A surrounding rock reinforcement device and construction method for open TBM construction of soft surrounding rock

Abstract

A surrounding rock reinforcement device and construction method for open-type TBM construction of soft surrounding rock, the reinforcement device has a structure with a main frame as the center and symmetrical on both sides, the main frame is arranged in the middle of the device, and the main frame is fixedly connected to the TBM saddle frame II through the main frame fixing flange; the axial ends of the main frame are respectively connected to one end of the middle moving beam through flanges, and the other end of the middle moving beam is connected to one end of the end moving beam, the end moving beam is a hollow structure, a telescopic cylinder is arranged in the hollow part, the extended part of the telescopic cylinder faces the other end of the end moving beam, the extended part of the telescopic cylinder is connected to one end of the end telescopic beam, the other end of the end telescopic beam is provided with an elastic spacer, the elastic spacer is connected to the steel template through a steel template fixing pin and a ball and socket joint, the steel template is a semicircular structure perpendicular to the horizontal plane and with the center facing inward, and a grouting ball valve and a quick connector are arranged at the upper center of the semicircular structure.

Description

Technical Field

[0001] The invention relates to the technical field of open TBM construction, and in particular to a soft surrounding rock reinforcement device combined with a TBM main machine and a corresponding construction method thereof. Background Art

[0002] In order to stabilize the tunnel wall and ensure the safety of personnel and equipment when excavating in relatively soft surrounding rock, an open TBM tunnel boring machine must synchronously support the excavated rock wall by erecting steel arches, driving tracing rods, hanging steel mesh, spraying concrete, etc., so that the TBM can operate normally. However, when facing faults and broken zones of Class IV and V surrounding rock, or rock wall collapse, rock burst and other working conditions, especially when there is collapsed or broken surrounding rock on the side wall of the tunnel, the side wall of the tunnel is not enough to support the open TBM's support shoe, and the support shoe will slip or twist, so that the TBM loses the sufficient support reaction force required for forward excavation and cannot excavate. In serious cases, the joints of the support shoe or related structural parts will be damaged.

[0003] At present, when encountering the above-mentioned fault or broken zone surrounding rock during the construction of open TBM, and the surrounding rock of the side wall facing the support shoe is loose or there is a collapse cavity, there are two common practices that are usually adopted: artificially filling concrete into the collapse cavity to reinforce the surrounding rock, or taking temporary solutions such as lining the collapse cavity with wood. The manual concrete filling method has high labor intensity and low construction efficiency, and the arc-shaped hole surface forming quality of the tunnel side wall is poor, resulting in poor fit when the subsequent TBM support shoe tightens the hole wall, low tightening force, and the forward excavation support reaction force obtained by the TBM is still limited. The support reaction force obtained by lining the collapse cavity with wood support shoes is also limited, and the wood is prone to torsion. This operation has poor safety and is only suitable for temporary response solutions for sporadic and occasional small faults.

[0004] When encountering the above-mentioned fault or broken zone surrounding rock, a current engineering practice is to modify the TBM main machine, adding a set of tightening shield, a set of tightening cylinder (usually more than 20 sets), a set of steel pipe segment assembly machine, and a set of steel pipe segment removal machine to the original TBM main machine structure. In this way, when encountering a large-scale long-distance fault or broken zone, the forward thrust of the TBM is raised by assembling the steel template on the cave wall and then tightening the side section of the assembled steel template with the tightening cylinder to make the TBM move forward. The disadvantage of this method is that it requires large-scale modification of the open TBM, and it is necessary to customize the tightening shield, tightening cylinder device, template assembly machine, template removal machine from the TBM manufacturer. At the same time, it is also necessary to add a steel template lifting system. The investment cost of the modified equipment is high (up to millions), the cycle is long, and the timeliness and economic benefits are poor when facing relatively short local faults or broken zones. Summary of the invention

[0005] Purpose of the invention: To utilize the existing open TBM construction operation mode without significantly increasing the equipment cost, and to relatively quickly and efficiently solve the construction and excavation operation problems of the open TBM facing the surrounding rock of faults or broken zones, and propose a surrounding rock reinforcement device for open TBM construction in soft surrounding rock and its construction method.

[0006] Technical solution: A surrounding rock reinforcement device for open-type TBM construction in soft surrounding rock. The reinforcement device has a structure symmetrical on both sides with a main frame as the center. A main frame is arranged in the middle of the device, and the main frame is fixedly connected to the TBM saddle frame II through a main frame fixing flange; the axial ends of the main frame are respectively connected to one end of the middle moving beam through flanges, and the other end of the middle moving beam is connected to one end of the end moving beam. The end moving beam is a hollow structure, and a telescopic cylinder is arranged in the hollow part. The extended part of the telescopic cylinder faces the other end of the end moving beam, and the extended part of the telescopic cylinder is connected to one end of the end telescopic beam. The other end of the end telescopic beam is provided with an elastic spacer ring, which is connected to the steel template through a steel template fixing pin and a ball and socket joint. The steel template is a semicircular structure perpendicular to the horizontal plane and with the center facing inward, and a grouting ball valve and a quick connector are provided at the upper center of the semicircular structure.

[0007] Rectangular long holes are opened on the left and right sides of the frame of the main frame, and two intermediate movable beams pass through the rectangular long holes on both sides and are horizontally placed inside the main frame. The two intermediate movable beams have holes opened at positions corresponding to the translation guide rods, and guide sleeves are fixed in the holes. The translation guide rods pass through the two fixed guide sleeves respectively, so that a moving pair is formed between the intermediate movable beam and the translation guide rod. The intermediate movable beam is hinged to the main frame through a translation cylinder, and the intermediate movable beam can move parallel to the two translation guide rods. The two ends of the two intermediate movable beams are respectively connected to the end movable beams through the intermediate movable beam flange and the end movable beam flange.

[0008] The translation guide rod is vertically arranged with the middle moving cross beam, and the two sets of steel formworks are connected by the translation guide rod; the extended end of the translation guide rod is provided with a main frame fixing flange.

[0009] The two intermediate moving beams are respectively connected to the translation cylinder a and the translation cylinder b. One end of the translation cylinder a is fixed to the support inside the main frame, and the other end is fixed to the side support of an intermediate moving beam. The two ends of the translation cylinder b are respectively fixed to the side supports of the two intermediate moving beams.

[0010] The steel formwork forms a rotating pair with the ball and socket joint of the end telescopic beam through the ball and socket joint.

[0011] The outer diameter of the end telescopic beam is smaller than the inner diameter of the end movable beam.

[0012] The center of the steel formwork faces inward, that is, the center of the circle is located at the center of the symmetrical structure.

[0013] Construction method of surrounding rock reinforcement device for open-type TBM construction with soft surrounding rock: by moving the TBM saddle forward on the TBM main beam, the device can be positioned at the soft surrounding rock at a fast speed; the telescopic cylinder extends to drive the end telescopic beam to extend so that the steel template is close to the side wall surrounding rock; the relative positions of the two middle moving beams are fine-tuned separately by the telescopic cylinder a and the translation cylinder b, so that it drives the steel template to fine-move forward and backward to adjust the steel arch frame assembled on the side wall of the open surrounding rock; the telescopic cylinder continues to extend to tighten the steel template against the side wall of the surrounding rock, and maintains the tightening state with sufficient pressure; the grouting ball valve and quick connector on the steel template are connected to the grouting pipeline to perform pressure grouting on the soft surrounding rock or collapsed cavity behind the steel template; when the grouting is sufficient and solidified to a certain extent, the telescopic cylinder a and the translation cylinder b are retracted to make the steel template out of contact with the side wall of the surrounding rock; after the weak surrounding rock after grouting is completely solidified, the TBM tightening shoe can tighten the surrounding rock at that place, and the TBM continues to advance forward.

[0014] Beneficial effects: The present invention has a simple structure and can be organically combined with an open TBM through a modular mounting method, without affecting the functional actions and basic excavation and excavation procedures of the original TBM. Compared with the method of manually grouting to reinforce the surrounding rock collapse cavity, it can improve the grouting efficiency, ensure construction safety, save labor costs, and the surrounding rock side wall molding quality is high after grouting reinforcement. Compared with the existing technical solutions of making major structural improvements to the TBM main engine and adding a tightening shield and a steel pipe segment assembly machine, it has a simple structure and does not require modification or reconstruction of the original TBM main engine structure, which can greatly save the TBM modification cost and equipment modification cycle, and does not require the preparation of a large number of steel pipe segments during the construction process, which can greatly save the cost of auxiliary tooling preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The device of the present invention and its corresponding construction process steps are described in detail below in conjunction with the accompanying drawings and embodiments.

[0016] Figure 1 It is a front view structural schematic diagram of the device of the present invention;

[0017] Figure 2 yes Figure 1 A partial enlarged view of the ball joint of the steel formwork;

[0018] Figure 3 yes Figure 1 AA section view;

[0019] Figure 4 yes Figure 1 A top view of

[0020] Figure 5 It is a side cross-sectional view after the device of the present invention and the open TBM main machine are assembled;

[0021] Figure 6yes Figure 5 A partial enlarged view of the assembly connection portion between the device of the present invention and the TBM host;

[0022] Figure 7 yes Figure 5 A top view of

[0023] Figure 8 It is a schematic diagram of the working structure of the device of the present invention in a soft surrounding rock working condition.

[0024] Reference numerals:

[0025] 1. Main frame, 2. Middle moving beam, 3. Middle moving beam flange, 4. End moving beam flange, 5. End moving beam, 6. Telescopic cylinder, 7. End telescopic beam, 8. Elastic spacer, 9. Steel template fixing pin, 10. Ball and socket joint, 11. Steel template, 12. Grouting ball valve, 13. Quick connector, 14. Translation guide rod, 15. Main frame fixing flange, 16. Main frame welding flange, 17. Translation cylinder a, 18. Translation cylinder b, 19. Ball joint; I. Complete set of surrounding rock equipment, II. TBM saddle frame, III. TBM main beam. DETAILED DESCRIPTION

[0026] Combined with Figure 1-3 A surrounding rock reinforcement device for soft surrounding rock open-type TBM construction, the reinforcement device has a structure with a main frame 1 as the center and symmetrical on both sides, a main frame 1 is arranged in the middle of the device, and the main frame 1 is fixedly connected to the TBM saddle frame II through a main frame fixing flange; the axial ends of the main frame 1 are respectively connected to one end of the middle moving beam 2 through flanges, and the other end of the middle moving beam 2 is connected to one end of the end moving beam 5, and the end moving beam 5 is a hollow structure, wherein a telescopic oil cylinder 6 is arranged in the hollow part, and the extended part of the telescopic oil cylinder 6 is toward the other end of the end moving beam 5, and the extended part of the telescopic oil cylinder is connected to one end of the end telescopic beam 7, and the other end of the end telescopic beam 7 is provided with an elastic spacer ring 8, and the elastic spacer ring 8 is connected to the steel template 11 through a steel template fixing pin 9 and a ball and socket joint 10, and the steel template 11 is a semicircular structure perpendicular to the horizontal plane and with the center facing inward, and a grouting ball valve 12 and a quick connector 13 are arranged at the upper center of the semicircular structure;

[0027] See attached for details Figure 1 , Figure 4The left and right sides of the main frame 1 shown in the figure are provided with rectangular long holes, and two intermediate movable beams 2 are placed horizontally inside the main frame through the rectangular long holes on both sides, and the two intermediate movable beams 2 are provided with holes at positions corresponding to the translation guide rods 14, and guide sleeves are fixed in the holes, and the translation guide rods 14 pass through two fixed guide sleeves respectively, so that a moving pair is formed between the intermediate movable beams 2 and the translation guide rods 14, and the intermediate movable beams 2 and the main frame 1 are hinged by a translation cylinder, and the intermediate movable beams 2 can move parallel to the two translation guide rods 14, and the two ends of the two intermediate movable beams 2 are respectively connected to the end movable beams 5 through the intermediate movable beam flanges 3 and the end movable beam flanges 4;

[0028] Specifically, a telescopic cylinder 6 is installed inside the end movable beam 5, one end of the telescopic cylinder 6 is fixed on a support inside the end movable beam 5, and the other end is fixed on a support inside the end telescopic beam 7. A ball joint 19 is designed at one end of the end telescopic beam 7, and the ball joint 19 is connected to the ball and socket joint 10 to form a ball joint rotating pair. The steel template fixing pin 9 and the elastic spacer ring 8 are used to fix and adjust the movement amplitude of the ball joint rotating pair. The ball and socket joint 10 is connected to the steel template 11 through a flange, and a grouting ball valve 12 is connected to the steel template 11, and a quick connector 13 is connected to one end of the grouting ball valve 12.

[0029] More specifically, the outer diameter of the end telescopic beam 7 is smaller than the inner diameter of the end movable beam 5 .

[0030] The translation guide rod 14 is vertically arranged with the middle moving cross beam 2 , and the two sets of steel templates 11 are connected by the translation guide rod 14 ; the extended end of the translation guide rod 14 is provided with a main frame fixing flange 15 .

[0031] Specifically, the center of the steel template 11 faces inward, that is, the center of the circle is located at the center of the symmetrical structure.

[0032] The two intermediate movable beams 2 are respectively connected to the translation cylinder a17 and the translation cylinder b18. One end of the translation cylinder a17 is fixed to the support inside the main frame 1, and the other end is fixed to the side support of an intermediate movable beam 2. The two ends of the translation cylinder b18 are respectively fixed to the side supports of the two intermediate movable beams 2. The two intermediate movable beams 2 can be moved and adjusted on the translation guide rod 14 under the drive of the translation cylinder a17 and the translation cylinder b18.

[0033] Specifically, the middle moving beam 2 and the translation guide rod 14 form a moving pair, and the middle moving beam 2 and the main frame 1 are hinged by a translation cylinder. The end moving beam 5 has an inner guide sleeve, and the end telescopic cylinder 6 is arranged inside the guide sleeve. The end telescopic beam 7 is driven and connected with the end moving beam 7 through the telescopic cylinder 6, and a ball and socket joint 10 is arranged on the outer side of the end telescopic beam 7; the steel template 11 forms a rotating pair with the ball and socket joint 10 of the end telescopic beam 7 through the ball and socket joint 10, and the ball and socket joint 10 is connected to the steel template 11 through the steel template fixing pin 9. The steel template 11 is provided with a grouting ball valve 12 and a quick connector 13, which can be connected to the grouting pipeline to perform pressure grouting on the collapse cavity of the rotating rock; the hydraulic power source of the whole set of reinforcement device can be taken from the main hydraulic station of the open TBM, and no additional hydraulic power device is required.

[0034] The working principle of this device is: Figure 5-8 :The device is installed as a whole on an open TBM saddle frame II. The TBM saddle frame II can quickly translate forward and backward along the main beam on the TBM main beam III, so that the device as a whole can translate forward and backward along the tunnel axis along the TBM main beam III with the TBM saddle frame II. At the same time, the two translation cylinders a17 and the translation cylinder b18 can respectively perform micro-translation adjustment on the two middle moving beams 2 in the tunnel axis direction. The four end moving beams 5 can drive the steel template 11 to extend or retract in the horizontal radial direction under the action of the four telescopic cylinders 6, and can tighten the steel template to the rock wall with sufficient tightening force. The ball and socket joint 10, the steel template fixing pin 9, and the elastic spacer ring 8 can provide a micro-rotational freedom, so that when the steel template is tightened on the rock wall, the moving beam 5 and the steel template 11 can freely adjust their relative position and posture, so as not to cause dead points and damage to the structure. In this way, when weak surrounding rock or collapsed cavity appears on the side wall of the tunnel, the steel template can be flexibly aligned with the location of the weak surrounding rock or collapsed cavity through the device, and the micro-translation of the translation cylinder a17 and the translation cylinder b18 can make the steel template avoid the already erected steel arch frame (a consumable material of the surrounding rock support structure during TBM rotation) and then tighten the rock wall. When the steel template is tightened to the rock wall, the grouting hose can be connected through the grouting ball valve 12 and the quick connector 13 on it, and the grouting reinforcement can be carried out to the weak surrounding rock or collapsed cavity through the grouting pump. After the reinforced surrounding rock strength can bear the excavation and tightening force of the TBM support shoe, the TBM continues to move forward.

[0035] The construction method of this device is: Figure 8As shown, the whole set of reinforcement device is installed on the middle side end face of the open TBM saddle frame II through the fixed flange of the main frame, so that the reinforcement device can perform the main translation movement along the axis of the tunnel along the TBM main beam III together with the TBM saddle frame II. Under normal circumstances, the end moving crossbeam 5 of the reinforcement device is in a retracted state under the control of the telescopic cylinder 6. When a collapse cavity appears on the side wall of a certain part of the tunnel, the whole set of reinforcement device can be quickly translated together with the TBM saddle frame II to preliminarily position the steel template 11 at the collapse cavity; if a collapse cavity appears on the surrounding rock of the side wall for a long distance, the reinforcement device can continuously support and reinforce the collapse cavity along with the TBM saddle frame II. When the steel template 11 is initially positioned at the collapsed cavity, the telescopic cylinder 6 extends to drive the end moving beam 5 to extend outward. When the steel template 11 is about to approach the surrounding rock of the tunnel side wall, the end moving beam 5 stops extending outward. At this time, the two middle moving beams 2 can be fine-tuned by the translation cylinder, so that the gap between the two sets of steel templates 11 just avoids the steel arch frame that has been erected on the inner wall of the tunnel. Then the telescopic cylinder 6 is continued to be extended to tighten the steel template 11 at the collapsed cavity of the inner wall of the tunnel, and the tightening pressure of the telescopic cylinder 6 is maintained by the hydraulic control system. After tightening and fixing the steel template 11, the quick connector 13 on the steel template 11 can be connected to the grouting pipeline of the pressure grouting equipment equipped on the trailer behind the TBM, and then the grouting ball valve 12 on the steel template 11 is opened to inject cement mortar into the collapsed cavity behind the steel template 11 to reinforce the collapsed cavity by pressure grouting. When the back of the collapsed cavity is filled and initially solidified by pressure grouting, the telescopic cylinder 6 of the end movable crossbeam 5 is retracted to make the steel template 11 out of contact with the cave wall. When the surrounding rock of the collapsed cavity is completely solidified and has sufficient strength, the TBM support shoe can be adjusted to support the cave wall and the TBM continues to excavate the surrounding rock in front.

[0036] The device of the present invention provides a relatively simple, effective, mechanically automated device and construction method for reinforcing surrounding rock during open-type TBM construction in soft surrounding rock. The advantage is that it is flexibly fixed to the idle space below the TBM saddle frame II and the TBM main beam III in the form of flange installation, and can quickly translate forward and backward along the axial translation main motion on the TBM main beam III with the TBM saddle frame II, so as to facilitate the rapid positioning of the steel template on the surrounding rock collapse cavity. At the same time, the reinforcement device has the freedom of fine-tuning translation of the moving beam and micro-motion telescopic adjustment of radial telescopic. The application of the hydraulic system can flexibly and reliably ensure that the functional actions and operation sequence are organically matched with the grouting reinforcement and the operation sequence of the TBM main machine. The functional components of the whole set of reinforcement devices adopt a modular architecture, which can be combined and mounted according to the engineering conditions. Under the working conditions where the surrounding rock conditions are relatively good, the end telescopic beam and the steel template can be not mounted, and assembled when necessary.

[0037] The device has a simple structure and can be installed in a modular manner. It does not change the original excavation principle and overall excavation steps of the open TBM, and is highly compatible with the construction sequence of the open TBM. When facing weak surrounding rocks such as faults and broken zones, the device can use the pressure grouting method to synchronously grout the side wall surrounding rock of the tunnel. The steel formwork can make the grouting-reinforced tunnel wall completely consistent with the theoretical tunnel shape of the tunnel design, providing a perfect fit and sufficient support reaction force for the subsequent tightening of the open TBM support shoe. At the same time, the device has a flexible degree of freedom of mechanism, and can flexibly adjust the relative position of the support shoe and the steel formwork, and flexibly avoid the steel arch frame that has been installed. From the perspective of process methods, it can be fully compatible with the original open TBM excavation and support technology.

Claims

1. A surrounding rock reinforcement device for open-type TBM construction of soft surrounding rock, the reinforcement device is a structure with a main frame (1) as the center and symmetrical on both sides, characterized in that: The device is fixedly connected to the idle space below the TBM saddle frame (II) and the TBM main beam (III) in the form of flange installation. A main frame (1) is provided in the middle of the device. The main frame (1) is fixedly connected to the TBM saddle frame (II) through a main frame fixing flange. The axial ends of the main frame (1) are respectively connected to one end of the middle moving beam (2) through flanges, and the other end of the middle moving beam (2) is connected to one end of the end moving beam (5). The end moving beam (5) is a hollow structure, and a telescopic cylinder (6) is provided in the hollow part. The extended portion of the telescopic oil cylinder (6) moves toward the other end of the end movable beam (5), the extended portion of the telescopic oil cylinder is connected to one end of the end telescopic beam (7), the other end of the end telescopic beam (7) is provided with an elastic spacer ring (8), the elastic spacer ring (8) is connected to the steel template (11) through a steel template fixing pin (9) and a ball and socket joint (10), the steel template (11) is a semicircular structure perpendicular to the horizontal plane and with the center facing inward, and a grouting ball valve (12) and a quick connector (13) are provided at a position slightly above the center of the semicircular structure.

2. The surrounding rock reinforcement device for soft surrounding rock open-type TBM construction according to claim 1 is characterized by: The left and right sides of the frame of the main frame (1) are provided with rectangular long holes, and two intermediate movable beams (2) are placed horizontally inside the main frame through the rectangular long holes on both sides. The two intermediate movable beams (2) are provided with holes at positions corresponding to the translation guide rods (14), and guide sleeves are fixed in the holes. The translation guide rods (14) pass through the two fixed guide sleeves respectively, so that a moving pair is formed between the intermediate movable beams (2) and the translation guide rods (14). The intermediate movable beams (2) and the main frame (1) are hinged through a translation cylinder, and the intermediate movable beams (2) can move parallel to the two translation guide rods (14). The two ends of the two intermediate movable beams (2) are respectively connected to the end movable beams (5) through the intermediate movable beam flanges (3) and the end movable beam flanges (4).

3. The surrounding rock reinforcement device for soft surrounding rock open-type TBM construction according to claim 1 is characterized by: The translation guide rod (14) is vertically arranged with the middle moving cross beam (2), and the two sets of steel templates (11) are connected by the translation guide rod (14); the extended end of the translation guide rod (14) is provided with a main frame fixing flange (15).

4. The surrounding rock reinforcement device for soft surrounding rock open-type TBM construction according to claim 1 is characterized by: The two intermediate movable crossbeams (2) are respectively connected to the translation cylinder a (17) and the translation cylinder b (18); one end of the translation cylinder a (17) is fixed to a support inside the main frame (1), and the other end is fixed to a side support of an intermediate movable crossbeam (2); and both ends of the translation cylinder b (18) are respectively fixed to the side supports of the two intermediate movable crossbeams (2).

5. The surrounding rock reinforcement device for soft surrounding rock open-type TBM construction according to claim 1 is characterized by: The steel template (11) forms a revolving pair with the ball and socket joint (10) of the end telescopic crossbeam (7) via the ball and socket joint (10).

6. The surrounding rock reinforcement device for soft surrounding rock open-type TBM construction according to claim 1 is characterized by: The outer diameter of the end telescopic crossbeam (7) is smaller than the inner diameter of the end movable crossbeam (5).

7. The surrounding rock reinforcement device for soft surrounding rock open-type TBM construction according to claim 1 is characterized by: The center of the steel template (11) faces inwards, that is, the center of the circle is located at the center of the symmetrical structure.

8. A construction method for the surrounding rock reinforcement device for open-type TBM construction of soft surrounding rock according to claim 1, characterized in that: By moving the TBM saddle frame (II) forward on the TBM main beam (III), the device can be positioned at the weak surrounding rock at a fast speed; the telescopic cylinder (6) is extended to drive the end telescopic crossbeam (7) to extend so that the steel template (11) is close to the side wall surrounding rock; the relative positions of the two middle moving crossbeams (2) are fine-tuned separately by the translation cylinder a (17) and the translation cylinder b (18), so that they drive the steel template (11) to fine-move forward and backward to adjust the steel arch frame assembled on the side wall of the surrounding rock; the telescopic cylinder ( 6) Continue to extend the steel template (11) to press against the side wall of the surrounding rock and maintain the tightened state with sufficient pressure; connect the grouting pipeline through the grouting ball valve (12) and the quick connector (13) on the steel template (11) to perform pressure grouting on the weak surrounding rock or collapsed cavity behind the steel template (11); when the grouting is sufficient and has solidified to a certain extent, the telescopic cylinder retracts to make the steel template break away from the contact with the side wall of the surrounding rock; after the weak surrounding rock after grouting is completely solidified, the TBM tightening shoe can tighten the surrounding rock at that location, and the TBM continues to advance forward.

Images