Foundation pit support for pipeline relocation and transformation in complex environment and construction method

Abstract

The invention provides a pipeline relocation foundation pit support and construction method in a complex environment, and belongs to the technical field of building construction, and the method comprises the following steps: S100, foundation pit structure design; s200, excavation construction of a foundation pit; s300, foundation pit supporting construction is conducted; s400, bottom sealing of the foundation pit; s500, transferring and modifying the pipeline; large mechanical equipment is not used, the clearance requirement is avoided, the pipeline can be protected, and the influence on the pipeline can be reduced to the minimum; due to the fact that the construction technology of step-by-step excavation and step-by-step pouring of the protection arms is used, the foundation pit protection arms form an integral structure, the stability of the foundation pit is high, the safety risk of the foundation pit is greatly reduced, settlement monitoring points are arranged on the foundation pit, real-time monitoring is conducted in the construction process, and it is verified that the foundation pit designed and constructed through the method meets the designed settlement requirement.

Description

Technical Field

[0001] The present invention relates to the technical field of building construction, and in particular to a pipeline relocation foundation pit support and construction method under a complex environment. Background Art

[0002] With the acceleration of urbanization, subway construction projects are increasing, and the spatial conflict between new subway projects and existing municipal pipelines is becoming increasingly prominent. During the implementation of the project, pipeline relocation is a conventional solution to resolve such conflicts, and its foundation pit excavation operations often face severe challenges: limited construction space, complex distribution of surrounding pipelines, and difficulty in accessing large-scale machinery and equipment have seriously affected construction efficiency, cost, safety, and construction period. The existing foundation pit support and construction methods for pipeline relocation mostly use two construction methods: 1) Slope excavation method, which uses mechanical equipment to excavate the slope step by step and spray anchor support on the slope; this construction method has the following problems: due to the use of mechanical construction, the site requirements are large, the surrounding roads need to be excavated, and the construction period is long; the municipal pipeline network is complex, and the use of mechanical construction slope excavation method cannot effectively protect the unexplored pipelines; if the excavation depth is greater than 5m, there is still a risk of collapse of the foundation pit after the slope spray anchor support. 2) Steel sheet pile support method: Steel sheet piles are installed on both sides of the pipeline, and mechanical equipment is used for vertical excavation. When the excavation reaches 50 cm from the top of the pipeline, manual excavation is performed. This construction method has the following problems: Since support components such as steel plates, steel purlins and steel supports are used in the construction, a crane is required for construction, and a crane cannot be used under an overpass; and the unexplored pipelines cannot be protected during the steel sheet pile installation process. Summary of the invention

[0003] The purpose of the present invention is to provide a foundation pit support and construction method for pipeline relocation in a complex environment, so as to solve the problem that the existing foundation pit support and construction method for pipeline relocation proposed in the above background technology cannot meet the construction requirements when encountering a complex environment with limited urban space.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A pipeline relocation foundation pit support and construction method under complex environment, comprising the following steps:

[0006] S100, foundation pit structure design: the foundation pit includes a plurality of rectangular wells connected in series, each of which is connected into one by two longitudinal guard arms and two transverse earth partition walls, the guard arms are located on the side walls of the foundation pit, and the earth partition walls are perpendicular to the guard arms; the earth partition walls are provided with pipeline holes, assuming that the pipeline holes are circular holes with a hole diameter d, the height of the earth partition walls is b and the length is L, and the diameter d of the pipeline holes should be smaller than the minimum value of the height b of the earth partition walls or the length L of the earth partition walls; the bottom of the well is also provided with a bottom seal, which is provided below 0.5m below the pipeline hole;

[0007] S200, foundation pit excavation construction: The foundation pit is constructed by artificial well excavation, that is, the odd-numbered well structure is constructed first during excavation, and after the bottom of the odd-numbered well is sealed, the even-numbered well structure is constructed; each well is excavated in construction sections, and the operation is carried out in a downward cycle section by section, and the excavation depth of each construction section is 0.8-1.0m;

[0008] S300, foundation pit support construction: adopting a step-by-step support method, the guard arm of each construction section of the foundation pit is supported by a plurality of vertical main reinforcements and horizontal distribution reinforcements tied together;

[0009] S400, foundation pit bottom sealing: pouring concrete in layers;

[0010] S500, Pipeline Relocation:

[0011] S501, opening a pipe hole in the earth partition wall;

[0012] S502, installing the pipeline: installing the changed pipeline into the pipeline hole.

[0013] Furthermore, in step S100, the diameter of the pipeline hole, the position range of the pipeline hole, the thickness of the earth partition wall, and the thickness of the guard arm are calculated as follows:

[0014] S101. Calculation of pipeline hole diameter

[0015] The diameter d of the pipeline hole should be smaller than the minimum value of the height b of the earth partition wall or the length L of the earth partition wall, and the formula is as follows:

[0016] d≤0.45min(b,L) ①

[0017] Where: the diameter of the pipe hole is d, m; the height of the earth partition wall is b, m; the length of the earth partition wall is L, m;

[0018] S102. Calculation of the location range of pipeline holes

[0019] Horizontal position: Let the horizontal point of the center of the pipe hole be x, the length of the earth partition wall be L, and the minimum edge distance from the edge of the pipe hole to the left or right edge of the earth partition wall be m, then the horizontal position of the pipe hole is:

[0020]

[0021] Where: the diameter of the pipe hole is d, m; the length of the earth partition wall is L, m; the minimum edge distance from the edge of the pipe hole to the left or right edge of the earth partition wall is m, m; the horizontal point of the center of the pipe hole is x, m;

[0022] Vertical position: Let the vertical point of the center of the pipe hole be y, the height of the earth partition wall be b, and the minimum edge distance from the edge of the pipe hole to the top or bottom edge of the earth partition wall be n, then the vertical position of the pipe hole is:

[0023]

[0024] Where: the diameter of the pipe hole is d, m; the height of the earth partition wall is b, m; the minimum edge distance from the edge of the pipe hole to the top or bottom edge of the earth partition wall is n, m; the vertical point at the center of the pipe hole is y, m;

[0025] S103. Calculation of earth partition wall thickness

[0026] The thickness of the earth partition wall is related to the length of each foundation pit and the soil index. It is necessary to ensure that it can withstand the soil pressure and remain stable. The steps for calculating the thickness of the earth partition wall are as follows:

[0027] The thickness t of the earth partition wall must meet the bending and shearing requirements, and the formula is:

[0028]

[0029] Where: f c is the concrete compressive strength, kPa; b is the height of the earth partition wall, m; P is the earth pressure, kN; L is the length of the earth partition wall, m; α is the adjustment coefficient, dimensionless;

[0030] The soil pressure P is calculated according to the following formula:

[0031]

[0032] Where: K is the earth pressure coefficient; H is the depth of the foundation pit, m; γ is the soil weight, kN / m 2 ;

[0033]

[0034] in: is the soil internal friction angle, °;

[0035] S104, Armguard Thickness Calculation

[0036] Arm thickness t c It needs to meet the requirements of bending and shear resistance, the formula is:

[0037]

[0038] Where: f c is the concrete compressive strength, kPa; h is the height of the guardrail, m; P is the soil pressure, kN; S is the length of the guardrail, m; β is the adjustment coefficient, dimensionless;

[0039] If the earth partition walls or guard arms in the same foundation pit have different heights, the larger height shall be used for calculation.

[0040] Furthermore, in step S200, settlement monitoring points are arranged around the foundation pit before excavation. The settlement monitoring points are arranged at the outer edges of the rectangular wells connected in series with the foundation pits. One monitoring point is arranged on each of the earth partition walls at the head and tail ends, and at least one monitoring point is arranged on the guard arm of each well. The settlement control value of the foundation pit pavement is less than 30 mm.

[0041] Furthermore, after the monitoring points are arranged in step S200 and before the foundation pit excavation construction, keyhole construction is also included, and the keyhole construction includes:

[0042] S201. According to the design of the arm dimensions, the pipeline position is inserted into the plane diagram and the corner points of the four construction sections of the excavated foundation pit are measured through construction layout;

[0043] S202, burying a steel chisel at the corner point and reinforcing and protecting it with mortar, and breaking the road surface after the layout is completed;

[0044] S203. After the road surface is broken, a lock is constructed. The top surface of the lock is flat, 0.6-0.8m wide, 0.2-0.4m thick, 300-400mm higher than the original ground, and cast-in-place concrete is used.

[0045] Furthermore, the opening of the pipeline hole is reinforced with a grid steel frame or an I-beam around it.

[0046] Furthermore, in step S300, the guard arm is a concrete guard arm, and concrete is poured on the guard arm after excavation of each construction section is completed, and the concrete strength is greater than c25; the formwork is removed 12 hours after the concrete pouring is completed, or when the strength reaches 2.5Mpa.

[0047] Furthermore, in step S100, the steel ring is provided at the original pipe hole on the earth partition wall, and the steel ring is filled with plain concrete.

[0048] Furthermore, in the pipeline relocation step S500, step S501 may also be: removing the plain concrete in the steel ring on the earth partition wall to obtain a steel pipeline hole.

[0049] In summary, the beneficial effects of the present invention are:

[0050] 1. In the case where the construction site space is small, the surrounding pipelines are complexly distributed, and machinery cannot be used, the present invention divides the foundation pit into a plurality of rectangular wells connected in series for a long narrow foundation pit. Each well is connected into a force-bearing whole by a transverse earth partition wall + a longitudinal guard arm. The earth partition wall provides a transverse support force to the foundation pit that is equivalent to the transverse support in the ordinary foundation pit support; the guard arm provides a lateral support force to the foundation pit that is equivalent to the retaining piles in the ordinary foundation pit support. In the construction of the long narrow foundation pit, this structure can evenly disperse the load, effectively resist the lateral pressure of the soil body, ensure that the foundation pit is not easy to deform, settle, and collapse, provide a foundation for subsequent foundation construction, and ensure the quality and durability of the entire project; at the same time, for complex site conditions and special foundation pit shapes, the well-divided construction method shows extremely high flexibility, is not limited to a plurality of wells connected in series, and can flexibly adjust the size and number of the rectangular wells according to actual conditions to adapt to different geological conditions and construction requirements. Compared with traditional construction methods, it can better cope with various complex and changeable construction scenes;

[0051] 2. In the design of foundation pit, the calculation formula of the diameter of the opening on the earth partition wall is obtained by the correlation between the height and length of the earth partition wall, and the safety range of the opening position of the pipeline hole is also limited; in the calculation of the thickness of the earth partition wall, the calculation formula of the thickness of the earth partition wall is obtained by finding the correlation between the thickness of the earth partition wall and the soil indicators such as the compressive strength of concrete and soil pressure, and the height of the earth partition wall and the length of the earth partition wall; in the calculation of the thickness of the guard arm, the calculation formula of the thickness of the guard arm is obtained by finding the correlation between the thickness of the guard arm and the soil indicators such as the compressive strength of concrete and soil pressure, and the height of the guard arm and the length of the guard arm.

[0052] 3. The foundation pit adopts the construction method of step-by-step excavation and step-by-step support, which can effectively control ground subsidence and deformation of surrounding buildings, reduce the risk of collapse, and adjust the support plan according to geological conditions to enhance the adaptability of construction and ensure smooth construction;

[0053] In summary, the present invention does not use large-scale mechanical equipment, has no clearance requirements, and can protect pipelines, minimizing the impact on pipelines. Moreover, due to the use of a construction process of step-by-step excavation and step-by-step casting of guard arms, the foundation pit guard arms form an integral structure, the foundation pit has high stability, and is not prone to collapse. In addition, by arranging settlement monitoring points in the foundation pit and real-time monitoring during the construction process, it is verified that the foundation pit designed and constructed by this method meets the designed settlement requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 It is a flow chart of the foundation pit support and construction method for pipeline relocation under complex environment of the present invention;

[0055] Figure 2 It is a structural elevation diagram of the foundation pit for pipeline relocation under a complex environment of the present invention;

[0056] Figure 3 It is a cross-sectional view of the foundation pit structure for pipeline relocation under a complex environment of the present invention;

[0057] Figure 4 It is a structural plan of the foundation pit for pipeline relocation under a complex environment of the present invention;

[0058] Among them: 100-foundation pit, 110-Well No. 1, 120-Well No. 2, 130-Well No. 3, 140-Well No. 4, 150-earth partition wall, 151-steel ring, 160-guard arm, 170-bottom cover, 200-pipeline area, 210-original pipeline, 220-changed pipeline, 300-underground passage, DB1.1-Well No. 4 earth partition wall monitoring point, DB1.2-Well No. 4 guard arm monitoring point, DB1.3-Well No. 3 guard arm monitoring point, DB1.4-Well No. 2 guard arm monitoring point, DB1.5-Well No. 1 guard arm monitoring point, DB1.6-Well No. 1 earth partition wall monitoring point, DB1.7-Well No. 1 guard arm monitoring point, DB1.8-Well No. 2 guard arm monitoring point, DB1.9-Well No. 3 guard arm monitoring point. DETAILED DESCRIPTION

[0059] The specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments given here are only used to illustrate and explain the present invention, and cannot be used to limit the present invention.

[0060] It should be noted that many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention may also have other implementations and variations thereof. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0061] The embodiment of the present invention is a dark excavation underground passage 300 of a rail transit interchange station, above which there is an original pipeline 210, and the original pipeline 210 conflicts with the structural section of the dark excavation underground passage 300 of the rail transit interchange station, and the path of the original pipeline 210 needs to be permanently relocated; the location where the original pipeline 210 needs to be relocated is under the overpass, and the clearance under the overpass is only 5m, and it is impossible to use large equipment such as cranes and pile drivers for assistance, and the construction scope is under the motor vehicle lane of the city's main road, with a large daily traffic volume and complex construction conditions. The original pipeline 210 to be relocated has an inner diameter of 0.8m and a buried depth of 5.5m. In order to facilitate the subsequent pipeline relocation construction, a personnel working space of more than 0.5m needs to be set on both sides of the pipeline, so , the width of the foundation pit 100 needs to be more than 1.8m; the cross-sectional length of the concealed excavation crossing passage is 7.7m, which provides cutting and welding space for subsequent pipeline relocation. The length of the foundation pit 100 needs to be more than 10.8m. Taking the above considerations into consideration, the internal dimensions of the foundation pit 100 are designed to be 12.2m long and 1.9m wide. According to the actual construction needs on site, the foundation pit 100 is divided into four wells of the same size, namely, Well No. 1 10, Well No. 2 120, Well No. 3 130, and Well No. 4 140. Each well is 2.9m long and 1.9m wide. Well No. 110 is 4.8m deep, Well No. 2 120 is 4.8m deep, Well No. 3 130 is 5.8m deep, and Well No. 4 140 is 6.4m deep.

[0062] like Figure 1-4 As shown, a foundation pit support and construction method for pipeline relocation in a complex environment includes the following steps:

[0063] S100, foundation pit structure design

[0064] Since the construction site is small and machinery cannot be used, and the pipeline foundation pit 100 is a long narrow foundation pit 100, under these complex construction conditions, a plurality of rectangular wells are connected in series to form a long foundation pit 100, and a single well is provided with a transverse soil partition wall 150 and a guard arm 160. The transverse soil partition wall 150 is a transverse support of the foundation pit 100 formed perpendicular to the length direction of the foundation pit 100, which divides the long foundation pit 100 into a plurality of small rectangular areas, thereby reducing the scope of soil excavated in a single time and reducing construction risks; the guard arm 160 is a concrete structure cast on the surface of the side wall of the foundation pit 100, which enhances the stability of the side wall of the foundation pit 100 and prevents soil from sliding;

[0065] The foundation pit 100 includes a plurality of rectangular wells connected in series, and the wells are formed by connecting two guard arms 160 and two earth partition walls 150. The guard arms 160 are located on the side walls of the foundation pit 100, and the earth partition walls 150 are perpendicular to the guard arms 160. A bottom cover 170 is also provided at the bottom of the well. A pipeline hole (not shown) is provided on the earth partition wall 150. Assuming that the pipeline hole is a circular hole with an aperture d, the height of the earth partition wall 150 is b and the length is L, the aperture d of the pipeline hole should be less than the minimum value of the height b of the earth partition wall or the length L of the earth partition wall, and the bottom cover 170 is provided below 0.5 m below the pipeline hole;

[0066] In step S100, the reasonable limit of the aperture of the pipeline hole is usually related to the height of the partition wall, the strength of the wall material, the load distribution and the structural stability. In actual engineering, if the opening size is too large, the wall stiffness will decrease and affect the overall stability of the structure. Therefore, the opening size needs to be strictly controlled. To ensure the safety of the foundation pit, the calculation of the pipeline hole diameter, the pipeline hole position range, the thickness of the earth partition wall 150, and the thickness of the guard arm 160 are as follows:

[0067] S101. Calculation of pipeline hole diameter

[0068] The diameter d of the pipeline hole should be smaller than the minimum value of the height b of the earth partition wall 150 or the length L of the earth partition wall 150, and the formula is as follows:

[0069] d≤0.45min(b,L) ①

[0070] Where: the diameter of the pipe hole is d, m; the height of the earth partition wall is b, m; the length of the earth partition wall is L, m;

[0071] In this embodiment, it is known that the width of each well, i.e., the length L of the earth partition wall 150, is 1.9 m, and the minimum depth of the foundation pit 100, i.e., the height b of the earth partition wall 150, is 4.8 m. Taking the minimum value of the two, i.e., the length L of the earth partition wall 150 is 1.9 m, the diameter d of the pipeline hole is:

[0072] d≤0.45×1.9≤0.86m

[0073] The pipeline hole diameter d is 0.85m, the inner diameter of the original pipeline 210 to be relocated is 0.8m, 0.8m≤0.85m, therefore, the pipeline hole diameter d meets the installation hole diameter requirement of the original pipeline to be relocated;

[0074] The pipe hole position range is as follows:

[0075] Horizontal position: Assume that the horizontal point of the center of the pipe hole is x, the length of the earth partition wall 150 is L, and the minimum edge distance from the edge of the pipe hole to the left or right edge of the earth partition wall 150 is m, then the horizontal position of the pipe hole is:

[0076]

[0077] Wherein: the diameter of the pipeline hole is d, m; the length of the earth partition wall 150 is L, m; the minimum edge distance from the edge of the pipeline hole to the left or right edge of the earth partition wall 150 is m, m; the horizontal point of the center of the pipeline hole is x, m;

[0078] In this embodiment, it is known that the width of each well, i.e., the length L of the earth partition wall 150 is 1.9 m, the diameter d of the pipeline hole is 0.85 m, and the minimum edge distance m from the edge of the pipeline hole to the left or right edge of the earth partition wall 150 is 0.2 m, then the horizontal position of the pipeline hole is:

[0079]

[0080] 0.63m≤x≤1.28m

[0081] In order to ensure that there is a working space of more than 0.5m on both sides of the changed pipeline, the horizontal position of the pipeline hole is 0.95m;

[0082] Vertical position: Assume that the vertical point at the center of the pipe hole is y, the height of the earth partition wall 150 is b, and the minimum edge distance from the edge of the pipe hole to the top or bottom edge of the earth partition wall 150 is n, then the vertical position of the pipe hole is:

[0083]

[0084] Wherein: the diameter of the pipeline hole is d, m; the height of the earth partition wall is b, m; the minimum edge distance from the edge of the pipeline hole to the top or bottom edge of the earth partition wall 150 is n, m; the vertical point of the center of the pipeline hole is y, m;

[0085] In this embodiment, it is known that the height b1 of the soil partition wall 150 of the No. 1 well 110h and the No. 2 well 120 is 4.8m, the height b3 of the soil partition wall 150 of the No. 3 well 130 is 5.8m, and the height b4 of the soil partition wall 150 of the No. 4 well 140 is 6.4m. The diameter d of the pipeline hole is 0.85m, and the minimum edge distance n from the edge of the pipeline hole to the top or bottom edge of the soil partition wall 150 is 0.5m. Then, the vertical positions of the pipeline holes of the No. 1 well 110, the No. 2 well 120, the No. 3 well 130, and the No. 4 well 140 are:

[0086] The vertical position y1 of the pipeline hole of No. 1 well 110 and No. 2 well 120 is:

[0087]

[0088] 0.83m≤y1≤3.98m

[0089] The vertical position y3 of the 130 pipe hole in the No. 3 well is:

[0090]

[0091] 0.83m≤y3≤4.98m

[0092] The vertical position y4 of the 140 pipe hole in the No. 4 well is:

[0093]

[0094] 0.83m≤y4≤5.58m

[0095] In this embodiment, for the convenience of construction, the vertical position of the pipeline holes of the No. 1 well 110, the No. 2 well 120, and the No. 3 well 130, and the No. 4 well 140 are the vertical positions of the pipeline holes on the earth partition wall 150 connected to the No. 3 well, that is, the vertical position of the pipeline hole from the top of the earth partition wall 150 downward to the upper edge of the pipeline hole. a Take 3m, the vertical position of the pipeline hole on the soil partition wall 150 on the other side of the No. 4 well 140, that is, the vertical position of the pipeline hole from the top of the soil partition wall 150 to the upper edge of the pipeline hole b Take 5.2m.

[0096] The thickness of the earth partition wall 150 and the thickness of the guard arm 160 are calculated as follows:

[0097] S103. Calculation of earth partition wall thickness

[0098] The thickness of the earth partition wall is related to the length of each foundation pit and the soil index. It is necessary to ensure that it can withstand the soil pressure and remain stable. The steps for calculating the thickness of the earth partition wall are as follows:

[0099] The thickness t of the earth partition wall must meet the bending and shearing requirements, and the formula is:

[0100]

[0101] Where: f c is the concrete compressive strength, kPa; b is the height of the earth partition wall, m; P is the earth pressure, kN; L is the length of the earth partition wall, m; α is the adjustment coefficient, dimensionless;

[0102] The soil pressure P is calculated according to the following formula:

[0103]

[0104] Where: K is the earth pressure coefficient; H is the depth of the foundation pit, m; γ is the soil weight, kN / m 2 ;

[0105]

[0106] in: is the soil internal friction angle, °;

[0107] It is known that the width of each well, i.e., the length L of the earth partition wall 150, is 1.9 m, the depth of the foundation pit 100, i.e., the height b of the earth partition wall 150, is 6.4 m, the adjustment coefficient α is 602.01, and the concrete compressive strength f c Take 17860kPa, soil internal friction angle is 25°;

[0108] First calculate the earth pressure coefficient K:

[0109]

[0110] Then calculate the earth pressure P:

[0111]

[0112] Get the thickness t of the earth partition wall 150:

[0113]

[0114] In this embodiment, the thickness t of the earth partition wall 150 is 0.3 m;

[0115] S104, Armguard Thickness Calculation

[0116] Arm thickness t c It needs to meet the requirements of bending and shear resistance, the formula is:

[0117]

[0118] Where: f c is the concrete compressive strength, kPa; h is the height of the guardrail, m; P is the soil pressure, kN; S is the length of the guardrail, m; β is the adjustment coefficient, dimensionless;

[0119] Where: f c is the concrete compressive strength, kPa; h is the height of the guardrail, m; P is the soil pressure, kN; S is the length of the guardrail, m; β is the adjustment coefficient, dimensionless;

[0120] If the earth partition walls or guard arms in the same foundation pit have different heights, the larger height shall be used for calculation.

[0121] It is known that the length L of each well, i.e. the length S of the guard arm 160, is 2.9 m, the depth of the foundation pit 100, i.e. the height h of the guard arm 160, is 6.4 m, the soil pressure P is about 159.89 kN, and the concrete compressive strength f c Take 17860kPa, the adjustment coefficient β is 473.31; the thickness of the arm 160 is tc for:

[0122]

[0123] In this embodiment, for the convenience of construction, the thickness of the arm guard 160 is t c Take 0.3m;

[0124] S200, foundation pit excavation construction: the foundation pit 100 is constructed by artificial well excavation, that is, the odd-numbered well structure is constructed first during excavation, and after the odd-numbered well is concrete-sealed 170, the even-numbered well structure is constructed; each well is excavated in construction sections, and the operation is cyclically carried out section by section. The excavation depth of each construction section depends on the ability of the hole wall to stabilize itself. The excavation depth of each construction section is 0.8-1.0m, and the excavation depth is reduced when encountering special geological conditions;

[0125] S300, foundation pit support construction: adopt the step-by-step support method for construction, the guard arm 160 of each construction section foundation pit 100 includes vertical main reinforcement and horizontal distribution reinforcement, the vertical main reinforcement adopts Φ14@250 steel bar; the horizontal distribution reinforcement adopts Φ14@250 steel bar when the excavation depth is 0-3m, and adopts Φ16@250 steel bar when the excavation depth is 3-7.5m, and a number of the vertical main reinforcement and horizontal distribution reinforcement are tied together to form a construction section support; in step S300, the guard arm 160 is a concrete guard arm, and the guard arm 160 is poured with concrete after each construction section excavation is completed, and the concrete strength is greater than c25; the formwork is removed 12h after the concrete pouring is completed, or when the strength reaches 2.5Mpa;

[0126] S400, foundation pit concrete bottom sealing

[0127] S401. Clean the foundation pit: remove debris, stagnant water and loose soil;

[0128] S402, Install the template: Install the template according to the design requirements;

[0129] S403, pouring concrete: pour in layers, control the thickness of each layer to 30-50cm, and vibrate to make it dense;

[0130] S404, demoulding: demoulding after the concrete strength reaches the design requirements;

[0131] S500, Pipeline Relocation

[0132] S501, drilling a pipe hole in the earth partition wall 150: according to the design drawing, mark the position and size of the pipe hole on the earth partition wall 150, drill several small holes within the outline of the pipe hole, use an electric drill or an impact drill to drill along the outline, use a tool to chisel away the wall between the drill holes, and gradually expand the hole until the hole is completed;

[0133] S502, installing the pipeline: installing the changed pipeline 220 into the pipeline hole.

[0134] like Figure 4 As shown, in step S200, in order to determine the impact of the excavation process on the settlement of the surrounding roads, settlement monitoring points are arranged in the foundation pit 100 before excavation. The settlement monitoring points are arranged at the outer edges of the rectangular wells connected in series in the foundation pit 100, and one monitoring point is arranged on each of the earth partition walls 150 at the head and tail ends. At least one monitoring point is arranged on the guard arm 160 of each well, and the settlement control value of the pavement of the foundation pit 100 is less than 30 mm.

[0135] In this embodiment, the foundation pit 100 is divided into wells No. 1 to No. 4, and the soil partition wall 150 at the head and tail ends of wells No. 1 and No. 4 is respectively provided with a monitoring point, and the guard arms 160 on both sides of wells No. 1 to No. 3 are respectively provided with a monitoring point, and the guard arm 160 on one side of well No. 4 is provided with a monitoring point, for a total of 9 monitoring points, which are monitored throughout the excavation process, and the monitoring frequency is twice a day;

[0136] The excavation of foundation pit 100 is divided into four stages: excavation of construction sections 1 and 3, bottom sealing 170 of construction sections 1 and 3, excavation of construction sections 2 and 4, and bottom sealing 170 of construction sections 2 and 4; when the bottom sealing 170 of the four construction sections has been completed, the entire foundation pit 100 guard arm 160 forms a whole, and the lateral soil pressure is converted into the bending moment of the guard arm 160 acting on the bottom concrete bottom sealing 170. The entire force system has been stabilized and there is no obvious change in the monitoring data. Therefore, this stage is not listed separately for analysis. The analysis of the remaining stages is shown in the table below;

[0137]

[0138]

[0139] It can be inferred from the detection data in the above table that in each construction stage of the excavation of the pipeline foundation pit 100, the settlement value data of the roads around each measuring point did not reach the yellow warning, that is, 70% of the road surface settlement control value of 30 mm, which proves that the support and construction method of the pipeline relocation foundation pit 100 of the present invention meets the requirements for the settlement of the surrounding roads during the excavation of the pipeline foundation pit 100, and the structure is in a stable state.

[0140] During the actual construction, after the monitoring points are arranged in step S200 and before the excavation of the foundation pit 100, the keyhole construction is also included, and the keyhole construction includes:

[0141] S201, according to the size design of the guard arm 160, the position of the pipeline is inserted into the plane diagram, and the corner points of the four construction sections of the excavation pit 100 are measured through construction layout;

[0142] S202, burying a steel chisel at the corner point and reinforcing it with mortar for protection, using a demolition device to demolish the road surface after the lofting is completed, using a steel chisel to pull the diagonal line for size correction during the demolition process to ensure that the clearance size and the thickness of the guard arm 160 meet the requirements;

[0143] S203. After the road surface is broken, a lock mouth is constructed to prevent rainwater from flowing into the well mouth and to prevent the well mouth from sinking when the lower section of the well wall is excavated; the top surface of the lock mouth is flat, 0.7m wide, 0.3m thick, and slightly higher than the original ground by 300mm, and C35 concrete is cast in place.

[0144] In actual implementation, the opening of the pipeline is reinforced with a grid steel frame or an I-beam around it.

[0145] like Figure 3 As shown, in step S100 , the steel ring 151 is provided at the original pipe hole on the earth partition wall 150 , and the steel ring 151 is filled with plain concrete to ensure the integrity of the earth partition wall 150 .

[0146] During actual construction, in the pipeline relocation step S500, step S501 can also be: removing the plain concrete in the steel ring on the earth partition wall to obtain a steel pipeline hole, thereby eliminating the hole drilling step and saving construction time.

[0147] It should be understood that the above-mentioned embodiments are one or more embodiments of the present invention, and there are many other embodiments and variations thereof based on the present invention; the variations and modifications made by ordinary technicians in this industry through the present invention without making pioneering innovations all fall within the scope of protection of the present invention.

Claims

1. A foundation pit support and construction method for pipeline relocation in a complex environment, characterized in that: The following steps are involved: S100, foundation pit structure design: the foundation pit includes a plurality of rectangular wells connected in series, each of which is connected into one by two longitudinal guard arms and two transverse earth partition walls, the guard arms are located on the side walls of the foundation pit, and the earth partition walls are perpendicular to the guard arms; the earth partition walls are provided with pipeline holes, assuming that the pipeline holes are circular holes with a hole diameter d, the height of the earth partition walls is b and the length is L, and the diameter d of the pipeline holes should be smaller than the minimum value of the height b of the earth partition walls or the length L of the earth partition walls; the bottom of the well is also provided with a bottom seal, which is provided below 0.5m below the pipeline hole; S200, foundation pit excavation construction: The foundation pit is constructed by artificial well excavation, that is, the odd-numbered well structure is constructed first during excavation, and after the bottom of the odd-numbered well is sealed, the even-numbered well structure is constructed; each well is excavated in construction sections, and the operation is carried out in a downward cycle section by section, and the excavation depth of each construction section is 0.8-1.0m; S300, foundation pit support construction: adopting a step-by-step support method, the guard arm of each construction section of the foundation pit is supported by a plurality of vertical main reinforcements and horizontal distribution reinforcements tied together; S400, foundation pit bottom sealing: pouring concrete in layers; S500, Pipeline Relocation: S501, opening a pipe hole in the earth partition wall; S502, installing the pipeline: installing the changed pipeline into the pipeline hole.

2. The method for foundation pit support and construction of pipeline relocation in complex environment according to claim 1, characterized in that: In step S100, the calculation of the pipe hole diameter, pipe hole position range, soil partition wall thickness, and arm thickness is as follows: S101. Calculation of pipeline hole diameter The diameter d of the pipeline hole should be smaller than the minimum value of the height b of the earth partition wall or the length L of the earth partition wall, and the formula is as follows: d≤0.45min(b,L)① Where: the diameter of the pipe hole is d, m; the height of the earth partition wall is b, m; the length of the earth partition wall is L, m; S102. Calculation of the location range of pipeline holes Horizontal position: Let the horizontal point of the center of the pipe hole be x, the length of the earth partition wall be L, and the minimum edge distance from the edge of the pipe hole to the left or right edge of the earth partition wall be m, then the horizontal position of the pipe hole is: Where: the diameter of the pipe hole is d, m; the length of the earth partition wall is L, m; the minimum edge distance from the edge of the pipe hole to the left or right edge of the earth partition wall is m, m; the horizontal point of the center of the pipe hole is x, m; Vertical position: Let the vertical point of the center of the pipe hole be y, the height of the earth partition wall be b, and the minimum edge distance from the edge of the pipe hole to the top or bottom edge of the earth partition wall be n, then the vertical position of the pipe hole is: Where: the diameter of the pipe hole is d, m; the height of the earth partition wall is b, m; the minimum edge distance from the edge of the pipe hole to the top or bottom edge of the earth partition wall is n, m; the vertical point at the center of the pipe hole is y, m; S103. Calculation of earth partition wall thickness The thickness of the earth partition wall is related to the length of each foundation pit and the soil index. It is necessary to ensure that it can withstand the soil pressure and remain stable. The calculation steps of the thickness of the earth partition wall are as follows: The thickness t of the earth partition wall must meet the bending and shearing requirements, and the formula is: Where: f c is the concrete compressive strength, kPa; b is the height of the earth partition wall, m; P is the earth pressure, kN; L is the length of the earth partition wall, m; α is the adjustment coefficient, dimensionless; The soil pressure P is calculated according to the following formula: Where: K is the earth pressure coefficient; H is the depth of the foundation pit, m; γ is the soil weight, kN / m 2 ; in: is the soil internal friction angle, °; S104, Armguard Thickness Calculation Arm thickness t c It needs to meet the requirements of bending and shear resistance, the formula is: Where: f c is the concrete compressive strength, kPa; h is the height of the guardrail, m; P is the soil pressure, kN; S is the length of the guardrail, m; β is the adjustment coefficient, dimensionless; If the earth partition walls or guard arms in the same foundation pit have different heights, the larger height shall be used for calculation.

3. The foundation pit support and construction method for pipeline relocation in complex environment according to claim 1, characterized in that: In step S200, settlement monitoring points are arranged around the foundation pit before excavation. The settlement monitoring points are arranged at the outer edges of the rectangular wells connected in series with the foundation pit. One monitoring point is arranged on each of the earth partition walls at the head and tail ends. At least one monitoring point is arranged on the guard arm of each well. The settlement control value of the foundation pit pavement is less than 30 mm.

4. The foundation pit support and construction method for pipeline relocation in complex environment according to claim 3 is characterized by: After the monitoring points are arranged in step S200, before the foundation pit excavation construction, the keyhole construction is also included, and the keyhole construction includes: S201. According to the design of the arm size, the pipeline position is inserted into the plane diagram and the corner points of the four construction sections of the excavation pit are measured through construction layout; S202, burying a steel chisel at the corner point and reinforcing and protecting it with mortar, and breaking the road surface after the layout is completed; S203. After the road surface is broken, a lock is constructed. The top surface of the lock is flat, 0.6-0.8m wide, 0.2-0.4m thick, 300-400mm higher than the original ground, and cast-in-place concrete is used.

5. The method for foundation pit support and construction of pipeline relocation in complex environment according to claim 4 is characterized by: The opening of the pipeline hole is reinforced around with a grid steel frame or an I-beam.

6. The method for foundation pit support and construction of pipeline relocation in complex environment according to claim 1, characterized in that: In step S300, the guard arm is a concrete guard arm, and concrete pouring of the guard arm is carried out after excavation of each construction section is completed, and the concrete strength is greater than c25.

7. The method for foundation pit support and construction of pipeline relocation in complex environment according to claim 1, characterized in that: In step S100, the steel ring is provided at the original pipeline hole on the earth partition wall, and the steel ring is filled with plain concrete.

8. The method for foundation pit support and construction of pipeline relocation in complex environment according to claim 7, characterized in that: In the step S500 of pipeline relocation, step S501 may also be: removing the plain concrete in the steel ring on the earth partition wall to obtain a steel pipeline hole.

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