A construction method for safe conversion from CD method to step method

Abstract

The construction method for the safe conversion of the CD method to the bench method of the present invention includes steps S1 to S6. The construction method of the present invention provides construction guidance for the safe conversion of the CD method to the bench method, avoiding construction risks brought by relying on experience guidance. After step S2 of this method, the vertical temporary support is removed. On the one hand, it can provide a larger space for subsequent construction and facilitate mechanized construction. On the other hand, it can analyze the tunnel stability without the vertical temporary support to ensure the safety during the conversion stage. After the vertical temporary support is removed, the faces of the first chamber and the third chamber form construction area A. The excavation of construction area A is carried out in sub-areas to ensure construction safety. That is, if the surrounding rock is unstable, situations such as face instability and excessive convergence of the initial support may occur during the excavation of construction area A1. Since construction area A2 has not been excavated yet, the degree of influence of the risk is within a controllable range.

Description

Technical Field

[0001] The present invention relates to the field of tunnel construction, and particularly to a construction method for safely converting the CD method to the bench method. Background Art

[0002] Stability is one of the key concerns during the construction of tunnels and underground projects. Affected by complex geological structures, there are significant differences in the surrounding rock conditions at different mileage of tunnel projects. To ensure the stability of the tunnel, it is necessary to select an appropriate excavation method according to the on-site geological conditions during the tunneling construction. For example, in good surrounding rock conditions, construction methods such as the full-face method and the bench method can be used, but in the case of weak surrounding rock, methods such as the CD method and the CRD method need to be adopted.

[0003] A reasonable construction plan for method conversion can effectively reduce the disturbance to the surrounding rock caused by method conversion, can reduce the construction difficulty while ensuring the safety of the support structure, and has the effects of accelerating the construction progress and saving construction costs. With the development of engineering technology and the accumulation of engineering experience, engineering personnel have established the relationship between tunnel excavation methods and engineering geological conditions by qualitative methods, but no specific construction methods that can be examined have been formed, resulting in great blindness and randomness during the construction method conversion of newly built tunnels. During the implementation process, due to the complex geological conditions in the tunnel area, some engineering accidents will inevitably occur, causing significant economic losses and casualties, indicating that there are great risks in mainly relying on experience for construction.

[0004] In summary, there is an urgent need for a construction method for safely converting the CD method to the bench method to solve the problem of lack of construction guidance in the conversion of the CD method to the bench method in the prior art. Summary of the Invention

[0005] The purpose of the present invention is to provide a construction method for safely converting the CD method to the bench method to solve the problem of lack of construction guidance in the conversion of the CD method to the bench method in the prior art. The specific technical solutions are as follows:

[0006] A construction method for safely converting the CD method to the bench method includes the following steps:

[0007] Step S1: Divide the C-section chamber in the CD-method construction section into a first chamber and a second chamber distributed vertically, and divide the D-section chamber in the CD-method construction section into a third chamber and a fourth chamber distributed vertically;

[0008] Step S2: After excavating the first chamber to the stake number of the converted method, stop excavation; excavate the second chamber until it is at a distance of L 1 from the first chamber, then stop excavation; excavate the third chamber until it is flush with the face of the first chamber, and then stop excavation;

[0009] Step S3: Remove the vertical temporary support in the CD-method construction section;

[0010] Step S4: The A construction area formed by the faces of the first chamber and the third chamber is divided into an A 1 construction area and an A 2 construction area from top to bottom; First, excavate the A 1 construction area, and then the A 1 construction area and the A 2 construction area are staggered by L 2 and excavated forward;

[0011] Step S5: The second chamber and the fourth chamber are alternately staggered by L 3 and excavated forward. When the second chamber reaches the pile number for the construction method conversion, stop the excavation; After the fourth chamber is excavated to be flush with the second chamber, the face areas of the second chamber and the fourth chamber together form the lower bench of the bench method construction section;

[0012] Step S6: Accelerate the excavation speed of the A 2 construction area so that the face of the A 2 construction area is flush with the face of the A 1 construction area. The faces of the A 1 construction area and the A 2 construction area together form the upper bench of the bench method construction section, and the construction method conversion is completed.

[0013] Preferably, in step S4, the A 2 construction area includes an A 21 construction area and an A 22 construction area. The A 1 construction area, the A 21 construction area, and the A 22 construction area are successively staggered by L 2 and excavated forward.

[0014] Preferably, in step S4, the height of the A construction area is H meters, and the height H 1 of the A 1 construction area is H meters.

[0015] Preferably, the L 1 , L 2 , and L 3 are all 3 - 5m.

[0016] Preferably, in step S3, when removing the vertical temporary support, observe the deformation amounts of the crown settlement and horizontal convergence of the tunnel during the removal; If the deformation amount exceeds the allowable value for safe construction, stop the removal work in time and take reinforcement measures to reinforce the tunnel, otherwise continue the removal until it is completely removed.

[0017] Preferably, before performing step S1, it is first determined whether the construction method can be converted and the length of the construction method conversion transition section in the front, specifically as follows:

[0018] In the first step, it is confirmed whether the construction method can be converted according to the stability of the surrounding rock in the front;

[0019] In the second step, the length L of the transition section 总 satisfies: L 总 = 0.5L 安全 , where L 安全 represents the safe excavation step distance.

[0020] Applying the technical solution of the present invention has the following beneficial effects:

[0021] (1) The construction method for the safe conversion of the CD method to the bench method of the present invention includes steps S1 to S6. The construction method of the present invention provides construction guidance for the safe conversion of the CD method to the bench method, avoiding construction risks brought by relying on experience guidance. And after performing step S2, the vertical temporary support is removed. On the one hand, it can provide a larger space for subsequent construction and facilitate mechanized construction. On the other hand, it can analyze the tunnel stability without the vertical temporary support to ensure the safety of the conversion stage. After the vertical temporary support is removed, the faces of the first chamber and the third chamber form construction area A, and the construction area A is excavated in sub-areas to ensure construction safety, that is, if the surrounding rock is unstable, 1 instability of the face and excessive convergence of the primary support may occur during the excavation of construction area A, and since construction area A 2 has not been excavated yet, the degree of influence of the risk is within the controllable range.

[0022] (2) The construction area A of the present invention 2 includes construction area A 21 and construction area A 22 . Construction area A 1 , construction area A 21 and construction area A 22 are excavated forward in sequence with a stagger of L 2 , that is, they can be excavated in sequence, further reducing the degree of influence of the risk caused by abnormalities during the excavation of construction area A 1 .

[0023] (3) The present invention avoids the leading construction area (i.e., construction area A 1 ) from being too large, thereby avoiding excessive overall impact when abnormalities occur during the construction of the leading construction area.

[0024] In addition to the purposes, features, and advantages described above, the present invention has other purposes, features, and advantages. The present invention will be further described in detail below with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0026] In the drawings:

[0027] Figure 1 is a schematic diagram of the excavation from step S1 to step S2 of this embodiment;

[0028] Figure 2 is a schematic diagram of the removal of the vertical temporary support from step S2 to step S3 of this embodiment;

[0029] Figure 3 is a schematic diagram of the excavation from step S3 to step S4 of this embodiment;

[0030] Figure 4 is a schematic diagram of the excavation from step S4 to step S5 of this embodiment;

[0031] Figure 5 is a schematic diagram of the excavation from step S5 to step S6 of this embodiment;

[0032] Figure 6 is a schematic flow diagram of the construction method of this embodiment;

[0033] Among them, 1, the first chamber; 2, the second chamber; 3, the third chamber; 4, the fourth chamber. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The following will describe the embodiments of the present invention in detail with reference to the drawings. However, the present invention can be implemented in many different ways defined and covered by the claims.

[0035] Embodiment:

[0036] A construction method for the safe conversion of the CD method to the bench method. The construction method specifically includes steps S1 to S6. Among them, in order to ensure the safety during the conversion of the construction method in this embodiment, before step S1 (i.e., before actual excavation), the following steps need to be carried out:

[0037] Step 1: Determine whether the construction method can be converted ahead. In the method of this embodiment, by judging whether the surrounding rock ahead is stable, it is confirmed whether the construction section ahead can be subjected to construction method conversion. The means for judging whether the surrounding rock ahead is stable are, for example, determined by analyzing the surrounding rock conditions of the heading face, geological exploration reports, advanced geological forecasts, etc.; in addition, other means in the existing methods can also be referred to for judging whether the surrounding rock ahead is stable; when the surrounding rock ahead is in a stable state, the construction method can be converted, otherwise, the construction method cannot be converted;

[0038] Step 2: After determining that the construction method can be converted, it is necessary to determine the length of the overall transition section of the construction method conversion. The length L of the transition section 总 satisfies: L 总 = 0.5L 安全 , where L 安全 represents the safe excavation step (i.e., the safe excavation step allowed under the current surrounding rock grade, and the surrounding rock grade is judged according to the existing method).

[0039] In this embodiment, the length L of the transition section and the excavation length of each part can be determined through construction experience. Further, in order to ensure construction safety, the excavation process can be simulated by three-dimensional numerical simulation (referring to the existing technology) to determine the primary support deformation. If the primary support deformation does not meet the construction requirements, L can be reduced 总 , and the excavation process is simulated again by three-dimensional numerical simulation until the primary support deformation meets the requirements, and finally the corrected length L of the transition section 总 and the excavation length of each part are obtained. 总 Steps S1 to S6 are as

[0040] shown in (a) to (f) of Figures 1 to 5 as follows:

[0041] Step S1 is as shown in (a) of Figure 1 : The C-section chamber (i.e., the chamber labeled C in Figure 1 ) in the CD-method construction section is divided into the upper and lower distributed first chamber 1 and second chamber 2, and the D-section chamber in the CD method (i.e., the chamber labeled D in Figure 1 ) is divided into the upper and lower distributed third chamber 3 and fourth chamber 4;

[0042] Step S2: As shown in (b) of Figure 1 , it is specifically as follows:

[0043] Step S2.1: After excavating the first chamber 1 to the pile number of the converted construction method (the pile number of the converted construction method indicates the position where the construction method conversion starts), stop excavation and seal the heading face;

[0044] Step S2.2: Excavate the second chamber 2 until the second chamber 2 is at a distance of L from the first chamber 1 1When it reaches a certain time (e.g., 5m), stop the excavation and seal the tunnel face;

[0045] Step S2.3: Excavate the third chamber 3 until the tunnel face of the third chamber 3 is flush with that of the first chamber 1, then stop the excavation and seal the tunnel face;

[0046] Step S3: As Figure 2 shown, remove the vertical temporary supports in the CD method construction section. Specifically, when removing the vertical temporary supports, observe the deformation of the vault settlement and horizontal convergence of the tunnel during the removal of the temporary supports; if the deformation exceeds the allowable value for safe construction (the allowable value for safe construction is determined according to the construction situation or construction standards), stop the removal work in a timely manner and take reinforcement measures to reinforce the tunnel (continue the original CD method excavation after the reinforcement is completed), otherwise continue the removal until it is completely removed;

[0047] Step S4: As Figure 3 shown in (d) of

[0048] Step S4.1: Divide the A construction area formed by the tunnel faces of the first chamber 1 and the third chamber 3 into A 1 construction area and A 2 construction area from top to bottom;

[0049] Step S4.2: First, excavate the A 1 construction area, then stagger the A 1 construction area and the A 2 construction area by L 2 and excavate forward; in this embodiment, preferably, the A 2 construction area includes the A 21 construction area and the A 22 construction area in the horizontal direction. The A construction area, the A 21 construction area, and the A 22 construction area are staggered by L 2 and excavated forward in sequence. For example, the A 1 construction area is first excavated forward by 15m, the A 21 construction area is excavated forward by 10m, and the A 22 construction area is excavated forward by 5m, that is, they are staggered by 5m and excavated forward in this way.

[0050] Among them, the height of the A construction area in the vertical direction is H meters, and the height H 1 of the A 1 construction area is H

[0051] Step S5: As Figure 4 shown,

[0052] The second chamber 2 and the fourth chamber 4 are alternately staggered by L 3Excavate forward. When the second chamber 2 reaches the pile number for the construction method conversion, stop the excavation;

[0053] After the fourth chamber 4 is excavated to be flush with the second chamber 2 (i.e., the tunnel faces are flush), the tunnel face areas of the second chamber 2 and the fourth chamber 4 together form the lower bench P of the bench method construction section 1 ;

[0054] Step S6: As Figure 5 shown, accelerate the excavation speed of the A 2 construction area, so that the A 2 construction area (i.e., including A 21 and A 22 ) can be excavated to be flush with the tunnel face of the A 1 construction area. The tunnel faces of the A 1 construction area and the A 2 construction area together form the upper bench P of the bench method construction section 2 , and the construction method conversion is completed.

[0055] In this embodiment, the L 1 , L 2 and L 3 are all 3 - 5m.

[0056] Preferably, in this embodiment, during the excavation of the construction method conversion, the tunnel stability is analyzed and monitored. For example, the tunnel stability can be determined by analyzing the on - site monitoring data and the numerical simulation results. The specific construction parameters are determined according to factors such as the relevant requirements of the specifications and the actual on - site situation.

[0057] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A construction method for safely converting the CD method to the step method, characterized in that: The steps include: Step S1: dividing the C-section cavern in the CD method construction section into a first cavern (1) and a second cavern (2) distributed vertically, and dividing the D-section cavern in the CD method construction section into a third cavern (3) and a fourth cavern (4) distributed vertically; Step S2: After excavating the first cavern (1) to the pile number of the conversion method, excavation is stopped; excavating the second cavern (2) until it is L1 away from the first cavern (1), excavation is stopped; excavating the third cavern (3) until it is flush with the face of the first cavern (1), excavation is stopped; Step S3: removing the temporary vertical support of the CD method construction section; Step S4: dividing the A construction area formed by the tunnel faces of the first cavern (1) and the third cavern (3) into an A1 construction area and an A2 construction area from top to bottom; first excavating the A1 construction area, and then excavating the A1 construction area and the A2 construction area forward with a gap of L2 between them; Step S5: the second cavern (2) and the fourth cavern (4) are excavated forward alternately with a staggered distance L3, and when the second cavern (2) reaches the pile number for the conversion method, the excavation is stopped; after the fourth cavern (4) is excavated to be flush with the second cavern (2), the tunnel face areas of the second cavern (2) and the fourth cavern (4) together constitute the lower step (P1) of the step method construction section; Step S6: speed up the excavation speed of the A2 construction area to make the A2 construction area flush with the A1 construction area's tunnel faces. The A1 construction area and the A2 construction area's tunnel faces together form the upper step (P2) of the step method construction section, and the construction method conversion is completed; In step S4, the construction area A2 includes A 21 Construction area and A 22 Construction area, A1 construction area, A 21 Construction area and A 22 The construction areas are staggered and excavated forward from L2 in sequence; In step S4, the height of the A construction area is H meters, and the height of the A1 construction area is H1 meters.

2. The construction method for safe conversion from CD method to step method according to claim 1, characterized in that: The lengths of L1, L2 and L3 are all 3-5 m.

3. The construction method for safe conversion from CD method to step method according to claim 1, characterized in that: In step S3, when removing the vertical temporary support, observe the deformation of the tunnel vault settlement and horizontal convergence during the demolition; if the deformation exceeds the allowable value for safe construction, the demolition work should be stopped in time and reinforcement measures should be taken to reinforce the tunnel, otherwise the demolition should be continued until it is completely demolished.

4. The construction method for safe conversion from CD method to step method according to claim 1, characterized in that: Before performing step S1, it is first determined whether the working method conversion can be performed ahead and the length of the working method conversion transition section, as follows: The first step is to determine whether the construction method can be changed based on whether the surrounding rock is stable. The second step is the length of the transition section L 总 Satisfaction: L 总 =0.5L 安全 , L 安全 Indicates the safe step distance for excavation.

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