Patent Application
20230349291
The present disclosure relates to the technical field of underground structures such as urban rail transit, railways, heating, electric power, water conservancy, utility tunnels, and municipal engineering, in particularly, to a system and construction method of a single-layer lining tunnel structure based on a mine-tunnelling method.
In 1980s, based on the principle of the new austrian tunnelling method, Chinese technicians developed a composite lining structure, a flexibly support can be used as an initial support under a good surrounding rock condition, so as to give full play capability of a surrounding rock structure; and a rigid support can be used under a shallow buried and poor surrounding rock condition, to reduce stratum deformation. The composite lining structure was first used in a railway tunnel in Dayaoshan, and popularized and developed in subway project in Beijing.
A subway section tunnel structured by a shallow-buried excavation method generally has a surrounding rock with V-class or VI-class, in which grid steel frames combined with sprayed concrete is used as an initial support, and molded reinforced concrete is used as a secondary lining structure. During a construction process, earthwork is excavated truss by truss, concrete is sprayed, grid arch frames are erected, and then concrete is sprayed again. On this basis, excavation and support operations will continue to be carried out circularly. After an initial supporting hole of the tunnel is opened, waterproof boards are laid in sections of 20 meters (m) to 30 m, secondary lining steel bars are bound manually, a formwork is erected, and concrete is poured. After the concrete reaches a designed strength, the second lining structure is repeatedly poured by advancing section by section. With respect to the shallow-buried excavation method, there are many technological defects such as a bad construction environment, a complicated construction process, and inadequate concrete pouring quality.
A section of a single-span tunnel constructed by a mine-tunnelling method is suitable for a single-hole single-track standard section tunnel (with a span of about 6.5 m), a civil air defense section tunnel (with a span of about 9.5 m), and a section tunnel with wiring or double lines (with a span of about 9 m to 14 m) of type A and/or type B subway vehicles. The constructed tunnel is suitable for various strata, such as sandy soil with or without water, cohesive soil, sandy pebbles, and rocks.
At present, for the existing tunnel supporting system based on mine-tunnelling method, a composite lining structure section is adopted. An initial support is used to resist a stratum soil load and control stratum deformation during the construction process, and a secondary lining can resist a soil and water load, civil air defense and earthquake load during using the tunnel without considering the initial support.
Under the condition of single-hole and single-track standard section tunnel (with the span of about 6.5 m), a bench method can be generally used for subsurface excavated construction. Firstly, an upper section of the tunnel is constructed and grid arch frames of the upper section is erected for support, and then a lower section is excavated and a grid arch of the lower section is erected. During constructing the secondary lining structure, an inverted arch structure is poured manually first, and then an arch wall structure is constructed by a trolley section by section. Under the condition of the civil air defense section tunnel (with the span of about 9.5 m), a cross diaphragm (CRD) method is generally used for subsurface excavated construction. The tunnel is divided into four pieces, and earthwork is excavated one by one, and the grid arch frames are erected, for forming a tunnel section supporting structure with vertical and horizontal supports; during constructing the secondary lining structure, it is necessary to dismantle a lower partition wall in the tunnel section by section, pour an inverted arch structure, then dismantle the remaining upper partition wall and center partition wall section by section, and pour an arch wall structure by a manual formwork support manner. Under the condition of the section tunnel with wiring or double lines (with the span of about 9 m to 14 m), a double-side heading method is generally used for subsurface excavated construction, and the tunnel is divided into six blocks, and earthwork is excavated one by one, and grid arch frames are erected, for forming a tunnel section supporting structure with vertical and horizontal supports. During constructing a second lining structure, it is necessary to dismantle lower partition walls on both sides one by one, pour an inverted arch structure, erect horizontal supports at both ends of the inverted arch structure, and then dismantle an initial support such as the remaining partition walls, and partitions section by section, and pour an arch wall structure.
Based on the principle of “strong support” of the 18-character policy of the shallow-buried excavation method, it is necessary to strengthen the stiffness of the initial support; a large-section tunnel is excavated in silos, but the poor construction conditions of the secondary lining structure, poor concrete pouring quality, a complex construction process and a slow construction speed have always been the shortage in the design and construction of the subsurface excavated construction.
For a traditional composite lining structure, a tunnel is excavated and an initial support is erected first, and then a waterproof layer is constructed after an initial supporting hole of the tunnel is opened, and then the conversion between the initial support and a secondary lining structure is carried out. A small-section tunnel is relatively simple, but a large-section tunnel needs to be constructed needs to be carried out in different warehouses and sections, and the construction process is complicated and the construction efficiency is lower. In addition, because of the poor construction condition, the construction quality of second lining construction joints and vault concrete is generally poor.
In view of this, based on the above defects, a designer of the present disclosure has studied and designed a system and construction method of a single-layer lining tunnel structure based on a mine-tunnelling method by concentrating on research and design and integrating the experience and achievements in related industries, so as to overcome the above defects.
Objectives of the present disclosure is to provide a system and construction method of a single-layer lining tunnel structure based on a mine-tunnelling method, the method is applied to construct a shallow-buried and underground-excavated tunnel, which effectively overcomes the defects of the related art, improve the resistance of a surrounding rock, prevents water from entering the tunnel in a construction stage, and improves the impermeability of the surrounding rock-tunnel system in a use stage.
From the above, it can be seen that the system and construction method of the single-layer lining tunnel structure based on the mine-tunnelling method of the present disclosure at least have the following effects.
The details of the present disclosure can be obtained from the following description and the accompanying drawings.
Referring to
As shown, the construction method of the single-layer lining tunnel structure based on a mine-tunnelling method includes following steps:
Through the above steps, the construction method of the single-layer lining tunnel structure based on a mine-tunnelling method aims at the problems existing in the composite lining structure, removes the waterproof boards and the secondary lining structure, and adopts the single-layer lining structure. Combined with the advanced pretreatment of water-bearing strata, a tunnel water stop ring is set. It fundamentally improves the structural stiffness and durability, and maximize the maximum performance and utility of tunnel pretreatment measures and the tunnel structure. It simplifies the construction process, reduces the amount of earthwork excavation in the tunnel, and saves the amount of reinforcement and concrete in the lining structure, so that the construction speed can be greatly improved.
In an embodiment, the method may further include the following steps.
In a process of tunnel excavation, leading conduits are strictly arranged, an arrangement angle of each of the leading conduits is in a range from 25° to 35°, and a length of each of the leading conduits is in a range from 2.2 m to 2.4 m. The leading conduits are arranged truss by truss according to the grid steel frames and are welded with the grid steel frames, two adjacent leading conduits in two trusses are horizontally overlapped, and an overlapping length of the two adjacent leading conduits is 1 m. A wall of each of the leading conduits is provided with thermals, and each of the leading conduits is configured for performing grouting on a stratum to achieve the reinforcement effect of the stratum. The leading conduits are welded with the reinforcing meshes and the grid steel frames to form a combined supporting structure together with the stratum.
Specifically, the spraying of the concrete is performed by a wet spraying process. The wet sprayed concrete has the characteristics of rapid strength growth, high early strength, strong adhesion, high density, and good impermeability; and can better fill a gap between the surrounding rock and the supporting structure, increase the integrity of the supporting structure and the surrounding rock, and work together with the supporting structure, and does not need molds, which saves construction costs and improves a construction speed.
Fiber concrete can be used as the concrete, which can improve the durability of the wet sprayed concrete. The brittle material essence of the concrete can be obviously improved by uniformly and randomly distributed high-strength fiber, so that the impact shear resistance, wear resistance and corrosion resistance of an initial supporting structure can be obviously improved. In addition, the high-strength fiber sprayed concrete can still maintain its bearing capacity after large deformation, which can effectively improve the supporting effect and bonding ability of the sprayed concrete to a weak surrounding rock when an early strength of the sprayed concrete is lower.
Requirement on indexes of strength and durability of the single-layer lining concrete is higher than that of ordinary sprayed concrete. Therefore, based on adding the fiber to the concrete to improve crack resistance, an external additive such as silicon powder and mineral powder can be used in the concrete to make the sprayed concrete have higher impermeability. Using polyolefin fiber as the high-strength fiber instead of the reinforcing mesh can make cracks with a dimension less than 0.2 millimeters (mm) in the concrete evenly distributed and improve the compactness of the wet sprayed concrete.
In an embodiment, as illustrated in
In an embodiment, as illustrated in
In an embodiment, as illustrated in
In an embodiment, as illustrated in
According to an actual condition of the stratum where the tunnel is located, a stress state of the tunnel in the stratum is simulated using a finite element software. According to a simulation result, a dimension of the single-layer lining tunnel structure and reinforcement configuration results are adjusted. The single-layer lining has greatly improved the deformation resistance, the amount of reinforced concrete and the mechanical performance of the tunnel, and the durability design also meets the specified requirements.
A thickness of the single-layer lining tunnel structure is adjusted according to the actual condition of the stratum. Taking a single-hole single-track section and a single-hole double-track section as examples, after calculation and comparison, it is found that under the condition of single-hole double-track cross-section tunnel, the thickness of the single-layer lining tunnel structure should be 400 mm, a spacing of the grid steel frames should be 400 mm, and a main bar of each of the grid steel frames should be a type of E25; under the condition of the single- hole double-track cross-section tunnel, the thickness of the single-layer lining tunnel structure should be 550 mm, the spacing of the grid steel frames be 400 mm, and the main bar of the grid steel frame should be a type of E25. C35 concrete is adopted to meet the requirement of design life of 100 years. A thickness of a reinforcement protective layer is 40 mm, and a crack width is controlled according to 0.2 mm outside and 0.3 mm inside.
At present, for the existing tunnel support system based on the mine-tunnelling method, the composite lining structure section is adopted. An initial support is used to resist a stratum soil load and control stratum deformation during the construction process, and a secondary lining can resist a soil and water load, civil air defense and earthquake load during using the tunnel without considering the initial support.
In contract, the single-layer lining tunnel supporting structure described in the present disclosure considers the bearing capacity and durability requirements in the construction stage and the use stage. In areas with large deformation, such as soft soil, a section size of the tunnel can be appropriately increased, and sufficient post-reinforcement conditions can be reserved to extend the service life of the tunnel.
1.1 Types of main materials
Concrete and reinforcing bar: for the composite lining tunnel structure, the secondary lining concrete uses concrete C40, and the reinforcing bar uses reinforcing bar HRB400; for the single-layer lining tunnel structure, the concrete uses concrete C35, and the reinforcing bar uses reinforcing bar HRB400.
1.2 A thickness of a concrete protective layer of the stressed main bar
(1) for the composite lining tunnel structure, a thickness of a primary lining is 35 mm, a thickness of a second lining is 35 mm outside and 35 mm inside;
(2) for the single-layer lining tunnel structure, a thickness thereof is 40 mm outside and 40 mm inside.
1.3 Calculation explanation
(1) A parameter of the lining is calculated by a load-structure method; for an interaction between the lining and the surrounding rock, an elastic support conforming to Winkler's assumption is adopted to reflect the elastic resistance of the surrounding rock. In the present disclosure, a spring that can only bear a pressure (automatically fail in tension) is used to simulate the action of the surrounding rock.
(2) In the construction stage, the calculation is performed according to a no water working condition; in the use stage, the long-term effect of groundwater is considered, and the calculation is performed based on estimating water and earth pressure separately according to an anti-floating water level.
(3) When an overburden thickness is more than 2.0 times the excavation width of the primary lining, a vertical overburden load is calculated and reduced according to Terzaghi K. formula; when the overburden thickness is less than 2.0 times the excavation width of the primary lining, the vertical overburden load is calculated according to a full soil column load. When calculating a lateral earth pressure, a static earth pressure is used, and a value of the lateral earth pressure is an equivalent earth overburden load multiplied by a static lateral earth pressure coefficient.
1.4 Proposed design conditions
The proposed conditions are as follows: an overburden thickness at the top of the tunnel is 12 m, the static lateral earth pressure coefficient is 0.35, a spring coefficient of each of horizontal and vertical foundations is 30 micro Newtons per meter (MN/m), and an earth natural density is 20 kilopascals per meter (KPa/m). A ground overload is 20 kilopascals (KPa).
1.5 Load Calculation
A load of the surrounding rock of the tunnel is calculated as follows.
An earth load at the top of the tunnel is calculated by 20 KPa/m×12 m=240 KPa.
A lateral earth pressure at the top of the tunnel is calculated by 240 KPa×0.35=84 KPa.
An elevation lateral earth pressure at the bottom of the tunnel is calculated by 20 KPa/m×(12 m+7 m)×0.35=133 KPa.
At present, the water level is considered to drop below a floor of the tunnel. A long-term anti-floating water level is considered as 4 m below the ground. A water pressure on the roof of the tunnel is calculated by 10 KPa/m×(12 m−4 m)=80 KPa.
A water pressure on the floor of the tunnel is calculated by 10 KPa/m×(18 m−4 m)=140 KPa.
1.6 Load combinations are shown in Table 1 below.
1.7 As shown in
(1) Bending moment curves (with the unit of KN.m) corresponding to a short-term low water level are illustrated in
(2) Bending moment curves (with the unit of KN.m) corresponding to a long-term anti-floating water level are illustrated in
Since a deep-buried tunnel structure is generally not controlled in civil air defense and earthquake conditions, no calculation and analysis are performed herein.
1.8 As shown in
(1) Bending moment curves (with the unit of KN·m) corresponding to a short-term low water level are illustrated in
(2) Bending moment curves (with the unit of KN·m) corresponding to a long-term anti-floating water level are illustrated in
The following is a comparative analysis of designs, constructions, and economy.
2.1 Comparison of single-hole and single-track tunnels
When the calculation for the secondary lining of the composite lining structure is performed, the function of the initial support is not considered, and the construction is performed in the form of molded concrete, with C40 concrete and E25@100 main bar. An excavation area of the section is 36.4 m2. Waterproof boards are arranged outside the second lining, with a length of 19.8 m per linear meter. The single-layer lining structure is constructed by wet sprayed concrete using C35 concrete, is erected with dense grids, with 5 grids every 2 m, and is provided with E25@200 main bar (short-term working condition control). An excavation area of the section is 32.9 m2.
Compared with the original composite lining structure, the single-layer lining structure reduces the earthwork excavation by 10% per linear meter. A reinforcement amount of a main bar per linear meter of a structural section of the single-layer lining structure is 80703 mm2·m, reinforcement amount of a main bar per linear meter of a structural section of the composite lining structure is 133705 mm2·m, and the reinforcement amount of the single-layer lining structurer is reduced by 40%. The amount of concrete per linear meter of a structural section of the single-layer lining structure is 0.4 m3, the amount of concrete per linear meter of a structural section of the composite lining structure is 0.75 m3, and the amount of the concrete of the single-layer lining structurer is reduced by 46%. In terms of construction period, a construction speed of the initial support is about 1.5 m per day, and a construction speed of the second lining structure of the tunnel with the step method is about 2 m per day. Therefore, a construction period of the single-layer lining tunnel per linear meter is about 0.6 days, and a construction period of the composite lining tunnel is 1.1 days. The construction period of the single-layer lining tunnel is increased by 45%.
2.2 Comparison of single-hole double-track tunnels
When the calculation for the secondary lining of the composite lining structure is performed, the function of the initial support is not considered, and the construction is performed in the form of molded concrete, with C40 concrete and E25@100 main bar. An excavation area of the section is 94.8 m2. Waterproof boards are arranged outside the second lining, with a length of 32.7 m per linear meter. The single-layer lining structure is constructed by wet sprayed concrete using C35 concrete, is erected with dense grids, with 5 grids every 2 m, the main bars of the grids are provided with double-layer steel bars, and is provided with E25@100 main bar. An excavation area of the section is 82.3 m2. If necessary, grouting water-stop rings shall be set on the outside of the tunnel for self-waterproofing of the surrounding rock.
Compared with the original composite lining structure, the single-layer lining structure reduces the earthwork excavation by 13% per linear meter. A reinforcement amount of a main bar per linear meter of a structural section of the single-layer lining structure is 405916 mm2·m, reinforcement amount of a main bar per linear meter of a structural section of the composite lining structure is 493944 mm2·m, and the reinforcement amount of the single-layer lining structurer is reduced by 17%. The amount of concrete per linear meter of a structural section of the single-layer lining structure is 34.785 m3, the amount of concrete per linear meter of a structural section of the composite lining structure is 42.96 m3, and the amount of the concrete of the single-layer lining structurer is reduced by 19%. In terms of construction period, take a tunnel with a length of 100 m as an example. A construction period of the initial support is about 1.5 m per day. Considering the excavation with a staggered distance of 10 m between pilot headings, the initial support time is (100 m+50 m)/1.5m per day=100 days, the second lining is constructed section by section, one section is demolished for 9 m, and the inverted arch is constructed with 7 days. It takes 14 days to dismantle the center diaphragms and the center partitions, erect scaffolding, tie steel bars, and pour concrete. There are 10 sections in total. Considering two working faces, the construction period is about 21 days×5=105 days (if the geology is good, the initial supports of three warehouses will be demolished at one time, and the construction speed of the second lining structure of the tunnel using the double-side heading method is about 2 m per day, 7+100/2=57 days). Therefore, the construction period of the single-layer lining tunnel per linear meter is about 1 day, and the construction period of the composite lining tunnel is between 1.5 days and 2 days. The construction period of the single-layer lining tunnel is increased by 33% to 50%.
On the whole, compared with the composite lining structure, for the single-layer lining structure, the earthwork excavation is reduced by 10% to 13%, the reinforcement amount is reduced by 17% to 40%, the amount of concrete is reduced by 19% to 46%, and the construction period is increased by 33% to 50%.
It is apparent that the above description and records are merely examples and are not intended to limit the present disclosure. Although the embodiments have been described and the embodiments are illustrated in the accompanying drawings, the present disclosure is not limited to specific implementations illustrated in the drawings and described in the embodiments as the best mode at present to implement the teachings of the present disclosure, and any embodiments that fall within the foregoing description and the appended claims are included in the scope of protection of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022104655384 | Apr 2022 | CN | national |
