An implementation method for simultaneously restoring tunnel heave deformation and horizontal deformation

Abstract

The present invention discloses an implementation method for simultaneously restoring the uplift deformation and horizontal deformation of a tunnel, comprising the steps of: performing numerical simulation before excavating a foundation pit to obtain the positions and sizes of vertical grouting holes and the positions and sizes of inclined drilling holes in the unloading hole area located below the existing tunnel; preparing a grouting device and a hole-expanding drill bit; drilling holes; inserting the grouting device into each vertical grouting hole; excavating the foundation pit inside the diaphragm wall, and simultaneously observing the displacement monitoring devices at the monitoring points installed on the inner wall of the existing tunnel and the track bed. If a certain ring of segments generates displacement and deformation, grout is injected into the vertical grouting hole corresponding to the position of this ring of segments, and at the same time, hole-expanding construction is carried out at the bottom of the inclined drilling hole corresponding to the position of this ring of segments by using the hole-expanding drill bit. When the horizontal displacement, vertical displacement, and ovality of the tunnel are restored to the set values, stop grouting and drilling. By using this method, the recovery rate of the vertical rigid body displacement is close to 0.4.

Description

Technical Field

[0001] The invention relates to an active controlled grouting and unloading method, in particular to a grouting and unloading method for restoring horizontal rigid body displacement, vertical rigid body displacement and ovality of a tunnel. Background Art

[0002] High-rise buildings are increasingly densely populated around subway lines. To maximize space utilization, the horizontal distance between buildings and subway lines is kept close, and the depth of building basements is gradually increasing. Excavation work to develop underground space inevitably causes deformation in the surrounding soil, which in turn causes deformation in the tunnels embedded within it. This poses a threat to the structural and operational safety of subway lines and presents new challenges to foundation pit design and construction techniques.

[0003] Many literatures have reported that foundation pit construction has caused large deformations in adjacent subway shield tunnels or station structures, and even caused serious damage such as cracking of pipe segments, cracking of walls, and water leakage. In order to reduce the impact of foundation pit construction on adjacent existing tunnels, active and passive protection measures are often required. Passive protection measures mainly include: (1) strengthening the support system; (2) optimizing the excavation method; (3) reinforcing the soil in the pit; and (4) isolating walls (piles).

[0004] Passive measures typically result in significantly increased excavation costs and construction time. In most cases, these passive measures are unlikely to achieve millimeter-level deformation control within adjacent operational tunnels. Grouting is one active control measure, widely used to elevate buildings, tunnels, and pipelines. Grouting adjacent to existing tunnels can also intentionally induce a certain amount of horizontal deformation in the tunnel, thereby actively controlling and correcting horizontal deformation. Grouting simultaneously controls both tunnel and vertical deformation. Currently, there is much research on grouting to elevate existing buildings or tunnels, but less on controlling horizontal deformation in tunnels. When the tunnel is located in an uplifted area, oblique grouting above the tunnel near the excavation has some effect on controlling vertical deformation, but the effect is limited. Furthermore, vertical grouting, while more effective at restoring horizontal deformation, can slightly increase vertical deformation. Drilling unloading holes is also an active control measure. By removing a moderate amount of soil from the tunnel's lower portion, the surrounding soil fills the holes, which can alleviate tunnel uplift. However, constructing unloading holes below the tunnel's lower portion, away from the excavation, can significantly cause tunnel subsidence. However, there is currently a lack of systematic grouting theories and strategies for simultaneously controlling the horizontal and vertical deformation of tunnels. Summary of the Invention

[0005] The object of the present invention is to overcome the shortcomings of the prior art and propose a method that can better restore the horizontal rigid body displacement, vertical rigid body displacement and ellipticity of the tunnel. Especially for the vertical rigid body displacement, when the vertical rigid body recovery rate reaches 0.4, the tunnel uplift and horizontal deformation can be restored at the same time.

[0006] To solve the above technical problems, the following technical solutions are implemented.

[0007] An implementation method for simultaneously restoring the tunnel uplift deformation and horizontal deformation of the present invention includes the following steps:

[0008] Step 1: Before excavating the foundation pit, the position and size of the vertical grouting holes between the diaphragm wall at the location of the existing tunnel and the outer wall of the to-be-excavated foundation pit can be obtained through numerical simulation software, as well as the position and size of the inclined drilling holes in the unloading hole area below the existing tunnel; within the length range of the to-be-excavated foundation pit and at the corresponding positions of each ring segment of the existing tunnel, one of the above-mentioned vertical grouting holes and one inclined drilling hole are respectively arranged; the inclined drilling hole is drilled from the ground on the side far from the foundation pit into the ground.

[0009] Step 2: Prepare a grouting device and an underreaming bit. The grouting device includes a grouting pipe. A plurality of slurry outlet holes are opened on the pipe wall at the lower end of the grouting pipe, and a bladder is fixedly sleeved on the outer wall of the grouting pipe at the positions corresponding to the plurality of slurry outlet holes.

[0010] Step 3: Drill holes according to the position and size of the vertical grouting holes determined in Step 1; drill holes according to the position and size of the inclined drilling holes.

[0011] Step 4: Insert the grouting device into each vertical grouting hole.

[0012] Step 5: Excavate the foundation pit inside the diaphragm wall, and at the same time observe the displacement monitoring equipment at the monitoring points installed on the inner wall of the existing tunnel and the track bed. If a certain ring segment generates displacement and deformation, grout into the vertical grouting hole corresponding to the ring segment, and at the same time use the underreaming bit to perform underreaming construction at the bottom of the inclined drilling hole corresponding to the ring segment. The displacement monitoring equipment includes tunnel horizontal displacement monitoring equipment, vertical displacement monitoring equipment, and ellipticity monitoring equipment.

[0013] Step 6: The slurry flows into the bladder at the slurry outlet holes of the grouting pipes of each grouting device arranged in the vertical direction and solidifies to form a vertical grouting body. The underreaming bit punches out the unloading hole area at the inclined drilling hole obliquely below the tunnel. During the process of grouting and punching the unloading hole, continuously observe the data output by the displacement monitoring equipment installed in the existing tunnel. When the tunnel horizontal displacement, vertical displacement, and ellipticity are restored to the set values, stop grouting and punching.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] This method combines grouting with unloading holes to simultaneously control both horizontal and uplift deformation in the uplift zone, resolving the issue of grouting only controlling horizontal deformation while ignoring uplift deformation. This combined approach effectively restores both horizontal and vertical rigid body displacements and ellipticity. Specifically for vertical rigid body displacement, the combined approach achieves a vertical rigid body recovery rate of 0.4, compared to -0.09 using vertical grouting alone. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the combined structure of vertical grouting and unloading holes in the method for simultaneously restoring tunnel uplift deformation and horizontal deformation according to the present invention;

[0017] Figure 2 A schematic diagram of the structure of the bag grouting device before grouting, used in the method for simultaneously restoring the uplift deformation and horizontal deformation of a tunnel according to the present invention;

[0018] Figure 3 for Figure 2 The schematic diagram of the structure of the bag grouting device after grouting is shown;

[0019] Figure 4 for Figure 1 Top view of the structure shown. DETAILED DESCRIPTION

[0020] In order to make the purpose, solution and advantages of the present invention clearer, the present invention is further described below with reference to the accompanying drawings and a specific implementation case.

[0021] A method for simultaneously restoring tunnel uplift deformation and horizontal deformation according to the present invention comprises the following steps:

[0022] Step 1: Before excavating the foundation pit, numerical simulation software (Plaxis can be used but is not limited to) can be used to perform numerical simulation to obtain the position and size of the vertical grouting holes between the existing tunnel 1 and the ground-connected wall at the outer wall of the foundation pit to be excavated, as well as the position and size of the oblique boreholes 5 in the unloading hole area 3 located below the existing tunnel; within the length range of the foundation pit to be excavated and at the position corresponding to each ring segment of the existing tunnel 1, one vertical grouting hole and one oblique borehole (such as Figure 4 The oblique borehole 5 is drilled into the ground from the ground away from one side of the foundation pit.

[0023] Step 2: Prepare the grouting device and the hole - expanding drill bit. The grouting device includes a grouting pipe 4. Multiple slurry - discharging holes are opened on the wall of the lower end of the grouting pipe 4. A bladder 6 is fixedly sleeved on the outer wall of the grouting pipe 4 at positions corresponding to the multiple slurry - discharging holes. The grouting pipe 4 can be composed of multiple pipe segments fixedly connected in sequence up and down. The bladder and the grouting pipe can be connected by a hoop 7.

[0024] Step 3: Drill holes according to the positions and sizes of the vertical grouting holes determined in Step 1; drill holes according to the positions and sizes of the inclined drill holes 5.

[0025] Step 4: Insert the grouting device into each vertical grouting hole.

[0026] Step 5: Excavate the foundation pit on the inner side of the diaphragm wall. At the same time, observe the displacement monitoring equipment at the monitoring points installed on the inner wall of the existing tunnel and the track bed. If a certain ring of segments generates displacement and deformation, grout into the vertical grouting hole corresponding to the position of this ring of segments (arrange the grouting pipe as shown Figure 4 ). At the same time, use the hole - expanding drill bit to expand the hole at the bottom of the inclined drill hole 5 corresponding to the position of this ring of segments. The displacement monitoring equipment includes tunnel horizontal displacement monitoring equipment, vertical displacement monitoring equipment, and ovality monitoring equipment.

[0027] For the displacement monitoring equipment, for vertical displacement, static level gauges can be used for automated monitoring, for horizontal displacement, displacement sensors can be used for monitoring, and for the tunnel convergence condition, i.e., ovality, laser rangefinders can be used for monitoring. Of course, all existing equipment that can monitor displacement and deformation can be selected, not limited to the above equipment. The detection method can refer to the instruction manuals of the corresponding monitoring equipment.

[0028] Step 6: The slurry flows into the bladder 6 at the slurry - discharging holes of the grouting pipes of each grouting device arranged vertically and solidifies to form the vertical grouting body 2. The hole - expanding drill bit punches out the unloading hole area 3 through the inclined drill hole 5 obliquely below the tunnel. During the grouting and punching of the unloading holes, continuously observe the data output by the displacement monitoring equipment installed in the existing tunnel. When the tunnel horizontal displacement, vertical displacement, and ovality return to the set values, stop grouting and punching.

[0029] As an implementation mode of the present invention, through simulation calculation by Plaxis, the shortest horizontal distance b between the vertical grouting body 2 and the existing tunnel 1 in the direction of the horizontal axis of the existing tunnel is 3 m - 3.5 m, and the vertical distance a between the horizontal center line of the vertical grouting body and the horizontal axis of the tunnel is 1 m. The length L of the vertical grouting body can be taken as 5 m - 6 m. When drilling unloading holes obliquely below the tunnel, a small drill bit can be used to drill an inclined hole 5 at the beginning of drilling into the soil body to minimize the impact of drilling on the tunnel; subsequently, when controlling the deformation of the tunnel, the drilling area is treated with an enlarged head to leave the unloading hole area 3. When all the soil removed obliquely by the unloading hole is filled by the surrounding soil and the deformation of the tunnel is restored to the required level, it is considered that the repair of the tunnel deformation is completed. The included angle between the axes of the inclined hole 5 and the unloading hole area 3 and the horizontal line is 30° - 35°, the length of the unloading hole area is 9 m, and the diameter is 9 cm - 10 cm. A perpendicular line is drawn from the center position of the tunnel to the central axis of the unloading hole, and the foot of the perpendicular is at one-third of the length of the unloading hole area. The length of the unloading hole area above the foot of the perpendicular is greater than the length of the unloading hole area below the foot of the perpendicular. The shortest distance c between the outer contour of the unloading hole area 3 and the outer contour of the existing tunnel 1 of the perpendicular line is 3 m - 3.5 m. In actual engineering, the specific dimensions and positions of the unloading hole and the grouting body can be obtained through calculation by numerical simulation software (including but not limited to Plaxis), and are not limited to the values given above.

[0030] Although the preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific implementation manners. The above specific implementation manners are merely illustrative and not restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many forms without departing from the purpose of the present invention and the scope protected by the claims. All of these fall within the protection scope of the present invention.

Claims

1. A method for simultaneously restoring tunnel uplift and horizontal deformation, characterized in that The following steps are involved: Step 1: Before excavating the foundation pit, numerical simulation software is used to perform numerical simulation to determine the position and size of the vertical grouting holes between the existing tunnel and the ground-connected wall at the outer wall of the foundation pit to be excavated, as well as the position and size of the oblique boreholes in the unloading hole area below the existing tunnel; within the length of the foundation pit to be excavated and at positions corresponding to each ring segment of the existing tunnel, one vertical grouting hole and one oblique borehole are respectively set; the oblique boreholes are drilled into the ground from the ground away from the side of the foundation pit; Step 2: prepare a grouting device and a reaming drill bit, wherein the grouting device includes a grouting pipe, a plurality of slurry outlet holes are opened on the pipe wall at the lower end of the grouting pipe, and a bag is fixed on the outer wall of the grouting pipe at positions corresponding to the plurality of slurry outlet holes; Step 3: Drill holes according to the position and size of the vertical grouting holes determined in step 1; drill holes according to the position and size of the oblique holes; Step 4: insert a grouting device into each vertical grouting hole; Step 5: excavate a foundation pit inside the ground-connected wall, and simultaneously observe the displacement monitoring equipment installed at the monitoring points on the existing tunnel inner wall and the track bed. If a ring segment produces displacement and deformation, grouting is injected into the vertical grouting hole corresponding to the ring segment, and at the same time, a reaming drill is used to expand the bottom of the oblique drill hole corresponding to the ring segment. The displacement monitoring equipment includes tunnel horizontal displacement monitoring equipment, vertical displacement monitoring equipment, and ovality monitoring equipment. Step 6. The slurry flows into the bag at the outlet holes in the grouting pipes of each grouting device arranged in the vertical direction, solidifies to form a vertical grouting body, and the reaming drill bit passes through the oblique drill hole obliquely below the tunnel to drill a unloading hole area. During the grouting and unloading hole drilling process, the output data of the displacement monitoring equipment installed in the existing tunnel is continuously observed. When the horizontal displacement, vertical displacement and ovality of the tunnel return to the set values, the grouting and drilling are stopped.

2. The method for simultaneously restoring tunnel uplift and horizontal deformation according to claim 1, characterized in that: After simulation calculation by Plaxis, the shortest horizontal distance between the vertical grouting body and the existing tunnel along the horizontal axis of the existing tunnel is 3m-3.5m, the vertical distance between the horizontal center line of the vertical grouting body and the horizontal axis of the tunnel is 1m, the length of the vertical grouting body is 5m-6m, the angle between the axis of the inclined drilling and unloading hole area and the horizontal line is 30°~35°, the length of the unloading hole area is 9m and the diameter is 9cm-10cm; a perpendicular line is drawn from the center position of the tunnel to the center axis of the unloading hole, and the foot of the perpendicular is at one-third of the length of the unloading hole area, where the length of the unloading hole area above the foot of the perpendicular is greater than the length of the unloading hole area below the foot of the perpendicular, and the closest distance of the perpendicular line between the outer contour of the unloading hole area and the outer contour of the existing tunnel is 3m-3.5m.

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