Open type TBM over slow dip soft rock stratum partition section coordinated support construction method

Abstract

The application discloses an open TBM over-gently-inclined soft rock stratum partitioned and segmented cooperative supporting construction method, which comprises the following steps: S1, shield tail immediate supporting; S2, supporting reinforcement behind the support shoe; and S3, bottom arch anchor supporting closed regulation and control. According to the structural features of the open TBM equipment and the deformation law of the gently-inclined soft rock stratum, the supporting region is divided into three operation sections, namely, the near-shield tail immediate supporting area, the supporting reinforcement area behind the support shoe and the bottom arch anchor supporting closed regulation and control area, differential supporting is implemented in stages, the time-space progressive construction of the prestressed anchor cable and the anchor rod is combined, the matching between the supporting rigidity and the stratum deformation is ensured through prestress dynamic adjustment, a dynamic cooperative supporting system of 'immediate supporting-reinforcement and reinforcement-closed loop regulation and control' is formed, and the dual improvement of the supporting efficiency and safety is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of tunnel engineering, and particularly relates to a method for open TBM passing through soft rock stratum with low inclination and sectioned partitioned cooperative support. BACKGROUND

[0002] Long and large tunnels inevitably pass through soft rock strata with low inclination (including mudstone, shale, phyllite, red-bed soft rock and the like), which brings great challenges to tunnel TBM construction. The soft rock strata with low inclination have the characteristics of broken surrounding rock, low strength and developed joint bedding, and have significant anisotropy. In the cross section, the deformation of the surrounding rock is uneven, the deformation rate of the crown region is fast because the normal line of the free face intersects with the layer surface at a large angle, and the deformation rate of the side wall region is relatively slow because the normal line of the free face intersects with the layer surface at a small angle. The support work of the soft rock tunnel section is large and difficult to implement, and if not properly handled, it can lead to TBM excavation obstruction and even overall collapse of the surrounding rock, which seriously threatens the TBM excavation efficiency and construction safety. For open TBM passing through soft rock strata with low inclination, the traditional support scheme mainly has the problems of space limitation, low efficiency and poor cooperation, which seriously restricts the play of TBM advantages, and the specific problems are as follows:

[0003] (1) The crown of the soft rock stratum with low inclination deforms fast and has strong timeliness of support, while the space behind the TBM shield is small, the traditional system support scheme concentrates construction in the single area of the shield tail, and is easy to lead to low construction efficiency;

[0004] (2) The support structure such as steel arch and anchor rod is not implemented in sections combined with the space characteristics of the TBM equipment, and has low efficiency; the operation space is crowded and the process conflicts when synchronously installed, and the downtime is prolonged;

[0005] (3) The operation space behind the shield tail is limited, and the full-face support cannot be efficiently completed, the support demand and efficiency do not match the TBM excavation speed, the TBM downtime for waiting for support is prominent, and the TBM continuous excavation is affected;

[0006] (4) The traditional support method lacks flexibility, the support parameters are fixed, and a dynamic regulation mechanism based on real-time monitoring is lacked. SUMMARY

[0007] The application is proposed to solve the above problems, and aims to provide an open TBM passing through soft rock stratum with low inclination and sectioned partitioned cooperative support method. The method solves the problems of low TBM support efficiency and long downtime in the soft rock stratum with low inclination through space decomposition, time sequence optimization and dynamic regulation, realizes parallel operation of excavation and support, and provides an innovative path for efficient and safe TBM construction in soft rock strata.

[0008] In order to achieve the above purpose, the application adopts the following scheme:

[0009] An open type TBM over-slow-inclined soft rock stratum partitioned and segmented cooperative support construction method, comprising the following steps:

[0010] S1: shield tail real-time support

[0011] S101: within the range of 0.5-0.8 m behind the shield tail, using TBM intermittent propulsion, a steel arch is quickly assembled by using a TBM arch assembly device, the height of the steel arch is H1, and the steel arch spacing is D1;

[0012] S102: within the range of 1.0-3.0 m of the exposed shield, concrete is sprayed within the range of 240-270° of the side top arch, the sprayed concrete thickness is H2, and H2≥H1+2 cm;

[0013] S103: within the range of 3.0-5.0 m of the exposed shield, a top arch prestressed anchor cable is constructed along the range of 100-120° of the tunnel top, the top arch anchor cable pre-tension force applied value is P s1 ;

[0014] S2: support behind the support shoe

[0015] S201: side wall prestressed anchor cables are constructed within the range of 120-140° of the side walls on both sides of the support shoe rear operation platform, the side wall anchor cable pre-tension force applied value is P s2 ;

[0016] S202: bottom arch concrete is sprayed within the range of 90-120° behind the support shoe, the sprayed concrete thickness is H2;

[0017] S3: bottom arch anchor support closed regulation and control

[0018] When the construction space is available behind the TBM machine head, long anchor rods and short anchor rods are arranged in a ring direction with a spacing within the range of 120° of the bottom arch.

[0019] As a preferred embodiment, in the step S1, the assembly of the steel arch is synchronized with the TBM tunneling and is completed within the range of 0.5-0.8 m behind the shield tail; the concrete spraying of the side top arch is immediately constructed after the assembly of the steel arch, and is constructed by using a TBM emergency concrete spraying system; the top arch prestressed anchor cable is constructed after the sprayed concrete of the side top arch reaches 80% of the design strength.

[0020] As a preferred embodiment, in the step S103, the prestressed anchor cable spacing is 1.0-2.0 m, the row spacing D2=D1~2D1, D1 is the steel arch spacing; the anchor cable length L s ≥L p1 +2, L s is the anchor cable length, and L p1 is the depth of the surrounding rock relaxation zone of the side top arch, and the units are both m.

[0021] As a preferred embodiment, in the step S103, the anchoring segment length of the prestressed anchor cable is calculated according to the following formula:

[0022] L m1 =1.1×K×P s1 / π×D×C;

[0023] In the formula, L m1 is the anchoring segment length, K is the safety coefficient of the anchoring segment length, P s1 is the prestressed anchor cable prestressed force application value, D is the anchor cable diameter, and C is the bonding strength of the cementing material and the hole wall.

[0024] The anchoring segment length of the prestressed anchor cable is checked according to the following formula:

[0025] L m1 =1.1×K×P s1 / π×d×C1;

[0026] In the formula, L m1 is the anchoring segment length, K is the safety coefficient of the anchoring segment length, P s1 is the prestressed anchor cable prestressed force application value, d is the diameter of the prestressed steel strand, and C1 is the gripping force of the cementing material and the prestressed steel strand.

[0027] As a preferred embodiment, in the step S2, the side wall prestressed anchor cable and the bottom arch shotcrete are made behind the support shoe when the support shoe moves to the next cycle position.

[0028] As a preferred embodiment, in the step S201, the side wall anchor cable prestressed force application value is P s2 calculated according to the following formula:

[0029] P s2 = P s1 +α1×E s ×A s ×δ1 / L f1 ;

[0030] In the formula, P s1 is the prestressed anchor cable prestressed force application value, α1 is the stiffness matching coefficient, E s is the elastic modulus of the anchor cable steel strand, A s is the cross-sectional area of the anchor cable steel strand, δ1 is the incremental deformation of the side wall surrounding rock within the time difference of the arch and side wall anchor cable construction, L f1 is the free segment length of the prestressed steel strand, and L f1 =L s -L m1 .

[0031] As a preferred embodiment, in the step S3, the length of the short anchor rod is L g1 , L g1 ≈R, R is the TBM excavation radius, and the pre-tension value of the short anchor rod is P g1 ; the length of the long anchor rod is L g2 , L g2 ≥L p2 +2, L p2 is the depth of the surrounding rock relaxation zone of the bottom arch, and the unit is m; and the pre-tension value of the long anchor rod is P g2 .

[0032] As a preferred embodiment, in the step S3, the pre-tension values of the long and short anchor rods are adjusted according to the following formula:

[0033] P g2 =P g1 +α1×E g ×A g ×δ2 / L f2 ;

[0034] In the formula, P g1 is the pre-tension value of the short anchor rod, P g2 is the pre-tension value of the long anchor rod, E g is the elastic modulus of the anchor rod, A g is the cross-sectional area of the anchor rod, δ2 is the incremental deformation of the surrounding rock within the time difference of the long and short anchor rods, L f2 is the length of the free section of the pre-stressed anchor rod, and α1 is the stiffness matching coefficient.

[0035] As a preferred embodiment, in the step S3, the short anchor rod is completed after 1-2 excavation cycles of the lagging wall stress anchor cable behind the support shoe.

[0036] As a preferred embodiment, in the step S3, if the deformation rate of the bottom arch exceeds 5 mm / d, there is a risk of bottom arch uplift deformation, and the long anchor rod is immediately implemented; if the deformation rate of the bottom arch is less than 5 mm / d, the long anchor rod can be implemented 30-35 m behind the support shoe of the TBM.

[0037] Compared with the prior art, the present application has the following beneficial effects:

[0038] Firstly, the zoning and segmenting collaborative support method provided by the present application solves the problems of low efficiency and poor collaboration of the open TBM in soft rock stratum construction through spatial decomposition, time sequence optimization, dynamic control and other methods, and provides an innovative path for efficient and safe construction of the soft rock stratum TBM.

[0039] Secondly, based on the non-uniform deformation law of the gently inclined soft rock stratum, the present application makes full use of the spatial characteristics of different parts of the TBM, decomposes the supporting process into the shield tail immediate support area, the support area behind the support shoe, the bottom arch anchor closed control area, and the core idea of time and space cooperation and dynamic adjustment, avoids concentrated operation, improves the space utilization rate, and realizes the parallel of TBM tunneling and supporting.

[0040] Thirdly, the present application implements differentiated support in stages, combines the time and space progressive construction and reinforcement of the "top arch prestressed anchor cable-side wall prestressed anchor cable-bottom arch long and short combined prestressed anchor rod", and ensures the matching of the supporting stiffness and the stratum deformation through prestressed dynamic adjustment, forms the time and space dynamic cooperative supporting system of "immediate support-reinforcement and reinforcement-closed loop control", fully develops the bearing capacity of the supporting structure, efficiently inhibits the deformation of the gently inclined soft rock, and realizes the double improvement of supporting efficiency and safety.

[0041] Fourthly, in the "shield tail immediate support area", the present application improves the overall stiffness and bearing capacity of the arch through the combination of "steel arch + sprayed concrete + top arch prestressed anchor cable", the thickness of the sprayed concrete and the height of the steel arch are not less than 2.0 cm, that is, more than 2.0 cm of protective layer is left; the steel arch can effectively share the surrounding rock pressure to form an overall arch-shaped supporting structure; the sprayed concrete leaves enough protective layer, which is beneficial to corrosion and rust prevention, and can also provide a reliable working surface for the subsequent anchor cable close to the concrete layer; the TBM arch assembly device and the emergency sprayed concrete system can complete the primary support in the shortest time and control the surrounding rock relaxation; thus, in the tunneling process, the top arch and the surrounding rock obtain timely and sufficient stiffness support, reducing the risk of top arch surrounding rock deformation and collapse.

[0042] Fifthly, the present application aims at the top prestressed anchor cable of the shield tail immediate support area, which plays the role of active support, sets the prestressed anchor cable in the arch part, quickly applies the "reverse" restraining force to the surrounding rock, effectively inhibits the early deformation of the layered soft rock of the top arch; precise anchoring length: based on the specification calculation and combined with the actual relaxation depth, the anchor cable is fully anchored in the stable rock mass, which is safe and avoids waste; strong operability: given specific anchor cable parameters and length range, it is convenient for on-site rapid execution to ensure the consistency and reliability of the supporting effect. Therefore, by timely and actively controlling the arch top surrounding rock, the deformation influence on subsequent construction can be significantly reduced, and the TBM jamming can be prevented.

[0043] Sixthly, the present application proposes the idea of "dynamic prestress correction according to the incremental deformation of the sidewall" for the prestressed anchor cables on both sides of the sidewall in the support area behind the support shoe, and differentially applies prestress: the sidewall and the crown arch anchor cable construction time offset may have caused a certain incremental deformation of the sidewall, which can be guaranteed by the incremental term δ1 correction to ensure the coordination of support stiffness; the sidewall reinforcement and the crown reinforcement work together to form a complete and uniform support ring around the tunnel. The prestress compensation for the incremental deformation of the sidewall helps to control the overall deformation of the tunnel and reduce the risk of late lining settlement or bulging.

[0044] Seventhly, the present application sprays the same thickness of polypropylene coarse fiber concrete as the crown arch in the same section behind the support shoe, and forms a full-face closed ring with the crown arch and sidewall sprayed layer; forms a closed support system: the closure of the sprayed concrete ring can evenly disperse the surrounding rock stress to the arch crown and both sides, reducing stress concentration; enhances the bottom anti-deformation ability: the bottom arch sprayed concrete can inhibit the bottom heave, especially in soft strata, which can prevent water and soil or rock uplift in advance; cooperates with the upper arch frame: cooperates with the support measures of the crown arch and sidewall to build a "ring" and "longitudinal" composite bearing system. The closed ring can improve the overall stiffness of the tunnel as a whole and reduce the disturbance risk of surrounding rock to the lining and equipment.

[0045] Eighthly, the present application uses self-drilling prestressed anchor rods in the bottom arch anchor support closed control area, which are arranged in a ring shape with long and short anchor rods; "long and short combination" layered control: short anchor rods can quickly reinforce the shallow surrounding rock, and long anchor rods can strengthen the control of deep plastic zones; improve efficiency: short anchor rods are easy to install and can be quickly laid behind the shield tail to control the initial bottom arch deformation; long anchor rods can be strengthened more specifically in the later period; construction operability: self-drilling anchor rods have the advantage of one-time drilling and anchoring in soft rock, saving operation time and reducing disturbance to the surrounding rock. It can not only inhibit early bottom arch displacement in time, but also provide greater support intensity when deep deformation appears later.

[0046] In summary, the present application proposes a three-region partitioned support process of "shield tail immediate support area, support shoe rear support reinforcement area, and bottom arch anchor support closed control area", as well as the core idea of time and space coordination and dynamic adjustment; the tunnel support is divided into different regions and time periods, and the most suitable support strategy is implemented according to the surrounding rock characteristics, exposure time, and construction conditions; the support process is coordinated with the TBM tunneling process to minimize construction interference and downtime, and improve tunneling efficiency; through real-time monitoring and anchor (rod) prestress regulation, the support stiffness is dynamically matched with the development of the surrounding rock deformation to avoid over-supporting or under-supporting. This comprehensive method can effectively prevent the surrounding rock from producing excessive relaxation or large deformation in the early stage of excavation, and significantly improve the construction safety and efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1Open type TBM over slow soft rock strata partition segmental collaborative support construction schematic diagram for the present application;

[0048] Figure 2 Anchor partition segmental collaborative support section view;

[0049] Figure 3 Partition segmental collaborative support construction process flow chart;

[0050] In the figure: 1 - cutter head, 2 - shield, 3 - shield tail, 4 - TBM emergency spray mixing system, 5 - support shoe, 6 - drilling machine, 7 - excavation contour line, 8 - TBM machine body, 9 - tunnel axis, 10 - shield tail immediate support area, 11 - support shoe rear reinforcement support area, 12 - bottom arch anchor support closed control area, 13 - short anchor rod construction area, 14 - long anchor rod construction area, 15 - top arch prestressed anchor cable, 16 - side wall prestressed anchor cable, 17 - short anchor rod, 18 - long anchor rod. DETAILED DESCRIPTION

[0051] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0052] The open type TBM over slow soft rock strata partition segmental collaborative support construction method of the present application comprises the following steps:

[0053] 1) Partition segmental support

[0054] (1) Shield tail immediate support area (within 5m range from the shield tail to the rear of the shield tail)

[0055] Steel arch assembly: within the range of 0.5~0.8m behind the shield tail 3, use TBM propulsion interval, use TBM arch assembly device to quickly assemble steel arch, steel arch height H1, steel arch bay spacing D1.

[0056] Side and top arch injection of polypropylene coarse fiber concrete: complete the injection of concrete in the range of 240°~270° of the side and top arch within the range of 1.0~3.0m of the exposed shield 2, considering that the steel arch needs at least 2cm of protective layer thickness, the thickness of the injected concrete H2≥H1+2cm, H1, H2 are in cm.

[0057] Top 100°~120° prestressed anchor cable: arrange the top arch prestressed anchor cable along the range of 100°~120° of the top of the tunnel within the range of 3.0~5.0m of the exposed shield 2, interval 1.0~2.0m, row spacing D2=D1~2D1; the anchor cable diameter can generally be Φ21.8mm, the anchor cable length Ls ≥L p1 +2,L s is the anchor length, L p1 is the edge arch surrounding rock relaxation zone depth, unit is m. The relaxation zone depth is determined by theoretical analysis or acoustic testing; when the TBM on-board drill is insufficient, a handheld pneumatic anchor cable drill can be used to drill holes, and the top arch anchor pre-tension value P s1 (Φ21.8mm anchor cable, P s1 250kN can be taken).

[0058] The prestressed anchor length is calculated according to formula ① and reviewed according to formula ② in 《Water Conservancy Prestressed Anchoring Design Specification》SL / T 212-2020: ①L m1 =1.1×K×P s1 / π×D×C, ②L m1 =1.1×K×P s1 / π×d×C1. In the formula, L m1 is the anchoring length, K is the safety factor of the anchoring length, D is the anchor hole diameter, C is the bonding strength of the cementing material and the hole wall, C1 is the gripping force of the cementing material and the prestressed steel strand, and d is the diameter of the prestressed steel strand.

[0059] The prestressed anchor is a active support means, which quickly compensates the stress of the gently inclined layered rock mass of the top arch, forms a "combined arch" effect, and inhibits the early deformation of the surrounding rock of the top arch. The shotcrete and steel arch are large-stiffness passive supports, which provide higher support resistance and prevent further development of the deformation of the surrounding rock.

[0060] (2) Reinforced support area behind the support shoe (within 3m range behind the support shoe)

[0061] The prestressed anchor of the remaining two side walls 120°-140°: The prestressed anchor of the two side walls is made on the working platform behind the support shoe, and the anchor diameter, length, and row spacing are the same as those of the top arch prestressed anchor; the prestressed anchor pre-tension value of the side wall is P s2 .

[0062] Shotcrete of the bottom arch: Shotcrete is made in the range of 90°-120° of the bottom arch behind the support shoe, and the shotcrete thickness H2 is the same as that of the top arch, and the shotcrete is closed into a ring.

[0063] (3) Bottom arch anchor closed control area (within 3-35m range behind the support shoe)

[0064] The space under the TBM equipment is narrow, and it is difficult to install anchor rods (cables); for the anchor rods of the bottom system, the strategy of "combination of long and short anchor rods and implementation at appropriate time" is adopted. The deformation rate and the development depth of the relaxation zone of the bottom arch are smaller than those of the side and top arches due to the pressure of the TBM machine head. Therefore, the installation of the anchor rods of the bottom arch is slightly delayed, and the anchor rods are installed in time after the space under the TBM equipment is available.

[0065] The self-drilling prestressed anchor rods are used in the range of 120° of the bottom arch, and the long and short anchor rods are arranged in a ring shape with a certain interval. The diameter of the anchor rods is generally Φ25~Φ38; the length of the short anchor rods is L g1 , L g1 ≈R, R is the radius of the TBM excavation, which facilitates early implementation and early function, and the pre-tensioning force of the short anchor rods is P g1 ; the length of the long anchor rods is L g2 , L g2 ≥L p2 +2, L p2 is the depth of the relaxation zone of the bottom arch, which is determined by theoretical analysis or acoustic testing; the implementation time of the long anchor rods is determined according to the deformation rate of the surrounding rock. For example, if the deformation rate of the bottom arch is large (the deformation rate is greater than 5 mm / d), there is a risk of deformation of the bottom arch, and the long anchor rods should be installed immediately; if the deformation of the bottom arch is controllable (the deformation rate is less than 5 mm / d), the long anchor rods can be installed in the range of 30~35 m (L2 zone) behind the support shoe of the TBM; the pre-tensioning force of the long anchor rods is P g2 , as shown in Figure 1 The bottom arch anchor support closed control zone 12 is arranged in the range of 3~35 m behind the support shoe, and the short anchor rod installation zone 13 and the long anchor rod installation zone 14 are arranged therein. The TBM machine body 8 is arranged along the tunnel axis 9, the TBM is arranged within the excavation contour line 7, and the drilling is performed by the drilling machine 6.

[0066] 2) Time and space coordinated control method

[0067] Process connection: the steel arch installation is synchronized with the TBM tunneling to advance, and the installation is completed in the range of 0.5~0.8 m behind the shield tail 3; the polypropylene coarse fiber concrete of the side and top arches is immediately installed after the steel arch is assembled, and the TBM emergency spraying system is adopted; the top anchor cable is installed after the sprayed concrete reaches 80% of the design strength; the pre-stressed anchor cables of the side walls and the sprayed concrete of the bottom arch are installed behind the support shoe when the support shoe moves to the next cycle position; the short anchor rods of the bottom arch are installed after 1~2 tunneling cycles of the anchor cables of the side walls are completed, and the long anchor rods are installed at appropriate time according to the deformation rate of the bottom arch.

[0068] Dynamic adjustment of prestress: according to the monitoring data of the surrounding rock (such as the convergence deformation and the anchor cable axial force), the pre-tensioning force value of the anchor cables and anchor rods is adjusted by the intelligent tensioning equipment to ensure that the support stiffness matches the stratum deformation.

[0069] Considering that the timing of the installation of the side wall anchor cables is relatively delayed, compared with the top arch anchor cables, the side walls have undergone incremental deformation before the anchor cables are installed. In order to ensure that the support stiffness in the section matches the stratum deformation, the pre-tensioning force of the side wall anchor cables is appropriately increased according to the incremental deformation. The pre-tensioning force applied to the side wall anchor cables is P s2 = P s1 +α1×E s ×A s ×δ1 / L f1 , where P s1 is the pre-tensioning force applied to the top arch anchor cable, E s is the elastic modulus of the anchor cable strand, A s is the cross-sectional area of ​​the anchor cable strand, δ1 is the incremental deformation of the side wall surrounding rock during the time difference between the construction of the top arch and the side wall anchor cables, and L f1 is the free section length of the prestressed steel strand, and α1 is the stiffness matching coefficient introduced to take into account the possible incomplete coordination between the deformation of the anchor cable and the surrounding rock, with a value of 0.5~1.0.

[0070] The bottom anchor rods are of different lengths, and the long anchor rods are installed later, so the pre-tensioning force value needs to be adjusted dynamically: P g2 =P g1 +α1×E g ×A g ×δ2 / L f2 , where P g1 is the pre-tensioning force applied to the short anchor rod, E g is the elastic modulus of the anchor rod, A g is the cross-sectional area of ​​the anchor, δ2 is the incremental deformation of the surrounding rock during the time difference between the long and short anchors, and L f2 is the free section length of the prestressed anchor rod, α1 is the stiffness matching coefficient, and its value ranges from 0.5 to 1.0.

[0071] Example:

[0072] The following is an example of a deep, long water diversion tunnel using an open TBM through soft rock formations, with accompanying drawings and an actual construction process. In this example, an open TBM was used for the tunnel, with a cutterhead diameter of 9.83m. Other projects can adjust the cutterhead diameter based on actual conditions.

[0073] The method for implementing zoning and segmented collaborative support in gently dipping soft rock formations using an open TBM in this embodiment includes the following steps:

[0074] S1: Shield tail immediate support area (from the shield tail to the 5m range behind the shield tail)

[0075] like Figure 1As shown, the shield tail immediate support area 10 is within the range of 0.5-0.8 m behind the shield tail 3, and the H175 steel arch is assembled and installed by using the TBM arch assembly device intermittently during the TBM advancing, with a distance of 55 cm and a longitudinal connection of half-section I20 steel to enhance the stability and load-bearing capacity of the support structure.

[0076] When the surrounding rock gradually exposes the range of 1.0-3.0 m of the shield 2, the open TBM emergency spraying system is started, and the TBM emergency spraying system 4 immediately sprays polypropylene fiber concrete within the range of 240° of the side and top arch, with a thickness of 20 cm (a protective layer thickness of 2.5 cm), to ensure the thickness and quality of the sprayed concrete.

[0077] Within the range of 5 m of the shield tail (the sprayed early strength concrete reaches 80% of the design strength), 6 top arch prestressed anchor cables 15 are arranged along the top of the tunnel within the range of 110°, the anchor cable body uses 1x19S steel strand with a nominal diameter of 21.8 mm, the tensile strength is 1860 MPa, the design uplift capacity is 350 kN, and the top arch anchor cable pre-tension force P s1 is taken as 250 kN. The anchor cable anchoring segment length is calculated according to formula ① and reviewed according to formula ②: ① L m1 =1.1×K×P s1 / π×D×C, ② L m1 =1.1×K×P s1 / π×d×C1. K is taken as 2.2, D is 42 mm, the anchoring segment uses resin anchoring agent, C is taken as 1.6 MPa according to the recommended value in the specification, C1 is taken as 12.0 MPa, and d is taken as 21.8 mm. Through calculation, the anchoring segment length L m1 is 2.865 m, the anchoring segment length L m1 is taken as 3.0 m for safety consideration. The circumferential spacing of the prestressed anchor cable is 1.5 m, and the row spacing is 1.1 m; the soft rock tunnel section is measured by drilling and sonic wave to obtain the depth L p1 of the side and top arch surrounding rock relaxation area, which is about 7.5 m, the anchor cable length L s ≥L p1 +2=9.5 m, and L s is taken as 10.0 m.

[0078] S2: Reinforced support area behind the support shoe (within the range of 3 m behind the support shoe to the support shoe)

[0079] The reinforced support area 11 behind the support shoe is arranged with 8 side wall prestressed anchor cables 16 within the range of 130° of the two side walls 3 m behind the support shoe 5, the anchor cable diameter is Φ21.8 mm, the circumferential spacing is 1.5 m, and the row spacing is 1.1 m; considering the incremental deformation of the side wall surrounding rock within the time difference of the top arch and side wall anchor cable construction, which is about 0.5-1.0 cm, to ensure that the support stiffness in the section matches the stratum deformation, the side wall anchor cable pre-tension force P s2= P s1+α1×E s×A s×δ1 / Lf1 wherein P s1 has a value of 250 kN, Es is 195 GPa, As is 313 mm 2 , δ1 takes a value of 10 mm, L f1 is 7000 mm, and α1 takes a value of 0.5. Through calculation, the value of the pre-tension of the sidewall anchor cable Ps2 is 290 kN.

[0080] The polypropylene coarse fiber concrete is sprayed in a range of 120° of the floor arch behind the support shoe 5, and the sprayed concrete is closed into a ring with a thickness of 20 cm.

[0081] S3: Floor arch anchor closed control area (range of 3-35 m behind the support shoe)

[0082] The floor arch anchor closed control area 12 adopts a "long and short combination" scheme for the floor system anchor rod, and the anchor rod is a Φ25 self-drilling prestressed anchor rod, and the long anchor rod 18 and the short anchor rod 17 are arranged in a ring shape with an interval; the length L g1 of the short anchor rod is 4.5 m, and the pre-tension is 90 kN, which is completed after 1-2 excavation cycles of the lagging sidewall anchor cable behind the support shoe 5, so as to achieve the effect of early implementation and early function; the long anchor rod is completed according to the deformation rate of the floor arch, and in this embodiment, the deformation rate of the floor arch of the soft rock tunnel section is controllable, about 0.5-1.0 mm / d, the long anchor rod 18 is implemented in the L2 area (30-35 m behind the support shoe) of the TBM, the depth L p2 of the floor arch surrounding rock relaxation area is about 6.0 m, and the length L g2 of the long anchor rod is 8.0 m; the incremental deformation of the surrounding rock within the time difference of the long and short anchor rods is generally 0.5 cm-1.0 cm, and the pre-tension of the long anchor rod is 120 kN.

[0083] The partitioned and segmented collaborative support construction method greatly reduces process conflicts and downtime through space-time dislocation construction, and improves the daily average tunneling efficiency by 25%-30%. At the same time, combined with dislocation arrangement and dynamic adjustment (the pre-tension of the anchor cable and the anchor rod is dynamically modified according to the stratum deformation), the mechanical behavior of the gently inclined soft rock is more matched, the "dynamic reinforcement" is realized, and the collaborative bearing capacity of the support is improved.

[0084] The above embodiment is only an example of the technical solution of the present application. The present application is not limited to the content described in the above embodiment, but is limited to the scope defined by the claims. Any modification or supplement or equivalent replacement made by the skilled in the art on the basis of the above embodiment is within the scope claimed by the claims of the present application.

Claims

1. An open TBM over-steeply inclined soft rock stratum zoned and segmented coordinated support construction method, characterized in that: The method comprises the following steps: S1: shield tail instant support S101: in the range of 0.5-0.8 m behind the shield tail, the type steel arch is quickly assembled by using the TBM arch assembly device in the intermittent TBM propulsion, the height of the type steel arch is H1, and the type steel arch distance is D1; S102: the concrete is sprayed in the range of 240-270° of the side top arch in the range of 1.0-3.0 m of the exposed shield, the thickness of the sprayed concrete is H2, and H2 is greater than or equal to H1+2 cm; S103: In the range of 3.0-5.0 m of exposed shield 3.0-5.0 m, along the tunnel roof 100°-120°, the top arch prestressed anchor cable is constructed, and the top arch anchor cable pre-tensioning force is P s1 ; S2: support behind the support shoe S201: prestressed anchor cables are arranged on the side walls of the working platform at the rear of the support shoe, and the prestressed anchor cables are arranged within a range of 120°-140°; the prestressed anchor cables have a prestressed tension value of P s2 ; S202: the concrete is sprayed in the range of 90-120° of the bottom arch behind the support shoe, and the thickness of the sprayed concrete is H2; S3: bottom arch anchor support closed regulation and control When the construction space is provided behind the TBM machine head, the long anchor and the short anchor are arranged in the range of 120° of the bottom arch by using the self-drilling prestressed anchor; In the step S1, the type steel arch is assembled and synchronously propelled with the TBM tunneling, and is completed in the range of 0.5-0.8 m behind the shield tail; the side top arch concrete spraying is immediately performed after the type steel arch assembly, and is performed by using the TBM emergency concrete spraying system; the top arch prestressed anchor is performed after the side top arch concrete spraying reaches the design strength of 80 %; The interval of the pre-stressed anchor cable is 1.0-2.0 m, the row distance D2=D1-2D1, D1 is the interval of the steel arch frame, the anchor cable length L s ≥L p1 +2, L s is the anchor cable length, L p1 is the depth of the side top arch surrounding rock relaxation zone, and the unit is m The anchoring segment length of the prestressed anchor is calculated according to the following formula: L m1 = 1.1 x K x P s1 / π x D x C; In the formula, L m1 is the anchoring segment length, K is the safety factor of the anchoring segment length, P s1 is the top arch anchor cable pre-tensioning force application value, D is the anchor cable diameter, and C is the bonding strength of the cementing material and the hole wall. The anchoring segment length of the prestressed anchor is rechecked according to the following formula: L m1 = 1.1 x K x P s1 / π x d x C1; In the formula, L m1 is the anchoring segment length, K is the safety factor of the anchoring segment length, P s1 is the top arch anchor cable pre-tension force application value, d is the diameter of the pre-stressed steel strand, C1 is the gripping force of the cementing material and the pre-stressed steel strand; In the step S2, the side wall prestressed anchor and the bottom arch sprayed concrete are performed behind the support shoe when the support shoe moves to the next cycle position; The step S201, the side wall anchor cable pre-tension force applied value is P s2 According to the following formula: P s2 = P s1 + α1×E s × A s × δ1 / L f1 ; In the formula, P s1 is the top arch anchor cable pretension value, α1 is the stiffness matching coefficient, E s is the elastic modulus of the anchor cable steel strand, A s is the cross-sectional area of the anchor cable steel strand, δ1 is the incremental deformation of the side wall surrounding rock within the time difference of the top arch and side wall anchor cable construction, L f1 is the free length of the prestressed steel strand.

2. The method of claim 1, wherein: The length of the long anchor rod is L g2 , L g2 ≥ L p2 + 2, and L p2 is the depth of the surrounding rock relaxation zone of the bottom arch, and the units are meters.

3. The method of claim 2, wherein: In the step S3, the pre-tension value of the long and short anchors is adjusted according to the following formula: P g2 = P g1 + α1×E g × A g × δ2 / L f2 ; In the formula, P g1 is the pre-tension value of the short anchor rod, P g2 is the pre-tension value of the long anchor rod, E g is the elastic modulus of the anchor rod, A g is the cross-sectional area of the anchor rod, δ2 is the incremental deformation of the surrounding rock within the time difference of the short and long anchor rods, L f2 is the length of the free section of the pre-stressed anchor rod, and α1 is the stiffness matching coefficient.

4. The method of claim 3, wherein: In the step S3, the short anchor is completed 1-2 tunneling cycles behind the side wall stress anchor.

5. The method of claim 4, wherein: In the step S3, if the bottom arch deformation rate exceeds 5 mm / d, the long anchor is immediately implemented when there is a risk of bottom arch bulging deformation; if the bottom arch deformation rate is less than 5 mm / d, the long anchor can be implemented 30-35 m behind the support shoe of the TBM.

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