Construction method for tunnel connecting channel

Abstract

A construction method for a tunnel connecting channel, the construction method comprising: step S1, providing inside a first tunnel a plurality of divergent grouting holes extending towards a second tunnel; step S2, performing grouting reinforcement on the part between the first tunnel and the second tunnel by means of the grouting holes, and injecting liquid nitrogen for cooling so as to form a water-stop curtain corresponding to a connecting channel; step S3, synchronously excavating the connecting channel from the first channel and the second channel to the middle; step S4, mounting initial support steel bars in a support-while-excavating mode, and performing concrete sealing from the middle to two sides after the excavation of the connecting channel is completed; and step S5, after sealing concrete reaches a preset strength, removing freezing pipes and performing blocking, and after the water-stop curtain thaws, performing grouting reinforcement by means of the freezing pipes. When there is no need to construct a dewatering well on the ground, there is also no need for dewatering after grouting reinforcement, and the stabilizing effect is good during a tunneling process.

Description

Tunnel connecting passage construction method TECHNICAL FIELD

[0001] The application belongs to the technical field of tunnel construction, and particularly relates to a tunnel connecting passage construction method. BACKGROUND

[0002] With the development and application of the shield method in urban rail transit and the continuous progress and improvement of tunnel engineering technology, the shield method plays an increasingly important role in construction and becomes a mainstream construction method for urban subway construction.

[0003] At present, subway shield construction is mostly in busy areas, so the connecting passage is under a busy road, and the upper ground surface pipeline is dense, which affects the rotary jet grouting reinforcement. In addition, the connecting passage is generally the lowest point of the tunnel and has a deep burial depth. If it is in a sand layer, the rotary jet grouting reinforcement quality is difficult to guarantee. When surface dewatering is used for auxiliary construction, the ground conditions limit the arrangement of dewatering well points, and the water level cannot be lowered to the bottom plate, which causes a large settlement and water and sand gushing risk in the connecting passage excavation process.

[0004] Therefore, it is necessary to provide an improved technical solution for the above-mentioned deficiencies of the prior art. SUMMARY

[0005] The purpose of the application is to overcome the deficiencies in the prior art, and the application provides a tunnel connecting passage construction method.

[0006] In order to achieve the above-mentioned purpose, the application provides the following technical solution:

[0007] A tunnel connecting passage construction method comprises the following steps:

[0008] Step S1, measuring and lofting the connecting passage inside the first tunnel and the second tunnel, and setting a plurality of grouting holes extending to the second tunnel from the first tunnel, wherein the plurality of grouting holes are uniformly distributed around the connecting passage;

[0009] Step S2, grouting and reinforcing the part between the first tunnel and the second tunnel through the grouting holes, plugging the grouting holes after grouting is completed, setting a freezing hole around the connecting passage, plugging the freezing tube after the freezing tube is inserted into the freezing hole, injecting liquid nitrogen into the freezing tube to cool it, so as to form a water stop curtain corresponding to the connecting passage;

[0010] Step S3, erecting a working platform corresponding to the opening of the connecting passage in the first tunnel and the second tunnel, cutting the lining in the first tunnel and the second tunnel according to the profile of the connecting passage through a cutting device, and synchronously excavating the connecting passage from the first tunnel and the second tunnel to the middle part;

[0011] Step S4, install the initial support steel bars by the method of supporting as digging, and close the concrete from the middle to both sides after the communication passage is through; before the concrete is closed, the grouting holes extending to the first tunnel are punched in the second tunnel; the grouting holes diverge and extend to the first tunnel; the grouting holes are evenly distributed around the communication passage;

[0012] Step S5, after the closed concrete reaches the preset strength, remove the freezing pipe and block it, and after the water stop curtain is melted, grouting reinforcement is carried out through the freezing pipe;

[0013] The grouting holes punched from the first tunnel extend to the plane corresponding to the center line of the second tunnel or the outer wall of the second tunnel; the grouting holes punched from the second tunnel extend to the plane corresponding to the center line of the first tunnel or the outer wall of the first tunnel;

[0014] In step S3, first, the full-face excavation is carried out on the horn mouth parts corresponding to both ends of the communication passage, and after the excavation is completed, the initial support is carried out through the grid steel frame; after the initial support of the horn mouth is completed, the main body excavation of the communication passage is carried out, and the initial support part is sprayed with concrete during the excavation process; the leading work face of the excavation process does not exceed two bays ahead of the grid steel frame support progress;

[0015] After the main body excavation of the communication passage and the initial spraying of the concrete are carried out, the waterproof layer is laid inside the communication passage; after the waterproof layer is laid, the reinforcement cage corresponding to the communication passage is bound; the reinforcement cage is provided corresponding to the horn mouth structure at both ends of the communication passage; the formwork is provided inside the reinforcement cage; the formwork is provided with pouring ports and vibrating equipment corresponding to the concrete; the closed structure is formed by pouring the concrete;

[0016] In step S3, during the binding process of the reinforcement cage, the prestressed support is arranged at the horn mouth of the interval communication passage; the prestressed support is internally provided with a plurality of support jacks evenly distributed along the circumference; the prestressed support is bound to the reinforcement cage during the reinforcement binding process; after the reinforcement binding is completed, the support jacks are withdrawn to install the formwork;

[0017] The prestressed support includes a plurality of spliced pieces spliced with each other; the prestressed support is internally provided with a truss; the truss is externally provided with a plurality of support jacks extending along the radial direction of the communication passage; the plurality of support jacks and the plurality of spliced pieces are one-to-one corresponding; a spacer plate is arranged between any two adjacent spliced pieces.

[0018] Beneficial effect: without the need for ground construction of a dewatering well, grouting reinforcement is carried out without the need for dewatering; the stability effect is good during the tunneling process; it is safe and reliable; the soil under the site is not emptied; the safety of the site, nearby buildings and slopes is ensured.

[0019] The first grouting reinforcement is performed before the excavation is completed to reinforce the outer periphery of the connecting passage, and the second grouting reinforcement is performed after the excavation is completed to fully release the internal stress, so that the stability of the connecting passage is greatly improved after the second grouting. BRIEF DESCRIPTION OF DRAWINGS

[0020] Fig. 1 is a schematic diagram of the distribution of grouting holes in the specific embodiment provided in the present application;

[0021] Fig. 2 is an installation structure diagram of the orifice pipe in the specific embodiment provided in the present application.

[0022] In the figure: 1, first tunnel; 2, second tunnel; 3, connecting passage; 4, trumpet; 5, grouting hole; 6, freezing pipe; 7, segment; 8, orifice pipe; 9, expansion screw; 10, small valve; 11, gate valve; 12, adapter; 13, conical rubber plug; 14, baffle. DETAILED DESCRIPTION

[0023] As shown in Figs. 1-2, a tunnel connecting passage construction method comprises the following steps: step S1, determining the specific position of the connecting passage 3 according to the actual engineering, measuring and laying out the connecting passage 3 inside the first tunnel 1 and the second tunnel 2, and setting a plurality of grouting holes 5 extending towards the second tunnel 2 inside the first tunnel 1, the plurality of grouting holes 5 being uniformly distributed about the circumference of the connecting passage 3;

[0024] The diameter of the circle passing through the grouting holes 5 is less than the diameter of the circle passing through the trumpet 4 at both ends of the connecting passage 3, the grouting pipe is cut during excavation after grouting and initial setting, so that the grouting pipe does not protrude inside the connecting passage 3, and the strength of the connecting passage 3 can be improved by closing the lining inside the connecting passage 3;

[0025] The grouting is performed by the segmented back-pulling grouting method, and the general back-pulling step distance is 0.3 m;

[0026] Step S2, performing grouting reinforcement on the part between the first tunnel 1 and the second tunnel 2 through the grouting holes 5, plugging the grouting holes 5 after grouting, setting freezing holes on the outer periphery of the connecting passage 3, plugging the freezing pipes 6 after inserting the freezing pipes 6 into the freezing holes, injecting liquid nitrogen into the freezing pipes 6 to cool them, and forming a water-stopping curtain corresponding to the connecting passage 3;

[0027] The freezing hole is located at a circumference diameter larger than the circumscribed circle diameter of the trumpet mouth 4 at both ends of the connecting passage 3, so that the freezing area does not affect the normal excavation of the connecting passage 3. Before the construction of the connecting passage 3, the surrounding stratum is reinforced by freezing method, so that the excavation and construction of the connecting passage 3 is carried out in the frozen soil curtain structure, the leakage of underground water is avoided, the temperature measuring holes are arranged in the frozen soil curtain, so that whether the frozen soil curtain is closed and the thickness of the frozen soil curtain is determined, and the pressure relief holes are arranged at both ends of the connecting passage 3, so as to reduce the influence of the soil frost heaving on the first tunnel 1 or the second tunnel 2, and the holes can be used as observation holes of the pressure change of the frozen curtain;

[0028] Since the concrete is easier to dissipate heat than the soil layer, the freezing speed of the soil layer near the segment 7 is affected, thereby affecting the overall stability and water sealing property of the frozen soil curtain. In particular, the thickness and strength of the frozen soil curtain at the trumpet mouth 4 part of the connecting passage 3 and the complete cementation with the segment 7 are ensured, two rows of holes (four rows at the vault part) are arranged at the trumpet mouth 4 part of the construction end of the freezing hole to strengthen freezing, and the cold freezing plate is arranged at the opposite tunnel. The outer two rings of the segment 7 outside the connecting passage 3 are insulated by PE boards to reduce the loss of cold quantity, and the temperature measuring points are placed at the cementation part of the frozen soil wall and the segment 7 to strengthen the detection of the cementation condition of the frozen soil wall and the segment 7;

[0029] Step S3, a working platform is erected in the first tunnel 1 and the second tunnel 2 corresponding to the opening of the connecting passage 3, the lining in the first tunnel 1 and the second tunnel 2 is cut according to the contour of the connecting passage 3 by cutting equipment, and the connecting passage 3 is excavated synchronously from the middle part of the first tunnel 1 and the second tunnel 2; the segment 7 is cut by a core drill in blocks, and after the segment 7 is removed, the formal excavation can be carried out; the work adopts the combination of air pick, shovel and hand pick, and the earth is excavated manually, the earth on the working face is transported to the special earth removal box near the wellhead by a trolley, and is lifted to the ground by a lifting machine for removal;

[0030] Step S4, the initial support steel is installed by the way of digging and supporting at the same time, and the concrete is closed from the middle part to both sides after the connecting passage 3 is through; before the concrete is closed, the grouting hole 5 extending to the first tunnel 1 is punched in the second tunnel 2, a plurality of grouting holes 5 extend to the first tunnel 1 in divergence, and the plurality of grouting holes 5 are uniformly distributed about the circumference of the connecting passage 3;

[0031] The initial support steel adopts a grid steel frame, and one shotcrete operation is carried out after each excavation of the passage part; the concrete closure is permanent support, and cast-in-place reinforced concrete is adopted; the grouting holes 5 punched in the second tunnel 2 and the grouting holes 5 punched in the first tunnel 1 are opposite in direction, and are distributed in interlacing on the axial projection of the connecting passage 3, so that the punching path can be optimized when the grouting holes 5 and the freezing holes are designed, and interference between them is avoided;

[0032] The grouting hole 5 set from the first tunnel 1 extends to the plane corresponding to the center line of the second tunnel 2 or the outer wall of the second tunnel 2; the grouting hole 5 set from the second tunnel 2 extends to the plane corresponding to the center line of the first tunnel 1 or the outer wall of the first tunnel 1, and the actual position of the grouting hole 5 is specifically determined;

[0033] After the interval connection channel 3 and the connection channel 3 are excavated, the original stress balance in the stratum is destroyed, causing the stress in the stratum around the channel to be redistributed. The secondary grouting support performed in a timely manner after excavation is an important technical measure to maintain the stability of the stratum and ensure the safety of construction. The directions of the first grouting and the second grouting are opposite, so as to stagger the support network and ensure the support effect and stability;

[0034] In step S5, after the closed concrete reaches the preset strength, the freezing pipe 6 is removed and the freezing hole is blocked. After the water stop curtain is melted, the freezing pipe 6 is grouted again to reinforce it, so as to avoid damage to the strength of the soil layer caused by the freezing hole;

[0035] In step S3, first, the corresponding trumpet 4 parts at both ends of the connection channel 3 are fully excavated. After excavation, the initial support is performed through the grid steel frame. After the initial support of the trumpet 4 is completed, the main body of the connection channel 3 is excavated. The initial support part is sprayed with concrete during the excavation process. The lead of the excavation working face is not more than two bays ahead of the progress of the grid steel frame support. If the stability of the soil layer is good, the grid steel frame is erected once and for all while excavating. If the soil layer condition is very poor and it is difficult to support the side, a short section of channel steel plate column is used for advanced support of the side, and the excavation is completed in sections.

[0036] Before the initial support is sprayed with concrete, the steel mesh needs to be hung first. The steel mesh is processed in advance according to the design drawing. After excavation is completed, the mesh can be hung directly. After the hanging of the mesh and the embedding of the grouting pipe are completed, the concrete spraying construction is performed;

[0037] After the main body of the connection channel 3 is excavated and the concrete is initially sprayed, a waterproof layer is laid on the inner side of the connection channel 3. After the waterproof layer is laid, the steel reinforcement cage corresponding to the connection channel 3 is bound. The steel reinforcement cage is arranged corresponding to the trumpet 4 structure at both ends of the connection channel 3. The formwork is arranged inside the steel reinforcement cage. The formwork is provided with pouring openings and vibrating equipment corresponding to the concrete. The closed layer is formed by pouring the concrete. Before the waterproof layer is laid, the initial support must be roughly leveled;

[0038] In step S3, during the binding of the steel reinforcement cage, a prestressed support is arranged at the trumpet 4 of the interval connection channel 3. The prestressed support is provided with a plurality of support jacks uniformly distributed in the circumferential direction. The prestressed support is bound to the steel reinforcement cage during the binding of the steel reinforcement. The stability of the stratum during construction can be improved. After the binding of the steel reinforcement is completed, the support jacks are withdrawn for formwork installation. The prestressed support is poured into the concrete closed layer to ensure the structural strength. The shape of the prestressed support is matched with the inner wall of the trumpet 4;

[0039] The prestressed support comprises a plurality of splicing pieces spliced with each other, and a truss is arranged inside the prestressed support; the truss is welded by an I-beam or a square steel, and can be an equal ratio reduced trumpet mouth 4 section; a plurality of supporting jacks extending along the radial direction of the connecting channel 3 are arranged outside the truss, the plurality of supporting jacks correspond to the plurality of splicing pieces one by one, one end of the supporting jack is fixed on the prestressed support, and the other end is in contact with the splicing piece; a groove corresponding to the supporting jack can be arranged on the splicing piece; a plurality of shims are arranged between any two adjacent splicing pieces, and after the jacks are tightened, the shims with proper number or thickness are inserted between the adjacent splicing pieces, so that the supporting stability of the prestressed support is ensured.

[0040] A groove corresponding to the prestressed support is arranged on the inner wall of the trumpet mouth 4, and is reserved by a formwork during initial support; a stress meter can be arranged on the supporting jack, and the jacking force of each jack can be adjusted according to the actual measurement of the convergence deformation of the trumpet mouth 4.

[0041] The frozen hole is lofted by a total station in the first tunnel 1, the inside of the segment 7 of the first tunnel 1 is holed by a hole opening device, the hole mouth pipe 8 is fixed in the hole by the expansion screw 9 after the hole is opened, and the drill bit passes through the hole mouth sealing device to drill.

[0042] The hole position should avoid the main stress reinforcement in the segment 7, the hole is opened by a hole opener (with a diamond drill bit) at the designed angle, the hole diameter is 130 mm, and the core drilling is stopped when the depth reaches 250 mm, and the hole mouth pipe 8 is installed.

[0043] The installation method of the hole mouth pipe 8 is as follows: first, the hole mouth of the segment 7 is chiseled flat, four expansion screws 9 are arranged, then the outer wall of the hole mouth pipe 8 is wrapped with sealing materials such as sealing rubber, raw material belt, hemp silk or cotton silk, the hole mouth pipe 8 is hammered into the hole, the buckle plate in the middle of the hole mouth pipe 8 is tightened by the expansion screw 9, the gate valve 11 is installed and opened, the hole opener passes through the ball valve to perform secondary hole opening, the secondary hole opening diameter is 108 mm, the segment 7 is continuously holed and drilled to the outer wall of the second tunnel 2 by the opening device, and the small valve 10 is closed in time when sand gushing occurs.

[0044] The orifice pipe 8 is provided with a tapered adapter 12 at one end of the first tunnel 1 through a connecting flange. The adapter 12 is provided with a tapered rubber plug 13. The middle part of the tapered rubber plug 13 is provided with a hole corresponding to the frozen pipe 6. An annular baffle 14 is arranged on the side of the tapered rubber plug 13 away from the adapter 12. The baffle 14 is connected to the adapter 12 through bolts to seal the frozen pipe 6 by extrusion. Specifically, the taper of the tapered rubber plug 13 is matched with the taper of the adapter 12. The tapered rubber plug 13 is inserted into the tapered adapter 12 through the extrusion of the baffle 14. The frozen pipe 6 is extruded through the radial limitation of the adapter 12, so that the sealing can be realized. A small valve 10 is arranged on the orifice pipe 8. The drill bit is installed in the orifice device. The 1.5" small valve 10 is connected to the orifice device. First, dry drilling is adopted. When the drilling is difficult and no footage is obtained, water injection drilling is carried out from the drilling machine. At the same time, the small valve 10 is opened. The water and sand discharge conditions are observed. The slurry discharge amount is controlled by the opening and closing of the valve to ensure the safety of the ground and prevent settlement.

Claims

1. A method of constructing a tunnel communication passage, characterized by, The method comprises the following steps: Step S1, measuring and lofting the communication passage inside the first tunnel and the second tunnel, and setting a plurality of grouting holes extending to the second tunnel inside the first tunnel, the grouting holes being uniformly distributed around the communication passage; Step S2, grouting and reinforcing the part between the first tunnel and the second tunnel through the grouting holes, plugging the grouting holes after grouting, setting freezing holes around the communication passage, plugging the freezing holes after inserting freezing pipes, injecting liquid nitrogen into the freezing pipes to cool, so as to form a water-stop curtain corresponding to the communication passage; Step S3, setting a working platform corresponding to the opening of the communication passage in the first tunnel and the second tunnel, cutting the inner lining of the first tunnel and the second tunnel according to the profile of the communication passage through cutting equipment, and synchronously excavating the communication passage from the first tunnel and the second tunnel to the middle part; Step S4, installing the initial support steel bars in the way of digging and supporting at the same time, and closing the concrete from the middle part to both sides after the communication passage is penetrated; before the concrete is closed, setting grouting holes extending to the first tunnel inside the second tunnel, the grouting holes extending to the first tunnel, and the grouting holes being uniformly distributed around the communication passage; Step S5, after the closed concrete reaches the preset strength, removing the freezing pipes and plugging them, and grouting and reinforcing through the freezing pipes after the water-stop curtain melts; The grouting holes set from the first tunnel extend to the plane corresponding to the center line of the second tunnel or the outer wall of the second tunnel; the grouting holes set from the second tunnel extend to the plane corresponding to the center line of the first tunnel or the outer wall of the first tunnel; In step S3, the full-face excavation is first performed on the parts corresponding to the trumpet mouths at both ends of the communication passage, the initial support is performed on the trumpet mouths through the grid steel frame after the excavation, the main body of the communication passage is excavated after the initial support of the trumpet mouths is completed, the concrete is initially sprayed on the initial support part during the excavation, and the working face of the excavation leads the progress of the grid steel frame support by no more than two bays; After the main body of the communication passage is excavated and the concrete is initially sprayed, a waterproof layer is laid on the inner side of the communication passage, the reinforcement cage corresponding to the communication passage is bound after the waterproof layer is laid, the reinforcement cage is arranged corresponding to the trumpet mouth structure at both ends of the communication passage, the formwork is arranged inside the reinforcement cage, the pouring opening and the vibrating equipment corresponding to the concrete are arranged on the formwork, and the closed structure is formed by pouring the concrete; In step S3, during the binding process of the reinforcement cage, a prestressed support is arranged at the trumpet mouth of the interval communication passage, a plurality of support jacks uniformly distributed along the circumference are arranged inside the prestressed support, the prestressed support is bound to the reinforcement cage during the binding process of the reinforcement, and the support jacks are removed for formwork installation after the binding of the reinforcement is completed; The prestressed support comprises a plurality of spliced pieces spliced with each other, a truss is arranged inside the prestressed support, a plurality of support jacks extending along the radial direction of the communication passage are arranged outside the truss, the plurality of support jacks and the plurality of spliced pieces are in one-to-one correspondence, and a spacer plate is arranged between any two adjacent spliced pieces.

2. The tunnel gallery construction method according to claim 1, characterized by The freezing holes are lofted inside the first tunnel through the total station, the inner side of the segment of the first tunnel is opened through the opening equipment, the hole mouth pipe is fixed in the opening through the expansion screw after the opening, and the drill bit is drilled through the hole mouth sealing device.

3. The method of claim 2, wherein, The orifice pipe is connected with a tapered adapter at one end of the first tunnel through a connecting flange, a tapered rubber plug is arranged in the adapter, a middle hole corresponding to the frozen pipe is arranged in the middle of the tapered rubber plug, and an annular baffle is arranged on the side of the tapered rubber plug away from the adapter, the baffle is connected with the adapter through bolts, so that the frozen pipe is sealed through extrusion.

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