阅读说明：本技术 一种城市复杂环境下大跨双连拱隧道开挖方法 (Large-span double-arch tunnel excavation method under urban complex environment ) 是由 李利强 白柱 陈栋 汶帅飞 范新阳 冯欢 刘朋 高智龙 吴腾 张旭祥 汶文钊 于 2021-09-10 设计创作，主要内容包括：本发明公开了一种城市复杂环境下大跨双连拱隧道开挖方法,包括：开挖三导洞,采取中导洞先行,左右侧导洞拉开步距跟进的方式进行三导洞的开挖；三导洞开挖完成后,浇注左导洞的左侧墙、右导洞的右侧墙和中导洞的中隔墙；左侧墙、右侧墙和中隔墙浇注完成后,对双连拱隧道的正洞采用上台阶CD工法贯通方式先施工,再对中下台阶后施工的方式进行开挖,其中,正洞开挖时初期支护的支撑点均在左侧墙、右侧墙和中隔墙上。采用先贯通正洞上台阶,同时施作初期支护,使其形成连拱盖隧道结构,然后开挖中台阶和下台阶的施工方法合理,保证了施工安全。(The invention discloses a method for excavating a large-span double arch tunnel in a complex urban environment, which comprises the following steps: excavating three pilot tunnels, wherein the excavation of the three pilot tunnels is carried out in a way that a middle pilot tunnel is firstly adopted, and left and right side pilot tunnels are pulled apart by step distance to follow; after the three pilot tunnels are excavated, pouring a left side wall of the left pilot tunnel, a right side wall of the right pilot tunnel and a middle partition wall of the middle pilot tunnel; after the left side wall, the right side wall and the middle partition wall are poured, the front tunnel of the double arch tunnel is firstly constructed in a mode of going through by an upper step CD construction method, and then is excavated in a mode of constructing a middle lower step, wherein supporting points of primary support during the excavation of the front tunnel are all arranged on the left side wall, the right side wall and the middle partition wall. The construction method that the upper step of the main tunnel is firstly penetrated, and the primary support is simultaneously carried out, so that the tunnel structure with the double arch covers is formed, and then the middle step and the lower step are excavated is reasonable, and the construction safety is ensured.)

1. A method for excavating a large-span double arch tunnel in a complex urban environment is characterized by comprising the following steps:

step (1): excavating three pilot tunnels, wherein the excavation of the three pilot tunnels is carried out in a way that a middle pilot tunnel is firstly adopted, and left and right side pilot tunnels are pulled apart by step distance to follow;

step (2): after the three pilot tunnels are excavated, pouring a left side wall of the left pilot tunnel, a right side wall of the right pilot tunnel and a middle partition wall of the middle pilot tunnel;

and (3): after the left side wall, the right side wall and the middle partition wall are poured, the front tunnel of the double arch tunnel is firstly constructed in a mode of going through by an upper step CD construction method, and then is excavated in a mode of constructing a middle lower step, wherein supporting points of primary support during the excavation of the front tunnel are all arranged on the left side wall, the right side wall and the middle partition wall.

2. The excavation method of the long-span double arch tunnel under the urban complex environment according to claim 1, wherein in the step (1), when three-pilot-tunnel excavation is performed, after the middle pilot tunnel and the left pilot tunnel are at least 30m steps apart, the left pilot tunnel is excavated, and after the right pilot tunnel and the left pilot tunnel are at least 30m steps apart, the right pilot tunnel is excavated; and after the step pitch of the middle pilot tunnel and the right pilot tunnel is at least 30m, excavating the right pilot tunnel, and after the step pitch of the left pilot tunnel and the right pilot tunnel is at least 30m, excavating the left pilot tunnel.

3. The excavation method of the large-span double-arch tunnel under the urban complex environment according to claim 1 or 2, characterized in that three pilot tunnels are excavated by adopting an upper-lower step method, and the construction of the lower step is carried out after the upper step is constructed for at least 3 m.

4. The excavation method for the large-span double arch tunnel under the urban complex environment according to claim 1, wherein in the step (3), the upper step construction comprises the following steps:

step (3.1): firstly, excavating the outer side of an upper step of any main tunnel of the double-arch tunnel, and constructing a first-layer primary support and a temporary support, wherein a supporting point of the first-layer primary support is on the left side wall or the right side wall;

step (3.2): after a certain step distance is constructed in the step (3.1), excavating the outer side of the upper step of the other unearthed main tunnel of the double arch tunnel, and constructing a first layer of primary support and temporary support, wherein the support point of the first layer of primary support is on the left side wall or the right side wall;

step (3.3): excavating the inner side of the upper step of any one main tunnel of the double arch tunnel while performing the step (3.2), and constructing a first layer of primary support, wherein the supporting point of the first layer of primary support is on the middle partition wall;

step (3.4): after the step (3.2) and the step (3.3) are constructed for a certain step distance, excavating the inner side of the upper step of the other main tunnel of the double arch tunnel, and constructing a first layer of primary support, wherein the supporting point of the first layer of primary support is on the middle partition wall;

step (3.5): and (5) repeating the steps (3.1) to (3.4) to ensure that the upper steps of the double-arch tunnel main tunnel are communicated.

5. The excavation method of the large-span double arch tunnel under the urban complex environment according to claim 4, wherein the step distance is not less than 2m when the outer side and the inner side of the same main tunnel are constructed; the step distance is more than or equal to 2m when the outer sides of the two main holes are constructed; the step distance is more than or equal to 2m when the inner sides of the two main holes are constructed.

Technical Field

The invention belongs to the technical field of excavation of underground excavation double-arch tunnels, and particularly relates to a large-span double-arch tunnel excavation method in a complex urban environment.

Background

Under the complex environment of the city, the rise-to-span ratio of the large-span double arch tunnel passing through the main trunk of the city is very small, the section is relatively flat, the soil body is particularly easy to be cut short or opened along the joint direction, the damage area is large, and the common bearing arch is difficult to form. Therefore, the main tunnel arch falling bearing capacity is increased by adopting a three-pilot tunnel excavation method so as to meet the requirements of safe and stable main tunnel excavation. According to the current state of the construction technology at home, the construction method of the large-span double arch tunnel is summarized into two types: the main tunnel excavation under the V-level surrounding rock is mostly a temporary middle partition wall method, a double-side wall pit guiding method, a three-step seven-step method and the like.

However, the analysis of the longitudinal excavation space of the tunnel in the common three-pilot-tunnel large-span double-arch tunnel is less, and the problems of poor geological conditions, large span and high requirement on the safety of the upper-span urban main road cannot be solved at the same time.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a method for excavating a large-span double arch tunnel in a complex urban environment.

The technical problem to be solved by the invention is realized by the following technical scheme:

a method for excavating a large-span double arch tunnel in a complex urban environment comprises the following steps:

step (1): excavating three pilot tunnels, wherein the excavation of the three pilot tunnels is carried out in a way that a middle pilot tunnel is firstly adopted, and left and right side pilot tunnels are pulled apart by step distance to follow;

step (2): after the three pilot tunnels are excavated, pouring a left side wall of the left pilot tunnel, a right side wall of the right pilot tunnel and a middle partition wall of the middle pilot tunnel;

and (3): after the left side wall, the right side wall and the middle partition wall are poured, the front tunnel of the double arch tunnel is firstly constructed in a mode of going through by an upper step CD construction method, and then is excavated in a mode of constructing a middle lower step, wherein supporting points of primary support during the excavation of the front tunnel are all arranged on the left side wall, the right side wall and the middle partition wall.

Further, in the step (1), when three-pilot-hole excavation is performed, after the middle pilot hole and the left pilot hole are at least 30m apart, the left pilot hole is excavated, and after the right pilot hole and the left pilot hole are at least 30m apart, the right pilot hole is excavated; and after the step pitch of the middle pilot tunnel and the right pilot tunnel is at least 30m, excavating the right pilot tunnel, and after the step pitch of the left pilot tunnel and the right pilot tunnel is at least 30m, excavating the left pilot tunnel.

And further, excavating three pilot tunnels by adopting an upper step and lower step method, and constructing the upper step for at least 3m and then constructing the lower step.

Further, in the step (3), the step construction comprises the following steps:

step (3.1): firstly, excavating the outer side of an upper step of any main tunnel of the double-arch tunnel, and constructing a first-layer primary support and a temporary support, wherein a supporting point of the first-layer primary support is on the left side wall or the right side wall;

step (3.2): after a certain step distance is constructed in the step (3.1), excavating the outer side of the upper step of the other unearthed main tunnel of the double arch tunnel, and constructing a first layer of primary support and temporary support, wherein the support point of the first layer of primary support is on the left side wall or the right side wall;

step (3.3): excavating the inner side of the upper step of any one main tunnel of the double arch tunnel while performing the step (3.2), and constructing a first layer of primary support, wherein the supporting point of the first layer of primary support is on the middle partition wall;

step (3.4): after the step (3.2) and the step (3.3) are constructed for a certain step distance, excavating the inner side of the upper step of the other main tunnel of the double arch tunnel, and constructing a first layer of primary support, wherein the supporting point of the first layer of primary support is on the middle partition wall;

step (3.5): and (5) repeating the steps (3.1) to (3.4) to ensure that the upper steps of the double-arch tunnel main tunnel are communicated.

Furthermore, the step distance is more than or equal to 2m when the outer side and the inner side of the same main tunnel are constructed; the step distance is more than or equal to 2m when the outer sides of the two main holes are constructed; the step distance is more than or equal to 2m when the inner sides of the two main holes are constructed.

The invention has the beneficial effects that:

1. the excavation method mainly occurs in the excavation stage of the upper step of the main tunnel according to the deformation and the stress of the middle partition wall, the two side walls and the primary support of the multi-arch tunnel, the influence of excavation of the middle step and the lower step is small, the construction method firstly penetrates through the upper step of the main tunnel and simultaneously performs the primary support to form the multi-arch tunnel structure, and then the construction method for excavating the middle step and the lower step is reasonable, so that the construction safety is ensured.

2. When the CD method for the upper step of the main tunnel is used for construction, reasonable step distances are adopted among all parts, so that the minimum main stress value of the primary support during the excavation of the main tunnel is minimum; the effects of vault subsidence, road subsidence and ground subsidence can be minimized.

3. The excavation method is suitable for tunnel construction under the conditions of weak surrounding rocks, has high safety requirements and strict sedimentation control requirements, and passes through urban arterial roads and other urban complex environments.

Drawings

FIG. 1 is a schematic structural view of three pilot holes;

FIG. 2 is a schematic view of the excavation process of the front tunnel cave cover;

fig. 3 is a schematic diagram of the excavation step of the main tunnel cave cover.

Description of reference numerals:

1-left pilot hole; 2-middle pilot hole; and 3-right pilot hole.

Detailed Description

The present invention will be described in further detail with reference to specific examples, but the embodiments of the present invention are not limited thereto.

Referring to fig. 1 to 3, an embodiment of the present invention provides a method for excavating a long-span double arch tunnel in a complex urban environment, which includes the following steps:

step (1): the construction excavation of the three pilot tunnels is carried out firstly, and the excavation of the three pilot tunnels is carried out in a mode that the middle pilot tunnel is firstly adopted, and the left and right side pilot tunnels are pulled apart by step distance to follow.

Specifically, during pilot tunnel construction, a step following mode that a middle pilot tunnel is firstly adopted and left and right side pilot tunnels are pulled apart by steps is adopted, namely after the middle pilot tunnel and a left pilot tunnel are pulled apart by steps of 30m, the left pilot tunnel is excavated into a tunnel; digging a tunnel after the right pilot tunnel and the left pilot tunnel are separated by 30m steps; or after the step distance between the middle pilot tunnel and the right pilot tunnel is increased by 30m, the right pilot tunnel is excavated, and after the step distance between the left pilot tunnel and the right pilot tunnel is increased by 30m, the left pilot tunnel is excavated. The excavation mode and the step pitch can reduce the surface subsidence and shorten the construction period, and if the step pitch is too short, the surface subsidence can be aggravated; if the step distance is too short, the construction period is prolonged.

Specifically, after 30m of excavation is carried out on the upper step of the middle pilot tunnel, excavation of a left pilot tunnel or a right pilot tunnel is carried out; and excavating the other pilot tunnel after excavating the upper step of the left pilot tunnel or the right pilot tunnel by 30 m.

Specifically, three pilot tunnel excavation is carried out by adopting an upper-lower step method, after the upper step is excavated for 3m, after the primary support of the upper step is stabilized, the lower step is excavated, the footage is fed for 0.6 m/roof beam in each cycle, and the primary spray sealing is carried out on the tunnel face after the excavation of each roof beam is finished; the method greatly shortens the construction period.

The pilot tunnel is slagging off and is adopted and take off sediment, the integral type machinery of slagging off, transports the dregs of the tunnel face of pilot tunnel to machinery rear, falls to dump truck on, is carried out the dregs by dump truck again, excavates and adopts excavator cooperation quartering hammer, and the rock mass can't be abolished completely to the local machinery of vault, adopts artifical handheld machinery, utilizes the operation platform to chisel, and local hard rock is excavated with boring and exploding the assistance.

Step (2): and after the three pilot tunnels are excavated, pouring the left side wall of the left pilot tunnel, the right side wall of the right pilot tunnel and the middle partition wall of the middle pilot tunnel.

Specifically, the side wall pouring is divided into an upper part and a lower part for pouring, and before the upper part and the lower part are poured, a cushion layer is poured at the bottom of the pilot tunnel, wherein the thickness of the cushion layer is 20 cm.

When the side wall is poured, pouring part of concrete firstly, and then pouring part of concrete, wherein the pouring of the part of concrete comprises the construction of a steel plate embedded part connected with an inverted arch foot of the step I-shaped steel under the main tunnel; pouring concrete on the lower part of the main tunnel, wherein the pouring concrete comprises the construction of a steel plate embedded part connected with an I-shaped steel arch foot of an upper step of the main tunnel; and during pouring, the casting is carried out in a retreating mode from the inside of the hole to the opening.

Specifically, concrete pouring is carried out on the left side of the lower portion of the left pilot tunnel by taking the primary support surface as a template, a splicing type wood template is adopted during right side pouring, concrete pouring is carried out on the right side of the lower portion of the right pilot tunnel by taking the primary support surface as the template, the splicing type wood template is adopted during left side pouring, the opening positions of steel plate connectors are reserved on the template, it is guaranteed that steel plates can be exposed at the steel plate connector positions of the next die when the template is closed, the steel plates are fixed on side wall reinforcing steel bars through welding, and concrete pouring is carried out according to 3.6m of each die for mold pouring construction.

Specifically, the construction of the intermediate wall is divided into an upper part and a lower part for pouring, and before the upper part and the lower part are poured, a cushion layer is poured at the bottom of the intermediate pilot tunnel, wherein the thickness of the cushion layer is 20 cm.

When the intermediate wall is cast, firstly casting the lower part of concrete, and then casting the lower part of concrete, wherein the lower part of concrete is cast to contain the construction of a steel plate embedded part connected with an inverted arch foot of the step I-shaped steel under the main tunnel; the concrete pouring of the lower part comprises the construction of other related embedded parts such as a steel plate embedded part connected with an I-shaped steel arch foot of an upper step of the main tunnel, a transverse temporary supporting embedded part, a water stop steel plate embedded part and the like; and during pouring, the casting is carried out in a retreating mode from the inside of the hole to the opening.

In order to ensure the stability of the wall body of the intermediate wall when the wall body of the intermediate wall is excavated by the left and right main tunnels to be reliable, after the intermediate wall is poured, a transverse temporary support needs to be additionally arranged between the intermediate wall and the initial supporting surface of the intermediate pilot tunnel, the support adopts I18I-shaped steel, and the transverse temporary support I-shaped steel is connected with an initial supporting steel arch frame by adopting a connecting steel plate and an M22 bolt.

Specifically, the lower part of the intermediate wall is poured by adopting an assembled template, an interface at the opening of a steel plate is reserved, the joint of the steel plate can be exposed when the template is closed, the steel plate is fixed on the reinforcing steel bars of the intermediate wall by welding, each lower part is constructed by 3.6m, and the construction process is advanced by 3 moulds at the upper part.

Specifically, after the step pitch of the middle partition wall is expanded during the construction, graded broken stone backfill construction is carried out on the lower part which is poured, and C15 plain concrete is poured on each mould after the backfill of each mould is finished. And (3) pouring concrete in the upper part by using the poured C15 backfill platform, adopting assembled template pouring construction, adopting an outer truss crane of the working well and a movable bottom type slag hopper to transport to the bottom of the working well in the pit, then transporting to a conveying pump hopper in the pilot tunnel by a small dump truck, and completing pouring concrete in the upper part by pumping concrete.

And (3): after the left side wall, the right side wall and the middle partition wall are poured, excavating a main tunnel of the double-arch tunnel, wherein supporting points of primary support and secondary primary support during main tunnel excavation are all arranged on the left side wall, the right side wall and the middle partition wall; the method comprises the steps of firstly constructing in a CD (compact disc) construction method for the upper step, and then excavating the double arch tunnels in a mode of constructing the middle and lower steps.

Specifically, when the construction of the three-guide-tunnel wall body is finished and the strength reaches the design requirement, the front tunnel is excavated,

specifically, the step (3) includes the steps of:

step (3.1): firstly, excavating a part I of an upper step of a left main hole of the double-arch tunnel, and constructing a first-layer primary support and a temporary support, wherein a supporting point of the first-layer primary support is on a left side wall;

step (3.2): after a certain step distance is constructed, excavating a part II of an upper step of a right main hole of the double arch tunnel, and constructing a first layer of primary support and temporary support, wherein a support point of the first layer of primary support is arranged on a right side wall;

step (3.3): excavating a part III of the upper step of the left main tunnel of the double arch tunnel while excavating a part II, and constructing a first layer of primary support, wherein the supporting point of the first layer of primary support is on the partition wall;

step (3.4): after constructing a certain step distance in the step (3.2) and the step (3.3), excavating the IV part of the upper step of the right main tunnel of the double arch tunnel, and constructing a first layer of primary support, wherein the supporting point of the first layer of primary support is on the middle partition wall;

step (3.5): and (5) repeating the steps (3.1) to (3.4) to ensure that the upper steps of the double-arch tunnel main tunnel are communicated.

Further, when excavation is performed, the step distance between the first part and the third part of the left main tunnel is 2m, the step distance between the second part and the fourth part of the right main tunnel is 2m, the step distance between the first part of the left main tunnel and the second part of the right main tunnel is 2m, and the step distance between the third part of the left main tunnel and the fourth part of the right main tunnel is 2m, as shown in fig. 3.

In the embodiment of the present invention, the step distance means a distance, for example, in "the step distance between the i portion and the iii portion of the left main tunnel is 2 m", the step distance means that the i portion is excavated for 2m, then the iii portion is excavated, and the excavation distance between the i portion and the iii portion is 2 m.

Furthermore, when the left hole is excavated, a second-layer primary support is constructed in time, the step distances of 1 part and 2 parts of the face of the second-layer primary support are controlled to be 15m, and the step distances of 3 parts and 4 parts of the face are controlled to be 13 m. And before constructing the primary support of the second layer, dismantling the temporary support.

Specifically, the front hole is excavated, the length of each circle is 0.6 m/roof truss, and the tunnel face is primarily sprayed and sealed after each roof truss is excavated.

It should be noted that, because the main tunnel excavation section is too large and the excavated geological condition is poor, the reserved deformability is set to be 3 cm.

When left and right main holes are excavated, the upper steps of the main holes are firstly penetrated, and primary supports are constructed at the same time, so that the multi-arch-cover tunnel is formed, the deformation and the stress of the intermediate wall, the left side wall, the right side wall, the primary supports of the multi-arch-cover tunnel are mainly generated in the excavation stage of the upper steps of the main holes, and the influence of the excavation of the middle and lower steps is small.

Under the complex environment of city, the construction degree of difficulty of upper step is big, and the accident takes place very easily, in order to avoid tunnel collapse to cause bigger damage, link up positive hole upper step earlier, guarantee that the upper step is under construction smoothly and accomplish, carry out the excavation of well step and lower step again, this kind of mode has also further reduced the earth's surface and has subsided.

The double-arch tunnel excavation method is applied to double-arch tunnel construction of a second west channel of a building door, is suitable for tunnel construction under urban complex environments such as a weak surrounding rock condition, high in safety requirement, strict in settlement control requirement, and a city main road and the like, guides the tunnel to safely pass the city main road, is safe in construction, saves the construction period, is praised by supervision and owners, and has obvious application effect and popularization value.

Simulating 3 working conditions under the construction environment of V-level surrounding rock crossing urban main roads and tunnel bias, large span and shallow burying by 5-15 m, wherein the step pitch of the left main tunnel and the right main tunnel is 3m, 2m and 1 m; the following analysis shows that:

(1): the maximum value of the minimum main stress of the primary support of the left hole is always larger than the maximum value of the minimum main stress of the primary support of the right hole and is possibly influenced by excavation of the right hole, and the minimum main stress of the primary support of the left hole is slightly larger than the minimum main stress of the primary support of the right hole. And only the angle contrastive analysis that the minimum main stress maximum value of the primary support is the most unfavorable stress part of the structure shows that the minimum main stress maximum value of the primary support is as follows: the excavation step distance is 3m, the excavation step distance is 1m, and the excavation step distance is 2 m. The larger the stress, the more unfavorable the structure stress, so the excavation step distance of the left and right holes of the tunnel is more safe by adopting a 2m structure.

(2): when the excavation step distances of the left and right positive holes are respectively 3m, 2m and 1m, the test results show that the vault subsidence of the tunnel is 29.32mm, 28.76mm and 44.37mm, the maximum convergence values are respectively 11.07mm, 11.50mm and 17.5mm, the maximum subsidence values of the road are 22.40mm, 25.04mm and 37.28mm, the maximum ground subsidence values are respectively 24.28mm, 21.70mm and 36.35mm, and the maximum minimum main stress values of primary support are respectively 10.23MPa, 9.97MPa and 10.38 MPa. When the excavation step distance is reduced, the displacement of each characteristic of the tunnel is increased. According to the control standard, when the excavation step distance of the left hole and the right hole is 1m, the vault crown settlement, the road settlement and the ground settlement exceed the standard values; according to the fact that the stress is larger, the stress of the tunnel structure is more unfavorable, and the minimum main stress maximum value of the excavation offset distance 2m is the largest. Therefore, according to the simulation calculation result, the excavation step distance of the two holes of the tunnel is not smaller than 2m, and the optimal value is 2 m.

The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.