Rock cap type water intake designing and forming method based on blasting demolition on outer side of diversion tunnel

Abstract

The invention discloses a method for designing and forming a rock cap type water intake based on blasting demolition on the outer side of a diversion tunnel, which comprises the following steps of: cutting a slope of a rock mass at the water intake of the diversion tunnel, and reserving a rock cap section at a water inlet and a water outlet of the diversion tunnel; the reserved rock cap section at the water intake position of the diversion tunnel and the opening of the diversion tunnel are reinforced; according to the cap top elevation, the bottom elevation, the thickness and the upstream side slope of the rock cap body design, layered excavation is conducted on the reserved rock cap section, and the rock cap body is obtained; during slope cutting, a diversion tunnel is excavated synchronously; when the diversion tunnel is excavated, extending excavation is conducted in the direction of the reserved rock cap section along the axis of the diversion tunnel at the design position of a water inlet and a water outlet of the diversion tunnel, and the obtained extending section of the diversion tunnel serves as a blasting slag buffering area and a diversion end; and blasting demolition is conducted on the rock cap body in the dry season. According to the method, a good section contour can be obtained, and then the good hydraulic condition of the diversion tunnel and the stability of the tunnel opening part in the long-term safe operation process are guaranteed.

Description

Technical Field

[0001] The present application relates to the technical field of water diversion tunnel construction for pumped storage power stations, and in particular to a design and forming method of a rock cap type water intake based on blasting and demolition of the outer side of the water diversion tunnel. Background Art

[0002] Nowadays, new pumped storage power stations and traditional hydropower station expansion and capacity increase projects have entered a rapid development stage. Usually, the water inlet of their water diversion system is located several meters or dozens of meters underwater, and the rock mass of the reserved water retaining section of the water intake is an important water retaining structure in the water diversion system. During the construction period, it temporarily plays the role of a water retaining cofferdam to ensure that the tunnels and gates behind the water intake are completed on dry land first. Finally, the blasting demolition method is used to connect the reservoir and the water diversion tunnel and meet the requirements of overflow water intake and power generation.

[0003] When extracting water from existing reservoirs for power generation and constructing inlets and outlets, given the power generation and flood control functions of existing hydropower stations, it is generally not feasible to drain the reservoir for extended periods or significantly lower the operating water level to construct a cofferdam. Furthermore, cofferdam construction is labor-intensive, requires difficult anti-seepage measures, and is expensive to remove later. In these situations, rock plug blasting is the only remaining option. However, rock plug blasting is extremely challenging. The up-tilted, conical-shaped plug not only requires a large excavation cross-section, but also requires careful coordination between the excavation and lining before blasting. After blasting, there is the need to manage the large amount of rock debris that flows into the tunnel and the water hammer effect on structures such as the gate shaft. Furthermore, the plug has demanding geological requirements. Since the water intake must be constructed in a tunnel under high head pressure, if the weathering and permeability of the strata adjacent to the water interface are poor, and the rock mass quality does not meet the safety review requirements for the reserved plug area, the construction risks of the water intake and the difficulty of post-breakthrough management are extremely difficult. Therefore, a new water intake construction solution is urgently needed. Summary of the Invention

[0004] In order to solve the technical problems mentioned in the background technology, the present application provides a rock cap type water intake design and forming method based on blasting demolition outside the water diversion tunnel.

[0005] To achieve the above-mentioned purpose, the present application provides a method for constructing a rock cap water intake based on blasting demolition outside a diversion tunnel, comprising: Cut the rock mass at the water intake of the diversion tunnel and reserve rock cap sections at the inlet and outlet of the diversion tunnel. Specifically, cut the rock mass above the intersection of the diversion tunnel axis and the strong weathering limit line. Reinforce the reserved rock cap section at the water intake of the diversion tunnel and the diversion tunnel entrance; According to the designed top elevation, bottom elevation, thickness, and waterside slope of the rock cap, the reserved rock cap section is excavated in layers to obtain the rock cap body. Specifically, a rock cap body is excavated outside the water inlet and outlet of the water diversion tunnel, and a partition pier is excavated between the two rock cap bodies. The shape of the partition pier matches the space between the two rock cap bodies. While cutting the slope, excavate the diversion tunnel simultaneously. When excavating the diversion tunnel, at the designed locations of the inlet and outlet of the diversion tunnel, extend the excavation by 1m to 3m along the axis of the diversion tunnel towards the reserved rock cap section. The resulting extended section of the diversion tunnel will serve as a blasting buffer zone. The rock cap is demolished by blasting during the dry season. During the demolition by blasting, the middle partition pier is retained or not, depending on the distance between the tunnel axes of the water inlet and the water outlet of the water diversion tunnel.

[0006] Furthermore, the rock mass above the intersection of the diversion tunnel axis and the strong weathering limit line is cut, including: 1.1 Based on the original slope topography of the rock mass at the water intake location of the diversion tunnel and the separation line between Class IV and Class V rock masses, determine the rock mass overburden, strong unloading rock mass, excavation slope ratio of the strong unloading rock mass, and the slope topography after slope cutting; 1.2 Excavate the overburden layer, then use step-by-step blasting to excavate the slope layer by layer from top to bottom, and reserve rock cap sections at the inlet and outlet of the water diversion tunnel.

[0007] Furthermore, a rock cap section is reserved at the inlet and outlet of the water diversion tunnel, which is: the slope is excavated to a height close to the designed cap top elevation of the rock cap body, and then the horizontal pre-splitting plus vertical shallow hole step blasting method is used to continue excavation until the designed cap top elevation of the rock cap body is reached.

[0008] Furthermore, when the diversion tunnel is excavated simultaneously, it is only excavated to a position 20m away from the lower limit of the weak weathering zone.

[0009] Furthermore, the reserved rock cap section at the water intake of the diversion tunnel and the diversion tunnel opening are reinforced, including: When the slope excavation reaches a height close to the designed cap top elevation of the rock cap, curtain grouting is carried out in sections on the reserved rock cap section. The entrance section of the diversion tunnel is lined and a slag collection pit is excavated at the bottom of the diversion tunnel.

[0010] Furthermore, a bamboo springboard is fixed on the surface of the lining side wall of the opening section, and the waste tires are fixed to the surface of the bamboo springboard using iron wire.

[0011] Furthermore, after the reserved rock cap section at the water intake of the water diversion tunnel and the entrance of the water diversion tunnel are reinforced, a slag protection device is preset at the water intake, which consists of steel rails and square timbers, and the square timbers are laid flatly or at intervals on the steel rails.

[0012] Furthermore, the reserved rock cap section is excavated in layers, including shallow-hole step blasting on the upper layer and deep-hole step blasting on the lower layer; wherein, the height of each step in the shallow-hole step blasting is 3m~5m, and the height of each step in the deep-hole step blasting is 10m~15m.

[0013] Furthermore, the rock cap body is demolished by blasting in layers, with the upper layer being demolished by dry-land drilling and dry-land blasting, and the lower layer being demolished by dry-land drilling and underwater blasting.

[0014] Furthermore, the two rock cap bodies are in the shape of an inverted square platform, and the middle partition pier is in the shape of a normal square platform.

[0015] This application aims to obtain a better cross-sectional profile for the water intake construction under tight schedule, water level fluctuation and scheduling restrictions, and rock fracture and fragmentation, thereby ensuring that the water diversion and power generation tunnel has good hydraulic conditions and the stability of the tunnel entrance during long-term safe operation.

[0016] Compared with the prior art, this application has the following advantages and beneficial effects: (1) The rock mass quality of the inlet and outlet and the stability of the reserved water retaining structure are safer and more reliable; (2) The water depth can be controlled within 25m and matches the depth of the rock cap blasting hole. The land drilling and blasting method is adopted, which reduces the construction difficulty of blasting and demolishing the reserved water retaining structure; (3) Since the rock cap is demolished by blasting using the out-of-tunnel excavation method, the strength degradation and stability disturbance of the plug body caused by the full row of drilling holes in the tunnel during traditional rock plug blasting are avoided, which is safer than the traditional rock plug scheme; (4) The blasting slag is cleared underwater outside the tunnel, and the inlet / outlet tunnel is sealed with wooden boards and filled with water for balancing, which can effectively prevent the influx of stone slag. Therefore, the slag collection pit in the tunnel is smaller or even can be removed, further reducing the difficulty of construction in the tunnel. (5) Reduced the difficulty of water seepage in the tunnel and the construction of the steep plug and the sunken slag pit; (6) Overcame the psychological fear of construction workers in front of the rock plug in the tunnel; (7) Compared with the cofferdam solution, the slope excavation volume is small, which solves the problem of huge excavation intensity within a limited construction period, avoids the strict anti-seepage treatment during the excavation of the foundation pit behind the weir, and reduces the risk of deep foundation pit construction. (8) The harmful effects of rock cap blasting can be prevented and controlled through flexible excavation plans, effective contour control technology, and multi-level reinforcement measures. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present application and / or the technical solutions in the prior art, the drawings required for use in the embodiments and / or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other embodiments can be obtained based on these partial embodiments without paying any creative work.

[0018] Figure 1 Schematic diagram of the diversion tunnel and outer slope in an embodiment of the present application; Figure 2 Schematic diagram of blasting excavation of the rock cap body and the intermediate pier in the embodiment of the present application; Figure 3 This is a technical roadmap for blasting and removing rock caps in the embodiments of this application; Figure 4 This is a cross-sectional view of the arrangement of blast holes for the rock cap body in the embodiment of the present application; Figure 5 This is a plan view of the blast hole arrangement of the rock cap body in the embodiment of the present application; Figure 6 A cross-sectional view of the arrangement of blast holes for the rock cap body in an embodiment of the present application; Figure 7 This is a diagram of the blasthole arrangement for removing the middle partition pier in an embodiment of the present application.

[0019] Description of the drawings: diversion tunnel 1, rock cap body 2, first rock cap body 2a, second rock cap body 2b, upper layer of rock cap body 2c, strong weathering limit line 3, original slope topography line 4, slope topography line after slope cutting 5, horseway 6, blasting buffer zone 7, slag collecting pit 8, intermediate pier 9, water inlet and outlet 10, water inlet 10a, water outlet 10b, shallow hole bench blasting section 11, deep hole bench blasting section 12, pre-crack hole 13, blasting hole 14, water diversion end valve 15, water outlet valve 16. DETAILED DESCRIPTION

[0020] The following will be combined with the accompanying drawings to clearly and completely describe the embodiments of the present application and / or the technical solutions in the prior art. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0021] See Figure 1 The rock cap body 2 is obtained by excavating the rock mass and is located outside the entrance of the water diversion tunnel 1. The rock cap body 2 mainly serves as a water retaining structure. After the construction of the water intake is completed, the rock cap body 2 is demolished by blasting to connect the reservoir and the water diversion tunnel 1.

[0022] The following will be combined Figures 1 to 7 , the specific implementation process of the rock cap type water intake design and forming method of this application is described in detail.

[0023] (1) Cut the slope of the rock mass at the water intake of the diversion tunnel 1 and reserve a rock cap section at the water inlet and outlet of the diversion tunnel 1; specifically, cut the slope of the rock mass above the intersection of the diversion tunnel axis and the strong weathering limit line 3; while cutting the slope, excavate the diversion tunnel 1 simultaneously; In this step, the rock mass at the water intake of the water diversion tunnel 1 is cut, which further includes: 1.1 Based on the original slope topographic line 4 of the rock mass at the water intake of the diversion tunnel 1 and the dividing line between Class IV and Class V rock masses, determine the rock mass overburden, strong unloading rock mass, excavation slope ratio of the strong unloading rock mass, and the slope topographic line 5 after slope cutting; 1.2 Use an excavator to dig the overburden layer, and then use step blasting to excavate the slope layer by layer from top to bottom and from high to low, and reserve rock cap sections at the inlet and outlet of water diversion tunnel 1.

[0024] The height of the steps in the excavated slope should be determined in combination with the water level drop speed and the equipment of on-site construction machinery. Usually, a step is 10m to 15m high, and a 1.5m to 3m wide horseway 6 is reserved at the top of each step. In this embodiment, the steps and horseway 6 can be seen in the figure. Figure 2 .

[0025] Before the above-mentioned excavation of the slope, blastholes are first arranged in the rock mass, including: using a CM-351 high-pressure drill or hydraulic drill to drill deep-hole step blasting holes, using a YQ-100B down-the-hole drill with a drill rig to drill pre-crack holes, and using a YT-28 hand-held pneumatic drill to drill shallow-hole blasting holes.

[0026] When implementing the above-mentioned step blasting, support should be followed closely.

[0027] The aforementioned reserved rock cap section at the inlet and outlet of diversion tunnel 1 is specifically constructed by excavating the slope to a point close to the designed cap top elevation. Excavation is then continued using horizontal pre-cracking combined with vertical shallow-hole step blasting until the designed cap top elevation is reached. This creates a reserved rock cap section and ensures a smooth excavation profile at the top of the reserved rock cap section, facilitating subsequent drilling and grouting, as well as preparation for cap removal.

[0028] In this embodiment, the top elevation of the rock cap is designed according to the dead water level of the reservoir. Specifically, the top elevation of the rock cap is designed to be 15m to 20m above the dead water level.

[0029] In order to avoid a large amount of water seepage or even water gushing during the excavation of the diversion tunnel 1, the diversion tunnel 1 was only excavated to a position 20m away from the lower limit of the weak weathering zone.

[0030] To reduce the influx of blasting debris into the diversion tunnel 1 during subsequent blasting and removal of the rock cap, during excavation of the diversion tunnel 1, a 1-3m extension of the excavation is made along the tunnel axis toward the reserved rock cap section at the designed inlet and outlet locations of the diversion tunnel 1. This extended section of the diversion tunnel 1 serves as a blasting debris buffer zone 7, which is a circular tunnel. The blasting debris buffer zone 7 is preferably constructed before the overburden is excavated and installed. This ensures that the outer overburden and the strong unloading layer contribute to construction safety.

[0031] When excavating slopes, it's best to conduct them during the reservoir drawdown period. This not only improves construction safety within the inlet and outlet tunnels, but also improves the quality of the rock mass in the rock cap section and the stability of the tunnel entrance slope. Slope cutting, preemptively removing the rock mass outside the rock cap section, can shorten the excavation depth of the diversion tunnel. Compared to the removal of high rock bank cofferdams, this slope cutting application requires significantly less rock excavation, offers greater flexibility in construction timing, and can be carried out in parallel with diversion tunnel excavation.

[0032] (2) Reinforce the reserved rock cap section at the water intake of diversion tunnel 1 and the opening of diversion tunnel 1; The purpose of the reinforcement treatment is to ensure the stability of the diversion tunnel during subsequent construction; this step further includes: 2.1 When the slope excavation reaches a height close to the designed cap top elevation, curtain grouting should be carried out in sections on the reserved cap section in advance; 2.2 Lining the entrance section of the diversion tunnel 1 and excavating a slag collection pit 8 at the bottom of the diversion tunnel 1.

[0033] The purpose of curtain grouting is to improve the rock mass quality of the rock cap section, enhance the safety of excavation near the entrance of diversion tunnel 1, and ensure the stability of the slope of the submerged portion of the rock cap section. In this embodiment, segmented curtain grouting is used to improve the quality grade of the reserved rock cap section from Class IV to Class III.

[0034] The above lining is used to prevent deformation or collapse of the rock mass at the entrance of the water diversion tunnel 1, thereby enhancing the stability of the water diversion tunnel 1. In this embodiment, the lining structure is 2m thick and is 50m away from the water intake.

[0035] The above-mentioned slag collection pit 8 is located in the water diversion tunnel 1 near the water intake. In this embodiment, the slag collection pit 8 is 30m long and half the diameter of the water diversion tunnel 1. Its end close to the tunnel entrance is 10m away from the water intake.

[0036] Furthermore, during the construction of the portal section of the water diversion tunnel, an advance small guide tube is used to reinforce the weak rock mass in front of the portal section, thereby jointly improving the quality grade of the rock mass in the rock cap section.

[0037] Furthermore, after completing the above-mentioned reinforcement treatment, a slag protection device is preset at the water intake location. It consists of steel rails and square timbers. The square timbers are laid flat or at intervals of 10cm~20cm on the steel rails. The residue after the blasting is retained on the slag protection device, which can be pulled out by ropes to clean it.

[0038] Furthermore, after completing the aforementioned reinforcement, to prevent subsequent blasting damage to the lining structure, bamboo gangplanks are fixed to the lining sidewalls. Used tires are then secured to the bamboo gangplanks using wire to prevent flying rocks from damaging the lining structure. In some embodiments, expansion bolts are used to secure the bamboo gangplanks to the lining sidewalls. Furthermore, a circle of pre-cracked holes can be pre-introduced into the face contour at the end of the diversion tunnel to protect the lining structure.

[0039] (3) According to the designed cap top elevation, bottom elevation, thickness, and waterside slope of the rock cap body, the reserved rock cap section is excavated in layers to obtain the rock cap body; In this embodiment, the rock cap body 2 is located behind the dividing line between the IV and V rock masses. The rock cap body 2 is in the shape of a square platform, and along the cross-sectional direction of the tunnel axis of the water diversion tunnel 1, the rock cap body 2 is in the shape of a parallelogram. Figure 1 and Figure 4 shown.

[0040] The design height of the rock cap body is determined based on the designed top elevation and bottom elevation of the rock cap body. In this embodiment, the design top elevation is 15m~20m above the dead water level, and the bottom plate elevation of the water intake tunnel is 10m~12m below the dead water level. The bottom elevation of the rock cap body is consistent with the bottom plate elevation of the water intake tunnel, so the design height of the rock cap body is 25m~32m.

[0041] Considering the stability of the underwater slope of the IV2 rock cap section, it is necessary to excavate and remove the external covering layer and V rock mass on the water-facing side of the rock cap in advance. The design slope of the water-facing side of the rock cap is 60°~75°.

[0042] To fully utilize the rock cap's water-retaining structural function and ensure its stability and reliability, the rock cap's thickness is designed to be 1.5 to 2 times the diameter of the inlet and outlet of diversion tunnel 1. For example, when the tunnel diameter is 9 meters, the intersection of the designed cap elevation and the dividing line between Class IV and Class V rock masses is used as the upper left reference point. The rock cap's thickness typically extends 20 meters horizontally into the slope.

[0043] To improve the effectiveness of onshore drilling and blasting demolition and reduce the blasting effort for the final rock cap removal, the reserved rock cap section was excavated in layers, including two layers of shallow-hole bench blasting and one layer of deep-hole bench blasting. Shallow-hole bench blasting section 11 was excavated in the upper layer 2c of the rock cap, and deep-hole bench blasting section 12 was excavated in the upper layer of the rock cap. Each bench in the shallow-hole bench blasting was 3m to 5m high, while each bench in the deep-hole bench blasting was 10m to 15m high. Shallow-hole bench blasting was used to minimize the impact on the tunnel entrance support structure and tunnel face slope. However, during the dry season, when work schedules are tight, the upper two layers of shallow-hole bench blasting can be combined into a single bench blasting.

[0044] (4) Blasting and demolishing the rock cap during the dry season; As a water retaining structure reserved for the construction of the water intake, the rock cap body can be demolished by blasting during the last dry season. The following four conditions must be met before demolition by blasting: (1) the front rock mass on the water-facing side of the rock cap body has been excavated; (2) the rock mass on the top of the rock cap body has been excavated and the upper slope support of the rock cap body has been completed; (3) the water diversion tunnel entrance on the water-retaining side of the rock cap body has been reinforced and the blasting buffer zone has been completed; (4) the construction of the gate opening and closing machine room and the shaft has been completed, and the tunnel is filled with water.

[0045] The above-mentioned blasting demolition adopts layered blasting excavation and non-electric millisecond difference blasting.

[0046] Furthermore, pre-crack holes 13 are arranged on the pre-crack surface, and two rows of blast holes 14 are set adjacent to the pre-crack surface. The hole diameter, charge, and hole pattern parameters are controlled according to the requirements of buffer blasting. To improve blasting efficiency, a large hole spacing and small resistance line layout are generally adopted. A continuous charge structure and slight differences between holes ensure that the blasted slag is more uniform, making it easier to clean.

[0047] Furthermore, the first two layers were drilled and blasted using dry-land methods, with a unit blasting charge of 0.45kg / m³ to 0.65kg / m³. The last layer was drilled and blasted underwater, with a main blasting hole spacing of 2m×1.5m and a hole depth of 15m. Taking underwater blasting into consideration, the unit blasting charge was 1.2kg / m³, the charge per hole was 54kg, the spacing between contour holes was 1m, the line charge density was 300g, and the charge per contour hole was 6kg. Finally, the unit charge and vibration attenuation coefficient were determined based on the blasting test.

[0048] In this embodiment, the drilling rigs selected are QZJ-100B fast drill, Atlas D7 hydraulic drill, CM-351 high air pressure drill and YT-28 air leg drill. Pre-splitting drilling is done quickly, while hydraulic drill and down-the-hole drill are mainly used for drilling blast holes and buffer holes.

[0049] In this embodiment, two rock cap bodies 2 are excavated, which are respectively recorded as the first rock cap body 2a and the second rock cap body 2b. Figure 2 As shown, open channels are excavated on both sides of the water intake. The horizontal distance between the outer contour of the diversion tunnel 1 and the boundary of the rock cap is 3m. The excavation slope ratio on both sides of the rock cap is 1:0.3. The rock mass between the two rock caps serves as a middle pier 10. The first and second rock caps 2a and 2b are located outside the water inlet 10a and outlet 10b of the diversion tunnel 1, respectively. The first and second rock caps 2a and 2b are in the shape of an inverted square platform, while the middle pier 10 is a square platform, which perfectly matches the space between the first and second rock caps 2a and 2b.

[0050] During blasting removal of the rock cap, the middle pier 10 can be retained or not, depending on the distance between the inlet 10a and the outlet 10b. Retaining the middle pier 10 can reduce some of the excavation and blasting work, while not retaining the middle pier 10 can increase the construction platform between the two rock caps.

[0051] Note that the above are only preferred embodiments of the present application and the technical principles employed. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, and substitutions can be made by those skilled in the art without departing from the scope of protection of the present application. Therefore, although the present application has been described in more detail through the above embodiments, the present application is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the scope of protection of the present application, all of which fall within the scope of protection of the present application.

Claims

1. A rock cap type water intake construction method based on blasting demolition outside the diversion tunnel, characterized by: include: Cut the rock mass at the water intake of the diversion tunnel and reserve rock cap sections at the inlet and outlet of the diversion tunnel. Specifically, cut the rock mass above the intersection of the diversion tunnel axis and the strong weathering limit line. Reinforce the reserved rock cap section at the water intake of the diversion tunnel and the diversion tunnel entrance; According to the designed top elevation, bottom elevation, thickness, and waterside slope of the rock cap, the reserved rock cap section is excavated in layers to obtain the rock cap body. Specifically, a rock cap body is excavated outside the water inlet and outlet of the water diversion tunnel, and a partition pier is excavated between the two rock cap bodies. The shape of the partition pier matches the space between the two rock cap bodies. While cutting the slope, excavate the diversion tunnel simultaneously. When excavating the diversion tunnel, at the designed locations of the inlet and outlet of the diversion tunnel, extend the excavation by 1m to 3m along the axis of the diversion tunnel towards the reserved rock cap section. The resulting extended section of the diversion tunnel will serve as a blasting buffer zone. The rock cap is demolished by blasting during the dry season. During the demolition by blasting, the middle partition pier is retained or not, depending on the distance between the tunnel axes of the water inlet and the water outlet of the water diversion tunnel.

2. The rock cap type water intake construction method based on blasting demolition outside the diversion tunnel as claimed in claim 1 is characterized by: The said rock slope cutting above the intersection of the water diversion tunnel axis and the strong weathering limit line includes: 1.1 Based on the original slope topography of the rock mass at the water intake location of the diversion tunnel and the separation line between Class IV and Class V rock masses, determine the rock mass overburden, strong unloading rock mass, excavation slope ratio of the strong unloading rock mass, and the slope topography after slope cutting; 1.2 Excavate the overburden layer, then use step-by-step blasting to excavate the slope layer by layer from top to bottom, and reserve rock cap sections at the inlet and outlet of the water diversion tunnel.

3. The rock cap type water intake construction method based on blasting demolition outside the diversion tunnel as claimed in claim 2 is characterized by: The rock cap section is reserved at the water inlet and outlet of the water diversion tunnel by excavating the slope to a height close to the designed cap top elevation of the rock cap body, and then continuing the excavation by using the horizontal pre-splitting plus vertical shallow hole step blasting method until the designed cap top elevation of the rock cap body is reached.

4. The rock cap type water intake construction method based on blasting demolition outside the diversion tunnel as claimed in claim 1 is characterized by: When the diversion tunnel is excavated simultaneously, it is only excavated to a position 20m away from the lower limit of the weak weathering zone.

5. The rock cap type water intake construction method based on blasting demolition outside the diversion tunnel as claimed in claim 1 is characterized by: The reinforcement treatment of the reserved rock cap section at the water intake position of the diversion tunnel and the opening of the diversion tunnel includes: When the slope excavation reaches a height close to the designed cap top elevation of the rock cap, curtain grouting is carried out in sections on the reserved rock cap section. The entrance section of the diversion tunnel is lined and a slag collection pit is excavated at the bottom of the diversion tunnel.

6. The rock cap type water intake construction method based on blasting demolition outside the diversion tunnel as claimed in claim 5 is characterized by: exist A bamboo springboard is fixed on the surface of the lining side wall of the opening section, and the waste tire is fixed to the surface of the bamboo springboard by using iron wire.

7. The rock cap type water intake construction method based on blasting demolition outside the diversion tunnel as claimed in claim 1 is characterized by: exist After the reserved rock cap section at the water intake of the water diversion tunnel and the entrance of the water diversion tunnel are reinforced, a slag protection device is preset at the water intake. It consists of steel rails and square timbers, and the square timbers are laid flatly or at intervals on the steel rails.

8. The rock cap type water intake construction method based on blasting demolition outside the diversion tunnel as claimed in claim 1 is characterized by: The reserved rock cap section is excavated by layered blasting, including shallow-hole step blasting in the upper layer and deep-hole step blasting in the lower layer; wherein, the height of each step in the shallow-hole step blasting is 3m~5m, and the height of each step in the deep-hole step blasting is 10m~15m.

9. The rock cap type water intake construction method based on blasting demolition outside the diversion tunnel as claimed in claim 1, characterized in that: The blasting demolition of the rock cap body adopts layered blasting excavation, with the upper layer adopting the method of dry land drilling and dry land blasting, and the lower layer adopting the method of dry land drilling and underwater blasting.

10. The rock cap type water intake construction method based on blasting demolition outside the diversion tunnel as claimed in claim 1, characterized in that: The two rock cap bodies are in the shape of an inverted square platform, and the middle partition pier is in the shape of a normal square platform.

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