Underground pressure pipeline penetrating through active fault zone

Abstract

The invention discloses an underground pressure pipeline penetrating through an active fault zone, relates to the field of underground pressure pipelines of hydropower stations, and solves the safety problem of the pressure pipeline when meter-scale dislocation happens to stratums on the two sides of the active fault zone. A lining is arranged on the outer side of the pressure pipeline, the middle of the lining is located in the fracture zone, the pipe diameter of the lining is gradually reduced from the middle to the two ends, the two ends of the lining are fixedly connected with the pressure pipeline, and a buffer cavity is formed between the lining and the pressure pipeline to provide sufficient deformation space for deformation of the pressure pipeline. And the pressure pipeline can adapt to meter-scale staggered floor displacement of stratums on the two sides of the fault zone. The buffering cavity is formed in the pressure pipeline, the yieldable supporting rod is arranged in the buffering cavity, the yieldable supporting rod elastically restrains the pressure pipeline, when stratums on the two sides of the fault zone are dislocated, the yieldable supporting rod yields, deformation of the pressure pipeline in the buffering cavity is prevented from being limited, and safety of the pressure pipeline is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of underground pressure pipelines for hydropower stations, specifically an underground pressure pipeline that traverses an active fault zone. Background Technology

[0002] my country's hydropower resources are mostly concentrated in the southwest region, which has complex geological conditions, numerous high mountains and deep valleys, and frequent and intense earthquakes, posing significant challenges to the design of underground pressure pipelines for hydropower stations. With the implementation of major national projects, underground pressure pipelines inevitably have to cross active fault zones. Currently, when underground pressure pipelines for hydropower stations face active fault zones, the main approach is avoidance. This involves identifying the fault location during the site selection phase and avoiding known active fault zones or shear zones. Avoidance is the most economical, effective, and safe method, suitable for projects where avoidance is feasible. However, many projects lack such conditions, and due to site constraints, pressure pipelines must cross active fault zones.

[0003] When avoidance is not feasible, the central axis of the pressure pipeline should be perpendicular to the fracture zone or at a large angle to its direction to minimize the impact of fracture zone displacement. Simultaneously, the strength of the pressure pipeline should be increased, for example, by using thick-walled or high-strength steel pipes. The solution of having the pressure pipeline pass perpendicularly or at a large angle through the fracture zone and reinforcing the pipeline is suitable for cases of minor fracture zone displacement, but cannot meet the requirements for meter-level displacement on both sides of the fracture zone.

[0004] Currently, expansion joints are commonly used in engineering to provide pressure pipelines with a certain degree of deformation adaptability. The main types are sleeve-type expansion joints and bellows-type expansion joints. Sleeve-type expansion joints can withstand high pressure and are inexpensive and easy to maintain, but they can only compensate for axial displacement, have poor sealing reliability, and are prone to leakage. Bellows-type expansion joints can compensate for both axial and lateral displacement, have good sealing reliability, but have lower pressure-bearing capacity and limited displacement compensation ability; when large lateral deformation occurs, they may experience excessive bending or breakage.

[0005] When an earthquake occurs, the strata on both sides of an active fault zone may experience meter-level displacement, posing a significant risk to the normal operation and structural safety of pressure pipelines. Developing an underground pressure pipeline capable of withstanding meter-level strata displacement is of great significance for the construction and operation of hydropower stations. Summary of the Invention

[0006] This invention provides an underground pressure pipeline that traverses an active fault zone, solving the safety problem of pressure pipelines when meter-level displacement occurs in the strata on both sides of the active fault zone.

[0007] The technical solution adopted in this invention is as follows: an underground pressure pipeline traversing an active fault zone, the pressure pipeline traversing the fault zone and the strata on both sides, the pressure pipeline is a circular pipe, the outer side of the pressure pipeline is lined with a tubular lining, the middle part of the lining is located in the fault zone, the diameter of the lining gradually decreases from the middle to both ends, the two ends of the lining are fixedly connected to the pressure pipeline, the central axis of the lining coincides with the central axis of the pressure pipeline, the inner wall of the lining and the outer wall of the pressure pipeline form a sealed buffer cavity, at least one ring of yieldable support rods is provided in the buffer cavity along the axial direction of the pressure pipeline, and yieldable support rods are provided at the fault zone, each ring of yieldable support rods includes at least three yieldable support rods arranged at intervals along the circumferential direction, one end of the yieldable support rod is connected to the inner wall of the lining, and the other end of the yieldable support rod is connected to the outer wall of the pressure pipeline.

[0008] To further reduce the impact of strata displacement on pressure pipelines on both sides of the fault zone, the central axis of the lining is perpendicular to the plane corresponding to the fault zone.

[0009] In order for the yieldable support rod to better dissipate the energy of the fault layer on both sides of the fault zone, the central axis of the yieldable support rod is perpendicular to the central axis of the pressure pipeline.

[0010] To facilitate lining construction and to make it easier for the lining to be damaged along a predetermined location when the strata shift on both sides of the fault zone, the lining can be further divided into at least two sections along the central axis, with adjacent sections spliced ​​together and the joints between adjacent sections sealed with flexible materials.

[0011] To ensure the strength of the pressure pipeline and lining, specifically: the pressure pipeline is made of steel pipe, and the lining is a reinforced concrete structure.

[0012] To facilitate the connection of one end of the yieldable support rod to the lining and the other end to the pressure pipeline, a connector is pre-embedded inside the lining. One end of the yieldable support rod is rotatably connected to the connector. A reinforcing ring is fixed to the outside of the pressure pipeline. Connecting seats are provided at intervals on the reinforcing ring. The other end of the yieldable support rod is rotatably connected to the connecting seat.

[0013] Specifically: the reinforcing ring has a T-shaped cross-section, the lower end of the T is welded to the outer wall of the pressure pipe, a stiffening plate is provided between the reinforcing ring and the pressure pipe, and the upper end of the T is connected to the pressure pipe.

[0014] To allow maintenance personnel to enter the buffer cavity for maintenance, the following additional features are provided: the pressure pipeline is equipped with an inspection hole that communicates with the buffer cavity, and an inspection door is provided at the inspection hole; or the stratum outside the lining is equipped with an inspection hole, and the lining is equipped with an inspection hole that communicates with the buffer cavity.

[0015] To facilitate maintenance operations within the buffer cavity, a ladder is further installed inside the buffer cavity, which passes through an inspection hole.

[0016] The following explains the values ​​for the lining length L and the diameter D at the midpoint of the lining. To ensure the safety of the pressure pipeline, specifically: the lining length L is equal to the maximum ground displacement S. max The ratio of the allowable deformation ratio Δ of the pressure pipeline.

[0017] Furthermore, the formula for calculating the diameter D of the lining center is: D = S max / ε+d, where ε is the design maximum strain of the yieldable support rod and d is the diameter of the pressure pipe.

[0018] The beneficial effects of this invention are as follows: the diameter of the lining gradually decreases from the middle to both ends, and the middle part of the lining is located in the fault zone, providing sufficient space for the deformation of the pressure pipeline during ground displacement. This allows the pressure pipeline to adapt to larger ground displacements, including meter-level displacements of the strata on both sides of the fault zone. A yieldable support rod is installed within the buffer cavity formed by the lining and the pressure pipeline. This yieldable support rod serves to fix the pressure pipeline, ensuring that the overall shape of the pressure pipeline within the buffer cavity meets the design alignment requirements. The yieldable support rod can undergo both tensile and compressive deformation, providing elastic constraint to the pressure pipeline. When significant ground displacement occurs, the support rod will yield under tension or compression, preventing excessive restriction and constraint on the deformation of the pressure pipeline within the buffer cavity. Furthermore, the energy dissipation through the yielding of the support rod reduces damage to the pressure pipeline, thereby ensuring its safety.

[0019] The yieldable support rod can be rotatably connected to both ends of the pressure pipeline and the lining, facilitating deformation under stress. No joints are required in the pressure pipeline sections crossing fracture zones, avoiding the risk of joint damage under pressure. The inner wall of the pressure pipeline is smooth and flat, eliminating the need for corrugated pipes with uneven inner walls and preventing a decrease in flow velocity due to uneven pipe walls. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the present invention before the occurrence of stratigraphic displacement on both sides of the fault zone.

[0021] Figure 2 This is a schematic diagram of the present invention after the formation of displaced layers on both sides of the fault zone.

[0022] Figure 3 yes Figure 1 A schematic diagram of the cross-section of the vertical plane corresponding to one of the rings of the yieldable support rod.

[0023] Figure 4 yes Figure 3A schematic diagram of the rotatable connection between the yieldable support rod and the pressure pipeline.

[0024] Figure 5 This is a schematic diagram showing the relationship between the axial displacement and axial force of the yieldable support rod in this invention.

[0025] Attached reference numerals: 1. Pressure pipeline; 2. Fault zone; 3. Formation; 4. Lining; 5. Yieldable support rod; 6. Reinforcing ring; 7. Stiffening plate; 8. Inspection door; 9. Ladder. Detailed Implementation

[0026] The invention will now be further described with reference to the accompanying drawings.

[0027] like Figure 1 and Figure 2 As shown, this invention discloses an underground pressure pipeline traversing an active fault zone. The pressure pipeline 1 traverses the fault zone 2 and the strata 3 on both sides. The pressure pipeline 1 is used to transport water. The pressure pipeline 1 is a circular pipe, meaning that in any cross-section, the inner wall and outer wall of the pressure pipeline 1 are both circular, and the corresponding circles on the inner and outer walls are concentric. To ensure the strength of the pressure pipeline 1, it is generally made of steel. The diameter of the steel pipe can be determined based on flow rate calculations, and the thickness of the steel pipe is determined based on strength verification when the strata undergo displacement.

[0028] The pressure pipeline 1 is lined with a lining 4 on its outer side. The middle part of the lining 4 is located in the fault zone 2, meaning the lining 4 is situated on the fault zone and its two sides. The lining 4 is tubular, meaning that in any cross-section, both the inner and outer walls of the lining 4 are circular, and the corresponding circles on the inner and outer walls are concentric. The diameter of the lining 4 gradually decreases from the middle to both ends, and both ends of the lining 4 are fixedly connected to the pressure pipeline 1. To ensure the strength of the lining 4, it is a reinforced concrete structure. The lining 4 can be a single integral structure. To facilitate the construction of the lining 4 and to make it easier for the lining 4 to fail at a predetermined location when the strata shift on both sides of the fault zone, the lining 4 can be divided into at least two segments along its central axis. Adjacent segments of the lining 4 are spliced ​​together, and the joint between adjacent segments is the reserved failure location. The joint between adjacent segments is sealed with a flexible material to prevent leakage.

[0029] The inner wall of lining 4 and the outer wall of pressure pipeline 1 form a sealed buffer cavity. In a cross-section passing through the central axis of pressure pipeline 1, the buffer cavity is two isosceles trapezoids. The lower base of the isosceles trapezoid corresponds to pressure pipeline 1, and the two sides of the isosceles trapezoids correspond to lining 4 within the strata 3 on both sides of fracture zone 2. The upper base of the isosceles trapezoids corresponds to lining 4 within fracture zone 2. The central axis of lining 4 coincides with the central axis of pressure pipeline 1. To reduce the impact of strata 3 displacement on pressure pipeline 1, the central axis of pressure pipeline 1 is perpendicular to the plane corresponding to fracture zone 2, and the central axis of lining 4 is also perpendicular to the plane corresponding to fracture zone 2.

[0030] At least one ring of yieldable support rods 5 is provided along the axial direction of the pressure pipe 1 within the buffer cavity, and yieldable support rods 5 are also provided at the fracture zone 2. The yieldable support rods 5 are generally arranged in multiple rings, with each ring spaced apart along the axial direction of the pressure pipe 1. The arrangement density is highest at the fracture zone 2, and gradually decreases from the middle to both ends. One ring of yieldable support rods 5 refers to a group of yieldable support rods 5 arranged circumferentially between the outer side of the pressure pipe 1 and the inner side of the lining 4. Each group of yieldable support rods 5 consists of at least three rods located in a plane perpendicular to the central axis of the pressure pipe 1. For example, in… Figure 3 In the middle, there are four yieldable support rods 5, which are evenly arranged. For any one yieldable support rod 5, one end of the yieldable support rod 5 is connected to the inner wall of the lining 4, and the other end of the yieldable support rod 5 is connected to the outer wall of the pressure pipeline 1.

[0031] The yieldable support rod 5 is made of a readily yieldable material, such as mild steel with a low yield point and high ductility. The yieldable support rod 5 is used to connect the external lining 4 and the internal pressure pipe 1, and to secure the pressure pipe 1. The yieldable support rod 5 can be constructed in sections for easy transport and installation. The yieldable support rod 5 exhibits the following stress characteristics when undergoing axial deformation.

[0032] When the yieldable support rod 5 is subjected to axial tension and the axial displacement does not exceed the yield displacement ε1, the axial force of the yieldable support rod 5 is the tensile force. Figure 5 The positive half of the longitudinal axis), the tension with axial displacement ( Figure 5 The axial displacement increases with the positive half-axis of the horizontal axis, and the two are linearly related until the axial displacement reaches the yield displacement ε1, and the tensile force reaches the yield force σ1. After the axial displacement exceeds the yield displacement ε1, the axial displacement of the yieldable support rod 5 increases, while the tensile force remains basically unchanged, that is, the tensile force is roughly maintained at the yield force σ1. After the axial displacement exceeds the ultimate displacement ε3, the yieldable support rod 5 fails. In the design, it should be ensured that the maximum design displacement ε2 of the yieldable support rod 5 under axial tensile conditions is less than the ultimate displacement ε3.

[0033] When the yieldable support rod 5 undergoes axial compression and the axial displacement does not exceed the yield displacement ε1′, the axial force of the yieldable support rod 5 is the compressive force ( Figure 5 The negative half of the longitudinal axis), pressure with axial displacement ( Figure 5 The axial displacement increases with the negative half-axis of the horizontal axis, and the two are linearly related until the axial displacement reaches the yield displacement ε1′ and the pressure reaches the yield force σ1′. After the axial displacement exceeds the yield displacement ε1′, the axial displacement of the yieldable support rod 5 increases, while the pressure remains basically unchanged, that is, the pressure is roughly maintained at the yield force σ1′. After the axial displacement exceeds the ultimate displacement ε3′, the yieldable support rod 5 fails. In the design, it should be ensured that the maximum design displacement ε2′ of the yieldable support rod 5 under axial compression conditions is less than the ultimate displacement ε3′.

[0034] The yieldable support rod 5 is primarily used to ensure that the overall shape of the pressure pipeline 1 within the buffer cavity meets the design alignment requirements, preventing excessive deflection and deformation of the pressure pipeline 1 under its own weight. At this stage, the yieldable support rod 5 is in its elastic phase, meaning its axial force increases linearly with axial displacement. When significant displacement deformation occurs in the strata 3 on both sides of the fault zone 2, the yieldable support rod 5 at the fault zone 2 location begins to deform under tension or compression. As the deformation increases, the axial force no longer increases, preventing the yieldable support rod 5 from excessively restricting and constraining the deformation of the pressure pipeline 1 within the buffer cavity. Simultaneously, the yieldable support rod 5 dissipates seismic energy through material yielding, protecting the safety of the pressure pipeline 1. To better dissipate the energy from the displacement of the strata 3 on both sides of the fault zone 2, the central axis of the yieldable support rod 5 is perpendicular to the central axis of the pressure pipeline 1. Figure 3 As shown.

[0035] During operation, pressure pipeline 1 may vibrate due to factors such as water hammer. To address this, pressure pipeline 1 or yieldable support rod 5 may be equipped with a vibration damping device, such as a tuned mass damper or a viscous damper, to prevent excessive vibration amplitude of pressure pipeline 1.

[0036] One end of the yieldable support rod 5 is connected to the lining 4, and the other end is connected to the pressure pipe 1. To facilitate the deformation of the yieldable support rod 5 under stress, both ends of the yieldable support rod 5 are rotatably connected to the lining 4 and the pressure pipe 1, respectively. To facilitate the connection between the yieldable support rod 5 and the lining 4, a connector is pre-embedded inside the lining 4, and one end of the yieldable support rod 5 is rotatably connected to the connector. For example, one end of the yieldable support rod 5 is connected to the connector via a pin, bolt, or similar means. To facilitate the connection between the yieldable support rod 5 and the pressure pipe 1 and to prevent the yieldable support rod 5 from damaging the pressure pipe 1, a reinforcing ring 6 is fixed to the outside of the pressure pipe 1. Connecting seats are spaced apart on the reinforcing ring 6, and the other end of the yieldable support rod 5 is rotatably connected to the connecting seat. For example, the other end of the yieldable support rod 5 is connected to the connecting seat via a pin, bolt, or similar means. The reinforcing ring 6 serves to distribute stress and prevent localized deformation of the pressure pipe 1. See, for example, [link to relevant documentation]. Figure 3 and Figure 4 The reinforcing ring 6 has a T-shaped cross-section. The lower end of the T is welded to the outer wall of the pressure pipe 1, and the upper end of the T is connected to the pressure pipe 1. The reinforcing ring 6 includes a vertical plate and a horizontal plate, which are perpendicular to each other. One side of the vertical plate is connected to the middle of one side of the horizontal plate, and the other side of the vertical plate is welded to the outer wall of the pressure pipe 1. The other side of the horizontal plate is connected to the pressure pipe 1. To improve the stability of the reinforcing ring 6, a stiffening plate 7 is provided between the reinforcing ring 6 and the pressure pipe 1. For example, stiffening plates 7 are provided on both sides of the reinforcing ring 6.

[0037] To allow maintenance personnel to access the buffer cavity for maintenance, including replacing the yieldable support rod 5, the pressure pipeline 1 is equipped with an inspection hole communicating with the buffer cavity. Maintenance personnel can enter the buffer cavity from inside the pressure pipeline 1 through the inspection hole. An inspection door 8 is provided at the inspection hole to close it. The inspection door 8 is circular, chamfered rectangular, or other suitable shapes. The inspection door 8 is normally closed and locked to prevent fluid leakage from the pressure pipeline 1. To prevent the pressure pipeline 1 from losing strength due to the inspection hole, an inspection tunnel can be provided in the stratum 3 outside the lining 4. The lining 4 is equipped with an inspection hole connecting the inspection tunnel to the buffer cavity. An inspection door is generally also provided at the inspection tunnel of the lining 4. To facilitate maintenance operations within the buffer cavity, a ladder 9 is also provided inside the buffer cavity, passing through the inspection hole.

[0038] The values ​​of the length L of lining 4 and the diameter D at the middle of lining 4 are explained below. To ensure the safety of pressure pipeline 1, the length L of lining 4 is equal to the maximum misalignment displacement S of stratum 3. maxThe ratio of the allowable deformation ratio Δ of pressure pipeline 1 to the allowable deformation ratio of pressure pipeline 1. Here, the allowable deformation ratio Δ is a constant, and its value can be determined by referring to relevant design standards, such as the allowable deflection values ​​for bending members in Table B.1.1 of the "Steel Structure Design Standard" GB50017-2017. For example, the allowable deformation ratio Δ of pressure pipeline 1 is 1 / 250. A specific calculation example is given below, where the maximum misalignment displacement S of stratum 3 is... max Given a length of 2m and an allowable deformation ratio Δ of 1 / 250, the length L of lining 4 is 500m. Furthermore, the formula for calculating the diameter D at the center of lining 4 is: D = S max / ε+d, where ε is the design maximum strain of the yieldable support rod 5, and d is the diameter of the pressure pipe 1. The design maximum strain ε of the yieldable support rod 5 is the deformation length per unit length. For example, the maximum dislocation displacement S of stratum 3. max The diameter of the pressure pipe 1 is 2m, the maximum design strain ε of the yieldable support rod 5 is 0.1, the diameter d of the pressure pipe 1 is 4m, and the diameter D of the middle part of the lining 4 is 24m.

Claims

1. An underground pressure pipeline traversing an active fault zone, wherein the pressure pipeline (1) traverses the fault zone (2) and the strata (3) on both sides thereof, and the pressure pipeline (1) is a circular pipe, characterized in that: The pressure pipeline (1) is provided with a lining (4) on the outside. The lining (4) is tubular. The middle part of the lining (4) is located in the fracture zone (2). The diameter of the lining (4) gradually decreases from the middle to both ends. The two ends of the lining (4) are fixedly connected to the pressure pipeline (1). The central axis of the lining (4) coincides with the central axis of the pressure pipeline (1). The inner wall of the lining (4) and the outer wall of the pressure pipeline (1) form a closed buffer cavity. At least one ring of yieldable support rods (5) is provided in the buffer cavity along the axial direction of the pressure pipeline (1). Yieldable support rods (5) are also provided at the fracture zone (2). Each ring of yieldable support rods (5) includes at least three yieldable support rods (5) arranged circumferentially. One end of the yieldable support rod (5) is connected to the inner wall of the lining (4), and the other end of the yieldable support rod (5) is connected to the outer wall of the pressure pipeline (1).

2. The underground pressure pipeline traversing an active fault zone as described in claim 1, characterized in that: The central axis of the lining (4) is perpendicular to the plane corresponding to the fracture zone (2), and the central axis of the yieldable support rod (5) is perpendicular to the central axis of the pressure pipe (1).

3. The underground pressure pipeline traversing an active fault zone as described in claim 1, characterized in that: The lining (4) can be divided into at least two sections along the central axis. The two adjacent lining sections (4) are spliced ​​together, and the joints of the two adjacent lining sections (4) are sealed with flexible materials to form yielding support rods.

4. The underground pressure pipeline traversing an active fault zone as described in claim 1, characterized in that: The pressure pipeline (1) is a steel pipe, and the lining (4) is a reinforced concrete structure.

5. The underground pressure pipeline traversing an active fault zone as described in claim 4, characterized in that: The lining (4) has a connector embedded inside. One end of the yieldable support rod (5) is rotatably connected to the connector. The pressure pipe (1) is fixed with a reinforcing ring (6) on the outside. The reinforcing ring (6) is provided with connecting seats at intervals. The other end of the yieldable support rod (5) is rotatably connected to the connecting seat.

6. The underground pressure pipeline traversing an active fault zone as described in claim 5, characterized in that: The reinforcing ring (6) has a T-shaped cross-section. The lower end of the T is welded to the outer wall of the pressure pipe (1). A stiffening plate (7) is provided between the reinforcing ring (6) and the pressure pipe (1). The upper end of the T is connected to the pressure pipe (1).

7. The underground pressure pipeline traversing an active fault zone as described in any one of claims 1 to 6, characterized in that: The pressure pipeline (1) is provided with an inspection hole that communicates with the buffer cavity, and an inspection door (8) is provided at the inspection hole; or the stratum (3) outside the lining (4) is provided with an inspection hole, and the lining (4) is provided with an inspection hole that communicates with the inspection hole and the buffer cavity.

8. The underground pressure pipeline traversing an active fault zone as described in claim 7, characterized in that: The buffer cavity is also equipped with a ladder (9), which passes through the inspection hole.

9. The underground pressure pipeline traversing an active fault zone as described in any one of claims 1 to 6, characterized in that: The length L of the lining (4) is the maximum dislocation S of the stratum (3). max The ratio of the allowable deformation ratio Δ of the pressure pipeline (1).

10. The underground pressure pipeline traversing an active fault zone as described in claim 9, characterized in that: The formula for calculating the diameter D of the middle part of the lining (4) is: D = S max / ε+d, where ε is the design maximum strain of the yieldable support rod (5) and d is the diameter of the pressure pipe (1).

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