Excavation construction method for large-section underwater tunnel surrounding rock in-situ middle partition reservation in soft broken surrounding rock

Abstract

The invention provides an excavation construction method for large-section underwater tunnel surrounding rock in-situ middle partition reservation in soft broken surrounding rock. The excavation construction method comprises the steps that S1, an excavation section is designed; s2, advanced drilling; s3, water plugging and grouting; s4, synchronously excavating the left pilot tunnel and the right pilot tunnel; s5, the middle partition surrounding rock is excavated at intervals; s6, excavating a lower step; s7, pouring a secondary lining; and S8, circulating construction is conducted according to the steps S3-S7, the synchronous excavation footage of the left pilot tunnel and the right pilot tunnel is controlled to be 5-8 m earlier than excavation of the middle partition surrounding rock, the excavation footage of the middle partition surrounding rock is controlled to be 8-12 m earlier than excavation of the lower step, and the distance between the secondary lining footage and the tunnel face of the lower step is controlled to be 8-10 m. According to the characteristics of underwater tunnel engineering in weak surrounding rocks, the middle partition surrounding rocks are formed through rock soil in-situ reservation between the upper left pilot tunnel and the upper right pilot tunnel, synchronous excavation construction is conducted on the left pilot tunnel and the right pilot tunnel, interval excavation is conducted in combination with the middle partition surrounding rocks, disturbance to the surrounding rocks is small, the construction period can be greatly shortened, and the construction efficiency is improved. And meanwhile, the safety requirement and the economic requirement of engineering are met.

Description

Technical Field

[0001] The invention relates to an excavation construction method for pre-reserving an in-situ partition in surrounding rock of a large-section underwater tunnel in soft and broken surrounding rock, and belongs to the technical field of tunnel construction. Background Art

[0002] When dealing with the construction of large-section underwater tunnels, step-by-step excavation methods such as the CD method, step method, CRD method, and double-sidewall pilot method are usually used. The main purpose is to reduce the large section into a small section and reduce the span of a single tunnel excavation to improve the stability and safety of the construction along the road. However, underwater tunnel excavation also faces engineering difficulties such as poor surrounding rock stability, large blasting disturbance to the surrounding rock, and infinite groundwater recharge. When excavating large-section underwater tunnels in soft and broken surrounding rocks in steps, too many excavated parts will aggravate the degree of surrounding rock disturbance, and each part must be excavated strictly in sequence, which greatly increases the construction period, making it difficult to meet the requirements of engineering economy. Summary of the invention

[0003] In view of the above problems, the purpose of the present invention is to provide an excavation construction method for an underwater tunnel with a large cross-section in soft and broken surrounding rock with an in-situ reserved middle partition in the surrounding rock. According to the characteristics of underwater tunnel projects in soft surrounding rock, the method utilizes the in-situ reserved rock and soil between the upper left pilot pit and the upper right pilot pit to form a middle partition surrounding rock. The left pilot pit and the right pilot pit are excavated simultaneously, and the excavation is combined with the interval excavation of the middle partition surrounding rock. This method not only causes little disturbance to the surrounding rock, but also can greatly shorten the construction period, while meeting the safety and economic requirements of the project.

[0004] The present invention is achieved through the following technical solutions.

[0005] The excavation construction method for in-situ partition reservation of surrounding rock of large-section underwater tunnel in soft and broken surrounding rock is characterized by comprising the following steps:

[0006] S1. Excavation section design

[0007] The excavation section is divided into an upper step and a lower step, and the upper step is divided from left to right into an upper left pilot pit, a middle partition surrounding rock, and an upper right pilot pit:

[0008] S2. Advance Drilling

[0009] Use the long and short drill rods of the anchor drill to conduct advance drilling behind the face;

[0010] S3, water blocking grouting

[0011] Select a suitable water plugging grouting method according to the result of the advance drilling in step S2;

[0012] S4: Synchronous excavation of left and right pilot pits

[0013] First, advance support for the upper left pilot pit and the upper right pilot pit are carried out simultaneously, and then the side wall rock mass of the upper left pilot pit and the side wall rock mass of the upper right pilot pit are excavated simultaneously, so that the rock and soil between the upper left pilot pit and the upper right pilot pit are reserved in situ to form a partition surrounding rock, and then the left side wall initial support and the right side wall initial support are carried out, and temporary support for the partition surrounding rock is carried out on both sides of the partition surrounding rock;

[0014] When the initial support of the left wall and the initial support of the right wall are applied, the upper mortar anchor rods of the surrounding rock are inserted obliquely upwards on the left and right sides of the top of the middle partition surrounding rock, and the lower ends of the mortar anchor rods of the surrounding rock top on the left and right sides are respectively connected with the initial support of the left wall and the initial support of the right wall, while the higher ends of the two are staggered along the tunnel direction. When the temporary support of the middle partition surrounding rock is applied, the lower mortar anchor rods of the surrounding rock are inserted obliquely upwards on both sides of the middle partition surrounding rock at a certain interval along the direction of the tunnel, so that the middle partition surrounding rock forms an alternately distributed middle partition surrounding rock reinforcement area and middle partition surrounding rock non-reinforcement area;

[0015] S5, Excavation with intervals between surrounding rocks

[0016] First, the temporary support of the septum surrounding rock in the non-reinforced area of ​​the septum surrounding rock is removed, and then the non-reinforced area of ​​the septum surrounding rock is excavated, and then the initial support of the non-reinforced area of ​​the septum surrounding rock is constructed on the top of each non-reinforced area of ​​the septum surrounding rock, and the initial support of the non-reinforced area of ​​the septum surrounding rock is connected with the initial support of the left wall and the initial support of the right wall on both sides to form a whole, and then the temporary support of the septum surrounding rock in the reinforced area of ​​the septum surrounding rock is removed, and then the reinforced area of ​​the septum surrounding rock is excavated, and then the initial support of the septum surrounding rock reinforcement area is constructed on the top of each reinforced area of ​​the septum surrounding rock, and the initial support of the septum surrounding rock reinforcement area is connected with the initial support of the left wall and the initial support of the right wall on both sides and the initial support of the non-reinforced area of ​​the septum surrounding rock to form a whole;

[0017] S6, excavation of lower steps

[0018] First, advance support is applied to the lower step, then the rock mass of the lower step is excavated, and finally, initial support is applied to the lower step to close the ring;

[0019] S7, pouring secondary lining;

[0020] S8. Carry out circular construction according to steps S3-S7, control the synchronous excavation progress of the left pilot pit and the right pilot pit to be 5-8m ahead of the excavation of the middle partition surrounding rock, control the excavation progress of the middle partition surrounding rock to be 8-12m ahead of the excavation of the lower step, and control the secondary lining progress to be 8-10m away from the heading face of the lower step.

[0021] Preferably, in step S2, 6 water exploration holes are drilled each time, and the outer deviation angle of the drilling hole is 10°.

[0022] Preferably, in step S3, according to the water inflow of the water exploration hole in the advance drilling result of step S2, full-section water blocking, local grouting water blocking or no water blocking is adopted.

[0023] Preferably, when 4 or more of the water exploration holes are full of water and the total water volume is greater than 15m 3 / h, full-section surface water blocking grouting is used; when the total water volume is less than 15m 3 / h but the water output of some holes is greater than 3m 3 / h, local water blocking grouting is used; when the water output of the six holes is less than 3m 3 / h and the total water output is less than 15m 3 / h, grouting is not used to block water, and the next construction step is directly entered.

[0024] Preferably, the width of the connection between the bottom of the middle partition surrounding rock and the lower step is 1.2 to 1.8 m.

[0025] Preferably, in steps S4, S5 and S6, a cantilever tunneling machine is used to excavate the rock mass.

[0026] Preferably, in steps S4, S5 and S6, the initial support is constructed by a combination of steel arch frames, shotcrete and mortar anchors.

[0027] Preferably, in steps S4 and S6, the advance support is constructed by combining advance small-duct grouting and advance pipe shed.

[0028] Preferably, the advanced small-duct grouting adopts a double-layer φ42mm×4mm advanced small-duct, L=4.5m, a ring longitudinal spacing of 0.4×3m, an external insertion angle of the first layer of 5°~15°, an external insertion angle of the second layer of 40°~45°, and a plum blossom shape arrangement.

[0029] Preferably, in step S4, the temporary support of the surrounding rock is constructed by combining temporary steel arches, steel mesh and shotcrete.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The present invention can effectively intercept water sources, reduce or eliminate water inflow in the tunnel, and ensure the safety of subsequent construction by using advance drilling and selecting a suitable grouting water blocking method according to the exploration results of the advance drilling.

[0032] (2) The present invention utilizes the in-situ reserved rock and soil between the upper left pilot pit and the upper right pilot pit to form a partition surrounding rock. Without the need to construct additional supporting and reinforcing facilities such as a partition wall, the present invention can reduce the span of a single tunnel excavation and weaken the disturbance between the upper left pilot pit and the upper right pilot pit during excavation through the supporting and isolating effect of the in-situ reserved partition surrounding rock, thereby enabling the left pilot pit and the right pilot pit to be excavated synchronously in an efficient and safe manner, thereby greatly shortening the construction period.

[0033] (3) The present invention forms alternatingly distributed mortar anchor rods on the upper surrounding rock and mortar anchor rods on the left and right sides of the top of the middle surrounding rock, which are staggered and connected upward along the tunnel direction, and mortar anchor rods on the lower surrounding rock are inserted upward at certain intervals on both sides of the middle surrounding rock. The middle surrounding rock can be reinforced and non-reinforced areas. The supporting stability of the middle surrounding rock can be ensured, and the interval excavation of the middle surrounding rock can be achieved, thereby reducing the disturbance to the nearby surrounding rock during the excavation of the middle surrounding rock, so as to ensure the safety of construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a front view of the excavation construction method of the present invention;

[0035] Figure 2 for Figure 1 Cross-section at AA in the middle;

[0036] Figure 3 for Figure 2 Cross-section at the middle BB;

[0037] Figure 4 It is a schematic diagram of the process of excavation in the middle interval of surrounding rock;

[0038] Figure 5 It is a front view of water plugging grouting in the present invention;

[0039] Figure 6 It is a cross-sectional view of the water plugging grouting in the present invention;

[0040] The meanings of the symbols in the above figures are: upper step 1, upper left pilot pit 101, upper right pilot pit 102, middle partition surrounding rock 103, middle partition surrounding rock reinforcement area 1031, middle partition surrounding rock non-reinforcement area 1032, lower step 2, middle partition surrounding rock temporary support 3, upper left pilot pit advance support 4, left side wall initial support 5, water exploration hole 6, upper right pilot pit advance support 7, right side wall initial support 8, heading face 9, surrounding rock upper mortar anchor 10, surrounding rock lower mortar anchor 11, middle partition surrounding rock non-reinforcement area initial support 12, middle partition surrounding rock reinforcement area initial support 13, lower step advance support 14, lower step initial support 15, secondary lining 16. DETAILED DESCRIPTION

[0041] The present invention is further described in the form of specific embodiments in conjunction with the accompanying drawings. It should be pointed out that the following implementation modes are only illustrative descriptions of the present invention in the form of examples, but the protection scope of the present invention is not limited thereto. The described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] This embodiment provides an excavation construction method for a large-section underwater tunnel in soft and broken surrounding rock with an in-situ partition reservation. Figures 1 to 6 , which comprises the following steps:

[0043] S1. Excavation section design

[0044] The excavation section is divided into an upper step 1 and a lower step 2, and the upper step 1 is divided from left to right into an upper left pilot pit 101, a middle partition surrounding rock 103 and an upper right pilot pit 102:

[0045] S2. Advance Drilling

[0046] See also Figure 5 and Figure 6 , use the long and short drill rods of the anchor drill to conduct advance drilling behind the face. Drill 6 water exploration holes each time, with an outer deviation angle of 10°. The water exploration holes can also be used as drainage holes to reduce the impact of water pressure on the surrounding rock;

[0047] S3, water blocking grouting

[0048] See also Figure 5 and Figure 6 According to the water inflow of the water exploration holes in the advance drilling results of step S2, full-section water blocking, local grouting water blocking or no water blocking is adopted. Specifically: when 4 or more water exploration holes are full of water and the total water volume is greater than 15m 3 / h, full-section water blocking grouting is used; when the total water volume is less than 15m 3 / h but the water output of some holes is greater than 3m 3 / h, local water blocking grouting is used; when the water output of the six holes is less than 3m 3 / h and the total water output is less than 15m 3 / h, no water blocking grouting is used, and the next construction step is directly entered;

[0049] The grouting range of water blocking grouting is: within the water outlet channel, 5 to 6 meters outside the outer contour line of the tunnel excavation, the effective diffusion radius of single hole grouting is R = 3.6m, and the final pressure after grouting is 2 to 3 times the net water pressure; after grouting, the total water output is less than 2m 3 / h and the water output at one place is less than 0.6m 3 / h, the grouting can be finished;

[0050] S4: Synchronous excavation of left and right pilot pits

[0051] See also Figures 1 to 3, firstly, the upper left pilot pit advance support 4 and the upper right pilot pit advance support 7 are synchronously constructed, and then the STR318H cantilever tunneling machine is used to synchronously excavate the side wall rock mass of the upper left pilot pit 101 and the side wall rock mass of the upper right pilot pit 102, so that the rock and soil between the upper left pilot pit 101 and the upper right pilot pit 102 are reserved in situ to form the middle partition surrounding rock 103, and the width of the connection between the bottom of the middle partition surrounding rock 103 and the lower step 2 is controlled to be 1.2-1.8m; then, the left side wall initial support 5 and the right side wall initial support 8 are constructed, and the middle partition surrounding rock temporary support 3 is constructed on both sides of the middle partition surrounding rock 103;

[0052] When constructing the left side wall initial support 5 and the right side wall initial support 8, the upper mortar anchor rods 10 of the surrounding rock are obliquely inserted upwards on the left and right sides of the top of the middle septum surrounding rock 103, and the lower ends of the surrounding rock top mortar anchor rods 10 on the left and right sides are respectively connected to the left side wall initial support 5 and the right side wall initial support 8, while the higher ends of the two are staggered along the tunnel direction. When constructing the temporary support 3 of the middle septum surrounding rock, the lower mortar anchor rods 11 of the surrounding rock are obliquely inserted upwards on both sides of the middle septum surrounding rock 103 at a certain interval along the direction of the tunnel, so that the middle septum surrounding rock 103 forms an alternately distributed middle septum surrounding rock reinforcement area 1031 and middle septum surrounding rock non-reinforcement area 1032;

[0053] S5, Excavation with intervals between surrounding rocks

[0054] See also Figure 4 , first remove the temporary support 9 of the septum surrounding rock non-reinforced area 1032, then excavate the septum surrounding rock non-reinforced area 1032, then construct the initial support 12 of the septum surrounding rock non-reinforced area on the top of each septum surrounding rock non-reinforced area 1032, and connect the initial support 12 of the septum surrounding rock non-reinforced area with the initial support 5 of the left wall and the initial support 8 of the right wall on both sides to form a whole, then remove the temporary support 9 of the septum surrounding rock reinforced area 1031, then excavate the septum surrounding rock reinforced area 1031, then construct the initial support 13 of the septum surrounding rock reinforced area on the top of each septum surrounding rock reinforced area 1031, and connect the initial support 13 of the septum surrounding rock reinforced area with the initial support 5 of the left wall and the initial support 8 of the right wall on both sides and the initial support 12 of the septum surrounding rock non-reinforced area to form a whole;

[0055] S6, excavation of lower steps

[0056] First, the lower step advance support 14 is applied, then the rock mass of the lower step 2 is excavated, and finally, the lower step initial support 15 is applied to close the ring;

[0057] S7, pouring secondary lining;

[0058] S8. Carry out circular construction according to steps S3-S7, control the synchronous excavation of the left pilot pit and the right pilot pit to be 5-8m ahead of the excavation of the middle partition surrounding rock, control the excavation of the middle partition surrounding rock to be 8-12m ahead of the excavation of the lower step, and control the distance between the secondary lining and the lower step face to be 8-10m;

[0059] In the above steps, the temporary support 3 of the middle partition surrounding rock is constructed by combining temporary steel arch frame, steel mesh and shotcrete;

[0060] In the above steps, the initial supports of the left wall 5, the right wall 8, the middle partition surrounding rock reinforcement area 13, the middle partition surrounding rock non-reinforcement area 12 and the lower step initial support 15 are constructed by combining steel arch frame, shotcrete, advance small pipe and mortar anchor rod; wherein, the advance small pipe L = 3-4.5m, and the mortar anchor rod L = 3.5-4.5m;

[0061] In the above steps, the advance supports such as the upper left pilot pit advance support 4, the upper right pilot pit advance support 7 and the lower step advance support 14 are constructed by combining advance small duct grouting and advance pipe shed; among them, the advance small duct grouting adopts a double-layer φ42mm×4mm advance small duct, L=4.5m, a longitudinal spacing of 0.4×3m, an external insertion angle of 5°~15° for the first layer, an external insertion angle of 40°~45° for the second layer, and a plum blossom shape arrangement.

Claims

1. An excavation construction method for large-section underwater tunnel surrounding rock with in-situ partition reservation in soft and broken surrounding rock, characterized in that: The steps include: S1. Excavation section design The excavation section is divided into an upper step (1) and a lower step (2), and the upper step (1) is divided from left to right into an upper left pilot pit (101), a middle partition surrounding rock (103) and an upper right pilot pit (102): S2. Advance Drilling Use the long and short drill rods of the anchor drill to conduct advance drilling behind the face; S3, water blocking grouting Select a suitable water plugging grouting method according to the result of the advance drilling in step S2; S4. Simultaneous excavation of left and right pilot pits First, the upper left pilot pit advance support (4) and the upper right pilot pit advance support (7) are synchronously implemented, and then the side wall rock mass of the upper left pilot pit (101) and the side wall rock mass of the upper right pilot pit (102) are synchronously excavated, so that the rock and soil between the upper left pilot pit (101) and the upper right pilot pit (102) are reserved in situ to form a middle partition surrounding rock (103), and then the left side wall initial support (5) and the right side wall initial support (8) are implemented, and the middle partition surrounding rock temporary support (3) is implemented on both sides of the middle partition surrounding rock (103); When constructing the left side wall initial support (5) and the right side wall initial support (8), the upper mortar anchor rods (10) of the surrounding rock are inserted upwardly and obliquely on the left and right sides of the top of the middle partition surrounding rock (103), and the lower ends of the surrounding rock top mortar anchor rods (10) on the left and right sides are respectively connected to the left side wall initial support (5) and the right side wall initial support (8), while the higher ends of the two are staggered and connected along the tunnel direction; when constructing the middle partition surrounding rock temporary support (3), the lower mortar anchor rods (11) of the surrounding rock are inserted upwardly and obliquely on both sides of the middle partition surrounding rock (103) at a certain interval along the tunnel direction, so that the middle partition surrounding rock (103) forms an alternately distributed middle partition surrounding rock reinforcement area (1031) and middle partition surrounding rock non-reinforcement area (1032); S5, Excavation with intervals between surrounding rocks First, the temporary support (3) of the middle partition surrounding rock non-reinforced area (1032) is removed, and then the middle partition surrounding rock non-reinforced area (1032) is excavated. Then, the initial support (12) of the middle partition surrounding rock non-reinforced area is constructed on the top of each middle partition surrounding rock non-reinforced area (1032), and the initial support (12) of the middle partition surrounding rock non-reinforced area is connected with the initial support (5) of the left wall and the initial support (8) of the right wall on both sides to form a whole. Then, the middle partition surrounding rock is removed. The intermediate partition surrounding rock temporary support (3) of the rock reinforcement area (1031) is constructed, and then the intermediate partition surrounding rock reinforcement area (1031) is excavated, and then the intermediate partition surrounding rock reinforcement area initial support (13) is constructed on the top of each intermediate partition surrounding rock reinforcement area (1031), and the intermediate partition surrounding rock reinforcement area initial support (13) is connected with the left side wall initial support (5), the right side wall initial support (8) and the intermediate partition surrounding rock non-reinforcement area initial support (12) to form a whole; S6, excavation of lower steps First, the lower step advance support (14) is applied, then the rock mass of the lower step (2) is excavated, and finally, the lower step initial support (15) is applied to close the ring; S7, pouring secondary lining; S8. Carry out circular construction according to steps S3-S7, control the synchronous excavation progress of the left pilot pit and the right pilot pit to be 5-8m ahead of the excavation of the middle partition surrounding rock, control the excavation progress of the middle partition surrounding rock to be 8-12m ahead of the excavation of the lower step, and control the secondary lining progress to be 8-10m away from the heading face of the lower step.

2. The excavation construction method for in-situ partition reservation of surrounding rock of large-section underwater tunnel in soft and broken surrounding rock according to claim 1 is characterized in that: In the step S2, six water exploration holes (6) are drilled each time, and the outer deviation angle of the drilling hole is 10°.

3. The excavation construction method for in-situ partition reservation of surrounding rock of large-section underwater tunnel in soft and broken surrounding rock according to claim 2 is characterized in that: In step S3, according to the water inflow of the water exploration hole in the advance drilling result of step S2, full-section water blocking, local grouting water blocking or no water blocking is adopted.

4. The excavation construction method for in-situ partition reservation of surrounding rock of large-section underwater tunnel in soft and broken surrounding rock according to claim 3 is characterized in that: When 4 or more of the water exploration holes are full of water and the total water volume is greater than 15m 3 / h, full-section surface water blocking grouting is used; when the total water volume is less than 15m 3 / h but the water output of some holes is greater than 3m 3 / h, local water blocking grouting is used; when the water output of the six holes is less than 3m 3 / h and the total water output is less than 15m 3 / h, grouting is not used to block water, and the next construction step is directly entered.

5. The excavation construction method for in-situ partition reservation of surrounding rock of large-section underwater tunnel in soft and broken surrounding rock according to claim 1 is characterized in that: The width of the connection between the bottom of the intermediate surrounding rock (103) and the lower step (2) is 1.2 to 1.8 m.

6. The excavation construction method for in-situ partition reservation of surrounding rock of large-section underwater tunnel in soft and broken surrounding rock according to claim 1 is characterized in that: In the steps S4, S5 and S6, a cantilever type tunnel boring machine is used to excavate the rock mass.

7. The excavation construction method for in-situ partition reservation of surrounding rock of large-section underwater tunnel in soft and broken surrounding rock according to claim 1 is characterized in that: In the steps S4, S5 and S6, the initial support is constructed by combining steel arch frame, shotcrete and mortar anchor rods.

8. The excavation construction method for in-situ partition reservation of surrounding rock of large-section underwater tunnel in soft and broken surrounding rock according to claim 1 is characterized in that: In the steps S4 and S6, the advance support is constructed by combining advance small-duct grouting and advance pipe shed.

9. The excavation construction method for in-situ partition reservation of surrounding rock of large-section underwater tunnel in soft and broken surrounding rock according to claim 8 is characterized in that: The advanced small pipe grouting adopts a double layer of φ42mm×4mm advanced small pipe, L=4.5m, the longitudinal spacing of the ring is 0.4×3m, the first layer has an external insertion angle of 5°~15°, the second layer has an external insertion angle of 40°~45°, and is arranged in a plum blossom shape.

10. The excavation construction method for in-situ partition reservation of surrounding rock of large-section underwater tunnel in soft and broken surrounding rock according to claim 1, characterized in that: In step S4, the temporary support of the surrounding rock is constructed by combining temporary steel arches, steel mesh and shotcrete.

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