Prestressed anchoring construction method for shield type TBM to penetrate through soft cavern section

Abstract

The invention relates to the field of TBM construction, in particular to a construction method for pre-stressed anchoring of a shield type TBM penetrating through a soft rock cave section, which is a construction method for performing active supporting by taking a pre-stress measure as a core on the basis of passive supporting of a duct piece, and construction of a pre-stressed anchor rod is rapidly completed while TBM tunneling is ensured. And the slab staggering and damage risks caused by large deformation of soft rock and the risk of subsequent repair of the formed segment are reduced, the construction quality of the TBM penetrating through the high-ground-stress soft rock cave section is guaranteed, the advantage of the shield type TBM penetrating through complex stratums such as weak and broken stratums is greatly played, and high popularization performance is achieved. Therefore, the technical problems that in the relatively limited in-hole operation space and the existing duct piece supporting construction process, deformation of the duct piece and clamping of a rear supporting machine of the TBM are prevented can be solved, and the purpose of performing active supporting measures on the later-period deformed surrounding rock for construction is achieved.

Description

Technical Field

[0001] The invention relates to the field of TBM construction, and in particular to a construction method for prestressed anchoring of a shield-type TBM passing through a soft rock cave section. Background Art

[0002] As an advanced equipment for fast construction of deep buried long tunnels, TBM (full-section tunnel boring machine) construction has the advantages of high excavation efficiency, small disturbance to surrounding rock, good excavation quality, and good working environment. TBM models are mainly divided into open type, shield type (including single shield and double shield), etc.

[0003] The use of open TBMs requires a large initial support workload, low construction efficiency, and poor safety. The support structure of the tunnel excavated by the shield TBM generally includes concrete segments and backfill grouting layers behind the wall. When the shield TBM is used for construction under complex formation conditions such as soft and broken formations, the protection of the shield body and assembled segments makes manual operations in the main machine area safer and the mechanized construction efficiency of the segments higher. Since the shield TBM has unique characteristics and advantages in complex formation conditions such as soft and broken formations, it achieves a good balance between construction safety and construction efficiency, and therefore becomes the preferred choice for TBMs to cross soft formations.

[0004] However, when the shield TBM construction passes through the soft rock cave section with high ground stress, the soft rock has obvious softening characteristics and rheological characteristics that increase with time, that is, the surrounding rock parameters gradually decrease with the development of deformation. The surrounding rock may produce plastic extrusion deformation under high ground stress, which will further increase the scope of the plastic zone after tunnel excavation, thereby causing an increase in plastic deformation pressure. Both engineering practice and research have shown that the damage of soft rock tunnels often has a certain hysteresis, and the rheology of the surrounding rock affects the mechanical properties of the deep tunnel construction period, thereby causing the damage of the lining structure. The general drilling and blasting method construction can allow the surrounding rock to undergo a certain deformation to release deformation energy under the premise of ensuring the stability of the surrounding rock, and add active support measures at the right time to ensure the stability and safety of the tunnel in the soft rock cave section. Since the support structure of the tunnel excavated by the shield TBM generally includes concrete segments and backfill grouting layers behind the wall. The construction of the segments is closely followed by the shield shell, and the backfill grouting behind the wall is closely followed by the segment construction. The space for the surrounding rock to release energy through deformation is relatively limited. In the soft rock cave section with high ground stress, the degree of stress release is often insufficient. As a rigid passive support structure, the deformation of the surrounding rock is too large, which will cause the deformation of the lining segments, and even cause problems such as misalignment and damage. In serious cases, it will cause the TBM's back-end equipment to get stuck, which will affect the difficulty of TBM excavation, operation safety and construction period guarantee.

[0005] Therefore, the existing open TBM construction method and shield TBM construction method have disadvantages such as misalignment and breakage due to deformation of the pipe segments when crossing high-stress soft rock cave sections, and may cause the TBM's rear accessories to get stuck. Summary of the invention

[0006] The purpose of the present invention is to provide a construction method for prestressed anchoring of a shield-type TBM passing through a soft rock cave section, which can solve the technical problems of constructing active support measures for late-stage deformed surrounding rocks when passing through a soft rock cave section with high ground stress, preventing deformation of the pipe segments and subsequent carding of the TBM.

[0007] To achieve the above object, the present invention provides a construction method for prestressed anchoring of a shield TBM through a soft rock cave section, comprising the following steps:

[0008] Install surrounding rock pressure and deformation monitoring devices on the shield and conventional tunnel segments to obtain surrounding rock deformation monitoring data throughout the TBM excavation support process;

[0009] When the monitoring data is abnormal, install a special segment suitable for the soft rock cave section in the surrounding rock, and install a pad near the rock surface at the reserved hole of the special segment;

[0010] After the installation of the special pipe segment is completed, backfill grouting is carried out behind the wall to push the pad away from the special pipe segment so that the pad is in contact with the surrounding rock and fixed;

[0011] After the backfill grouting behind the wall is completed, the prestressed anchor rods are installed;

[0012] Applying prestress to the prestressed anchor rod;

[0013] After applying prestress, grouting construction is carried out on the reserved holes of the special segment and the backfill layer behind the wall;

[0014] Finally, the reserved holes of the special pipe segments are sealed to complete the prestressed anchoring construction.

[0015] As a preferred solution, the installation of prestressed anchor rods specifically includes the following steps: anchor rod drilling, filling anchoring agent, anchor rod body installation, anchoring agent stirring, and drilling the prestressed anchor rod. After the drilling is completed, a resin anchoring agent is immediately placed in the hole for anchoring. The number of anchoring agent sections is determined according to the drilling depth. Subsequently, the prestressed anchor rod body is delivered by an anchor drilling rig. After the anchoring agent and anchor rod are in place, the anchor rod is rotated at high speed, and the anchoring agent is fully stirred to allow it to be quickly anchored to form a resin anchoring section.

[0016] Further, applying prestress to the prestressed anchor rod specifically comprises the following steps:

[0017] After the anchoring agent is quickly set, the tightening nut is put on the free thread of the prestressed anchor rod before prestressing;

[0018] Use a torque wrench to twist the nut in the reserved hole of the segment to apply prestress;

[0019] The order of applying the tension force is 25%, 50%, 75% and 100% of the designed prestress value;

[0020] After the last stage of tensioning and locking, check the prestress value to ensure that the anchor reaches the designed prestress value. If the prestress loss is greater than 10% of the tension design value of the prestressed anchor, perform compensatory tensioning.

[0021] Furthermore, the installation of prestressed anchor rods and the application of prestress are completed on the anchoring operation trolley. The prestressed anchoring operation trolley can be separated from the TBM machine and constructed independently. The size of the prestressed anchoring operation trolley must meet the requirements of TBM belt conveyor slag discharge, tunnel ventilation and rail transportation in the tunnel.

[0022] As a preferred solution, the reserved holes in the special segments are used as both prestressed anchor installation holes and backfill grouting holes.

[0023] As a preferred solution, a backing plate reserved hole is provided in the middle of the backing plate, and the aperture of the backing plate reserved hole is smaller than the aperture of the dedicated pipe segment reserved hole.

[0024] As a preferred solution, one side of the pad is magnetically attracted to the special pipe segment through a pre-buried magnetic sheet, and the other side of the pad is coated with an adhesive material for contact and fixation with the surrounding rock.

[0025] Beneficial effects of the present invention:

[0026] The present invention provides a construction method for prestressed anchoring of a shield type TBM passing through a soft rock cave section. On the basis of passive support of the pipe segment, the construction method for active support with prestressed measures as the core is carried out. While ensuring the excavation of the TBM, the construction of the prestressed anchor rods is quickly completed, and the risks of misalignment and damage of the formed pipe segment due to large deformation of the soft rock and the risk of subsequent repair are reduced, thereby ensuring the construction quality of the TBM passing through a soft rock cave section with high ground stress, greatly giving play to the advantages of the shield type TBM in passing through complex formations such as soft and broken formations, and having high popularization potential.

[0027] Therefore, the present invention can solve the technical problems of preventing deformation of the pipe segments and the subsequent clamping of the TBM in the relatively limited working space in the tunnel and the existing pipe segment support construction process, and achieve the purpose of constructing active support measures for the later deformed surrounding rock. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the overall diagram of the special segment support structure for the soft rock cave section.

[0029] Figure 2 This is a cross-sectional view of the connection between the pipe segment and the gasket.

[0030] Figure 3 Top view of the connection between the pipe segment and the gasket.

[0031] Figure 4 This is the detailed structure diagram of the prestressed anchor bolt.

[0032] Description of reference numerals:

[0033] Special segment 1, backfill layer behind the wall 2, prefabricated invert 3, reserved hole for special segment 4, surrounding rock surface 5, pad 6, reserved hole for pad 7, prestressed anchor rod 8, anchoring section 9, torque wrench torsion nut 10, free section 11. DETAILED DESCRIPTION

[0034] In order to make the technical problems solved by the present invention, the technical solutions adopted and the technical effects achieved clearer, the technical solutions of the present invention are further described below in conjunction with the accompanying drawings and through specific implementation methods. It is understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for the convenience of description, only the parts related to the present invention are shown in the accompanying drawings, not all.

[0035] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] The purpose of the present invention is to overcome the shortcomings of the above-mentioned background technology. In view of the limited deformation space allowed under the segment support structure of the soft rock cave section, the passive support form of "segment + backfill grouting layer" cannot provide sufficient resistance to resist the deformation of the surrounding rock, which eventually leads to deformation, dislocation, damage and other problems of the segment. After the segment installation and backfill grouting construction are completed, the TBM actively applies prestressing measures to the surrounding rock while excavating, improves the stress state of the surrounding rock and the bearing capacity of the rock around the cave, controls the pressure acting on the segment structure, and provides a construction method of actively supporting on the basis of the segment structure without affecting the normal excavation of the TBM, that is, applying prestressed anchoring measures, to ensure the shield TBM to the greatest extent possible to quickly excavate through the soft rock cave section, ensure the stability and safety of the support structure and the reliability of the construction period. Therefore, the present invention can solve the problem of implementing active support measures for late-stage deformed surrounding rocks in the relatively limited working space in the cave and the existing segment support construction process.

[0037] The present invention provides a construction method for prestressed anchoring of a shield type TBM passing through a soft rock cave section, comprising the following steps:

[0038] Step 1: Install surrounding rock pressure and deformation monitoring devices on the shield and conventional tunnel segments to obtain surrounding rock deformation monitoring data during the entire TBM excavation support process;

[0039] Step 2: When the monitoring data is abnormal, install a special segment suitable for the soft rock cave section in the surrounding rock, and install a pad near the rock surface at the reserved hole of the special segment;

[0040] Step 3: After the installation of the special pipe segment is completed, backfill grouting is performed behind the wall to push the pad away from the special pipe segment so that the pad is in contact with the surrounding rock and fixed;

[0041] Step 4: After the backfill grouting behind the wall is completed, the prestressed anchor rods are installed;

[0042] The installation of prestressed anchor rods specifically includes the following steps: anchor rod drilling, filling anchoring agent, anchor rod body installation, anchoring agent stirring, and drilling of prestressed anchor rods. After the drilling is completed, resin anchoring agent is immediately placed in the hole for anchoring. The number of anchoring agent sections is determined according to the drilling depth. Subsequently, the rod body of the prestressed anchor rod is sent in by an anchor drilling rig. After the anchoring agent and anchor rod are in place, the anchor rod is rotated at high speed, and the anchoring agent is fully stirred to make it quickly anchored to form a resin anchoring section.

[0043] Step 5, applying prestress to the prestressed anchor rod;

[0044] Applying prestress on the prestressed anchor rod specifically includes the following steps:

[0045] After the anchoring agent is quickly set, the tightening nut is put on the free thread of the prestressed anchor rod before prestressing;

[0046] Use a torque wrench to twist the nut in the reserved hole of the segment to apply prestress;

[0047] The order of applying the tension force is 25%, 50%, 75% and 100% of the designed prestress value;

[0048] After the last stage of tensioning and locking, check the prestress value to ensure that the anchor reaches the designed prestress value. If the prestress loss is greater than 10% of the tension design value of the prestressed anchor, perform compensatory tensioning.

[0049] Step 6: After applying prestress, grouting is performed on the reserved holes of the special segment and the backfill layer behind the wall;

[0050] Step 7. Finally, seal the reserved holes of the special segments to complete the prestressed anchoring construction.

[0051] It should be understood that the specific order or hierarchy of steps in the process disclosed by the present invention is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process can be rearranged without departing from the scope of protection of the present disclosure. The attached method claims provide the elements of the various steps in an exemplary order and are not intended to be limited to the specific order or hierarchy described.

[0052] The above steps are described in detail as follows:

[0053] 1. In combination with geological survey results, when the TBM is about to pass through complex strata such as soft and broken strata, surrounding rock pressure and deformation monitoring devices should be installed on the shield and conventional tunnel segments in a timely manner to obtain surrounding rock deformation monitoring data for the entire TBM excavation support process, providing a basis for the selection of support methods.

[0054] 2. When abnormal monitoring data occurs, the special segments for soft rock tunnel sections prefabricated in advance at the segment prefabrication factory outside the tunnel shall be transported in time and installed in the surrounding rock.

[0055] 3. The main differences between special segments for soft rock tunnel sections and conventional segments should be considered: 1) The backfill grouting holes on the segments are also used as prestressed anchor installation holes, achieving multiple uses of one hole. The diameter of the backfill grouting holes must take into account the requirements for the drill bit drilling and rod installation of the prestressed anchor; 2) A pad is installed in advance on the side of the reserved hole in the segment close to the rock surface.

[0056] 4. After the pipe segments are installed, when backfilling and grouting are carried out behind the wall, push the pad away from the pipe segments so that the pad is in contact with the surrounding rock and fixed.

[0057] 5. Use a prestressed anchoring operation trolley connected to the TBM machine to carry out the construction of prestressed support measures. The prestressed anchoring operation trolley can be separated from the TBM machine and constructed independently. In order not to affect the TBM excavation, the size of the prestressed anchoring operation trolley must meet the requirements of TBM belt conveyor slag discharge, tunnel ventilation and rail transportation in the tunnel.

[0058] 6. After the above preparation measures are completed, the prestressed anchor hole drilling, anchor body installation, rod body prestressing and grouting are carried out. In order to ensure the rapid provision of high-strength prestress, the segmented anchor grouting method is adopted. After the hole drilling is completed, the resin anchor and prestressed anchor are immediately sent into the rock borehole. First, the resin anchor is stirred by the prestressed anchor to achieve the purpose of rapid anchoring. After the prestress is applied, cement slurry is used to grout and seal the reserved holes of the prestressed anchor segments and the backfill grouting range behind the wall.

[0059] The present invention is further described in detail below in conjunction with the accompanying drawings and specific implementations so that those skilled in the art can understand. It should be understood that the embodiments described below are only part of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained without creative work are within the scope of protection of the present invention.

[0060] When the shield TBM in the present invention passes through complex formations such as soft and broken formations, when the surrounding rock deformation monitoring feedback shows that the segments or shield bodies are subjected to abnormal stress, the special segments for the soft rock tunnel section prefabricated in advance in the segment prefabrication plant outside the tunnel are transported in time.

[0061] Special segment support structure for soft rock tunnel section Figure 1 As shown, the special segment for the soft rock cave section includes a special segment 1, a backfill layer 2 behind the wall, a prefabricated invert 3, and a special segment reserved hole 4. The special segment 1 is an annular structure, the backfill layer 2 behind the wall covers the outside of the special segment 1, the prefabricated invert 3 is arranged on the inner side wall of the special segment 1, and there are multiple special segment reserved holes 4, which are respectively opened on the inner side of the special segment 1.

[0062] like Figure 2 , Figure 3 As shown, during the prefabrication of the pipe segment, magnetic suction plates are pre-buried around the reserved holes 4 of the pipe segment in advance. Before the pipe segment is transported into the cave, a pad 6 is placed on the side of the special pipe segment 1 close to the surrounding rock surface 5, and connected by the pre-buried magnetic suction plates to ensure that the pad 6 and the special pipe segment 1 do not separate during the transportation and installation of the pipe segment. One side of the pad 6 is magnetically attracted to the special pipe segment 1, and the other side is coated with adhesive material. At the same time, the aperture of the pad reserved hole 7 should be smaller than the aperture of the special pipe segment reserved hole 4 to ensure that the pad can be mechanically pushed through the pipe segment reserved hole 4. The pipe segment reserved hole 4 is also used as a prestressed anchor installation hole and a backfill grouting hole.

[0063] like Figure 4 As shown, after the special pipe segment 1 is assembled, when backfilling and grouting are performed behind the wall, the backing plate 6 is mechanically pushed out of the special pipe segment 1 in the reserved hole 4 of the pipe segment by means such as a grouting plug, and the other side of the backing plate 6 is coated with adhesive material in advance for contact and fixation with the surrounding rock surface 5, so as to prepare for the next step of installing the prestressed anchor rod 8.

[0064] In order not to affect the normal construction of TBM, the following construction process of prestressed anchor 8 includes the steps of anchor drilling, filling anchoring agent, rod installation, anchor mixing and prestressing application. These steps need to be completed on the anchoring work trolley. The size requirements of the work trolley must meet the requirements of TBM belt conveyor slag discharge, tunnel ventilation and rail transportation in the tunnel.

[0065] After the backfill grouting is completed, the construction of the prestressed anchor rod 8 is carried out, which specifically includes the drilling of the prestressed anchor rod. After the drilling is completed, in order to prevent the collapse and shrinkage of the hole, considering the long cement anchoring time and other factors, the resin anchoring agent is immediately put into the hole for anchoring. The number of anchoring agent sections is determined according to the drilling depth. Then, the anchor drilling machine is used to send the rod body of the prestressed anchor rod 8. After the anchoring agent and the anchor rod are in place, the anchor rod is rotated at a high speed, and the anchoring agent is fully stirred to make it quickly anchored, forming a resin anchoring section 9.

[0066] After the anchoring agent is quickly set, the tightening nut is put on the thread of the free section of the anchor rod 8 before prestressing, and the prestress is applied by twisting the nut 10 with a torque wrench in the reserved hole 4 of the segment. The tensioning force is applied in the order of 25%, 50%, 75%, and 100% of the designed prestressing value. After the last stage of tensioning is locked, the prestressing value is checked to ensure that the anchor rod 8 reaches the designed prestressing value. If the prestressing loss is greater than 10% of the designed value of the tension of the anchor rod 8, compensatory tensioning is performed.

[0067] After prestressing is locked or compensated, cement slurry matching the segment model is used to perform grouting construction on the free section 11 within the reserved hole 4 of the segment and the backfill layer 2 behind the wall. The main purpose is to reinforce and protect the backfill layer 2 behind the wall and the surrounding rock mass during the drilling process.

[0068] Finally, the reserved holes 4 of the segments are sealed, and the prestressed anchoring construction is now completed.

[0069] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A construction method for prestressed anchoring of a shield TBM through a soft rock cave section, characterized in that: The following steps are included: Install surrounding rock pressure and deformation monitoring devices on the shield and conventional tunnel segments to obtain surrounding rock deformation monitoring data throughout the TBM excavation support process; When the monitoring data is abnormal, install a special segment suitable for the soft rock cave section in the surrounding rock, and install a pad near the rock surface at the reserved hole of the special segment; After the installation of the special pipe segment is completed, backfill grouting is carried out behind the wall to push the pad away from the special pipe segment so that the pad is in contact with the surrounding rock and fixed; After the backfill grouting behind the wall is completed, the prestressed anchor rods are installed; Applying prestress to the prestressed anchor rod; After applying prestress, grouting construction is carried out on the reserved holes of the special segment and the backfill layer behind the wall; Finally, the reserved holes of the special pipe segments are sealed to complete the prestressed anchoring construction.

2. The construction method of prestressed anchoring of a shield TBM through a soft rock cave section according to claim 1 is characterized by: The installation of prestressed anchor rods specifically includes the following steps: The prestressed anchor is drilled, filled with anchoring agent, installed and stirred. After the drilling is completed, the resin anchor is immediately put into the hole for anchoring. The number of anchor sections is determined according to the drilling depth. The prestressed anchor body is then fed into the anchor drilling rig. After the anchor and anchor are in place, the anchor is rotated at high speed and the anchor is fully stirred to allow it to be quickly anchored to form a resin anchoring section.

3. The construction method of prestressed anchoring of a shield TBM through a soft rock cave section according to claim 2 is characterized in that: Applying prestress on the prestressed anchor rod specifically includes the following steps: After the anchoring agent is quickly set, the tightening nut is put on the free thread of the prestressed anchor rod before prestressing; Use a torque wrench to twist the nut in the reserved hole of the segment to apply prestress; The order of applying the tension force is 25%, 50%, 75% and 100% of the designed prestress value; After the last stage of tensioning and locking, check the prestress value to ensure that the anchor reaches the designed prestress value. If the prestress loss is greater than 10% of the tension design value of the prestressed anchor, perform compensatory tensioning.

4. The construction method of prestressed anchoring of a shield TBM through a soft rock cave section according to claim 3 is characterized by: The installation of prestressed anchor rods and the application of prestress are both completed on the anchoring operation trolley. The prestressed anchoring operation trolley can be separated from the TBM machine and constructed independently. The size of the prestressed anchoring operation trolley must meet the requirements of TBM belt conveyor slag discharge, tunnel ventilation and rail transportation in the tunnel.

5. The construction method of prestressed anchoring of a shield TBM through a soft rock cave section according to claim 1, characterized in that: The reserved holes in the special segments are used as prestressed anchor installation holes and backfill grouting holes at the same time.

6. The construction method of prestressed anchoring of a shield TBM through a soft rock cave section according to claim 1, characterized in that: A pad reserved hole is provided in the middle of the pad, and the aperture of the pad reserved hole is smaller than the aperture of the reserved hole of the special pipe segment.

7. The construction method of prestressed anchoring of a shield TBM through a soft rock cave section according to claim 1, characterized in that: One side of the pad is magnetically attracted to the special pipe segment through a pre-buried magnetic sheet, and the other side of the pad is coated with adhesive material for contact and fixation with the surrounding rock.

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