Soft rock tunnel yielding supporting structure

Abstract

The utility model discloses a soft rock tunnel yielding supporting structure which comprises a yielding steel sleeve embedded in a sprayed concrete layer, and the yielding steel sleeve is provided with an arc-shaped inner steel plate and an arc-shaped outer steel plate which are coaxially arranged at intervals. A plurality of bridge type yielding pieces are uniformly arranged between the inner steel plate and the outer steel plate; the yielding supporting structure further comprises at least two temporary supporting rods which are used for temporarily installing and supporting the wall face rock mass after excavation is completed and dismantling the supporting wall face rock mass after the tunnel wall face rock mass is stable. One end of the temporary supporting rod is connected to the sprayed concrete layer, and the other end is connected to the excavated ground. The structure solves the problem that an existing yielding supporting structure using I-shaped steel as a soft rock stratum is prone to being damaged at the arch angle position.

Description

TECHNICAL FIELD

[0001] The utility model belongs to tunnel support technical field, concretely relates to a soft rock tunnel yielding support structure. BACKGROUND

[0002] In the tunnel construction process, the structural damage caused by tunnel deformation is common, especially in high ground stress soft rock stratum tunnel, the surrounding rock brings great risk to tunnel construction. The current control method for large deformation of tunnel surrounding rock is to use the way of strengthening the primary support. This method can reduce the deformation of surrounding rock to a certain extent, but also increases the load borne by the support structure, thereby increasing the probability of damage to the support structure.

[0003] The structure of the yielding support system has greater flexibility and strength, which enables the support structure to deform cooperatively with the surrounding rock, reduces the load borne by the support structure, and thus reduces the risk of damage to the support structure, which is an important support method to deal with the challenge of large deformation of high ground stress soft rock tunnel.

[0004] The deformation characteristics of high ground stress soft rock tunnel are large and rapid deformation in the early stage and gradual stability in the later stage. The early strength of the sprayed concrete is low, and the strength of the sprayed concrete gradually increases with the increase of maintenance time. There is a time mismatch between the deformation of the surrounding rock and the strength of the sprayed concrete, which leads to the inability of the support structure to effectively constrain the deformation of the surrounding rock, and the large deformation of the surrounding rock also damages the sprayed concrete under low strength.

[0005] The existing technology usually uses grid arches and steel arches as the skeleton structure form for initial support of tunnels. The grid arch has weak bearing capacity and poor adaptability in soft rock tunnels. The steel arch has large overall stiffness and can bear load earlier, so it is widely used in soft rock tunnels. However, the steel arch has poor torsional stability under the condition of large deformation of soft rock, and is prone to sudden torsional instability and failure. The reason is that the flange area of H-shaped steel and I-beam is small, and the uneven stress on both sides of the flange leads to the overturning of the flange steel plate, which eventually leads to the failure of the support structure. UTILITY MODEL CONTENTS

[0006] The utility model aims at providing a soft rock tunnel yielding support structure to solve the problem that the existing yielding support structure using I-beam as the soft rock stratum is prone to failure at the arch corner.

[0007] The utility model adopts the following technical scheme: a soft rock tunnel yielding support structure, the side wall surface of the soft rock tunnel excavation surface, from inside to outside of the tunnel, is a mold concrete layer, a sprayed concrete layer and a stratum surrounding rock;

[0008] The yielding support structure comprises a yielding steel sleeve embedded in the sprayed concrete layer, the yielding steel sleeve has coaxially and spacedly arranged arc-shaped inner steel plates and arc-shaped outer steel plates, the inner steel plates and the outer steel plates are arranged along the section edge of the tunnel excavation; and a plurality of bridge-shaped yielding pieces are uniformly arranged between the inner steel plates and the outer steel plates;

[0009] Each bridge-shaped yielding piece comprises two inverted U-shaped rod pieces, the two rod pieces are crosswise arranged and stacked one above another, the bottom of each rod piece is connected to the outer steel plate through a gusset plate, and the top of the upper rod piece is connected to the inner steel plate; a groove is arranged at the intersection of the two rod pieces, and the two rod pieces are detachably connected through a connecting piece at the groove;

[0010] The yielding support structure further comprises at least two temporary support rods, each temporary support rod is a telescopic rod structure, is used for temporarily supporting the wall rock mass after the excavation is completed, and is removed after the tunnel wall rock mass is stable; one end of the temporary support rod is connected to the sprayed concrete layer, and the other end is connected to the ground of the excavation.

[0011] Further, a plurality of yielding steel sleeves are arranged along the excavation direction of the tunnel, a plurality of longitudinal steel bars are arranged along the circumference of the outer steel plate, each longitudinal steel bar is parallel to the axis direction of the outer steel plate, and the adjacent yielding steel sleeves are connected through the longitudinal steel bars.

[0012] Further, the yielding support structure further comprises a plurality of system anchor rods arranged in a ring array around the tunnel central axis, each system anchor rod comprises a hollow grouting anchor rod, and is used for penetrating through the sprayed concrete layer and being inserted into the stratum surrounding rock.

[0013] Further, the sprayed concrete layer and the molded concrete layer are filled with instant foaming sealing high polymer material, and the filling thickness is the same as the designed reserved deformation amount.

[0014] Further, the temporary support rod comprises a hydraulic jack, a pressure sensor and a displacement sensor module are arranged on the hydraulic jack, and are respectively used for monitoring the support pressure and the deformation displacement.

[0015] The soft rock tunnel yielding support structure has the advantages that: the inner steel plates and the outer steel plates have large contact areas with the tunnel hole wall, can be deformed cooperatively with the tunnel surrounding rock, the yielding piece units in the yielding steel sleeve are independent of each other, even if a certain yielding piece is damaged, the surrounding yielding pieces can still share the load, the anti-deformation capacity is relatively strong, and the instability damage is prevented. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is the structure schematic view of the utility model;

[0017] Figure 2 It is the local structure schematic view of the utility model in let pressure steel cover;

[0018] Figure 3 It is the structure schematic view of the utility model in bridge type let pressure spare;

[0019] Figure 4 It is the connection structure schematic view of the utility model in multiple let pressure steel covers;

[0020] Figure 5 It is the structure schematic view of the utility model in system anchor rod;

[0021] Figure 6 It is the structure schematic view of the utility model in temporary support rod;

[0022] Figure 7 It is the installation step schematic view of the utility model.

[0023] Wherein, 1. temporary support rod;11. hydraulic jack;111. pressure sensor;112. displacement sensor;

[0024] 12. lower bearing plate;13. force transmission column;14. upper bearing plate;

[0025] 2. system anchor rod;21. rod body;22. anchor pad;23. fastening nut;

[0026] 3. let pressure steel cover;31. inner steel plate;

[0027] 32. bridge type let pressure spare;321. pad;322. rod piece;324. recess;

[0028] 33. outer steel plate;34. longitudinal reinforcement;

[0029] 4. shotcrete layer;5. formwork concrete layer. DETAILED DESCRIPTION

[0030] The utility model will be explained in detail below in combination with the drawings and specific embodiment.

[0031] The utility model provides a kind of soft rock tunnel let pressure support structure, as shown in Figure 1 The side wall surface of soft rock tunnel excavation face, from inside to outside in tunnel, is formwork concrete layer 5, shotcrete layer 4 and stratum surrounding rock in sequence;

[0032] The let pressure support structure includes let pressure steel cover embedded in shotcrete layer 4, as shown in Figure 2As shown, the pressure relief sleeve has an arc-shaped inner steel plate 31 and an arc-shaped outer steel plate 33 arranged coaxially at intervals. The inner steel plate 31 and the outer steel plate 33 are arranged along the edge of the tunnel excavation section. Multiple bridge-shaped pressure relief members 32 are uniformly arranged between the inner steel plate 31 and the outer steel plate 33. The thickness of the inner steel plate 31 and the outer steel plate 33 is at least 3 mm.

[0033] Among them, such as Figure 3 As shown, each bridge-type pressure member 32 includes two inverted U-shaped rods 322. The two rods 322 are cross-shaped and stacked one on top of the other. The bottom of both rods 322 is connected to the outer steel plate 33 through a pad 321, and the top of the upper rod 322 is connected to the inner steel plate 31. A groove 324 is provided at the intersection of the two rods 322 for detachably connecting the two rods 322 through a connector.

[0034] The pressure support structure also includes at least two temporary support rods 1, each a telescopic rod structure, used to temporarily support the tunnel wall rock mass after excavation, and to be removed after the tunnel wall rock mass has stabilized; one end of the temporary support rod 1 is used to connect to the shotcrete layer 4, and the other end is used to connect to the excavated ground. Figure 6 As shown, the temporary support rod 1 includes a hydraulic jack 11, a lower bearing plate 12, an upper bearing plate 14, and a force transmission column 13. The hydraulic jack 11 is connected to the lower bearing plate 12, and one end of the force transmission column 13 is connected to the lower bearing plate 12 and the other end is connected to the upper bearing plate 14. The hydraulic jack provides temporary support for the tunnel wall by adjusting its elevation. The temporary support is removed after the tunnel deformation stabilizes.

[0035] In some embodiments, such as Figure 4 As shown, multiple pressure-relief steel sleeves are arranged at intervals along the tunnel excavation direction. Multiple longitudinal reinforcing bars 34 are installed along the circumference of the outer steel plate 33. Each longitudinal reinforcing bar 34 is parallel to the axial direction of the outer steel plate 33, and adjacent pressure-relief steel sleeves are connected by the longitudinal reinforcing bars 34. The width of a single pressure-relief steel sleeve along the tunnel depth direction is 20-30 cm.

[0036] In some embodiments, such as Figure 1 As shown, the pressure-bearing support structure also includes multiple system anchor bolts 2 arranged in a ring around the tunnel's central axis. For example... Figure 5 As shown, each system anchor 2 includes a hollow grouting anchor rod, used to penetrate the shotcrete layer 4 and insert into the surrounding rock. The anchor rod consists of a rod body 21, an anchor plate 22, and a fastening nut 23. One end of the rod body 21 is inserted into the surrounding rock stratum, and the rod body is fixed to the borehole wall of the surrounding rock stratum by grouting. The other end is fixed to the rock surface by the fastening nut and connected to the longitudinal reinforcing steel by welding.

[0037] In some embodiments, the shotcrete layer 4 is filled with instant foaming sealing polymer material between the shotcrete layer 4 and the cast-in-place concrete layer 5, and the filling thickness is the same as the design reserved deformation amount.

[0038] In some embodiments, the temporary support rod 1 includes a hydraulic jack 11, and a pressure sensor and a displacement sensor module are arranged on the hydraulic jack 11, which are respectively used for monitoring the support pressure and the deformation displacement.

[0039] As shown in Figure 7 A yielding support structure for a soft rock tunnel, in a tunnel excavated by a three-step method, the installation steps are as follows:

[0040] Step 1, assemble the yielding steel sleeve, make the lower steel plate, bridge-type yielding part, and upper steel plate in the prefabrication factory, assemble the yielding steel sleeve according to the curvature requirements of the upper step, middle step, and lower step of the tunnel, the assembly sequence is from top to bottom, which is the lower steel plate, bridge-type yielding part, and upper steel plate in sequence, and bolted connection is adopted, and then the longitudinal reinforcement is welded on the lower steel plate.

[0041] Step 2, excavate the upper step and initially spray concrete to close the rock surface.

[0042] Step 3, transport the assembled upper step yielding steel sleeve to the site and install it on site, after installation, align and weld the longitudinal reinforcement with the longitudinal reinforcement of the previous yielding steel sleeve.

[0043] Step 4, re-spray concrete on the upper step to form a complete shotcrete layer.

[0044] Step 5, install temporary support, adjust the stroke and support force, and monitor the pressure and stroke deformation of the hydraulic jack, and remove the temporary support after the deformation is stable.

[0045] Step 6, install the shotcrete layer on the middle step and lower step by the similar method as the upper step.

[0046] Step 7, excavate the inverted arch and spray concrete to close the rock surface.

[0047] Step 8, spray instant foaming sealing polymer material to prevent groundwater from seeping into the tunnel.

[0048] Step 9, install the secondary lining reinforcement cage, move the secondary lining trolley into position, pour concrete, and form a complete cast-in-place concrete layer after demolding. Embodiment

[0049] The thickness of the sprayed concrete layer 4 is 15-35 cm, the compressive strength of the material is greater than or equal to 20 MPa, and the proportion of the sprayed concrete is as follows in parts by weight: cement 450-500 parts; river sand 850-950 parts; broken pebbles 780-820 parts; water reducing agent 4.5-5.0 parts; quick setting agent 17.5-20 parts; and water 155-165 parts.

[0050] The thickness of the molded concrete layer 5 is 40-60 cm, the compressive strength of the material is greater than or equal to 35 MPa, and the proportion of the molded concrete is as follows in parts by weight: cement 340-400 parts; river sand 750-800 parts; broken pebbles 1100-1200 parts; water reducing agent 3-5 parts; and water 130-180 parts.

[0051] The spacing of the yielding steel sleeve 3 is 1.2 m, the diameter of the longitudinal reinforcement is 20 mm, and the spacing is 20 cm. The diameter of the system anchor rod is 25 mm, the length is 4 m, the radial spacing is 1.2 m, and the longitudinal spacing is 1.2 m. The stroke of the hydraulic jack is greater than 30 cm, the tonnage is greater than 50 t, and the longitudinal spacing is 1.2 m.

[0052] The utility model provides a kind of soft rock tunnel yielding support structure, and the structure is high in strength, and deformation adaptability is strong, and it is in line with the deformation characteristics of soft rock tunnel, can provide effective support while ensuring that structure does not occur damage, to improve the safety and reliability of tunnel construction purpose is reached. By setting yielding steel sleeve, the inner steel plate and outer steel plate in it contact area is large with tunnel hole wall, can be deformed with tunnel surrounding rock, simultaneously, each yielding piece unit in the inside of yielding steel sleeve is independent of each other, even if the destruction of certain yielding piece, surrounding yielding piece can still share load, and the deformation resistance is stronger, prevent instability damage. Simultaneously, when the early strength of sprayed concrete is low, temporary support provides temporary support force by temporary support, remove temporary support after deformation stabilizes, it is more in line with the characteristics that soft rock tunnel early deformation is large and then gradually tends to be stable, effectively control surrounding rock large deformation and support structure damage, improve the safety and stability of tunnel construction.

Claims

1. A soft rock tunnel yielding support structure, characterized by, The side wall of the soft rock tunnel excavation face, from inside to outside of the tunnel, is successively a molded concrete layer (5), a sprayed concrete layer (4) and a stratum surrounding rock; The yielding support structure comprises a yielding steel sleeve embedded in the sprayed concrete layer (4), the yielding steel sleeve has an arc-shaped inner steel plate (31) and an arc-shaped outer steel plate (33) arranged coaxially and spaced apart, the inner steel plate (31) and the outer steel plate (33) are arranged along the section edge of the tunnel excavation; a plurality of bridge-type yielding pieces (32) are uniformly arranged between the inner steel plate (31) and the outer steel plate (33); Each bridge-type yielding piece (32) comprises two inverted U-shaped rod pieces (322), the two rod pieces (322) are crosswise arranged and stacked one above another, the bottom of each of the two rod pieces (322) is connected to the outer steel plate (33) through a gusset plate (321), and the top of the rod piece (322) located above is connected to the inner steel plate (31); a groove (324) is arranged at the intersection of the two rod pieces (322) for detachably connecting the two rod pieces (322) through a connecting piece at the intersection; The yielding support structure further comprises at least two temporary support rods (1), each of the temporary support rods (1) is a telescopic rod structure, used for temporarily supporting the wall rock after the excavation is completed and removed after the tunnel wall rock is stable; one end of the temporary support rod (1) is connected to the sprayed concrete layer (4), and the other end is connected to the ground surface of the excavation.

2. A soft rock tunnel yielding support structure as claimed in claim 1, wherein, A plurality of the yielding steel sleeves are arranged along the direction of the tunnel excavation, a plurality of longitudinal steel bars (34) are arranged along the circumference of the outer steel plate (33), each of the longitudinal steel bars (34) is parallel to the axis direction of the outer steel plate (33), and the adjacent yielding steel sleeves are connected through the longitudinal steel bars (34).

3. A soft rock tunnel yielding support structure as claimed in claim 1 or 2, characterized in that The yielding support structure further comprises a plurality of system anchor rods (2) arranged in a ring array around the tunnel central axis, each of the system anchor rods (2) comprises a hollow grouting anchor rod, used for penetrating through the sprayed concrete layer (4) and inserted into the stratum surrounding rock.

4. A soft rock tunnel yielding support structure as claimed in claim 1 or 2, wherein, The sprayed concrete layer (4) and the molded concrete layer (5) are filled with instant foaming sealing high polymer material, and the filling thickness is the same as the designed reserved deformation amount.

5. A soft rock tunnel yielding support structure as claimed in claim 1 or 2, wherein, The temporary support rod (1) comprises a hydraulic jack (11), a pressure sensor and a displacement sensor module are arranged on the hydraulic jack (11) for monitoring the support pressure and deformation displacement, respectively.

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