Construction method of shallow-buried and unsymmetrical pressure tunnel portal section structure with ultra-small clear distance

Abstract

The application discloses a construction method of a shallow-buried bias super-small-clearance tunnel portal section structure, which comprises the following steps: S1, excavating a slope; S2, slope supporting, after the completion of the slope excavation of the tunnel portal section, adopting a net spraying anchor supporting for the slope surface; S3, bias retaining wall construction at the bias of the tunnel portal section; and S4, arch protection construction. The method combines the bias retaining wall with the arch protection construction at the position of the shallow-buried bias super-small-clearance tunnel portal section, can avoid large brushing and digging of the slope in the construction process, reduces the tunnel portal earthwork excavation, external transportation and slope protection, ensures the mountain stability, reduces the damage to the original landform, protects the natural landscape of the portal, effectively reduces the construction cost and construction period, and has the characteristics of reasonable structure design and convenient construction.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tunnel construction, in particular to a construction method of shallow-buried and unsymmetrical pressure tunnel portal section structure with ultra-small clear distance. BACKGROUND

[0002] With the continuous advancement of urbanization and the upgrading adjustment of urban space structure in China, in order to alleviate the pressure of urban ground road traffic and promote the development of urban traffic, the government departments gradually increase the investment and construction of urban underground traffic; affected by the urban mountain geological environment, the tunnel portal section inevitably appears unsymmetrical pressure and shallow burial, which leads to difficult entry into the tunnel;

[0003] The traditional construction method adopts large excavation, high slope brushing and strong support to construct the tunnel portal, which has the following problems difficult to solve during construction:

[0004] (1) The construction by large excavation and high slope brushing is prone to cause a large amount of soil and stone excavation and external transportation, high slope support, and high construction cost;

[0005] (2) The original topography and natural landscape are seriously damaged, which is not conducive to green construction;

[0006] (3) The side surrounding rock of the hidden hole loses support and causes the instability of the surrounding rock above, and the safety factor is low, so the deformation control of the surrounding rock of the portal construction is an important link of the portal construction;

[0007] Therefore, how to make a portal maintenance mechanism before tunnel construction to support the tunnel portal and prevent the instability and damage of the tunnel surrounding rock has become a problem to be solved in the field. SUMMARY

[0008] In view of the above problems, the present application aims to provide a construction method of shallow-buried and unsymmetrical pressure tunnel portal section structure, which combines the unsymmetrical pressure retaining wall with the arch construction at the position of the shallow-buried and unsymmetrical pressure tunnel portal section with ultra-small clear distance, so as to avoid large brushing and excavation of the slope during construction, reduce the excavation, external transportation and slope protection of the soil and stone of the tunnel portal, and ensure the stability of the mountain; at the same time, the damage to the original topography is reduced, the natural landscape of the portal is protected, the construction cost and period are effectively reduced, and the method has the characteristics of reasonable structure design and convenient construction.

[0009] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0010] A construction method of shallow-buried and unsymmetrical pressure tunnel portal section structure with ultra-small clear distance, comprising

[0011] Step S1. Excavate the slope

[0012] Before the construction of the tunnel portal, the light-dark junction pile number and the centerline coordinate of the tunnel portal are measured according to the design drawing, and the position of the slope excavation line at the tunnel portal section is laid out according to the design slope of the slope of the tunnel top slope, and the slope of the tunnel portal section is excavated in sections and layers along the excavation line;

[0013] Step S2. Slope support

[0014] After the slope excavation of the tunnel portal section is completed, the slope surface is supported by net spraying and anchor support;

[0015] Step S3. Construction of the bias retaining wall at the bias of the tunnel portal section

[0016] Step S3.1. After the slope support is completed, construction lofting and foundation pit excavation and support are performed at the bias outside the tunnel portal section;

[0017] Step S3.2. The foundation of the bias retaining wall is treated;

[0018] Step S3.3. Bias retaining wall foundation concrete construction;

[0019] Step S3.4. Bias retaining wall wall body concrete construction;

[0020] Step S3.5. Fastener and water release hole are installed on the bias retaining wall wall;

[0021] Step S3.6. The wall back can be backfilled after the strength of the retaining wall reaches the preset strength;

[0022] Step S4. Arch protection construction

[0023] Step S4.1. Construction lofting, arch foot foundation excavation and support;

[0024] Step S4.2. The arch foot foundation is treated, and the arch foot steel plate is installed;

[0025] Step S4.3. Steel frame manufacturing;

[0026] Step S4.4. Steel frame installation, and the steel frame is fixed by using fastener and arch foot steel plate;

[0027] Step S4.5. Construction of the locking steel pipe and grouting;

[0028] Step S4.6. Pouring of arch protection concrete.

[0029] Preferably, the lofting and support process of step S3.1 and step S4.1 comprises

[0030] (1) Before the foundation pit excavation, the surface water is first drained, and the centerline and foundation excavation boundary line of the foundation pit are laid out;

[0031] (2) The excavation process of the foundation pit of the eccentric retaining wall shall follow the principle of segmented and layered excavation and support. Large-area excavation is prohibited. After a section is excavated, the cushion layer shall be constructed in time. The slope of the foundation pit shall be excavated with a 1:0.5 slope support and the slope shall be measured with an angle ruler.

[0032] (3) Excavation is carried out using an excavator to excavate to 30cm above the base, and 30cm above the elevation is excavated manually to the design elevation. After excavation, the area is cleaned, leveled and compacted.

[0033] (4) The slope of the foundation pit is determined according to whether there is dynamic load on the top of the sandy soil and gravelly soil. Anchor spraying support is carried out. 3.5m long Φ22 explosive cartridge anchor rods are arranged in a quincunx pattern of 1.2×1.2m. The mesh is made of Φ8 steel mesh with a spacing of 200×200mm. C25 concrete is sprayed to a thickness of 10cm for support.

[0034] Preferably, the substrate processing steps S3.2 and S4.2 include...

[0035] (1) The foundation treatment area extends 0.8m beyond the foundation. After the foundation is properly repaired in accordance with the design requirements, the foundation construction shall be carried out immediately to prevent the foundation from being soaked in water and exposed for a long time.

[0036] (2) When the foundation is built on the rock strata, the silt and loose stones should be removed before the foundation is built, and the bearing capacity test of the foundation should be carried out.

[0037] (3) Test the bearing capacity of the foundation at the biased pressure section of the tunnel entrance. For the parts where the bearing capacity of the foundation does not meet 300 kPa, backfill with plain concrete to make its strength meet the bearing capacity requirements of the foundation.

[0038] Preferably, the process of constructing the wall concrete in step S3.4 includes...

[0039] (1) When constructing the wall, scaffolding work platforms and scaffolding ladders for personnel to go up and down shall be erected, and the distance between the ladder steps shall not exceed 300mm;

[0040] (2) Installation and reinforcement of templates and scaffolding

[0041] a. Large-area steel formwork is used on the outside of the wall formwork. The horizontal and vertical "bands" on the back of the formwork are supported by double steel pipes, butterfly buckles, Φ12 tie rods for diagonal and counter-tie, and C18 steel bars for internal bracing. The vertical spacing is 0.5 meters and the front and back spacing is 0.6 meters.

[0042] b. The inner curved side of the wall is assembled with small-sized steel formwork, and the formwork frame is supported and fixed by a combination frame;

[0043] The combined bent is made by I20a H-shaped steel according to the peripheral arc of the section hole lining and back rib reinforcement; single bent is longitudinally arranged with a spacing of 75 cm, and the bent is longitudinally reinforced with C20 steel bars; the inner side formwork is made of 0.3*1.5 m combined steel formwork, which is closely attached to the outer side of the bent arc; in addition to being pulled by a template Ф12 pull rod, being obliquely pulled by a C18 steel bar oblique support and being horizontally supported, the whole bent is also supported and reinforced by a back wood support;

[0044] (3) Wall body concrete pouring

[0045] During pouring, the wall body is poured in six times, each time is poured in layers, and a Φ50 soft shaft vibrating rod is inserted for vibration and compaction, the layer pouring thickness is not greater than 50 cm; the vibrating rod is vertically inserted during vibration, and is inserted into the previous layer of concrete by 5-10 cm; the vibrating rod moving interval is not greater than 1.5 times of the effective vibration operation radius, and the vibrating rod is not less than 10 cm away from the formwork; when the concrete stops falling, does not bubble, and the surface is flat during vibration, stop tamping, and after the pouring of the concrete is completed, timely curing is carried out, and the formwork is removed when the strength reaches 80%.

[0046] Preferably, the process of installing the steel frame in step S4.4 comprises

[0047] (1) Positioning measurement: first measure the route center line, determine the elevation, and then measure the lateral position and arch foot position;

[0048] (2) Preparation work before installation: the unit arch frame transported to the site is stacked according to unit number, the cross section size is checked before installation, the under excavation part is processed in time to ensure correct installation of the arch frame, and a 5 cm protective layer is reserved outside the arch frame; before installing the arch foot or wall foot steel frame, the loose ballast under the base plate is removed, the steel frame is placed on the original rock layer, and a pad arch foot steel plate is added under the arch foot in the soft section;

[0049] (3) The spacing of the steel frame is 50 cm, and the steel frame is installed from bottom to top, and when the first section of the steel frame is installed, attention should be paid to connecting the quick installation connecting piece reserved in the bias retaining wall closely, so as to ensure that the steel frame does not deviate during installation, and the Ф22 connecting steel is connected at an interval of 100 cm.

[0050] Preferably, the quick installation connecting piece comprises a pre-buried connecting body and a welded connecting body used in cooperation,

[0051] The pre-buried connecting body is arranged on the bias retaining wall and the arch foot steel plate, and a quick connection slot and a positioning clamping piece are arranged on the pre-buried connecting body;

[0052] The welding connector is arranged at both ends of the steel frame, and a quick connector and an extension positioning member are arranged on the welding connector, the quick connector is used in cooperation with the quick connector slot, and the positioning clamping member is used in cooperation with the extension positioning member, so as to connect the embedded connector and the welding connector.

[0053] Preferably, the embedded connector comprises a lower stiffening plate, an upper stiffening plate and a steel connector,

[0054] The lower stiffening plate is arranged on the lower side of the upper stiffening plate, and a embedded sleeve is welded on the bottom of the lower stiffening plate;

[0055] The upper stiffening plate is arranged on the upper side of the steel connector, and a guide groove for guiding the positioning clamping member is arranged on the lower stiffening plate and the upper stiffening plate;

[0056] The steel connector is a square steel sleeve fixed between the lower stiffening plate and the upper stiffening plate, the quick connector slot is arranged through the steel connector, and a plurality of first positioning holes are symmetrically arranged on the side wall of the steel connector.

[0057] Preferably, the quick connector further comprises a pull rod and a positioning plate,

[0058] One end of the pull rod is connected to the first connecting seat arranged on the positioning clamping member through a hinge pin, and a plurality of second positioning holes are arranged on the pull rod, the second positioning holes are used in cooperation with the threaded holes arranged on the positioning plate;

[0059] The positioning plate is arranged between the two symmetrically arranged pull rods and is used in cooperation with the positioning rod.

[0060] Preferably, the bottom plate of the welding connector is fixedly welded at the end of the steel frame, and a spring is arranged in the welding connector, the free end of the spring is connected to a pressing block, the pressing block is connected to the extension positioning member through a hinge rod, the extension positioning member is arranged in the extension hole on the welding connector and extends along the extension hole, and the extension positioning member is further used in cooperation with the positioning cavity on the positioning clamping member; an insertion rod is arranged on the outer end of the extension positioning member, the insertion rod is used in cooperation with the through hole arranged on the positioning clamping member; a positioning clamping block and a second connecting seat are further arranged on the extension positioning member, the positioning clamping block is used in cooperation with the sliding groove arranged on the bottom plate, and the second connecting seat is connected to the hinge rod through a pin rod.

[0061] Preferably, a pressing member is further arranged in the embedded connector, an external thread is arranged on the pressing member and is used in cooperation with an internal thread arranged on the embedded sleeve, a pressing block is arranged on the outside of the pressing member, and the pressing block is used in cooperation with the pressing block.

[0062] The beneficial effects of the present application are: the present application discloses a construction method of shallow-buried bias pressure super-small clear distance tunnel portal section structure, compared with the prior art, the improvement of the present application is that

[0063] 1. The present application designs a construction method of shallow-buried bias pressure super-small clear distance tunnel portal section structure, the method combines the bias pressure retaining wall and the arch protection construction at the position of the shallow-buried bias pressure super-small clear distance tunnel portal section, which can avoid large brushing and digging of the slope during the construction process, reduces the tunnel portal earthwork excavation, external transportation and slope protection, and ensures the stability of the mountain; at the same time, the damage to the original landscape is reduced, the natural landscape of the portal is protected, the construction cost and the construction period are effectively reduced, and the method has the advantages of reasonable structure design and convenient construction;

[0064] 2. In order to facilitate the quick connection of the steel frame with the bias pressure retaining wall during hoisting, the present application designs a quick mounting connector, which aligns the positions of the quick plug and the quick socket during use, and gradually lowers the steel frame, so that the quick plug is gradually inserted into the quick socket, the top block abuts against the pressing block, the spring is compressed, the two telescopic positioning members can be expanded outward under the action of the hinge rod, and are clamped in the positioning cavity, at the same time, the insertion rod passes through the through hole, and after installation, the insertion rod is fixed by using the screwing member, at the same time, the screwing member passes through the third positioning hole and the first positioning hole, the pre-buried connecting body and the welded connecting body are connected, and then the quick installation of the steel frame is realized, which has the advantages of convenient installation and good installation effect. BRIEF DESCRIPTION OF DRAWINGS

[0065] Figure 1 It is a construction technology flow chart of the shallow-buried bias pressure super-small clear distance tunnel retaining wall and arch protection of the present application.

[0066] Figure 2 It is a front view of the shallow-buried bias pressure super-small clear distance tunnel portal section structure of the present application.

[0067] Figure 3 It is a top view of the structure of the slope support of the present application.

[0068] Figure 4 It is a sectional view of the bias pressure retaining wall of the present application.

[0069] Figure 5 It is an installation effect drawing of the bias pressure retaining wall inside formwork and bent frame of the present application.

[0070] Figure 6 It is a hoisting effect drawing of the steel frame of the present application.

[0071] Figure 7 It is a local enlarged view of the bias pressure retaining wall A of the present application.

[0072] Figure 8 It is a local enlarged view of the bias pressure retaining wall B of the present application.

[0073] Figure 9 A sectional view of the pre-buried connecting body of the present application.

[0074] Figure 10 A structural schematic view of the pre-buried connecting body of the present application.

[0075] Figure 11 A structural schematic view of the positioning card of the present application.

[0076] Figure 12 A sectional view of the welded connecting body of the present application.

[0077] Wherein: 1. side slope, 11. support anchor rod, 12. steel mesh, 2. arch top backfill, 3. bias retaining wall, 31. C18 jointing bar, 32. combined steel formwork, 33. I20a I-beam, 34. C20 steel bar, 35. C18 jointing bar, 36. drainage hole, 4. arch protection, 41. steel frame, 5. quick-mounting connecting piece, 51. pre-buried connecting body, 511. quick-mounting slot, 512. pre-buried sleeve, 513. guide groove, 514. first positioning hole, 515. lower stiffening plate, 516. upper stiffening plate, 517. steel connecting body, 518. pre-buried positioning bar, 52. hinged rod, 53. positioning card, 531. positioning cavity, 532. through hole, 533. first connecting seat, 54. second positioning hole, 55. welded connecting body, 551. bottom plate, 552. sliding groove, 553. telescopic hole, 554. third positioning hole, 555. quick-mounting plug, 56. top pressure piece, 561. top block, 57. pull rod, 571. hinged bolt, 572. positioning plate, 573. positioning rod, 58. telescopic positioning piece, 581. insertion rod, 582. second connecting seat, 583. positioning block, 59. spring, 50. pressure block, 6. lock foot steel pipe, 7. arch foot steel plate. DETAILED DESCRIPTION

[0078] In order for those skilled in the art to better understand the technical solutions of the present application, the technical solutions of the present application are further described below in combination with the drawings and examples.

[0079] Example 1: referring to the construction method of a shallow-buried bias super-small-clearance tunnel portal section structure shown in the accompanying drawings, comprising Figures 1-12

[0080] Step S1. excavate the side slope 1

[0081] Before the tunnel portal construction, the light-dark junction pile number and the centerline coordinates of the tunnel portal are measured and set according to the design drawing, the position of the side slope excavation line at the tunnel portal section is laid out according to the design slope of the side slope of the tunnel top, and the side slope 1 of the tunnel portal section is excavated in sections and layers along the excavation line;

[0082] ​Note: (1) When the slope of the tunnel portal section is excavated, the top-down layer-by-layer excavation method is adopted, and the layer length and layer height depend on the surrounding rock conditions of the tunnel portal section; (2) The side excavation and support method is adopted for the slope excavation of the tunnel portal section;

[0083] Step S2. Slope support

[0084] After the slope 1 of the tunnel portal section is excavated, the slope surface 1 is supported by net spraying and anchor support, and the specific construction process includes:

[0085] Step S2.1. First, the support anchor rod 11 of the slope is embedded into the slope 1, and the support anchor rod 11 is arranged in a plum blossom type;

[0086] Step S2.2. After the support anchor rod 11 is arranged, the steel mesh 12 processed on site is installed on the support anchor rod, and a 2cm protective layer is left between the steel mesh 12 and the supported rock surface on the slope surface. The steel mesh and the support anchor rod are bound to form a slope net structure;

[0087] Step S2.3. After the slope net structure construction is completed, the slope concrete is sprayed, and the concrete is sprayed in layers according to the design thickness of the slope concrete during the spraying process;

[0088] Step S3. Construction of the bias retaining wall 3 at the bias of the tunnel portal section

[0089] Step S3.1. After the slope support is completed, the construction setting-out, foundation excavation and support are carried out at the bias outside the tunnel portal section;

[0090] (1) Before the foundation excavation, the surface water needs to be drained, and the center line and the foundation excavation boundary line are set out by the total station;

[0091] (2) The bias retaining wall foundation excavation process should follow the principles of segmented and layered excavation and support, and large-area excavation is prohibited. After excavating a section, the cushion should be constructed in time. The foundation slope is excavated and supported with a 1:0.5 slope, and the slope is measured with an angle ruler to prevent over-excavation and under-excavation;

[0092] (3) Excavation is carried out by excavator to 30cm above the base, and manual excavation is carried out to the design elevation above 30cm. After excavation is completed, it should be cleaned, leveled and compacted; the spoil is transported by 10t self-unloading truck, and the spoil should not be transported full load or overloaded. During transportation, a closed type shielding cloth should be used to cover it to prevent dust from falling;

[0093] (4) Foundation slope according to sand and pebble, gravel soil slope top with or without dynamic load, should be anchor shotcrete support, using 3.5m long Φ22 cartridge anchor rod 1.2x1.2m plum blossom shape arrangement, mesh using Φ8 reinforcement net spacing 200x200mm arrangement, sprayed C25 concrete thick 10cm support;

[0094] Step S3.2. Base treatment

[0095] The scope of foundation treatment is 0.8m out of the foundation, after the base is properly trimmed according to the design requirements, the foundation construction is immediately carried out to prevent the phenomenon of base immersion and long-term exposure; when the foundation is built on the rock layer, the silt and loose stones should be cleaned before the foundation is built, and the foundation bearing capacity test is conducted; the foundation bearing capacity of the tunnel portal section is tested by the foundation bearing capacity test, and the foundation bearing capacity must meet 300kpa; for the parts that cannot meet the bearing capacity requirements, the plain concrete is backfilled to make the strength meet the foundation bearing capacity requirements;

[0096] Step S3.3. Foundation concrete construction

[0097] (1) After the foundation pit is excavated, the foundation construction should be carried out in time, and the foundation plane size is accurately released. The foundation formwork adopts large-area combined steel formwork, the horizontal band is pulled and counter-pulled by double steel pipes, butterfly buckles and Φ12 pull rods, the upper and lower intervals are 0.5m, and the front and rear intervals are 0.6m;

[0098] (2) After the formwork support is completed, C18(80cm / root) jointing bars 31 are pre-buried in the foundation, 4 roots in the transverse direction, 30cm apart from the concrete edge, one row in the middle, 1.9m apart, two rows in total, 1m apart in the longitudinal direction;

[0099] (3) After the preparation is completed and the inspection is qualified, C30 / P8 concrete foundation is immediately poured. Since the concrete is commercial mixed, the concrete is pumped into the warehouse by the truck-mounted pump with an arm length of 47m after being transported to the site; manual Φ50 soft shaft vibrating rod is used for vibration and compaction, and the thickness of each layer is not greater than 50cm; when vibrating, the vibrating rod is vertically inserted into the concrete, and it is inserted into the previous layer of concrete by 5-10cm to ensure the close combination of the two layers of concrete; the moving interval of the vibrating rod is not greater than 1.5 times of the effective vibration operation radius; the vibrating rod is not less than 10cm away from the formwork; when vibrating, the concrete stops settling, and when there are no bubbles, no slurry and the surface is flat, stop vibrating;

[0100] At the same time, during the pouring process, since the concrete foundation belongs to mass concrete, during the pouring process, 30 thin-wall steel pipes S-shaped are arranged in the pouring layer to circulate water for cooling and heat dissipation to control the concrete temperature within 25℃;

[0101] Step S3.4. Wall body concrete construction

[0102] When the base concrete strength reaches 75%, the roughened base contacts the wall body, the wall body template is supported, and the wall body is poured in 6 layers. C18 interface bar 35 is required for each pouring layer according to the requirements, the longitudinal spacing of C18 interface bar 35 is 1m; the joint of each pouring layer needs to be roughened, and the settlement joint is consistent;

[0103] (1) When the wall body is constructed, a simple scaffold operation platform and a scaffold ladder for personnel to go up and down need to be set up, the ladder step spacing should not be greater than 300mm; refer to the edge slope scaffold, and strictly follow the scaffold erection specification and requirements for erection;

[0104] (2) Template and bent installation and reinforcement

[0105] a. Large-area steel template is used on the outside of the wall body template, double steel pipes, butterfly buckles and Φ12 pull rods are used for diagonal and counter-pulling of the horizontal and vertical "bands" on the back of the template, and C18 steel inside support, with an interval of 0.5m between the upper and lower, and an interval of 0.6m between the front and back, and the outside of the template is supported on stable surrounding rocks by square wood or round wood, etc.

[0106] b. Small-specification steel templates are used for the arc-shaped side of the inside of the wall body, and the template skeleton is supported and fixed by self-made combined bents; the template needs to be assembled with a smooth surface, tight joints, and firm and stable support;

[0107] The self-made combined bent is made of I20a H-beam 33 according to the outer arc of the lining of the section of the hole body and back rib reinforcement; the longitudinal spacing of a single bent is 75cm, and the longitudinal C20 steel bar 34 is used to connect the bents to form a whole; the inside template is a 0.3*1.5m specification combined steel template 32, which is closely attached to the arc-shaped outside of the bent; in addition to the diagonal and counter-pulling of the template Φ12 pull rod, the diagonal and horizontal support of the C18 steel bar, the template also needs to be reinforced by the method of supporting and reinforcing the back with square wood or round wood;

[0108] (3) Wall body concrete pouring

[0109] The template and reinforcement are poured after passing the inspection; the concrete is mixed commercially, and a 47m long pump truck is used for pouring, the wall body is poured in 6 times, each pouring is layered and laid flat, and a Φ50 soft shaft vibrating rod is inserted for manual vibration and compaction, the thickness of each layer is not greater than 50cm; when vibrating, the vibrating rod is vertically inserted into the concrete 5-10cm, to ensure the close combination of the two layers of concrete; the moving distance of the vibrating rod is not greater than 1.5 times the effective vibration operation radius, and the distance between the vibrating rod and the template is not less than 10cm; when vibrating, the concrete stops settling, does not bubble, and the surface is flat;

[0110] Ensure that the poured concrete is of high quality, with a straight and straight line; after the concrete pouring is completed, the curing should be done in time, and the strength reaches 80% when the template is removed.

[0111] Step S3.5. Applying the quick-mounting connector 5 and the drain hole 36

[0112] (1) The quick-mounting connector 5 is connected to the corresponding arch foot of the steel frame arch in the wall body load-bearing platform pre-buried, with a longitudinal spacing of 50 cm; the bottom of the quick-mounting connector 5 is welded with C20 anchor bars;

[0113] (2) The drain hole with a diameter of 110 mm is arranged in the soil part above the top of the wall body, with a spacing of 2.0 m in a quincunx arrangement, and an additional row of drain holes 36 should be provided at the load-bearing platform;

[0114] Step S3.6. Backfilling

[0115] (1) The backfilling of the wall back can be performed after the strength of the retaining wall reaches 70%, and M10 mortar rubble is used for backfilling below the original ground of the wall back;

[0116] (2) All materials (crushed stone) used for backfilling should meet the requirements of the technical specifications, the fillers should be fully compacted, have good water permeability, and not contain grass roots, rotten plants, or frozen soil blocks and other sundries; the backfilling of the foundation pit should be operated under the condition of draining accumulated water, and different soil should be filled in layers, not mixed; the backfilling soil should be selected, and the water content should be close to the optimal water content;

[0117] (3) Before backfilling, the backfilling levels are first divided on the section, the detection frequency is determined, and the detection record is filled in;

[0118] (4) The backfilling should be filled in layers, and a hand-held electric compactor is used for compaction, with a loose paving thickness of 10-15 cm per layer; the layer-by-layer filling ensures uniform and smooth paving thickness, and attention should be paid to not causing a large impact on the wall body during compaction;

[0119] (5) The backfilling of the structure should follow the principle of symmetry on both sides and be performed at substantially the same elevation to prevent uneven backfilling from causing damage to the structure;

[0120] (6) The compaction degree of each layer of backfilling should be tested, and the compaction degree test record must be equal to the filling height and meet the requirements of the technical specifications;

[0121] Step S4. Construction of the arch 4

[0122] Process flow: construction lofting → arch foot foundation excavation and slope support → arch foot treatment → steel frame fabrication and installation → setting up arch foot grouting small guide pipe → arch body concrete → backfilling

[0123] Step S4.1. Construction lofting, arch foot foundation excavation, and support

[0124] (1) The left arch foot of the left line is supported on the retaining wall on the left side and on the stable surrounding rock of the slope on the right side. Before excavating the right slope, surface water needs to be drained. The slope excavation boundary line and excavation depth are marked with a total station and the site technicians are briefed.

[0125] (2) The slope excavation shall be carried out in sections with simultaneous excavation and support. Large-area excavation is prohibited. The slope of the foundation pit shall be excavated with a 1:0.5 slope support. The slope shall be measured with an angle ruler to prevent over-excavation, under-excavation, etc.

[0126] (3) Excavation shall be carried out by excavator to 30cm above the base and 30cm above the elevation shall be carried out manually to the design elevation. After excavation, the soil shall be cleaned, leveled and compacted. The slag shall be transported by 10t dump truck. The slag shall not be transported fully loaded or overloaded. During the transportation process, the slag shall be covered with a sealed cover cloth to prevent dust from falling off.

[0127] (4) The foundation excavation slope support consists of 3.5m long Φ22 explosive cartridge anchor rods arranged in a quincunx pattern with 1.2×1.2m, and the mesh is made of Φ8 steel mesh with a spacing of 200×200mm. The C25 concrete is sprayed to a thickness of 10cm.

[0128] Step S4.2. Substrate Treatment

[0129] The foundation treatment area extends 0.5m beyond the foundation itself. After the foundation is properly prepared in accordance with the design requirements, foundation construction should be carried out immediately to prevent the foundation from being submerged in water or exposed for a long time. When the foundation is built on rock strata, silt and loose stones should be removed before the foundation is built. The bearing capacity of the foundation must meet the design requirements. Plain concrete should be used to backfill the parts that do not meet the bearing capacity requirements.

[0130] Step S4.3. Steel Frame Fabrication

[0131] The steel frame is cold-bent on a 1:1 fabrication template set up in the rebar processing shed. It is fabricated in sections by unit and then assembled and installed on site. The steel frame is fabricated to ensure accurate dimensions, smooth arcs, and that the length of the welded (or lapped) rebars meets the design requirements. After fabrication, a trial assembly is performed to check for any twisting. Each steel frame is divided into three types: I, II, and III, and is assembled in sections using connecting steel plates and bolts. Quick-connect fittings 5 ​​are welded to both ends of the steel frame 41.

[0132] Step S4.4. Steel frame 41 installation

[0133] (1) Positioning measurement: First, determine the centerline of the route and the elevation, and then determine its lateral position and the position of the arch foot;

[0134] (2) Preparation before installation: The unit arch frames delivered to the site are stacked according to unit numbers, and the cross-sectional dimension is checked before installation, and the under-excavation part is processed in time to ensure the correct installation of the arch frame, and 5 cm protective layer is reserved outside the arch frame; before installing the arch foot or wall foot steel frame, the loose ballast under the base plate must be removed, and the steel frame 4 is placed on the original rock stratum; and a pad arch foot steel plate 7 is added under the arch foot in the soft section;

[0135] (3) The steel frame spacing is 50 cm, and the steel frame is installed from bottom to top during installation. When installing the first section of steel frame, attention should be paid to connecting the quick installation connecting piece 5 reserved in the bias retaining wall tightly to ensure that the steel frame 41 does not deviate during installation, and the Φ22 connecting steel is connected in a ring at an interval of 100 cm;

[0136] Step S4.5. Construction of foot locking steel pipe 6 and grouting

[0137] After the steel arch frame is installed, the arch foot of the surrounding rock on the right side of the line is tightly packed with I-beam steel, and the grouting locking steel pipe is set at a longitudinal interval of 0.6 m (3 pipes per location) to lock the stable rock mass, and the arch foot steel plate 7 is locked; the foot locking steel pipe 6 is a grouting small pipe, L=4m, Φ42*3.5 steel flower pipe, and grouting is performed to fix the steel frame 41;

[0138] Step S4.6. Pouring concrete

[0139] After the formwork is installed and reinforced, C30 / P8 concrete is poured; the concrete is pumped into the mold using a 47m pump, and is poured symmetrically left and right, horizontally layered from bottom to top. The pouring thickness of the concrete is 70 cm, and the concrete must be poured and vibrated in layers in time after each layer is poured; the insert type vibrator should be inserted quickly and pulled out slowly, the insertion points should be arranged uniformly, and the points should be moved sequentially without omission, so as to achieve uniform vibration and a moving distance of no more than 1.5 times the action radius of the vibrating rod; when vibrating the upper layer, the vibrator should be inserted into the lower layer concrete surface by 50 mm to eliminate the joint between the two layers;

[0140] The outer formwork and side formwork are removed after the concrete strength reaches 50%; after the concrete is removed, it needs to be watered and maintained in time;

[0141] After the arch protection is completed, the monitoring and measurement of the arch protection should be done well, the information should be collected in time, and the preparation for the continuation of the tunnel construction should be done well;

[0142] Step S5. After the structure construction of the shallow-buried bias pressure super-small clear distance tunnel portal section is completed, the tunnel lining and construction are carried out.

[0143] Example 2: Different from example 1, in order to facilitate the quick connection of the bias retaining wall 3 and the steel frame 41 during hoisting, the quick installation connecting piece 5 includes a pre-buried connecting body 51 and a welded connecting body 55 which are used together, wherein

[0144] The pre-embedded connector 51 is arranged on the bias retaining wall 3 and the arch foot steel plate 7, and the quick-connection slot 511 and the positioning clamping piece 53 are arranged on the pre-embedded connector 51;

[0145] The welding connector 55 is welded and arranged at both ends of the steel frame 41, and the quick-connection plug 555 and the telescopic positioning piece 58 are arranged on the welding connector 55, and the quick-connection plug 555 is used in cooperation with the quick-connection slot 511, and the positioning clamping piece 53 is used in cooperation with the telescopic positioning piece 58, after installation, the pre-embedded connector 51 and the welding connector 55 are connected by using the pin bolt and the screwing piece, and the installation of the steel frame 41 is completed.

[0146] Preferably, in order to ensure the strength of the pre-embedded connector 51, the pre-embedded connector 51 is designed to include the lower stiffening plate 515, the upper stiffening plate 516 and the steel connector 517, wherein

[0147] The lower stiffening plate 515 is arranged on the lower side of the upper stiffening plate 516, and the pre-embedded sleeve 512 is welded on the bottom of the lower stiffening plate 515;

[0148] The upper stiffening plate 516 is arranged on the upper side of the steel connector 517, and the guide slot 513 is arranged on the lower stiffening plate 515 and the upper stiffening plate 516, the guide slot 513 is used in cooperation with the positioning clamping piece 53, the positioning clamping piece 53 is clamped and installed in the guide slot 513 during use, and the positioning clamping piece 53 is adjusted to move along the guide slot 513;

[0149] The steel connector 517 is a square steel sleeve fixedly welded between the lower stiffening plate 515 and the upper stiffening plate 516, the quick-connection slot 511 is a clamping slot arranged through the steel connector 517, and a plurality of first positioning holes 514 are symmetrically arranged on the steel connector 517.

[0150] Preferably, a plurality of pre-embedded positioning ribs 518 are welded on the bottom of the lower stiffening plate 515, the pre-embedded positioning ribs 518 are pre-embedded in the bias retaining wall 3, and in order to increase the contact area and ensure the adhesion between the pre-embedded positioning ribs 518 and the pre-embedded sleeve 512 pre-embedded in the bias retaining wall 3 and the corresponding position concrete, threaded wires are arranged on the outer sides of the pre-embedded positioning ribs 518 and the pre-embedded sleeve 512 and are used in cooperation with the concrete poured in the bias retaining wall.

[0151] Preferably, the bottom of the lower stiffening plate 515 is welded and connected with the arch foot steel plate 7, and the arch foot steel plate 7 is fixed on the original rock stratum through the locking foot steel pipe 6.

[0152] Preferably, in order to adjust the relative distance between the two symmetrical positioning clamps 53, the positioning clamps 53 can be completely clamped and locked with the telescopic positioning member 58, and a pull rod 57 and a positioning plate 572 are arranged between the two positioning clamps 53, wherein

[0153] One end of the pull rod 57 is rotatably connected with a first connecting seat 533 arranged in the inside of the positioning clamp 53 through a hinge pin 571, and a plurality of second positioning holes 54 are arranged on the pull rod 57 and used in cooperation with screw holes arranged on the positioning plate 572.

[0154] The positioning plate 572 is arranged between the two symmetrical pull rods 57 and connected with the pull rods 57 through a positioning rod 573.

[0155] Preferably, the bottom plate 551 of the welded connecting body 55 is fixedly welded at the end of the steel frame 41, and a spring 59 is arranged in the welded connecting body 55, the free end of the spring 59 is connected with a pressing block 50, the pressing block 50 is connected with the telescopic positioning member 58 through a hinge rod 52, the telescopic positioning member 58 is movably arranged in a telescopic hole 553 of the welded connecting body 55, when the spring 59 is compressed, the telescopic positioning member 58 can be clamped in a positioning cavity 531 of the positioning clamp 53 under the external force, and an insertion rod 581 is arranged at the outside end of the telescopic positioning member 58 and used in cooperation with a through hole 532 arranged on the positioning clamp 53, that is, when the insertion rod 581 passes through the through hole 532, it is fixed by using a screwing member, and the connection between the embedded connecting body 51 and the welded connecting body 55 is completed.

[0156] Preferably, in order to cooperate with the pressing block 50, the quick-connecting plug 555 can resist the pressing block 50 during the process of being inserted into the quick-connecting slot 511, so that the two telescopic positioning members 58 can be opened outward under the action of the hinge rod 52, and a pressing member 56 is arranged in the embedded connecting body 51, the pressing member 56 is provided with external threads which are used in cooperation with internal threads of the embedded sleeve 512, and a pressing block 561 is arranged on the outside of the pressing member 56 and used in cooperation with the pressing block 50.

[0157] Preferably, in order to make the telescopic positioning member 58 move linearly during the adjustment process, a positioning clamp block 583 is arranged on the telescopic positioning member 58 and used in cooperation with a sliding groove 552 arranged on the bottom plate 551, that is, during use, the movement of the telescopic positioning member 58 is guided by sliding the positioning clamp block 583 along the sliding groove 552.

[0158] Preferably, a plurality of second connecting seats 582 are arranged at the rear end of the telescopic positioning member 58 for facilitating installation and adjustment, and the second connecting seats 582 are connected with the hinge rod 52 through a pin rod.

[0159] Preferably, the embedded connecting body 51 is connected with the welded connecting body 55 through a screwing member after installation, and a plurality of third positioning holes 554 are arranged on the outer wall of the quick connecting plug 555 for cooperation with the first positioning holes 514.

[0160] The use and installation process of the quick mounting connecting member 5 in the embodiment includes:

[0161] First, the quick mounting connecting member 5 is adjusted before hoisting and installing the steel frame 41 according to the installation requirement, and then hoisting is performed after the adjustment is completed, the position of the quick connecting plug 555 is aligned with the quick connecting slot 511 during hoisting, and the steel frame 41 is gradually lowered, the quick connecting plug 555 is gradually inserted into the quick connecting slot 511, the top block 561 abuts against the pressing block 50, the spring 59 is compressed, the two telescopic positioning members 58 can be opened outward under the action of the hinge rod 52, and are clamped in the positioning cavity 531, meanwhile, the inserting rod 581 passes through the penetrating hole 532, and is fixed after installation by using a screwing member, the embedded connecting body 51 is connected with the welded connecting body 55 by using a screwing member passing through the third positioning hole 554 and the first positioning hole 514, and the external installation of the steel frame 41 is completed.

[0162] Note: When it is found that the distance between the positioning clamping members 53 is too small or too large during hoisting, which affects the installation effect, the distance between the two positioning clamping members 53 can be adjusted through the pull rod 57 to facilitate installation.

[0163] The basic principle, main features and advantages of the present application are shown and described above. It should be understood by those skilled in the art that the present application is not limited by the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principle of the present application, and various changes and improvements can be made to the present application without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A construction method for a shallow-buried, biased, ultra-small clearance tunnel portal section structure, characterized in that: Comprising Step S1. Excavating the slope Before the tunnel portal construction, the light-dark junction pile number and the centerline coordinates of the tunnel portal are measured according to the design drawing, and the position of the slope excavation line at the tunnel portal section is put out according to the design slope of the slope of the tunnel top slope, and the slope of the tunnel portal section is excavated in sections and layers along the excavation line; Step S2. Slope support After the tunnel portal section slope excavation is completed, the slope surface is supported by net spraying and anchor support; Step S3. Construction of the bias retaining wall at the bias of the tunnel portal section Step S3.

1. After the slope support is completed, the construction of the bias at the outside of the tunnel portal section is put into place, and the foundation pit is excavated and supported; Step S3.

2. The foundation of the bias retaining wall is treated; Step S3.

3. Bias retaining wall foundation concrete construction; Step S3.

4. Bias retaining wall wall body concrete construction; Step S3.

5. Fasten the connecting piece and the water hole on the bias retaining wall wall body; Step S3.

6. The wall back can be backfilled after the strength of the retaining wall reaches the preset strength; Step S4. Arch protection construction Step S4.

1. Construction of setting out, arch foot foundation excavation and support; Step S4.

2. Treat the arch foot foundation and install the arch foot steel plate; Step S4.

3. Steel frame making; Step S4.

4. Steel frame installation, and use the quick-connecting piece and the arch foot steel plate to fix the steel frame; Step S4.

5. Construction of the lock foot steel pipe and grouting; Step S4.

6. Pouring of the arch protection concrete; The quick-connecting piece comprises a pre-buried connecting body and a welded connecting body used in conjunction with each other, the pre-buried connecting body is arranged on the bias retaining wall and the arch foot steel plate, and the pre-buried connecting body is provided with a quick-connection slot and a positioning clamp; The welded connecting body is arranged at both ends of the steel frame, and the welded connecting body is provided with a quick-connection plug and an extension positioning piece, the quick-connection plug is used in conjunction with the quick-connection slot, and the positioning clamp is used in conjunction with the extension positioning piece to connect the pre-buried connecting body and the welded connecting body; The pre-buried connecting body comprises a lower stiffening plate, an upper stiffening plate and a steel connecting body, The lower stiffening plate is arranged on the lower side of the upper stiffening plate, and a pre-buried sleeve is welded on the bottom of the lower stiffening plate; The upper stiffening plate is arranged on the upper side of the steel connecting body, and a guide groove for guiding the positioning clamp is arranged on the lower stiffening plate and the upper stiffening plate; The steel connecting body is a square steel sleeve fixed between the lower stiffening plate and the upper stiffening plate, the quick-connection slot is arranged through the steel connecting body, and a plurality of first positioning holes are symmetrically arranged on the side wall of the steel connecting body; The quick-connecting piece further comprises a pull rod and a positioning plate, One end of the pull rod is connected to the first connecting seat arranged on the positioning clamp through a hinge pin, and a plurality of second positioning holes are arranged on the pull rod, the second positioning holes are used in conjunction with the threaded holes arranged on the positioning plate; The positioning plate is arranged between the two symmetrically arranged pull rods and is used in conjunction with the positioning rod; The bottom plate of the welding connector is fixedly welded at the end of the steel frame, and a spring is arranged in the welding connector, a free end of the spring is connected with a pressing block, the pressing block is connected with a telescopic positioning piece through a hinge rod, the telescopic positioning piece is arranged in a telescopic hole on the welding connector and is telescopic along the telescopic hole, and the telescopic positioning piece is further used in cooperation with a positioning cavity on a positioning clamping piece; an insertion rod is arranged at an outer end of the telescopic positioning piece, and the insertion rod is used in cooperation with a through hole arranged on the positioning clamping piece; a positioning clamping block and a second connecting seat are further arranged on the telescopic positioning piece, and the positioning clamping block is used in cooperation with a sliding groove arranged on the bottom plate, and the second connecting seat is connected with the hinge rod through a pin rod; The pre-embedded connector further comprises a top pressing piece, an external thread of the top pressing piece is arranged to be used in cooperation with an internal thread of a pre-embedded sleeve, and a top block is arranged outside the top pressing piece, and the top block is used in cooperation with the pressing block.

2. The construction method of a shallow-buried bias ultra-small clear distance tunnel portal section structure according to claim 1, characterized in that: The lofting and support processes of steps S3.1 and S4.1 include (1) Before the foundation pit is excavated, surface water is drained, and a center line and an excavation boundary line of the foundation pit are laid out; (2) The excavation process of the bias retaining wall foundation pit is performed according to the principles of segmented and layered excavation and support, large-area excavation is prohibited, and a cushion is timely constructed after one segment is excavated; the foundation pit slope is excavated and supported at a slope of 1:0.5, and the slope is measured by using an angle ruler; (3) The excavation is performed by using an excavator to excavate to 30 cm above the base, 30 cm above the elevation is excavated by using manual work to the design elevation, and after the excavation is completed, the site is cleaned, leveled and rammed; (4) The foundation pit slope is sloped according to whether the top of the sand soil and pebble and gravel soil has a dynamic load, anchor and shotcrete support is performed, 3.5 m long Φ22 cartridge anchor rods are arranged in a plum blossom shape with a spacing of 1.2*1.2 m, a steel mesh with a spacing of 200*200 mm is arranged, and C25 concrete is sprayed to a thickness of 10 cm to perform support.

3. The construction method of a shallow-buried bias ultra-small clear distance tunnel portal section structure according to claim 1, characterized in that: The base treatment processes of steps S3.2 and S4.2 include (1) The range of the foundation treatment is 0.8 m wider than the foundation, after the base is properly trimmed according to the design requirements, the foundation construction is immediately performed, and the phenomenon of base immersion and long-term exposure is eliminated; (2) When the foundation is constructed on a rock layer, the silt and loose stones are cleaned before the foundation is constructed, and a foundation bearing capacity experiment is performed; (3) The foundation bearing capacity at the bias position of the tunnel portal section is tested, the positions where the foundation bearing capacity does not satisfy 300 kpa are backfilled with plain concrete, so that the strength satisfies the foundation bearing capacity requirement.

4. The construction method of a shallow-buried bias ultra-small clear distance tunnel portal section structure according to claim 1, characterized in that: The wall body concrete construction process of step S3.4 includes (1) When the wall body is constructed, a scaffold operation platform and a scaffold ladder for personnel to go up and down are erected, and the step spacing of the ladder should not be greater than 300 mm; (2) Template and bent installation and reinforcement a. Large-area steel templates are used on the outside of the wall body template, double steel pipes, butterfly buckles and Φ12 pull rods are used for diagonal and counter-pulling of the horizontal and vertical bands on the back of the template, and C18 steel is used for internal support, the upper and lower intervals are 0.5 m, and the front and rear intervals are 0.6 m; b. Small-size steel templates are assembled for the arc side on the inside of the wall body, and a combined bent is used for supporting and fixing the template framework; The combined bent is made by I20a H-shaped steel according to the peripheral arc of the section hole lining and back rib reinforcement; single bent is arranged longitudinally with a spacing of 75 cm, and the bent is longitudinally reinforced with C20 steel bars; the inner side formwork is made of The combined steel formwork is closely attached to the outer side of the bent arc; the overall bent is reinforced by the method of supporting and reinforcing the formwork with square or round wood in the back part in addition to the opposite pulling of the formwork Ф12 opposite pulling rods, the inclined pulling and the C18 steel bar inclined support and horizontal support. (3) Wall body concrete pouring During pouring, the wall body is poured in 6 times, each time is poured in layers, and the Φ50 soft shaft vibrating rod is inserted for vibration and compaction. The thickness of each layer is not more than 50 cm. The vibrating rod is vertically inserted into the concrete during vibration, and is inserted into the previous layer of concrete for 5-10 cm. The moving distance of the vibrating rod is not more than 1.5 times of the effective vibration operation radius, and the distance between the vibrating rod and the formwork is not less than 10 cm. The concrete stops falling during vibration, and stops being tamped when there is no bubble, no slurry and the surface is flat. After the pouring of the concrete is completed, curing should be carried out in time, and the formwork should be removed when the strength reaches 80%.

5. The construction method of a shallow-buried bias ultra-small clear distance tunnel portal section structure according to claim 1, characterized in that: The process of installing the steel frame described in step S4.4 includes (1) Positioning measurement: First, determine the center line of the route, determine the elevation, and then determine the lateral position and arch foot position; (2) Preparation work before installation: The unit arch frame transported to the site is stacked according to the unit number, the cross-sectional size is checked before installation, and the under-excavated part is processed in time to ensure the correct installation of the arch frame. A 5cm protective layer is reserved outside the arch frame. Before installing the arch foot or wall foot steel frame, the loose debris under the base plate must be removed, the steel frame is placed on the original rock layer, and a pad arch foot steel plate is added under the arch foot in soft ground section; (3) The spacing of the steel frame is 50cm, and the steel frame is installed from bottom to top. During the installation of the first section of steel frame, attention should be paid to the connection of the quick installation connecting piece reserved in the bias retaining wall to ensure that the steel frame does not deviate during installation, and the Φ22 connecting steel is connected in a ring shape at an interval of 100cm.

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