side backslope, and strengthen on-site construction management to reduce the risk of sliding and instability at the edge of the cave entrance and the backslope.

[0039] On the basis of the above-mentioned embodiment, when the tunnel construction is carried out, it is necessary to use local materials for all exposed side slopes and to install bamboo anchor rods vertically on the slope to reinforce the slope.

[0040] At this time, bamboo anchor rods are used as fiberglass anchor rods. The diameter of bamboo anchor rods is 5cm~15cm, and the length is 5m~8m (subject to the actual bamboo that can be purchased). The arrangement spacing of bamboo anchor rods is 0.6m×0.6m. This can effectively enhance the slope structure strength and stability of the side slope and prevent the side slope from slipping.

[0041] It should be noted that when the existing surface vegetation outside the tunnel excavation range is damaged, the existing side slope should be sprayed with 40% grass as soon as possible to reduce soil loss caused by rain.

[0042] In one embodiment, in order to reduce the impact of tunnel excavation on the existing slope, according to the principle of early entry and late exit, the light-dark boundary mileage of the entrance of tunnel 100 is extended 10m outside the tunnel from the original design mileage. This measure is equivalent to extending the tunnel entrance so that arched tunneling can be used to enter the tunnel and reduce disturbance to the ground surface.

[0043] In the actual construction process, loose expansive mudstone strata are usually prone to engineering disasters such as slope sliding and surface collapse. This type of stratum has the characteristics of high water content and high porosity. Therefore, special protection of these unfavorable geological sections is required during construction.

[0044] For example, in an optional embodiment, the design of the side slope should follow the principle of strong footing, which means that a foot guard should be set for each level of the side slope, and anti-slip piles should be set at the foot of the slope when the stratum at the entrance of the cave is extremely poor.

[0045] Furthermore, the design of the side slope should also follow the principle of waist consolidation, which means that the stability of the slope can be increased by excavating in reasonable steps and setting reasonable step heights, while the protective measures of the side slope can be reasonably set according to the geological conditions to prevent the slope from peeling off and collapsing due to rain erosion and soaking.

[0046] Furthermore, the design of the side slope should also follow the principle of full protection, which means that the mudstone stratum hole should take full sealing protection measures on the side slope surface, thereby reducing rainwater erosion, infiltration, etc., which may cause slope sliding and collapse.

[0047] In actual construction, the terrain should be used as much as possible to achieve "zero excavation" entry into the tunnel, reducing the disturbance of existing surface excavation. The tunnel entrance 10 should be set along the ridge line as much as possible to avoid large-angle oblique intersection and biased entry into the tunnel. The step height of the side slope is usually set to 4m~6m, and the maximum should not exceed 8m. Reducing the step height is conducive to reducing the risk of collapse and spalling. The slope of the side slope should be slowed down as much as possible, and the parts with large local seepage can be protected by seepage ditches. The temporary entrance should be fully protected, and a complete drainage system should be set up to achieve "high interception and long-distance drainage".

[0048] When constructing the tunnel portal section 10 in shallow, biased, soft, and water-rich strata, if the portal is directly excavated, it is easy to cause engineering disasters such as slope sliding, surface collapse, and support structure damage. In this case, various auxiliary construction methods are often used for pre-reinforcement before tunnel 100 excavation to ensure that the surrounding rock is stable before excavation. Auxiliary construction methods mainly include construction methods with the main purpose of stabilizing the tunnel face, and construction methods with the purpose of enhancing the stability of the surrounding rock outside the tunnel (generally referring to the surface and slope); in addition, there are construction methods with the purpose of lowering the groundwater level and treating water gushing. Auxiliary construction methods for portal construction refer to various measures such as stabilizing the face, stabilizing the surface, and treating water gushing. Specifically, the auxiliary construction methods of the portal section can be divided into surface pre-reinforcement outside the tunnel and surrounding rock pre-reinforcement measures inside the tunnel.

[0049] In order to effectively solve the unfavorable construction environment such as shallow burial depth and terrain bias at the tunnel entrance, and achieve the purpose of "natural entry" and "safe entry", it is very necessary to take auxiliary construction measures such as surface grouting reinforcement and anti-slide piles before excavation. Commonly used surface pre-reinforcement measures include surface anchors, jet grouting piles, deep hole grouting, anti-slide piles, retaining walls, etc. The construction parameters of the pre-reinforcement area should be determined according to the specific construction conditions on site and the engineering geological terrain of the tunnel entrance.

[0050] The effects of surface pre-reinforcement measures include but are not limited to the following: ① Improving the self-bearing capacity and self-stabilization time of the surrounding rock, improving the physical and mechanical properties of the rock (soil), and reducing the scope of the relaxation zone caused by the deformation of the surrounding rock after entering the tunnel excavation, which can effectively reduce the pressure on the initial support and effectively improve the stability of the slope of the tunnel entrance section; ② Anchor rods and grouting pipes can play the role of suspending the rock and soil, and can effectively curb geological diseases such as tunnel collapse and roof collapse; ③ The grouting liquid can reinforce the holes and collapsed bodies in the filled rock (soil), so that the overall stability of the surrounding rock is enhanced; ④ The grouting liquid can also block the infiltration of surface water into the tunnel, which can prevent the infiltration of surface water from softening the surrounding rock and thus reducing the stability of the surrounding rock.

[0051] Under complex terrain and geological conditions (shallow burial, eccentric pressure, weak and broken surrounding rock, etc.), the surrounding rock has poor self-stabilization ability, and even if the excavation adopts split sections or shortens the excavation advance, it cannot achieve significant results. Therefore, in order to improve the stability of the face, arch and surrounding rock, certain surrounding rock pre-reinforcement measures must be taken in advance to ensure that Tunnel 100 can be safely constructed, otherwise it is easy to cause engineering geological disasters such as landslides and roof falls during construction.

[0052] Most of the pre-reinforcement methods for surrounding rock are implemented before the excavation of Tunnel 100, mainly to ensure the stability of the surrounding rock in front of the face. According to different functions, they can be divided into the following types: ① Supporting the surrounding rock by improving the bending stiffness of the components, such as small pipe advance support, large pipe shed 30, etc.; ② Improving the engineering geological properties of the surrounding rock, that is, improving its physical and mechanical parameters to enhance the self-stabilizing ability of the surrounding rock, such as face grouting, etc.; ③ Playing the role of anchor rods, generally mainly for fractured structural rock mass, by increasing the friction resistance between blocks to improve the stability of the surrounding rock, such as inclined anchor rods, front anchor rods, etc.; ④ Sprayed concrete reinforcement, etc.

[0053] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0054] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A construction method for zero-disturbance excavation of a tunnel entrance, characterized in that: The steps include: Fully understand the geological conditions and environmental conditions before tunnel construction, strengthen the observation of geological conditions and deformation during construction, continuously adjust the design parameters through measurement and analysis, and optimize the design and construction plan; Move the entrance light and dark boundary mileage to the outside of the tunnel by the designed distance, and construct the guide wall along the existing slope. No excavation is performed on the existing slope, and only the surface loose soil is cleaned. After the guide wall and the large pipe shed are completed, concrete is poured between the guide wall and the slope to seal it; Two bored piles are added on each side of the tunnel entrance, and a cap beam is set on the top of the piles to support the outward-moving guide wall and carry out zero-slope entry construction.

2. The construction method for zero-disturbance excavation of a tunnel entrance according to claim 1 is characterized in that: When entering the tunnel for construction, it is necessary to clear the surface vegetation within the tunnel excavation range and spray 15cm thick concrete to seal it.

3. The construction method for zero-disturbance excavation of a tunnel portal according to claim 1 is characterized in that: When entering the tunnel for construction, it is necessary to use local materials for all exposed side slopes, and to install bamboo anchor rods vertically on the slope to reinforce the slope, so that the bamboo anchor rods can be used as glass fiber anchor rods.

4. The construction method for zero-disturbance excavation of a tunnel portal according to claim 1 is characterized in that: In order to reduce the impact of tunnel excavation on the existing sliding slope, based on the principle of entering the tunnel early and exiting the tunnel late, the light and dark boundary mileage of the tunnel entrance is extended 10m outside the tunnel from the original design mileage.

5. The construction method for zero-disturbance excavation of a tunnel portal according to claim 1 is characterized in that: The design of the side slope should follow the principle of strong footing. Strong footing means that a protective footing should be set for each level of the side slope. When the stratum at the entrance of the tunnel is extremely poor, anti-slip piles should be set at the foot of the slope.

6. The construction method for zero-disturbance excavation of a tunnel portal according to claim 1, characterized in that: The design of the side slope should also follow the principle of waist consolidation. Waist consolidation means increasing the stability of the slope by excavating in reasonable steps and setting reasonable step heights, while also setting reasonable protection measures for the side slope based on geological conditions.

7. The construction method for zero-disturbance excavation of a tunnel portal according to claim 1, characterized in that: The design of the side slope should also follow the principle of full protection. Full protection means that full-enclosed protection measures should be taken for the side slope surface at the mudstone formation entrance.

8. The construction method for zero-disturbance excavation of a tunnel portal according to claim 1, characterized in that: The tunnel entrance should be set along the ridge line as far as possible, and the slope of the side slope should be as slow as possible.

9. The construction method for zero-disturbance excavation of a tunnel portal according to claim 1, characterized in that: The step height of the side slope is set to 4m~8m.

10. The construction method for zero-disturbance excavation of a tunnel portal according to claim 1, characterized in that: When entering the tunnel for construction, it is necessary to clear the surface vegetation within the tunnel excavation range and spray 15cm thick concrete to seal it.

Images