Construction method suitable for auxiliary rectangular shield tunneling of full-section sandy stratum

Abstract

This invention discloses a construction method for auxiliary rectangular shield tunneling applicable to full-section sandy strata, comprising the following steps: Step 1: symmetrically opening a pair of through holes in the lower cutterhead area of ​​the rectangular shield machine through the shield breast plate; Step 2: installing blowout preventers on the outside of the final holes of the pair of through holes, allowing two MJS drill rods to pass through the blowout preventers through the pair of through holes and enter the soil chamber of the rectangular shield machine; Step 3: before shield advancement, extending the two MJS drill rods into the soil chamber to a first length, performing grouting improvement while retracting; Step 4: after grouting improvement is completed, retracting the MJS drill rods from the soil chamber, closing the valve of the blowout preventer, and proceeding with the advancement of the rectangular shield machine; This invention overcomes the shortcomings of the prior art.

Description

Technical Field

[0001] This invention relates to a shield tunneling construction method, and more particularly to a construction method for auxiliary rectangular shield tunneling applicable to full-section sandy strata. Background Technology

[0002] To accommodate full-face cutting, the rectangular shield tunneling machine employs a double X-shaped cutterhead arrangement with two auxiliary cutterheads. Two smaller circular cutterheads are positioned centrally on the cutting face of the rectangular shield tunneling machine, staggered vertically behind the two larger cutterheads. Compared to typical soft soil strata, shield tunneling in sandy strata presents challenges such as high cutterhead torque, high total thrust, and slow advance speed, necessitating soil improvement at the face.

[0003] The conventional operation for soil improvement in existing technologies involves adding materials such as foaming agents or bentonite slurry to the soil chamber and cutterhead front during normal advance, improving the soil while advancing to reduce cutterhead torque and thrust. However, sandy strata with high density and high SPT values ​​are prone to forming "iron plate sand" compaction, siltation of the soil chamber, and encapsulation of the cutterhead after cutterhead disturbance and water loss, thus reducing the overall cutting capacity of the cutterhead, especially for the relatively weaker small cutterhead, making overall advance difficult.

[0004] Meanwhile, existing technologies for improving the frontal soil also have the following technical problems:

[0005] 1. Improved grouting hole layout has high requirements: Improved grouting is more difficult to cover the corners and dead corners inside the soil chamber, and is prone to siltation or mud cake formation, which affects the progress of construction.

[0006] 2. High cost: In order to ensure rapid and continuous tunneling in sandy strata, it is generally necessary to continuously inject foam modifier at high flow rates. If mud cake forms, the machine must be stopped. In addition, expensive construction materials such as dispersants are added, resulting in high costs in materials, equipment and manpower during construction.

[0007] 3. High equipment failure rate: When tunneling through sandy strata across the entire face, all components and parameters of the tunnel boring machine operate under high load, which increases the burden on the equipment and results in a high equipment failure rate.

[0008] Therefore, there is a need to provide a construction method for auxiliary rectangular shield tunneling applicable to full-section sandy strata, which can solve the above-mentioned technical problems. Summary of the Invention

[0009] The purpose of this invention is to provide a construction method for auxiliary rectangular shield tunneling applicable to full-section sandy strata, which can solve the above-mentioned technical problems.

[0010] This invention is implemented as follows:

[0011] A construction method for auxiliary rectangular shield tunneling applicable to full-section sandy strata includes the following steps:

[0012] Step 1: A pair of through holes are symmetrically opened in the lower cutterhead area of ​​the rectangular shield machine through the shield breast plate;

[0013] Step 2: Install blowout preventers on the outside of the final holes of the pair of through holes, so that the two MJS drill rods can pass through the blowout preventers through the pair of through holes and enter the soil chamber of the rectangular shield machine.

[0014] Step 3: Before the tunnel boring machine advances, insert two MJS drill rods into the soil chamber to the first length and perform shotcreting improvement while retreating;

[0015] Step 4: After the shotcrete improvement is completed, the MJS drill rod is retrieved from the soil chamber, the blowout preventer valve is closed, and the rectangular shield tunneling machine is advanced.

[0016] The pair of through holes are arranged symmetrically about the central axis of the rectangular shield machine.

[0017] The horizontal distance between the pair of through holes and the central axis of the rectangular shield tunneling machine is 930mm.

[0018] The end hole of each of the aforementioned through holes is located within the cutting range of the cutterhead, the end hole of the through hole is above the bottom end of the rectangular shield machine shell, and the angle between the axial direction and the horizontal direction of the through hole, i.e., the drilling angle, is an acute angle.

[0019] The end hole of the through hole is 830mm from the bottom of the rectangular shield machine shell, the end hole of the through hole is 112mm from the bottom of the rectangular shield machine shell, the drilling angle is 18°, and the diameter of the through hole is 108mm.

[0020] Each MJS drill pipe has a diameter of 90mm, and the angle of the MJS drill pipe is consistent with the angle of the blowout preventer.

[0021] The first length of the MJS drill rod extending into the soil chamber should satisfy the following: one end of the MJS drill rod is located at the end position of the through hole, and the horizontal distance between the projection point of one end of the MJS drill rod on the horizontal plane and the cutterhead is equal to the advancement length of a single ring of a rectangular shield machine.

[0022] The MJS drill pipe uses bentonite slurry for grouting, with a grouting pressure of 32 MPa and a grouting range that is the grouting improvement range of the soil, which is a full circle with a diameter of 1800 mm.

[0023] The grouting improvement ranges of the two MJS drill rods intersect, and the grouting improvement ranges of the two MJS drill rods intersect with the cutting range of the cutterhead.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] This invention combines the rectangular shield tunneling method with the horizontal MJS method. By pre-spraying grout to improve the soil before shield tunneling, it solves the construction difficulties of rectangular shield tunneling machines in the full-section sandy strata, such as high cutterhead torque, high thrust, and slow advance speed. It can better control the overall construction efficiency of shield tunneling, reduce construction risks and material consumption, and shorten the construction cycle. The rectangular shape reduces the burden on the shield machine itself, which is beneficial to the protection of the rectangular shield machine equipment. It has great reference value for subsequent tunnel projects constructed under similar working conditions. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the cross-section of the through hole in the construction method of the auxiliary rectangular shield tunneling applicable to full-section sandy strata of the present invention.

[0027] Figure 2 This is a schematic diagram of the longitudinal section of the through hole in the construction method of the auxiliary rectangular shield tunneling applicable to full-section sandy strata of the present invention.

[0028] Figure 3 This is a schematic diagram illustrating the improved shotcrete range of the construction method for auxiliary rectangular shield tunneling applicable to full-section sandy strata according to the present invention.

[0029] In the figure, 1 is the through hole, 101 is the end hole, 102 is the final hole, 2 is the cutting range of the cutter head, and 3 is the improved range of the spraying. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0031] A construction method for auxiliary rectangular shield tunneling applicable to full-section sandy strata includes the following steps:

[0032] Step 1: Create a pair of through holes symmetrically in the lower cutterhead area of ​​the rectangular shield machine through the shield breast plate.

[0033] The pair of through holes are symmetrically arranged about the central axis of the rectangular shield machine. Preferably, the horizontal distance between the pair of through holes and the central axis of the rectangular shield machine is 930mm, which ensures the uniformity and effectiveness of subsequent grouting improvement of the soil.

[0034] Preferably, the end hole (i.e. the starting point of the through hole) of each of the aforementioned through holes is located within the cutting range of the cutterhead, the end hole (i.e. the ending point of the through hole) is located above the bottom end of the rectangular shield machine shell, and the angle between the axial direction of the through hole and the horizontal direction, i.e. the drilling angle, is an acute angle.

[0035] The diameter of the through hole can be determined according to the size of the MJS drill rod used, and the horizontal position of the through hole, the height and angle of the end hole and the final hole can be adjusted according to the shotcrete requirements.

[0036] Preferably, the end hole of the through hole is 830mm from the bottom of the rectangular shield machine shell, the end hole of the through hole is 112mm from the bottom of the rectangular shield machine shell, the drilling angle is 18°, and the diameter of the through hole is 108mm.

[0037] Step 2: Install blowout preventers on the outside of the final holes of the pair of through holes, so that the two MJS (MetroJetSystem, all-around high-pressure jetting method) drill rods can pass through the blowout preventers through the pair of through holes and enter the soil chamber of the rectangular shield machine.

[0038] Specifically, first locate and install the MJS power head device, then install the MJS drill rod. After the MJS drill rod enters the blowout preventer, open the valve of the blowout preventer and continue installing the MJS drill rod until the MJS drill rod extends into the predetermined position in the soil chamber.

[0039] Targeted high-pressure jet grouting in areas prone to siltation within the soil chamber effectively resolves the issue of mud cake formation. The grouting path can be divided into two areas: the soil layer to be advanced (1.2m) and the excavated soil within the soil chamber. Depending on actual construction needs, during the MJS drill rod retraction process, full-path grouting can be implemented to improve the excavated soil within the soil chamber, or the area to be advanced can be improved separately. The excavated soil within the soil chamber is improved using the same method as the soil layer, employing jet grouting.

[0040] Preferably, each MJS drill rod has a diameter of 90mm, and the angle of the MJS drill rod is consistent with the angle of the blowout preventer.

[0041] Step 3: Before the tunnel boring machine advances, extend two MJS drill rods into the soil chamber to the first length and perform grouting improvement while retreating to improve the cross-sectional strata within the expected travel range of the rectangular tunnel boring machine.

[0042] Preferably, the first length of the MJS drill rod extending into the soil chamber should satisfy the following: one end of the MJS drill rod is located at the end position of the through hole, and the horizontal distance between the projection point of one end of the MJS drill rod on the horizontal plane and the cutterhead is equal to the advancement length of a single ring of a rectangular shield machine.

[0043] When the advancing length of a single ring of a rectangular shield tunneling machine is 1200mm and the angle of the MJS drill rod is 18°, that is, the length of the horizontal right-angled side is 1200mm and the apex angle is 18°, the length of the hypotenuse is calculated to be 2228mm using the trigonometric functions of a right triangle. That is, the first length of the MJS drill rod extending into the soil chamber is 2228mm.

[0044] Preferably, the grouting of the MJS drill rod uses bentonite slurry, the grouting pressure is 32 MPa, the grouting range, i.e. the grouting improvement range of the soil, is a full circle with a diameter of 1800 mm, the grouting improvement ranges of the two MJS drill rods intersect, and the grouting improvement ranges of the two MJS drill rods intersect with the cutting range of the cutterhead respectively.

[0045] The range of soil shotcrete improvement can be adjusted by adjusting the drilling depth and shotcrete angle, depending on the actual construction needs.

[0046] By using horizontal MJS for advanced shotcreting improvement, the strata of the cross section within the expected advancement range are improved in advance with bentonite slurry. This allows for a significant reduction in the amount of foaming agent used during the actual advancement phase of the rectangular shield machine, under low cutterhead torque conditions, thus lowering construction costs. The thrust of the rectangular shield machine can also be effectively reduced, thereby increasing the advancement speed.

[0047] Meanwhile, after the strata are improved in advance, the main construction parameters of the rectangular shield tunneling machine, including cutterhead torque and thrust, can be effectively reduced to a reasonable range during the tunneling stage of the pre-improved strata. This reduces the load on the rectangular shield tunneling machine, lowers the equipment failure rate, and thus enables continuous construction and saves construction time.

[0048] During the shotcrete improvement process, the head valve of the MJS drill rod can be opened to discharge slag based on the pressure feedback from the front end of the MJS drill rod, ensuring that the soil pressure in the soil chamber remains stable within the required range. The blowout prevention device requires high airtightness. Since the MJS improvement shotcrete is performed under high pressure, construction should be stopped and the sealing gasket replaced immediately if leakage is detected. The shotcrete operation while the MJS drill rod is retracting can be carried out using existing techniques, which will not be elaborated upon here.

[0049] Step 4: After the shotcrete improvement is completed, retrieve the MJS drill rod from the soil chamber, close the valve of the blowout prevention device, and then proceed with the advancement of the rectangular shield tunneling machine.

[0050] Example 1:

[0051] In a rectangular shield tunneling project of the first phase of a subway line, the section is approximately 87m long with a top burial depth of 17.3m to 18.2m. The strata at the tunneling section are: ① 41 silt and ② 51 fine sand. Given that the tunneling strata consist entirely of sand, to ensure sufficient improvement of the strata at the shield tunneling section and reduce adverse factors for advancement, and considering the controllable ground pressure characteristics of the MJS method, the construction method of this invention is adopted to assist in the advancement of the rectangular shield tunneling.

[0052] A rectangular earth pressure balance tunnel boring machine (TBM) was adopted, equipped with an MJS power head unit, main unit, and other supporting components. The MJS power unit was simulated and positioned according to the TBM equipment drawings to ensure that the position and angle of the through-hole did not interfere with the cutterhead and other components.

[0053] Please see the appendix Figure 1 and attached Figure 2 The drilling positions were determined on-site by surveying. Two φ108mm through holes were drilled in the lower cutterhead area through the shield's breast plate, symmetrically arranged along the central axis of the shield machine. The horizontal positioning of through hole 1 is 930mm from the axis. The vertical positioning of through hole 1 is as follows: the end hole 101 (at the breast plate) is 830mm from the bottom of the rectangular shield machine shell; the final hole 102 is 112mm from the bottom of the rectangular shield machine shell; the drilling angle is 18°.

[0054] A blowout preventer is installed outside the through hole. The φ90m diameter MJS drill rod passes through the blowout preventer and enters the soil chamber of the rectangular shield machine, ensuring that the angle of the MJS drill rod is 18°.

[0055] Before the tunnel boring machine (TBM) advances, the two MJS drill rods on the left and right are extended into the soil chamber by a length of 2280mm (projected length exceeds the cutterhead by 1200mm, i.e., the single-ring advance length), as shown in the attached figure. Figure 2 As shown, once the location is reached, bentonite slurry can be sprayed while retreating to improve the soil. Spraying pressure: 32 MPa; spraying improvement range 3: φ1800mm full circle, as shown in the attached diagram. Figure 3 As shown, the improved shotcrete range 3 extends downward from the bottom of the cutterhead cutting range 2 to the bottom of the housing. The improved shotcrete ranges 3 of the two MJS drill rods intersect, and the improved shotcrete ranges 3 of the two MJS drill rods intersect with the cutterhead cutting range 2 respectively.

[0056] During the improvement process, the valve at the head of the MJS drill rod can be controlled based on the pressure feedback at the front end of the MJS drill rod to discharge slag, ensuring that the soil pressure inside the chamber remains stable within the required range. After the improvement is completed, the MJS drill rod is retrieved from the soil chamber, and the rectangular shield tunneling machine is used for propulsion.

[0057] By performing soil shotcrete pre-modification, the torque and thrust of the cutterhead during shield tunneling can be greatly reduced, and the propulsion speed can be increased, making the overall construction more efficient and the safety risks more controllable. At the same time, it reduces the equipment burden of rectangular shield tunneling machines to a certain extent, which is beneficial to the protection of the equipment.

[0058] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the invention. Therefore, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A construction method suitable for auxiliary quasi-rectangular shield tunneling of full-face sandy strata, characterized in that: Includes the following steps: Step 1: A pair of through holes are symmetrically opened in the lower cutterhead area of ​​the rectangular shield machine through the shield breast plate; Step 2: Install blowout preventers on the outside of the final holes of the pair of through holes, so that the two MJS drill rods can pass through the blowout preventers through the pair of through holes and enter the soil chamber of the rectangular shield machine. Step 3: Before the tunnel boring machine advances, insert two MJS drill rods into the soil chamber to the first length and perform shotcreting improvement while retreating; Step 4: After the shotcrete improvement is completed, the MJS drill rod is retrieved from the soil chamber, the blowout preventer valve is closed, and the rectangular shield tunneling machine is advanced. The pair of through holes are arranged symmetrically about the central axis of the rectangular shield machine; The end hole of each of the aforementioned through holes is located within the cutting range of the cutterhead, the end hole of the through hole is above the bottom end of the rectangular shield machine shell, and the angle between the axial direction and the horizontal direction of the through hole, i.e. the drilling angle, is an acute angle. The end hole of the through hole is 830mm from the bottom of the rectangular shield machine shell, the end hole of the through hole is 112mm from the bottom of the rectangular shield machine shell, the drilling angle is 18°, and the diameter of the through hole is 108mm. The first length of the MJS drill rod extending into the soil chamber should satisfy the following: one end of the MJS drill rod is located at the end position of the through hole, and the horizontal distance between the projection point of one end of the MJS drill rod on the horizontal plane and the cutterhead is equal to the propulsion length of a single ring of a rectangular shield machine. The horizontal distance between the pair of through holes and the central axis of the rectangular shield tunneling machine is 930mm. Each MJS drill pipe has a diameter of 90mm, and the angle of the MJS drill pipe is consistent with the angle of the blowout preventer. The MJS drill pipe uses bentonite slurry for grouting, with a grouting pressure of 32 MPa and a grouting range that is the grouting improvement range of the soil, which is a full circle with a diameter of 1800 mm. The grouting improvement ranges of the two MJS drill rods intersect, and the grouting improvement ranges of the two MJS drill rods intersect with the cutting range of the cutterhead.

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