Integral structure of fixed pressure steel pipe, design method and construction method

Abstract

The invention discloses an integral structure, a design method and a construction method of a fixed pressure steel pipe. The overall structure comprises the reinforced concrete piles, the peripheral reinforced concrete structure and the pressure steel pipes, sliding of the pressure steel pipes is prevented through shearing resistance of the reinforced concrete piles and friction force between concrete and a foundation face, overturning of the pressure steel pipes is prevented through the combined effect of the piles and rock masses around the piles or a covering layer, and the effect of stabilizing the pressure steel pipes is achieved. Compared with a traditional anchor block which is large in size and complex in formwork erecting, the anchor block is more compact and light in structure, the corresponding formwork engineering amount is small, and the construction difficulty is remarkably reduced. The cast-in-situ bored piles or the rotary digging hole-forming cast-in-situ piles are adopted in a mature construction method, the construction process is standardized, the project quality can be guaranteed, and the construction efficiency can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of overall structure of fixed pressure steel pipe, design method and construction method, belong to water conservancy and hydropower engineering field. BACKGROUND

[0002] In water conservancy and hydropower engineering, pier is generally used to fix pressure pipeline to prevent its displacement, pier is a hydraulic structure arranged at the horizontal corner of pipeline to prevent pipeline displacement, usually reinforced concrete structure, mainly applicable to outlet pipe of hydropower station, pumped storage power station and pressure pipe of water supply engineering, and the friction between pier and foundation prevents the movement of pressure steel pipe. However, with the development of water conservancy and hydropower engineering, the stratum through which the pressure steel pipe passes is complex and diverse. Some pressure steel pipes may pass through poor geological conditions such as overburden layer, and it is difficult to meet the requirement of foundation bearing capacity by using traditional pier. In order to meet the requirement of pier foundation bearing capacity, enlarged foundation or various types of pile foundation treatment are adopted, which increases the project investment. In order to save land resources or meet the traffic needs, some pressure steel pipes are backfilled with earthwork after open excavation, and under the condition of heavy rain, the friction between pier and foundation is greatly reduced according to the calculation of floating weight of pier in saturated soil. In order to fix the pressure steel pipe, the amount of concrete of pier is large, and the investment is large. The pressure steel pipe at the end of some hydropower stations or pumped storage power stations has large water head, and when the ball valve is closed, the pressure steel pipe bears large horizontal axial tension. The amount of concrete of traditional pier used to fix the pressure steel pipe is large, and the investment is large.

[0003] Therefore, it is urgent to provide an overall structure of fixed pressure steel pipe, design method and construction method to solve the above technical problems. SUMMARY

[0004] The present application aims to overcome the shortcomings of conventional pier that is generally difficult to adapt to overburden layer and has large engineering quantity, and provides a reinforced concrete pile and peripheral concrete overall structure for fixing pressure steel pipe. The structure prevents the sliding of pressure steel pipe by the shear resistance of reinforced concrete pile and the friction between concrete and foundation surface, and prevents the overturning of pressure steel pipe by the combined action of pile and surrounding rock or overburden layer, thereby playing a role in stabilizing pressure steel pipe. The structure is simple in arrangement and small in construction difficulty, and has small engineering quantity and investment. In the following, a brief overview of the present application is given to provide a basic understanding of some aspects of the present application. It should be understood that this overview is not an exhaustive overview of the present application. It is not intended to determine the key or important parts of the present application, nor to limit the scope of the present application.

[0005] Technical scheme of the present application:

[0006] Scheme one, a whole structure of fixed pressure steel pipe, comprising reinforced concrete pile, peripheral reinforced concrete structure and pressure steel pipe, the pressure steel pipe bottom both sides are distributed with several reinforced concrete piles, the peripheral reinforced concrete structure surrounds the pressure steel pipe and is integrally cast with the reinforced concrete pile, the reinforced concrete pile and peripheral reinforced concrete structure jointly act, the shear resistance of the pile body of the reinforced concrete pile and the friction between the structure and the foundation surface prevent the sliding of the pressure steel pipe, and the joint action of the pile body of the reinforced concrete pile and the surrounding rock or cover layer prevents the overturning of the pressure steel pipe.

[0007] Preferably, the reinforced concrete pile is a cast-in-situ pile or a rotary drilling cast-in-situ pile.

[0008] Preferably, the reinforced concrete pile and the peripheral reinforced concrete structure are integrally formed.

[0009] Preferably, the base surface of the pressure steel pipe is consolidated and grouted before construction, the grouting holes are arranged in a plum blossom shape, and the hole row distance is 2.5m x 2.5m.

[0010] Preferably, the consolidation grouting is constructed by using the cover weight method, and the cover weight thickness is not less than 1m.

[0011] Preferably, the consolidation grouting is constructed in two sequences, including I sequence holes and II sequence holes, the first section grouting pressure of the I sequence holes is 0.1-0.3MPa, and the first section grouting pressure of the II sequence holes is 0.2-0.4MPa.

[0012] Preferably, the peripheral reinforced concrete structure is integrally cast after the installation of the pressure steel pipe is completed.

[0013] Scheme two, a design method of the whole structure of fixed pressure steel pipe in scheme one, comprising the following steps:

[0014] S1, load determination: determining all loads acting on the whole structure composed of the reinforced concrete pile, the peripheral reinforced concrete structure and the pressure steel pipe, i.e. self weight Gc and water weight in the whole structure Gw;

[0015] Axial water pressure F3 determined according to the operation condition of the pressure steel pipe;

[0016] All vertical loads ΣG=Gc+Gw;

[0017] All horizontal loads ΣH=F3;

[0018] S2, anti-sliding stability design and checking: based on the load determined in step S1, the anti-sliding stability of the whole structure is calculated to ensure that it meets the following formula:

[0019]

[0020] Wherein: f' is the shear friction coefficient between the bottom surface and the foundation; C' is the shear adhesion strength between the bottom surface and the foundation; A is the bottom area; Kc is the calculated anti-sliding safety factor;

[0021] S3, structure size iteration: [Kc] is the allowable anti-sliding safety factor required by the specification, when the Kc calculated in step S2 is less than [Kc], the number, diameter, depth of the reinforced concrete pile and / or the size of the peripheral reinforced concrete structure are adjusted to increase ΣG and / or A, and steps S1 and S2 are repeated until Kc≥[Kc] is met.

[0022] Preferably:

[0023] In step S1, the calculation of the axial water pressure F3 is divided into:

[0024] When the ball valve is not closed, F3=π(D1 2 -D2 2 ) p / 4

[0025] When the ball valve is closed or the nozzle is closed, F3=πD1 2 p / 4

[0026] Wherein, D1 is the inner diameter of the pressure steel pipe, D2 is the outer diameter of the pressure steel pipe, and p is the internal water pressure.

[0027] Scheme three, a construction method of a whole structure of a fixed pressure steel pipe, which is based on the whole structure of a fixed pressure steel pipe in scheme one, and is characterized by comprising the following steps:

[0028] Step 1, consolidating grouting on the foundation surface of the pressure steel pipe;

[0029] Step 2, constructing reinforced concrete piles on both sides of the pressure steel pipe;

[0030] Step 3, integrally pouring the peripheral reinforced concrete structure.

[0031] The present application has the following beneficial effects:

[0032] 1. The present application forms a whole structure by distributing reinforced concrete piles on both sides of the pressure steel pipe and the peripheral concrete, and bears force together. Its stability not only depends on the friction force of the traditional pier bottom surface, but also mainly uses the strong shear force provided by the pile body penetrating into the bedrock or stable stratum to resist sliding, and uses the pile-soil interaction to resist overturning, forming multiple insurance, and the fixing effect is more safe and reliable.

[0033] 2. The present application combines a relatively light pile with a concrete platform to replace the traditional gravity pier which requires a large amount of concrete. This greatly reduces the amount of concrete and steel, lowers the material cost and the amount of earth excavation, thereby significantly reducing the amount of work, optimizing the project investment, and having outstanding economic benefits;

[0034] 3. The present application overcomes the problem of high foundation bearing capacity requirement of traditional piers, which often requires complex and expensive foundation treatment in adverse geological conditions such as overburden and soft foundation. In the present application, the reinforced concrete pile can directly transmit the load to the deep stable bedrock, effectively solving the problem of insufficient bearing capacity of adverse foundation, making the fixation of the pressure steel pipe when passing through complex strata no longer difficult, and greatly expanding the application range of the structure;

[0035] 4. Compared with the traditional pier which is large in size and complex in formwork erection, the structure of the present application is more compact and light, and the corresponding formwork engineering quantity is small, which significantly reduces the construction difficulty. The bored pile or rotary excavated hole filling pile used in the present application is a mature construction method, the construction process is standardized, which is beneficial to ensure the engineering quality and improve the construction efficiency;

[0036] 5. The design method of the present application ensures the scientificity and accuracy of the structure design by systematically performing load calculation, using clear anti-sliding stability formula for safety checking, and introducing iterative design process. This quantitative design method can give the optimal structure size according to different engineering conditions and safety standards, thereby providing a strong guarantee for the engineering safety from the design source.

[0037] 6. In the construction method of the present application, the base surface of the pressure steel pipe is systematically consolidated and grouted, and the standard process such as plum blossom hole arrangement and sequence grouting is used, which significantly improves the integrity and bearing capacity of the shallow foundation rock mass, provides a uniform and stable foundation for the upper integral structure, and further improves the long-term safety and durability of the structure. BRIEF DESCRIPTION OF DRAWINGS

[0038] Fig. 1 is a structural schematic diagram of a whole structure for fixing a pressure steel pipe;

[0039] Fig. 2 is a matching installation diagram of a whole structure for fixing a pressure steel pipe;

[0040] Fig. 3 is a stress analysis diagram of an outer peripheral reinforced concrete structure.

[0041] In the figure: 1 - reinforced concrete pile, 2 - outer peripheral reinforced concrete structure, 3 - pressure steel pipe. DETAILED DESCRIPTION

[0042] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be described below in detail through specific embodiments shown in the drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present application. In addition, in the following description, the description of the known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present application.

[0043] The connection mentioned in the present application is divided into fixed connection and detachable connection. The fixed connection (i.e. non-detachable connection) includes but is not limited to conventional fixed connection modes such as flange connection, rivet connection, adhesive connection and welding connection, and the detachable connection includes but is not limited to conventional detachable modes such as threaded connection, buckle connection, pin connection and hinge connection. When the specific connection mode is not specifically limited, at least one connection mode can be found in the existing connection mode to realize the function, and the person skilled in the art can select it according to the needs. For example, the fixed connection selects welding connection, and the detachable connection selects hinge connection.

[0044] Specific implementation method one: combination Figs. 1-3 In this embodiment, the overall structure of a fixed pressure steel pipe includes reinforced concrete piles 1, peripheral reinforced concrete structures 2 and pressure steel pipes 3. The pressure steel pipes 3 are distributed with a plurality of reinforced concrete piles 1 on both sides of the bottom, and the peripheral reinforced concrete structures 2 surround the pressure steel pipes and are integrally poured with the reinforced concrete piles 1. The reinforced concrete piles 1 and the peripheral reinforced concrete structures 2 jointly act to prevent the pressure steel pipes 3 from sliding by the shear resistance of the pile body of the reinforced concrete piles 1 and the friction between the structure and the foundation surface, and to prevent the pressure steel pipes 3 from overturning by the combined action of the pile body of the reinforced concrete piles 1 and the surrounding rock or overburden.

[0045] The reinforced concrete piles 1 are bored piles or rotary drilling piles and are symmetrically arranged on both sides of the bottom of the pressure steel pipes 3.

[0046] Three reinforced concrete piles 1 are arranged on each side of the pressure steel pipes 3, totaling six. The center distance of the reinforced concrete piles 1 from the outer wall of the pressure steel pipes 3 is 1.2 meters, and the longitudinal pile spacing is 3.5 meters. The diameter of the reinforced concrete piles 1 is 800 millimeters, and the length of the reinforced concrete piles 1 is 20 meters, of which the anchoring depth penetrating the overburden into the lower bedrock is not less than 5 meters. The main reinforcement of the pile body of the reinforced concrete piles 1 adopts 22 HRB400 grade steel bars with a diameter of 25 millimeters, and the stirrup adopts HPB300 grade steel bars with a diameter of 10 millimeters with a spacing of 200 millimeters.

[0047] After the pressure steel pipe is installed in place and the pile foundation concrete strength reaches the design value, the reinforced concrete pile 1 and the surrounding reinforced concrete structure 2 are integrally cast into a single structure. This structure encloses the lower 120° wrap-around area of ​​the pressure steel pipe 3, forming a concrete cap with a height of 2.5 meters and a width of 4.5 meters. A double-layered, bidirectional steel mesh is installed inside the cap, reliably connected to the pile top reinforcement. All concrete is C30 strength grade.

[0048] Before construction, the foundation surface of the pressure steel pipe 3 is subjected to consolidation grouting treatment. The grouting holes are arranged in a quincunx pattern with a hole spacing of 2.5m × 2.5m.

[0049] The consolidation grouting is carried out using the covered weight method, with a covered weight thickness of not less than 1m.

[0050] The consolidation grouting is carried out in two phases, including phase I holes and phase II holes. The grouting pressure for the first phase of phase I holes is 0.1 to 0.3 MPa, and the grouting pressure for the first phase of phase II holes is 0.2 to 0.4 MPa.

[0051] The outer reinforced concrete structure 2 is integrally cast after the pressure steel pipe 3 is installed. The strong shear resistance provided by the reinforced concrete pile 1 penetrating deep into the bedrock serves as the main anti-slip mechanism, while the self-weight of the outer reinforced concrete structure 2 and its friction with the foundation serve as supplementary measures. Together, they prevent the pressure steel pipe from sliding and overturning under the enormous water hammer pressure, perfectly solving the problem of insufficient bearing capacity of the overburden foundation.

[0052] Specific Implementation Method Two: Combining Figs. 1-3 This embodiment, specifically the design method of the integral structure of a fixed pressure steel pipe described in Embodiment 1, includes the following steps:

[0053] S1. Load Determination: Determine all loads acting on the overall structure consisting of the reinforced concrete pile 1, the outer reinforced concrete structure 2, and the pressure steel pipe 3. Calculate the self-weight Gc of the structure composed of the outer reinforced concrete structure and the reinforced concrete pile, and the weight of the water inside the pressure steel pipe under operating conditions, Gw. Summing these two values ​​yields the total vertical load ΣG acting on the bottom of the structure.

[0054] Analyze the operating conditions of the pressure steel pipe to determine the maximum axial water pressure F3 that it may generate. Specifically, the calculation is performed using appropriate formulas depending on whether the pressure steel pipe is in normal operation (ball valve not closed) or in a water hammer condition with the ball valve / nozzle closed. That is, in step S1, the calculation of the axial water pressure F3 is divided into the following based on the operating conditions of the pressure steel pipe 3:

[0055] When the ball valve is not closed, F3 = π(D12 - D22)p / 4

[0056] When the ball valve is closed or the nozzle is shut off, F3 = πD12p / 4

[0057] Where D1 is the inner diameter of the pressure steel pipe, D2 is the outer diameter of the pressure steel pipe, and p is the internal water pressure.

[0058] The axial water pressure F3 is determined based on the operating conditions of pressure steel pipe 3;

[0059] The total vertical load ΣG = Gc + Gw;

[0060] Total horizontal load ΣH=F3;

[0061] S2. Anti-slip stability design and verification: Based on the load determined in step S1, calculate the anti-slip stability of the overall structure. Obtain the mechanical parameters of the foundation according to the geological survey report, including the shear friction coefficient f' and shear bond strength C' between the bottom surface and the foundation, and ensure that they satisfy the following formula:

[0062]

[0063] Where: f' is the shear friction coefficient between the bottom surface and the foundation; C' is the shear bond strength between the bottom surface and the foundation; A is the bottom area; Kc is the calculated anti-slip safety factor;

[0064] S3. Structural Dimension Iteration: [Kc] is the allowable anti-slip safety factor required by the standard. When Kc calculated in step S2 is less than [Kc], the initial design scheme is determined to not meet the anti-slip stability requirements. The number, diameter, and depth of the reinforced concrete piles 1 and / or the dimensions of the outer reinforced concrete structure 2 are adjusted. These adjustments aim to increase ΣG and / or A, thereby improving the anti-slip force. Steps S1 and S2 are repeated, i.e., load calculation and stability verification are performed again. This iterative process is repeated until the calculated safety factor Kc meets the standard requirements, i.e., Kc ≥ [Kc], thus finally determining a structural dimension that is both safe and economically reasonable.

[0065] Specific implementation method three: Combining Figs. 1-3 This embodiment, specifically the construction method of the integral structure of a fixed pressure steel pipe described in Embodiment 1, includes the following steps:

[0066] Step 1: Perform consolidation grouting on the foundation surface of pressure steel pipe 3;

[0067] Comprehensive consolidation grouting was performed on the foundation surface in the area where the pressure steel pipe was laid to enhance the integrity and bearing capacity of the foundation. Grouting holes were arranged in a quincunx pattern, with hole spacing and row spacing strictly controlled according to design requirements. A covered weight method was used during construction, utilizing the pre-excavated rock mass as a grouting cover.

[0068] The grouting process is as follows:

[0069] Step 1.1, Sequential Construction: Strictly adhere to the principle of two-stage construction, first constructing the first-stage boreholes, then the second-stage boreholes. The grouting pressure for the first-stage and second-stage boreholes in different grouting sections is determined based on design requirements and field tests, and follows the principle of increasing pressure sequentially.

[0070] Step 1.2, Segmented Blocking: Grouting is carried out using a top-down segmented, in-hole circulation method. The installation position of the grouting blocker must be strictly in accordance with the requirements: the first segment is blocked in the rock mass at a certain distance above the foundation surface, and the subsequent segments are blocked at a certain distance above the top of the previous grouting segment, ensuring that the distance between the grouting pipe opening and the bottom of the hole meets the specifications.

[0071] Step 1.3, Grout Control: Use Portland cement with a strength grade of not less than 42.5. The water-cement ratio of the grout is strictly prepared and adjusted according to the design mix ratio, with a larger value usually used for initial pouring.

[0072] Step 1.4, End Criteria: Grouting operations can only be terminated when the injection rate of the grouting section reaches the specification requirement of no more than 1L / min under the maximum design pressure, and after sufficient grouting time has elapsed.

[0073] Step 2: Construct reinforced concrete piles 1 on both sides of the pressure steel pipe 3;

[0074] After the consolidation grouting is completed and the foundation conditions are improved, pile foundation construction will proceed.

[0075] For the designed pile positions on both sides of the pressure steel pipe, the drilling and grouting pile or rotary drilling and grouting pile technology is selected according to the geological conditions.

[0076] After drilling, a prefabricated steel cage is installed and concrete is poured to form the reinforced concrete pile.

[0077] Step 3: Cast the outer reinforced concrete structure 2 as a whole.

[0078] After the pressure steel pipe 3 is installed and all reinforced concrete piles 1 are constructed, the construction of the outer reinforced concrete structure 2 is carried out. The pile cap reinforcement is tied to ensure a firm connection with the pile head reinforcement, and then the formwork is erected.

[0079] Finally, concrete is poured in one go to combine the pressure steel pipe 3, the reinforced concrete pile 1, and the outer reinforced concrete structure 2 into a complete load-bearing whole.

[0080] The consolidation grouting adopts a top-down segmented, in-hole circulation grouting method, and is carried out in two phases. The water-cement ratio of the grout is one of four grades: 2:1, 1:1, 0.7:1, and 0.5:1, with the initial water-cement ratio being 2:1.

[0081] The consolidation grouting is carried out using the covered weight method, which utilizes the protective layer reserved during excavation as the cover weight, and the thickness of the rock mass cover weight is not less than 1m.

[0082] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be permuted and combined. Those skilled in the art can exhaust all possibilities based on the mathematical knowledge of permutation and combination. Therefore, the present invention will not describe the technical solutions after permutation and combination one by one, but it should be understood that the technical solutions after permutation and combination have been disclosed by the present invention.

[0083] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An integral structure for a fixed pressure steel pipe, characterized in that: It includes reinforced concrete piles (1), an outer reinforced concrete structure (2) and a pressure steel pipe (3). Several reinforced concrete piles (1) are distributed on both sides of the bottom of the pressure steel pipe (3). The outer reinforced concrete structure (2) surrounds the pressure steel pipe and is integrally cast with the reinforced concrete piles (1). The reinforced concrete piles (1) and the outer reinforced concrete structure (2) work together to prevent the pressure steel pipe (3) from sliding through the shear resistance of the pile body of the reinforced concrete piles (1) and the friction between the structure and the foundation surface. The pressure steel pipe (3) is also prevented from overturning through the combined action of the pile body of the reinforced concrete piles (1) and the surrounding rock mass or overburden.

2. The integral structure of a fixed pressure steel pipe according to claim 1, characterized in that: The reinforced concrete pile (1) is a bored cast-in-place pile or a rotary bored cast-in-place pile.

3. The integral structure of a fixed pressure steel pipe according to claim 1, characterized in that: The reinforced concrete pile (1) and the surrounding reinforced concrete structure (2) are integrally formed.

4. The integral structure of a fixed pressure steel pipe according to claim 1, characterized in that: Before construction, the foundation surface of the pressure steel pipe (3) is consolidated and grouted. The grouting holes are arranged in a quincunx pattern with a hole spacing of 2.5m × 2.5m.

5. The integral structure of a fixed pressure steel pipe according to claim 4, characterized in that: The consolidation grouting is carried out using the covered weight method, with a covered weight thickness of not less than 1m.

6. The integral structure of a fixed pressure steel pipe according to claim 4, characterized in that: The consolidation grouting is carried out in two phases, including phase I holes and phase II holes. The grouting pressure for the first phase of phase I holes is 0.1 to 0.3 MPa, and the grouting pressure for the first phase of phase II holes is 0.2 to 0.4 MPa.

7. The integral structure of a fixed pressure steel pipe according to claim 1, characterized in that: The outer reinforced concrete structure (2) is integrally cast after the pressure steel pipe (3) is installed.

8. The design method of an integral structure for a fixed pressure steel pipe according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Load determination: Determine all loads acting on the overall structure consisting of the reinforced concrete pile (1), the outer reinforced concrete structure (2) and the pressure steel pipe (3), namely, the self-weight Gc and the water weight Gw in the overall structure. The axial water pressure F3 is determined based on the operating conditions of the pressure steel pipe (3); The total vertical load ΣG = Gc + Gw; Total horizontal load ΣH=F3; S2. Anti-slip stability design and verification: Based on the load determined in step S1, calculate the anti-slip stability of the overall structure to ensure that it satisfies the following formula: Where: f' is the shear friction coefficient between the bottom surface and the foundation; C' is the shear bond strength between the bottom surface and the foundation; A is the bottom area; Kc is the calculated anti-slip safety factor; S3. Structural size iteration: [Kc] is the allowable anti-slip safety factor required by the specification. When Kc calculated in step S2 is less than [Kc], adjust the number, diameter, depth and / or size of the reinforced concrete pile (1) and / or the outer reinforced concrete structure (2) to increase ΣG and / or A, and repeat steps S1 and S2 until Kc ≥ [Kc].

9. The design method for an integral structure of a fixed pressure steel pipe according to claim 1, characterized in that: In step S1, the calculation of the axial water pressure F3 is divided into the following based on the working conditions of the pressure steel pipe (3): When the ball valve is not closed, F3 = π (D1) 2 -D2 2 p / 4 When the ball valve is closed or the nozzle is shut off, F3 = πD1 2 p / 4 Where D1 is the inner diameter of the pressure steel pipe, D2 is the outer diameter of the pressure steel pipe, and p is the internal water pressure.

10. A construction method for an integral structure of a fixed pressure steel pipe, based on an integral structure of a fixed pressure steel pipe as described in any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Consolidation grouting is performed on the foundation surface of the pressure steel pipe (3); Step 2: Construct reinforced concrete piles (1) on both sides of the pressure steel pipe (3); Step 3, pour the outer reinforced concrete structure as a whole (2).

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