Design method and construction method of transverse counter-pulling system of triangular area of non-centering multi-arch tunnel

Abstract

The present application relates to a kind of no guide connected arch tunnel triangular area transverse counter-pulling system design method and its construction method, belong to connected arch tunnel design and construction technical field.The design method includes establishing no guide connected arch tunnel calculation model, the initial support arc length corresponding to the distribution range of plastic zone of no guide connected arch tunnel upper triangular area surrounding rock after construction is calculated;Surrounding rock in the distribution range of plastic zone of no guide connected arch tunnel upper triangular area is applied to average even cloth load, find the average even cloth load corresponding to the minimum value of plastic zone area;The total pre-tension required for the transverse counter-pulling system of no guide connected arch tunnel triangular area is calculated;The counter-pulling anchor rod design of the transverse counter-pulling system of no guide connected arch tunnel triangular area.The present application can play the role of reinforcement to the surrounding rock of connected arch tunnel upper triangular area, and can make the surrounding rock of triangular area in strong constraint state to improve its stability and ultimate bearing capacity, can effectively control the development of surrounding rock deformation and plastic zone of no guide connected arch tunnel upper triangular area, it has important significance to guarantee tunnel structure safety.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of multi-arch tunnel design and construction, and particularly relates to a design method and construction method of a transverse counter-pulling system for a non-center-pilot multi-arch tunnel. BACKGROUND

[0002] The non-center-pilot multi-arch tunnel has strong terrain adaptability in highway tunnel construction due to its unique structure, can effectively solve the problem of tunnel connection at both ends in highway construction, avoid intersection division, and improve space utilization. In addition, since the non-center-pilot multi-arch tunnel does not need to excavate a center pilot tunnel and construct a center partition wall, the construction process is simplified, the construction cost is reduced, and water leakage of the center partition wall is prevented. After the support structure is completely constructed, the stress of the non-center-pilot multi-arch tunnel structure is more reasonable compared to that of the center-pilot multi-arch tunnel structure, so the non-center-pilot multi-arch tunnel becomes the optimal solution under many limited conditions.

[0003] However, the treatment of the triangular area above the leading tunnel and the following tunnel of the non-center-pilot multi-arch tunnel has always been a difficult problem. As the area that is disturbed the most by construction, the triangular area is also a blind area of reinforcement. The surrounding rock of the triangular area is prone to collapse, deformation, and plastic failure, which increases the additional stress on the support structure, and thus easily causes the secondary lining of the leading tunnel to crack and the primary support of the following tunnel to collapse. Therefore, it is of great engineering significance to propose an effective reinforcement technology for the triangular area of the non-center-pilot multi-arch tunnel to control the development of the deformation and plastic zone of the surrounding rock of the triangular area. SUMMARY

[0004] In order to solve the problems of the prior art, the present application provides a design method and construction method of a transverse counter-pulling system for a non-center-pilot multi-arch tunnel. The method uses counter-pulling anchor rods to reinforce the plastic surrounding rock of the triangular area, improves the stability and ultimate bearing capacity of the triangular area through reinforcement and strong constraint, effectively controls the development of the deformation and plastic zone of the surrounding rock of the triangular area, and ensures the safety of the tunnel structure.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:

[0006] The design method of the transverse counter-pulling system for the non-center-pilot multi-arch tunnel comprises the following steps:

[0007] Step (1), according to the tunnel lining section design drawing, a non-center-pilot multi-arch tunnel stratum-structure method numerical calculation model is established, and the initial support arc length Lp corresponding to the distribution range of the plastic zone of the triangular area above the non-center-pilot multi-arch tunnel after construction is calculated (such as Figure 2 shown in Figure 9 (a) the red part of the triangular area above the non-center-pilot multi-arch tunnel is the plastic zone);

[0008] Step (2), in the step (1) to establish the calculation model, the uniform distributed load P is applied to the surrounding rock in the plastic zone distribution range (i.e. Lp) of the triangular area above the tunnel without middle support and arch tunnel, and the value of P is adjusted to try the model, so as to find the minimum value A of the plastic zone area MIN The corresponding uniform distributed load is recorded as the optimal solution P of the uniform distributed load m ;

[0009] Step (3), using the initial support arc length Lp obtained in step (1) and the optimal solution P of the uniform distributed load obtained in step (2) m , the total pre-tension P required by the transverse counter-pulling system of the triangular area of the tunnel without middle support and arch tunnel is calculated total ;

[0010] Step (4), the design of the counter-pulling anchor rod of the transverse counter-pulling system of the triangular area of the tunnel without middle support and arch tunnel, including the determination of the anchor rod arrangement mode, the anchor rod quantity, the anchor rod length and the anchor rod pre-tension.

[0011] Further, preferably, in step (2), the optimal solution P m is determined as follows:

[0012] Adjust the value of P to try the model, and the uniform distributed load of the model is P i , and the corresponding plastic zone area of the triangular area surrounding rock is A i , i=0,1,2,3,…,M, and M is the total number of trial;

[0013] The variation law of the plastic zone area A with the load P is fitted by formula (1):

[0014]

[0015] In formula (1), A amp is the initial amplitude, A0 is the equilibrium point, a is the attenuation factor, ω is the angular frequency, is the phase, and the above are fitting parameters;

[0016] Using the fitted formula (1), the minimum value A MIN of the plastic zone area is found, and the corresponding uniform distributed load is recorded as the optimal solution P of the uniform distributed load m .

[0017] Further, preferably, in step (2), M should be not less than 6.

[0018] Further, preferably, in step (3), the total pre-tension P total required by the transverse counter-pulling system of the triangular area of the tunnel without middle support and arch tunnel is calculated as follows:

[0019] P total =Pm Lp (2)

[0020] In formula (2), P m is the uniform load optimal solution, kN / m; Lp is the initial support arc length, m.

[0021] Further, preferably, in step (4), the anchor rod arrangement is in a quincunx arrangement;

[0022] The anchor rod pre-tension is calculated by formula (2):

[0023] P s = P total / N (3)

[0024] In formula (3), P s is the pre-tension of a single anchor rod; N is the number of anchor rods arranged per meter in the longitudinal direction of the tunnel in the triangular area of the continuous arch tunnel without a central guide.

[0025] The application also provides a construction method for a transverse anchor system in the triangular area of a continuous arch tunnel without a central guide, which uses the transverse anchor system design method for the triangular area of a continuous arch tunnel without a central guide.

[0026] S1, first excavate the upper steps of the pilot tunnel, with an excavation height greater than 2.0 m;

[0027] S2, drill the anchor rods of the upper step system of the pilot tunnel;

[0028] S3, construct the steel frame of the upper step of the pilot tunnel, hang the steel mesh, and weld the longitudinal connecting ribs; install the channel steel at the corresponding position of the anchor rod arrangement, and reserve a round hole at the corresponding position of the anchor rod passing through the channel steel; clamp the two ends of the channel steel on the flanges of the adjacent two steel frames on the side close to the surrounding rock, and weld the channel steel web and the contact parts of the flanges of the adjacent two steel frames firmly;

[0029] S4, mark the drilling position, and use a pneumatic drill to drill from the right side of the upper step of the pilot tunnel to the side of the following tunnel horizontally; the angle and depth of the drilling need to be strictly controlled to ensure that the anchor rod can be accurately inserted and can extend out of the design initial support surface of the following tunnel by not less than 30 cm;

[0030] S5, after the drilling is completed, clean the hole;

[0031] S6, insert the anchor rod into the hole in the surrounding rock through the round hole of the channel steel, with both ends exposed by 29-31 cm from the design initial support surface; the insertion length of the anchor rod needs to meet the design requirements and cannot be shorter than 95% of the design length;

[0032] S7, install the grout stopper and anchor pad on the anchor rod;

[0033] S8, the slurry is injected into the hole by a grouting machine until the slurry overflows the hole;

[0034] S9, after the grouting is completed, the grouting plug is tightly pressed and the nut is installed at the end of the tension anchor rod, the initial stress is applied by a torque wrench until the anchor pad is tightly attached to the channel steel;

[0035] S10, primary tensioning of the anchor rod: after the slurry is solidified, the nut is tightened by a torque wrench to tension the anchor rod until the tensioning force reaches 30% of the design required anchoring force;

[0036] S11, the primary hole initial support and the secondary lining are completed according to the designed excavation and support sequence;

[0037] S12, the same steps of S1-S11 are used to process the subsequent hole;

[0038] S13, the anchor rod of the subsequent hole is tensioned to ensure that the anchor rod reaches the design required anchoring force, and then the excess length of the anchor rod is cut off;

[0039] S14, subsequent process construction: after the transverse tensioning system of the triangular area of the no-center continuous arch tunnel is constructed according to the above steps, the excavation and support procedures of the lower steps of the subsequent hole can be sequentially performed.

[0040] In the present application, the stratum-structure method numerical calculation model of the no-center continuous arch tunnel is established as the basic method and model for tunnel numerical simulation, and the prior art is not specially limited in the present application.

[0041] In step (2) of the present application, when i=0, P i =0, A i =5.3754, which is calculated from step (1).

[0042] In the present application, the length and the number of anchor rods are determined according to the specific arrangement mode according to the tunnel lining section design drawing.

[0043] Compared with the prior art, the present application has the following beneficial effects:

[0044] The present application provides a kind of no guide continuous arch tunnel triangular area transverse counter-pulling system design method and its construction method.The prior art has not yet proposed effective design method for counter-pulling anchor rod used for reinforcing triangular area surrounding rock above continuous arch tunnel.For this problem, the design method of the present application can quickly calculate the pre-tension of counter-pulling anchor rod, thereby providing a theoretical basis for the rational design of anchor rod length, anchor rod quantity and arrangement. After the transverse counter-pulling system of the present application is implemented on site, it can effectively control the deformation of triangular area surrounding rock above continuous arch tunnel and the development of plastic zone. For example, in the example of this paper, 17 counter-pulling anchor rods with pre-tension of 143 kN arranged in each meter of triangular area surrounding rock can reduce the plastic zone area to 0, thereby significantly improving the stability and safety of the tunnel and supporting structure. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 The design of the transverse counter-pulling system of the present application for no guide continuous arch tunnel triangular area and the construction method flowchart;

[0046] Figure 2 The schematic diagram of the present application for calculating model water level load application;

[0047] Figure 3 The schematic diagram of the present application for mechanical reinforcement principle of no guide continuous arch tunnel triangular area;

[0048] Figure 4 The schematic diagram of the present application for the change rule of plastic zone area with water level load shown by fitting function;

[0049] Figure 5 The schematic diagram of the present application for no guide continuous arch tunnel construction process;

[0050] Figure 6 The anchor rod layout diagram of the transverse counter-pulling system of the present application for no guide continuous arch tunnel triangular area;

[0051] Figure 7 The anchor rod layout diagram of the transverse counter-pulling system of the present application for no guide continuous arch tunnel triangular area;

[0052] Figure 6 And Figure 7 In the above, 1 - counter-pulling anchor rod (the exposed part is processed into a screw thread, the processing length is 300 mm), 2 - nut, 3 - anchor pad, 4 - non-woven fabric wrapping protection, 5 - one-time drilling end position of anchor rod, 6 - longitudinal connecting piece of channel steel, 7 - drilling, 8 - anchor rod embedded part of surrounding rock, 9 - anchor agent slurry, 10 - surrounding rock, 11 - anchor end of pilot hole, 12 - triangular area surrounding rock, 13 - anchor end of subsequent hole, 14 - steel frame;

[0053] Figure 8 The stratum-structure method calculation model of no guide continuous arch tunnel in the application example;

[0054] Figure 9 The plastic zone distribution calculated for different uniformly distributed loads P in the application example; the red area in the figure is the plastic zone;

[0055] Figure 10 The fitting results of the plastic zone area calculated for different uniformly distributed loads in the application example; DETAILED DESCRIPTION

[0056] The application will be further described in detail below with reference to examples.

[0057] Those skilled in the art will understand that the following examples are only for illustration of the application and should not be regarded as limiting the scope of the application. If a specific technique or condition is not specified in the examples, it is performed according to the technique or condition described in the literature in the art or according to the product manual. If the manufacturer of the material or equipment is not specified, it is a conventional product that can be obtained by purchase.

[0058] Example 1

[0059] The design method of the transverse counter-pulling system of the triangular area of the non-centering multi-arch tunnel comprises the following steps:

[0060] Step (1), a stratum-structure method numerical calculation model of the non-centering multi-arch tunnel is established according to the tunnel lining section design drawing, and the initial support arc length Lp corresponding to the plastic zone distribution range of the triangular area above the non-centering multi-arch tunnel after the construction is completed is calculated;

[0061] Step (2), in the calculation model established in step (1), a uniformly distributed load P is applied to the surrounding rock in the plastic zone distribution range of the triangular area above the non-centering multi-arch tunnel, and the value of P is adjusted to perform a trial calculation on the model, so as to find the minimum value A of the plastic zone area MIN The corresponding uniformly distributed load is denoted as the uniformly distributed load optimal solution P m ;

[0062] Step (3), the initial support arc length Lp obtained in step (1) and the uniformly distributed load optimal solution P m obtained in step (2) are used to calculate the total pre-tension P required by the transverse counter-pulling system of the triangular area of the non-centering multi-arch tunnel total ;

[0063] Step (4), the counter-pulling anchor rod of the transverse counter-pulling system of the triangular area of the non-centering multi-arch tunnel is designed, including the determination of the anchor rod arrangement mode, the anchor rod quantity, the anchor rod length and the anchor rod pre-tension.

[0064] Example 2

[0065] The design method of the transverse counter-pulling system of the triangular area of the non-centering multi-arch tunnel comprises the following steps:

[0066] Step (1), according to the tunnel lining section design drawing, a numerical calculation model of the ground-structure method of the no-center continuous arch tunnel is established, and the initial support arc length Lp corresponding to the distribution range of the plastic zone of the surrounding rock in the triangular area above the no-center continuous arch tunnel after construction is calculated;

[0067] Step (2), in the calculation model established in step (1), a uniform distributed load P is applied to the surrounding rock in the plastic zone distribution range of the triangular area above the no-center continuous arch tunnel, and the value of P is adjusted to try the model, so as to find the minimum value A of the plastic zone area MIN The corresponding uniform distributed load is recorded as the optimal solution P of the uniform distributed load m ;

[0068] Step (3), using the initial support arc length Lp obtained in step (1) and the optimal solution P of the uniform distributed load obtained in step (2) m , the total pre-tension P required by the transverse counter-pulling system of the triangular area of the no-center continuous arch tunnel is calculated total ;

[0069] Step (4), the design of the counter-pulling anchor rod of the transverse counter-pulling system of the triangular area of the no-center continuous arch tunnel, including the determination of the anchor rod arrangement mode, the anchor rod quantity, the anchor rod length and the anchor rod pre-tension.

[0070] In step (2), the optimal solution P m is determined as follows:

[0071] Adjust the value of P to try the model, and the uniform distributed load of the model is P i , and the plastic zone area of the triangular area is A i , i=0,1,2,3,…,M, and M is the total number of trial times;

[0072] The change rule of the plastic zone area A with the load P is fitted by formula (1):

[0073]

[0074] In formula (1), A amp is the initial amplitude, A0 is the equilibrium point, a is the attenuation factor, ω is the angular frequency, is the phase, and the above are fitting parameters;

[0075] Using the fitted formula (1), the minimum value A MIN of the plastic zone area is found, and the corresponding uniform distributed load is recorded as the optimal solution P m of the uniform distributed load.

[0076] In step (2), M should be not less than 6.

[0077] The total pre-tension P required by the transverse counter-pulling system of the no-centering continuous-arch tunnel triangular area in step (3) total The calculation method is as follows:

[0078] P total = P m · Lp (2)

[0079] In formula (2), P m is the optimal solution of the horizontal distribution load, kN / m; and Lp is the initial support arc length, m.

[0080] In step (4), the anchor rod arrangement mode adopts the quincunx arrangement;

[0081] The anchor rod pre-tension is calculated by formula (2):

[0082] P s = P total / N (3)

[0083] In formula (3), P s is the pre-tension of a single counter-pulling anchor rod; and N is the number of counter-pulling anchor rods per meter along the longitudinal direction of the tunnel.

[0084] Embodiment 3

[0085] A construction method of a transverse counter-pulling system of a no-centering continuous-arch tunnel triangular area, which adopts the transverse counter-pulling system of a no-centering continuous-arch tunnel triangular area designed by the design method of the transverse counter-pulling system of a no-centering continuous-arch tunnel triangular area in the embodiment 1 or the embodiment 2, comprises the following steps:

[0086] S1, first excavate the upper step of the pilot hole, and the excavation height is greater than 2.0 m;

[0087] S2, drill the anchor rod of the upper step system of the pilot hole;

[0088] S3, construct the steel frame of the upper step of the pilot hole, hang the steel mesh, and weld the longitudinal connecting rib; install the channel steel at the corresponding position of the counter-pulling anchor rod, and reserve a round hole at the corresponding position of the anchor rod passing through the channel steel; clamp the two ends of the channel steel on the flanges of the adjacent two steel frames close to the surrounding rock, and weld the channel steel web and the contact parts of the flanges of the adjacent two steel frames firmly;

[0089] S4, mark the drilling position, and drill from the right side of the upper step of the pilot hole to the side of the following hole horizontally, and the angle and depth of the drilling need to be strictly controlled to ensure that the anchor rod can be accurately inserted and can extend out of the design initial support surface of the following hole by not less than 30 cm;

[0090] S5, after the drilling is completed, clean the hole;

[0091] S6, insert the anchor rod into the surrounding rock hole through the circular hole of the channel steel, with both ends exposed 29-31 cm from the designed primary support surface, the insertion length of the anchor rod needs to meet the design requirements and should not be shorter than 95% of the design length;

[0092] S7, install the grout stopper and anchor pad on the anchor rod;

[0093] S8, use the grouting machine to inject grout into the hole until the grout overflows the hole;

[0094] S9, after grouting is completed, tighten the grout stopper and install the nut on the end of the anchor rod, apply the initial stress using the torque wrench until the anchor pad is tightly attached to the channel steel;

[0095] S10, primary tensioning of the anchor rod: after the grout solidifies, tighten the nut using the torque wrench to tension the anchor rod until the tensioning force reaches 30% of the design required anchoring force;

[0096] S11, complete the primary support and secondary lining of the pilot tunnel according to the designed excavation and support sequence;

[0097] S12, use the same steps as S1-S11 to process the subsequent tunnel;

[0098] S13, tension the anchor rod of the subsequent tunnel to ensure that the anchor rod reaches the design required anchoring force, and then cut off the excess length of the anchor rod;

[0099] S14, subsequent process construction: after the transverse counter-pulling system of the triangular area of the non-centering continuous arch tunnel is constructed according to the above steps, the subsequent procedures (excavation and support procedures of the lower steps of the subsequent tunnel) can be sequentially performed.

[0100] Example 4

[0101] A design method of a transverse counter-pulling system of a triangular area of a non-centering continuous arch tunnel, comprising the following steps:

[0102] I. Determination of the pre-tension of the transverse counter-pulling system of the triangular area of the non-centering continuous arch tunnel:

[0103] Step (1), establish a "stratum-structure" calculation model of the non-centering continuous arch tunnel through the tunnel lining section design drawing, and calculate the primary support arc length Lp corresponding to the distribution range of the plastic zone of the triangular area surrounding rock above the non-centering continuous arch tunnel after construction is completed;

[0104] Step (2), in the calculation model established in step (1), apply an average distributed load P (such as Figure 2 ) to the surrounding rock in the plastic zone distribution range of the triangular area above the non-centering continuous arch tunnel, and adjust the P value to perform trial calculation on the model to find the optimal solution P m , which should make the plastic zone distribution area of the triangular area surrounding rock minimum after the model calculation is completed; m .

[0105] Step (3), calculate the total pre-tension P required for the transverse counter-pulling system of the triangular area of the non-centering multi-arch tunnel total .

[0106] II. Design of the counter-pulling anchor rod of the transverse counter-pulling system of the triangular area of the non-centering multi-arch tunnel

[0107] Step (4), the design of the counter-pulling anchor rod of the transverse counter-pulling system of the triangular area of the non-centering multi-arch tunnel includes the determination of the anchor rod arrangement, the number of anchor rods, the length of the anchor rod, and the pre-tension of the anchor rod.

[0108] In step (2), the optimal solution P m is determined as follows:

[0109] According to the theory of rock mechanics, before the tunnel is excavated, the stress state of a point in the triangular area above the non-centering multi-arch tunnel is as shown in FIG. 1, and under the condition of only considering the self-weight, the forces on the top and bottom surfaces of the micro-element are both σ1= γz, and the force on the side surface of the micro-element is σ3= λγz, where γ is the unit weight of the rock mass, λ is the lateral pressure coefficient, and z is the burial depth. The stress state is as shown in FIG. 1 ①. Figure 3 Figure 3 With the excavation of the tunnel, the lateral constraint of the triangular area surrounding rock gradually disappears, that is, σ3 gradually decreases. According to the Mohr-Coulomb failure criterion, when σ3 decreases to σ 3' , the stress circle is tangent to the shear strength line, and the rock mass fails and loses stability (as shown in FIG. 1 ②). The compressive strength of the rock mass can be calculated by the following formula:

[0110] Figure 3

[0111]

[0112] In the formula, R P is the compressive strength of the rock mass; σ3 is the lateral constraint force; c is the cohesion of the rock mass; and φ is the internal friction angle.

[0113] If the counter-pulling anchor rod is added during the tunnel excavation to apply a horizontal force to the triangular area surrounding rock, σ3 will increase, and the stress state of the rock mass will be below the envelope line and will not fail. However, if the lateral stress applied is too large to become the first principal stress, and the stress circle is tangent to the shear strength line, the rock mass will still fail (as shown in FIG. 1 ③). Figure 3

[0114] Therefore, in order to improve the stability and ultimate bearing capacity of the triangular area surrounding rock above the non-centering multi-arch tunnel, the horizontal uniformly distributed load P should be able to provide sufficient lateral constraint stress, but the lateral constraint stress should not be too large to cause the rock mass to fail.

[0115] Determination of the optimal solution P​​​​​m The method involves finding a horizontally distributed load P that minimizes the area of ​​the plastic zone. This load is the optimal solution P for a horizontally distributed load that satisfies safety and economic conditions. m Since the area of ​​the plastic zone in the triangular surrounding rock above the tunnel without a central guide arch exhibits a pattern of first decreasing and then increasing with the horizontally distributed load P, the model should be tested at least six times by adjusting the value of P, and the calculated area of ​​the plastic zone should fall as close as possible to the optimal solution P of the horizontally distributed load. m The corresponding plastic zone area on both sides, i.e., the calculation results can reflect the change law of the plastic zone area first decreasing and then increasing with the horizontally distributed load.

[0116] Let the uniformly distributed horizontal load be P during the model trial calculation. i (i = 0, 1, 2, 3, ... ≥ 6), the area of ​​the plastic zone of the surrounding rock in the triangular region is A. i (i = 0, 1, 2, 3, ... ≥ 6), the following formula is used to fit the variation of the plastic zone area A with the load P: when i = 0, P i =0, A i =5.3754

[0117]

[0118] In the formula, A amp Let A0 be the initial amplitude, a be the equilibrium point, a be the attenuation factor, and ω be the angular frequency. The above parameters are all fitting parameters, representing the phase.

[0119] This formula can intuitively reflect the change law of the plastic region area A(P) as the independent variable P first decreases rapidly and then increases slowly, with the minimum value of the plastic region area A. MIN The corresponding horizontally distributed load is the optimal solution P for the horizontally distributed load. m (like Figure 4 ).

[0120] In step (3), the total preload P required by the transverse tensioning system in the triangular area of ​​the tunnel without a central guide arch is... total The calculation method is as follows:

[0121] P total =P m ·Lp

[0122] In the formula, P m Lp represents the optimal solution for the horizontally distributed load (kN / m), and Lp is the initial support arc length (m).

[0123] In step (4), the method for determining the anchor bolt arrangement, number of anchor bolts, anchor bolt length, and anchor bolt preload in the transverse tie system of the triangular area of ​​the tunnel without a central guide arch is as follows:

[0124] The anchor rod arrangement adopts a quincunx arrangement; the anchor rod length and the anchor rod quantity are determined according to the specific arrangement mode from tunnel lining section design drawings; the anchor rod pre-tension is calculated by the following formula:

[0125] P s = P total · / N

[0126] In the formula, P s is the pre-tension of a single anchor rod; N is the number of anchor rods arranged per meter along the longitudinal direction of the tunnel in the triangular area of the non-centering continuous arch tunnel.

[0127] A construction method of a transverse anchor system in a triangular area of a non-centering continuous arch tunnel, which is based on the above-mentioned design method of the transverse anchor system in the triangular area of the non-centering continuous arch tunnel, comprises the following steps:

[0128] S1, excavate the upper step of the pilot tunnel: excavate the annular section I of the pilot tunnel, and the excavation height is greater than 2.0 m (for example, 2.5 m). Figure 5 )。

[0129] S2, install the system anchor rod: install the system anchor rod of the upper step of the pilot tunnel according to the conventional construction procedure.

[0130] S3, erect the steel arch: erect the steel frame of the upper step of the pilot tunnel, hang the steel mesh, and weld the longitudinal connecting rib; install the channel steel at the corresponding position (quincunx arrangement) of the anchor rod arrangement, and reserve a round hole at the position where the anchor rod passes through the channel steel; clamp the two ends of the channel steel on the flanges of the two adjacent steel frames close to the surrounding rock, and weld the web of the channel steel to the contact part of the flanges of the two adjacent steel frames.

[0131] S4, drill: mark the drilling position (quincunx arrangement), and drill from the right side of the upper step of the pilot tunnel to the side of the following tunnel horizontally, and the angle and depth of the drilling need to be strictly controlled to ensure that the anchor rod can be accurately inserted and can extend out of the design primary support surface of the following tunnel by not less than 30 cm.

[0132] S5, clean the hole: after the drilling is completed, the rock powder and accumulated water in the hole need to be cleaned to ensure that the hole is clean and free of debris.

[0133] S6, install the anchor rod: insert the anchor rod into the hole in the surrounding rock through the round hole of the channel steel, and the two ends protrude from the design primary support surface by 30 cm (for example, 30 cm and 35 cm). Figure 6 Figure 7 ), and the insertion length of the anchor rod needs to meet the design requirements and cannot be shorter than 95% of the design length.

[0134] S7, install the grout stopper and anchor pad: install the grout stopper and anchor pad on the anchor rod to ensure that the grout does not leak out during grouting and can provide sufficient anchoring force.

[0135] ​S8, Grouting: Grout is injected into the hole using a grouting machine until the grout overflows the hole. The grouting pressure and grouting amount need to be controlled during the grouting process to ensure that the grout can fill the anchor hole and penetrate into the fissure.

[0136] S9, Tighten the grout stopper and install the nut: After grouting is completed, the grout stopper is tightened and the nut is installed on the end of the anchor rod. A torque wrench is used to apply the initial stress until the anchor pad is tightly attached to the channel steel.

[0137] S10, Initial tensioning of anchor rod: After the grout solidifies, the nut is tightened using a torque wrench to tension the anchor rod. The tensioning force should not be too large, and it should reach 30% of the design required anchoring force.

[0138] S11, Construction of the first hole lining: The initial support and secondary lining of the first hole are constructed according to the designed excavation and support sequence (e.g. Figure 5 ).

[0139] S12, The same steps are used for the upper step excavation of the second hole, system anchor installation, drilling, hole cleaning, anchor installation, grout stopper and anchor pad installation, grouting, etc.

[0140] S13, Anchor tensioning: The nut is tightened using a torque wrench to tension the anchor rod of the second hole, ensuring that the anchor rod reaches the design required anchoring force, and then the excess length of the anchor rod is cut off.

[0141] S14, Subsequent process construction: After the construction of the triangular area transverse tensioning system of the no-center continuous arch tunnel is completed according to the above steps, the excavation and support process of the lower step of the second hole can be performed in sequence.

[0142] Application Example

[0143] The present example provides a tunnel inverted arch lining assembly type reinforcement design method, comprising the following steps:

[0144] Step (1), taking V-grade surrounding rock as an example, a "stratum-structure" calculation model of the no-center continuous arch tunnel is established through the tunnel lining section design drawing, as shown in Figure 8 . After calculation, the initial support arc length Lp corresponding to the distribution range of the plastic zone of the triangular area above the no-center continuous arch tunnel after construction is 5.4m, as shown in Figure 2 .

[0145] Step (2), a uniform distributed load P is applied to the surrounding rock within the plastic zone distribution range of the triangular area above the no-center continuous arch tunnel in the calculation model (e.g. Figure 2 ), and the model is trial calculated by adjusting the value of P to find the optimal solution P m of the uniform distributed load. The optimal solution P m of the uniform distributed load should make the distribution area of the plastic zone of the triangular area minimum after the model calculation;

[0146] Optimal solution P of uniform load m The determination method is as follows:

[0147] The model is tested for no less than 6 times by adjusting the value of P, and the plastic area of the triangular area surrounding rock should be as small as possible. m The corresponding plastic area on both sides, that is, the calculation result should reflect the change rule that the plastic area of the triangular area surrounding rock above the multi-arch tunnel decreases first and then increases with the uniform load P. After calculation, the result is as follows: Figure 9 As shown in Table 1.

[0148] Table 1 Plastic area calculated under different uniform loads

[0149] Uniformly distributed load P (kN / m) 0 200 400 800 1000 1500 2000 plastic zone area A (m 2 )]]> 5.38 1.42 0.16 0.12 0.37 1.43 3.17

[0150] The change rule of the plastic area A with the uniform load P in Table 1 is fitted by the following formula:

[0151]

[0152] In the formula, A0 is the initial amplitude, A0 is the equilibrium point, a is the attenuation factor, ω is the angular frequency, amp is the phase, and the above are fitting parameters.

[0153] The fitting result is as follows, and the function graph is shown in Figure 10 .

[0154]

[0155] As can be seen from Figure 10 , the plastic area of the triangular area of the model is 5.38 m 2 at the beginning, and with the increase of the uniform load, the plastic area decreases rapidly first and then increases slowly, wherein the curve bc segment shows that when the uniform load increases from b to c, the plastic area is always 0, that is, the load corresponding to point b is the optimal solution, and at this time P m = 450 kN / m.

[0156] Step (3), calculate the total pre-tension P required for the transverse counter-tension system of the triangular area of the multi-arch tunnel without intermediate support total .

[0157] The total pre-tension P required for the transverse counter-tension system of the triangular area of the multi-arch tunnel without intermediate support total The calculation method is as follows:

[0158] P total = P m ·Lp = 450 × 4.5 = 2430 kN

[0159] In the formula, P​m Lp is the initial support arc length (m) in the distribution range of the plastic zone of the surrounding rock in the triangular area.

[0160] Step (4) design of the counter-pulling anchor rod of the transverse counter-pulling system in the triangular area of the non-center guide multi-arch tunnel:

[0161] The design of the counter-pulling anchor rod of the transverse counter-pulling system in the triangular area of the non-center guide multi-arch tunnel includes the arrangement mode, the number, the length and the pre-tension of the anchor rod.

[0162] Specifically,

[0163] The arrangement mode of the anchor rod adopts the quincunx arrangement, and the length and the number of the anchor rod are determined according to the specific arrangement mode by the design drawing, such as Figure 5 The counter-pulling anchor rod adopts the Φ32 prestressed threaded steel, the spacing between the circumferential direction and the longitudinal direction adopts 60cm×50cm, and the pre-tension of the anchor rod is calculated by the following formula:

[0164] P s = P total / N = 2430 / (2×6+5) = 143kN

[0165] In the formula, P s is the pre-tension of a single counter-pulling anchor rod, and N is the number of the counter-pulling anchor rod per meter along the longitudinal direction of the tunnel in the triangular area of the non-center guide multi-arch tunnel.

[0166] The present example also provides a construction method of the transverse counter-pulling system in the triangular area of the non-center guide multi-arch tunnel; as shown in Figure 1 , the construction method of the transverse counter-pulling system in the triangular area of the non-center guide multi-arch tunnel comprises the following steps:

[0167] Step 1, first step excavation: first step annular excavation section I, the excavation height is greater than 2.0m (such as Figure 5 ).

[0168] Step 2, system anchor rod installation: set the first step system anchor rod according to the conventional construction steps.

[0169] Step 3, erect steel arch: make the first step steel frame, hang the steel mesh, weld the longitudinal connecting rib; install the channel steel at the corresponding position (quincunx arrangement) of the counter-pulling anchor rod, and reserve the round hole at the corresponding position of the anchor rod passing through the channel steel, clamp the two ends of the channel steel on the flanges of the adjacent two steel frames close to the surrounding rock, and weld the channel steel web and the contact part of the flanges of the adjacent two steel frames firmly.

[0170] Step 4, drilling: mark the drilling position (quincunx arrangement), use the air drill to drill from the right side of the first step of the tunnel to the side of the back tunnel, and the angle and depth of the drilling need to be strictly controlled to ensure that the anchor rod can be accurately inserted and can extend out of the back tunnel design initial support surface by not less than 30cm.

[0171] Step 5, hole cleaning: After drilling, the hole needs to be cleaned of rock dust and water to ensure that the hole is clean and free of debris.

[0172] Step 6, anchor rod installation: Insert the anchor rod through the round hole of the channel steel into the surrounding rock hole, with both ends protruding 30 cm from the designed primary support surface (e.g. Figure 6 and Figure 7 ). The insertion length of the anchor rod must meet the design requirements and must not be shorter than 95% of the design length.

[0173] Step 7, installation of the grout stopper and anchor pad: Install the grout stopper and anchor pad on the anchor rod to ensure that the grout does not leak during grouting and to provide sufficient anchoring force.

[0174] Step 8, grouting: Use a grouting machine to inject grout into the hole until the grout overflows the hole. During the grouting process, the grouting pressure and volume need to be controlled to ensure that the grout fills the anchor hole and penetrates into the fissures.

[0175] Step 9, tightening the grout stopper and installing the nut: After grouting is complete, tighten the grout stopper and install the nut on the opposite end of the anchor rod. Use a torque wrench to apply the initial stress until the anchor pad is tightly attached to the channel steel.

[0176] Step 10, initial tensioning of the anchor rod: After the grout solidifies, use a torque wrench to tighten the nut to tension the anchor rod. The tensioning force should not be too large, and it should reach 30% of the design required anchoring force.

[0177] Step 11, construction of the preceding hole lining: Follow the design excavation and support sequence (e.g. Figure 5 ) to complete the initial support and secondary lining of the preceding hole.

[0178] Step 12, use the same steps to perform the upper step excavation of the following hole, system anchor rod installation, drilling, hole cleaning, anchor rod installation, grout stopper and anchor pad installation, grouting, etc.

[0179] Step 13, anchor rod tensioning: Tighten the nut on the anchor rod of the following hole using a torque wrench to ensure that the anchor rod reaches the design required anchoring force, and then cut off the excess length of the anchor rod.

[0180] Step 14, subsequent process construction: After the construction of the triangular area transverse tensioning system of the no-central guide continuous arch tunnel is completed according to the above steps, the excavation and support procedures of the lower step of the following hole can be performed in sequence.

[0181] The present application provides a design method of a transverse counter-pulling system for a non-centering multi-arch tunnel triangular area and a construction method thereof. The prior art has not yet proposed an effective design method for the counter-pulling anchor rod used for reinforcing the surrounding rock of the triangular area above the multi-arch tunnel. In view of this problem, the design method of the present application can quickly calculate the pre-tension of the counter-pulling anchor rod, thereby providing a theoretical basis for the rational design of the anchor rod length, anchor rod quantity and arrangement mode. The transverse counter-pulling system can effectively control the deformation of the surrounding rock of the triangular area above the multi-arch tunnel and the development of the plastic zone after being implemented on site. Taking the examples in this paper, the arrangement of 17 counter-pulling anchor rods with a pre-tension of 143 kN in each meter of the triangular area surrounding rock can reduce the plastic zone area to 0, thereby significantly improving the stability and safety of the tunnel and the supporting structure.

[0182] The basic principles, 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 examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A design method for a transverse tension system in the triangular region of a tunnel without a central connecting arch, characterized in that, Includes the following steps: Step (1): Based on the tunnel lining section design drawings, establish a stratum-structure method numerical calculation model for the tunnel without a central guide arch, and calculate the initial support arc length Lp corresponding to the distribution range of the plastic zone of the surrounding rock in the triangular area above the tunnel without a central guide arch after construction. Step (2): In the calculation model established in step (1), a horizontally distributed load P is applied to the surrounding rock within the distribution range of the plastic zone in the triangular area above the tunnel without a central guide arch. The value of P is adjusted to perform trial calculations on the model, thereby finding the minimum area A of the plastic zone. MIN The corresponding uniformly distributed horizontal load, denoted as the optimal solution P of the uniformly distributed horizontal load. m ; Step (3) uses the initial support arc length Lp obtained in step (1) and the optimal solution P of the horizontally distributed load obtained in step (2). m Calculate the total preload P required for the transverse tension system in the triangular region of a tunnel without a central guide arch. total ; Step (4) involves designing the tie rods for the transverse tie system in the triangular area of ​​the tunnel without a central guide arch, including determining the arrangement of the tie rods, the number of tie rods, the length of the tie rods, and the preload of the tie rods.

2. The design method for the transverse tension system in the triangular region of a tunnel without a central guide arch, as described in claim 1, is characterized in that... In step (2), the optimal solution P m The method for determining it is as follows: The model was tested by adjusting the value of P. The horizontally distributed load was P during the model test. i The area of ​​the plastic zone of the surrounding rock in the corresponding triangular region is A. i , i = 0, 1, 2, 3, ..., M, where M is the total number of trials; The variation of the plastic zone area A with the load P is fitted using equation (1): In equation (1), A amp Let A0 be the initial amplitude, a be the equilibrium point, a be the attenuation factor, and ω be the angular frequency. For phase, the above are all fitting parameters; Using the fitted equation (1), the minimum area A of the plastic region is found. MIN The corresponding uniformly distributed horizontal load, denoted as the optimal solution P of the uniformly distributed horizontal load. m .

3. The design method for the transverse tension system in the triangular region of a tunnel without a central guide arch, as described in claim 2, is characterized in that... In step (2), M should be no less than 6.

4. The design method for the transverse tension system in the triangular region of a tunnel without a central guide arch, as described in claim 1, is characterized in that... In step (3), the total preload P required by the transverse tensioning system in the triangular area of ​​the tunnel without a central guide arch is... total The calculation method is as follows: P total =P m ·Lp (2) In equation (2), P m Lp is the optimal solution for the horizontally distributed load, kN / m; Lp is the initial support arc length, m.

5. The design method for the transverse tension system in the triangular region of a tunnel without a central guide arch, as described in claim 1, is characterized in that... In step (4), the anchor bolts are arranged in a quincunx pattern; The preload of the anchor bolt is calculated by equation (2): P s =P total / N(3) In the formula, P s N represents the preload of a single tie rod; N is the number of tie rods arranged per meter along the longitudinal direction of the tunnel in the triangular area of ​​a tunnel without a central guide arch.

6. A construction method for a transverse tie-down system in the triangular region of a tunnel without a central guide arch, characterized in that, The lateral tension system for a tunnel triangle without a central guide arch, designed using the design method described in any one of claims 1 to 5, includes the following steps: S1, the upper bench of the pilot tunnel is excavated, with an excavation height greater than 2.0m; S2, Install anchor bolts for the pilot tunnel upper step system; S3, construct the steel frame of the upper step of the pilot tunnel, hang the steel mesh, and weld the longitudinal connecting bars; install the channel steel at the corresponding position of the tie rod, and reserve the round hole at the corresponding position where the anchor rod passes through the channel steel. Weld the two ends of the channel steel onto the flange of the two adjacent steel frames near the surrounding rock, and weld the web of the channel steel to the contact part of the flange of the two adjacent steel frames firmly. S4, mark the drilling position, use a pneumatic drill to drill horizontally from the right side of the upper step of the tunnel's pilot tunnel to the side of the rear tunnel. The angle and depth of the drilling must be strictly controlled to ensure that the anchor rod can be accurately inserted and can extend out of the initial support surface of the rear tunnel design by no less than 30cm. S5. After drilling is completed, clean the inside of the hole. S6. Insert the anchor rod into the surrounding rock hole through the round hole of the channel steel, with both ends protruding 29-31cm from the initial support surface. The insertion length of the anchor rod must meet the design requirements and must not be less than 95% of the design length. S7, Install grout stop plugs and anchor plates on the anchor bolts; S8, use a grouting machine to inject grout into the hole until the grout overflows from the hole opening; S9. After grouting is completed, tighten the grout stop plug and install nuts at the ends of the tie rods. Apply initial stress with a torque wrench until the anchor plate and the channel steel are in close contact. S10, Initial tensioning of anchor bolts: After the grout has solidified, use a torque wrench to tighten the nuts to tension the anchor bolts until the tension force reaches 30% of the design anchoring force. S11, complete the initial support and secondary lining of the pilot tunnel according to the designed excavation and support sequence; S12, the same steps as S1 to S11 are used to process the subsequent tunnel; S13, tension the anchor bolts in the rear tunnel to ensure that the anchor bolts reach the anchoring force required by the design, and then cut off the excess length of the anchor bolts; S14, Subsequent Construction Procedures: After the transverse tie system of the triangular area of ​​the tunnel without a central guide arch is constructed according to the above steps, the excavation and support procedures of the lower bench of the subsequent tunnel can be carried out in sequence.

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