Temporary supporting system and construction method in limited space

Abstract

The application discloses a temporary supporting system in limited space and a construction method. The temporary supporting system is arranged in the limited space, safety avoidance design is simultaneously conducted in horizontal and vertical depth directions, then a supporting beam is selected and its stiffness parameter is obtained according to the principle of the lowest cost and the priority order of convenience, and the maximum deformation of the supporting beam in different single-pile safety intervals and different supporting beam stiffness states is calculated, and the steel pipe pile and the pile spacing meeting the conditions are determined when the condition of being lower than the maximum allowable deformation is met. The medium frequency and high frequency vibration hammers are respectively used in the pile insertion and pile extraction construction, so that the influence on the surrounding pipelines and existing buildings / structures can be maximally reduced.

Description

Technical Field

[0001] This invention belongs to the field of bridge construction technology, and particularly relates to the layout and construction technology of temporary support systems in confined spaces during the hoisting of steel truss bridge components. Background Technology

[0002] The construction of a fully welded steel truss bridge requires consideration of numerous factors, including the hydrological environment, nearby ground structures, underground pipelines, and construction costs and timelines. Furthermore, as the bridge span extends towards the center of the river, the cost of using an under-bridge support system increases significantly during bridge segment erection; therefore, a cantilever bridge erection machine is typically employed for this purpose.

[0003] The use of cantilever bridge erection machines requires a temporary support system, which includes two types: a temporary bridge support system (mainly a steel pipe pile system) and a gantry crane foundation for bridge structure hoisting (mainly a steel pipe pile system). During construction, the construction area is constrained by the hydrological environment, nearby buildings, underground pipelines, etc., meaning construction operations must be carried out within a limited space. Specifically, this limited space refers to the extremely limited area for arranging steel pipe piles within the bridge construction area, primarily due to the following four reasons:

[0004] (1) There are rigid pipes with a diameter greater than 500mm that cannot be relocated and are sensitive to the construction of steel pipe piles, such as Ф1.8m ring network water supply pipes and Ф800mm heating pipes.

[0005] (2) There are flexible pipelines that cannot be relocated, are sensitive to steel pipe pile construction, and cannot be accurately positioned (drag method construction), such as 110kV power pipelines, 10kV power pipelines, 35kV power pipelines, and DN350 medium and high pressure gas pipelines.

[0006] (3) There are flexible pipes that cannot be relocated, are not sensitive to steel pipe pile construction, cannot be accurately positioned (drag method construction), but have extremely serious consequences after damage, such as military defense optical cables.

[0007] (4) When there are permanent structures such as chimneys, bridges, and houses nearby, the impact of driving and removing steel pipe piles on the nearby structures should be considered when arranging the temporary support system.

[0008] For the aforementioned pipelines, national laws, administrative departments, and property owners have varying requirements regarding safety protection distances and safeguards, necessitating compliance with relevant requirements and regulations. Therefore, when temporary support steel pipe piles must be installed in the bridge construction area, but the pile length (controlled by the single pile bearing capacity) is incompatible with surrounding pipelines and structures, a new type of support pile design and a new construction method need to be developed. Summary of the Invention

[0009] Purpose of the invention: In view of the above-mentioned existing problems and deficiencies, the purpose of this invention is to provide...

[0010] Technical Solution: To achieve the above-mentioned objectives, the present invention adopts the following technical solution: a method for arranging a temporary support system in a confined space, characterized by comprising the following steps:

[0011] Step S1: Before the steel pipe pile driving construction, for existing shallow pipelines and / or shallow foundation buildings and structures, the driving construction area shall be avoided by horizontal avoidance in accordance with the construction safety distance requirements.

[0012] Step S2: After horizontally avoiding the pile driving area, it is also necessary to avoid the deep pipeline in the vertical direction and ensure that the bottom of the steel pipe pile is not lower than the top elevation of the deep pipeline.

[0013] Step S3, Determination of the stiffness of a single pile support

[0014] First, steel pipe pile driving operations are carried out in the construction area. The additional stress generated by each pile in the direction of the settlement calculation point is superimposed by the horizontal plane of the settlement calculation point. Then, the settlement of the soil layer is calculated by the uniaxial compression layer summation method to obtain the final settlement s of the single pile foundation. The calculation method is shown in Equation (1).

[0015]

[0016] In the formula, s represents the final settlement of the pile foundation (mm); m represents the number of piles within the horizontal influence range of a circle with the settlement calculation point as the center and a radius of 0.6 times the pile length; n represents the number of calculated soil layers within the settlement calculation depth range; the number of layers should be combined with the soil properties, and the layer thickness should not exceed 0.3 times the calculation depth; σ zi This represents the sum of additional vertical stresses generated by each pile within the horizontal influence range at a point half the thickness of the i-th soil layer below the pile tip plane of the stress calculation point; the stress calculation point should be the pile center point closest to the settlement calculation point; Δz i E represents the calculated thickness of the i-th soil layer (m); si Let Q represent the compression modulus (MPa) of the i-th soil layer, using the compression modulus from the soil's own weight pressure to the soil's own weight pressure plus additional pressure; j Let l represent the additional load (kN) at the top of pile j under the quasi-permanent combination of load effects. When the basement depth exceeds 5m, the total load under the quasi-permanent combination of load effects is taken as the equivalent additional load considering rebound and recompression. j A represents the length (m) of the j-th pile; ps α represents the cross-sectional area of ​​the pile; jThis represents the ratio of the total end resistance of the j-th pile to the pile top load, approximately taken as the ratio of the ultimate total end resistance to the ultimate bearing capacity of a single pile; I p,i , and I s,ij E represents the influence coefficients of the pile tip resistance and pile side resistance of the j-th pile on the stress at half the thickness of the i-th calculated soil layer along the calculation axis; c This represents the elastic modulus of the pile concrete; s e Indicates the calculation of pile compression; ξ e The coefficient of compression of the pile body is represented by 1.0 for end-bearing piles; for friction piles, it is 2 / 3 when l / d ≤ 30 and 1 / 2 when l / d ≥ 50; linear interpolation is used for values ​​between these two; Ψ represents the empirical coefficient for calculating pile foundation settlement, which is 1.0 when there is no local experience.

[0017] Calculate the depth Z for pile foundation settlement n This makes the Z-depth of the pile foundation settlement calculation point... n The additional stress caused by the pile, the additional stress caused by the earth pressure of the pile cap, and the soil self-weight stress satisfy the following relationship (2), and the settlement depth Z of the pile foundation is used as the calculation depth. n The calculated number of soil layers, n, is obtained.

[0018] σ z +σ zc =0.20σ c (2)

[0019] In the formula, σ z To calculate depth Z n Additional stress caused by piles; Z at the calculated depth n Additional stress σ caused by earth pressure on the pile cap zc , σ c The stress is the stress due to the soil's own weight.

[0020] Step S4, determine the stiffness of the support beam: based on the on-site construction conditions, select the support beam first according to the principle of lowest cost, and obtain the stiffness parameter data of the support beam;

[0021] Step S5, Determination of single pile spacing s: Under the premise that the center-to-center spacing of single piles does not exceed 3 times the pile diameter, the deformation of the single pile support pile under different single pile spacings is calculated by adjusting the single pile spacing.

[0022] Step S6: When the deformation of a single pile under the minimum single pile spacing is less than the maximum allowable deformation of a single pile, determine the specifications of the supporting beam under this condition and the single pile spacing that meets the condition of less than the maximum allowable deformation of a single pile; when the deformation of a single pile under the minimum single pile spacing is greater than the maximum allowable deformation of a single pile, reselect the supporting beam according to the principle of lowest cost, repeat step S5, thereby determining the specifications of the supporting beam and the single pile spacing that meets the condition of less than the maximum allowable deformation of a single pile, and completing the pile foundation layout.

[0023] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0024] (1) The present invention uses steel pipe piles to build a temporary support system. Compared with cement mixing piles, high pressure jet grouting piles, PHC precast steel pipes, precast square piles and bored piles, it has the advantages of minimal soil squeezing effect, minimal impact of driving on the surrounding area, and lowest cost. It also has the advantages of being recyclable and removable.

[0025] (2) Under the premise of ensuring safe protection distance by avoiding both horizontal and depth directions, the multi-point elastic support algorithm is used to determine the stiffness of the single pile support and the stiffness of the support beam, thereby determining the single pile spacing to ensure that the design requirements are met while meeting the minimum spacing requirements.

[0026] (3) During construction, the temporary support system of the present invention uses a medium-low frequency vibratory hammer to drive steel pipe piles and a high frequency vibratory hammer to remove steel pipe piles, which can completely minimize the impact on surrounding pipelines and existing buildings / structures. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating the method for arranging a temporary support system in a confined space as described in this invention.

[0028] Figure 2 This is a schematic diagram of the steel pipe pile avoiding pipelines in the vertical state of the temporary support system in a confined space as described in this invention.

[0029] Figure 3 This is a statistical chart showing the bearing capacity deviation of the support piles driven by vibratory hammers at different frequencies in an embodiment of the present invention.

[0030] Figure 4 This diagram illustrates the impact of vibratory hammers at different frequencies on the vertical displacement of the surrounding soil in an embodiment of the present invention.

[0031] Figure 5 This paper analyzes the impact of vibratory hammers of different frequencies on the vertical acceleration of the surrounding soil in an embodiment of the present invention. Figure 6 This paper analyzes the impact of vibratory hammers at different frequencies on the vertical displacement of the surrounding soil during the removal of support piles in this embodiment of the invention.

[0032] Figure 7 This paper analyzes the impact of vibratory hammers of different frequencies on the vertical acceleration of the surrounding soil during the removal of support piles in this embodiment of the invention. Detailed Implementation

[0033] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. After reading this invention, any modifications of the invention in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims.

[0034] This invention relates to bridge components (partial segments of the superstructure steel box girder are assembled using crawler cranes, while the remainder are assembled using gantry cranes). The gantry cranes use steel pipe piles as foundations, with a track beam mounted on top. The gantry cranes also use steel pipe piles as foundations, with double-layered HN700 I-beams or 1.5m I-beam track beams mounted on top. Due to the need for protection of the raw water pipeline, the bottom elevation of the steel pipe piles is set at -11.24, and the elevation of the bottom of the steel pipe piles is limited to -15.84. Furthermore, the distance from the raw water pipeline in the horizontal plane does not meet the requirements. Therefore, it is proposed to use two steel pipe piles supported by 1.5m I-beams as the support system.

[0035] The pile foundation layout principle of the temporary support system of this invention adopts the principle of horizontal avoidance, and also considers avoidance in the vertical direction. That is: for shallow pipelines and buildings and structures with shallow foundations nearby, the horizontal avoidance principle is directly applied; for deep pipelines, in addition to horizontal avoidance, vertical avoidance is also required, such as... Figure 1 As shown, the bottom of the steel pipe pile is no less than 1.0m below the top elevation of the deep pipeline—this measure is mainly used to avoid settlement caused by the removal of the soil carried by the steel pipe pile. Since the bearing capacity of a single steel pipe pile decreases sharply after the driving depth is reduced, this invention introduces the following new design concept to meet the needs of engineering applications. The specific process is as follows:

[0036] Step S1: First, the geological data of each exploration borehole point is sorted and summarized to obtain the relevant geological parameters of the temporary support pile. The soil geological data obtained from some exploration boreholes are shown in Table 1 below.

[0037] Table 1. Summary of Soil Layer Geological Data from IZK291 Exploration Bore Near the Gantry Crane

[0038]

[0039] Step S2, Calculation of vertical bearing capacity of foundation piles

[0040] This invention adopts As foundation piles, the ultimate vertical bearing capacity Q of a single steel pipe pile is calculated based on the mechanical parameters of the foundation piles. uk ,

[0041] Q uk =Q sk +Q pk =u∑q sik l i +λ pq pk A P

[0042] In the formula, Q sk Q pk These are the standard values ​​of total limiting side resistance and total limiting end resistance, respectively; q sik q pk These are the pile side resistance and pile end resistance, respectively; the end resistance is considered to be zero; λ p The coefficient of soil plugging effect at the pile tip is represented by u; the pile perimeter is represented by l. i This represents the thickness of the i-th layer of soil around the pile;

[0043] A p This indicates the area at the pile tip.

[0044] The standard value Q of the vertical ultimate bearing capacity of single piles with different foundation pile numbers was calculated using the above method. uk And ensure that it meets safety requirements.

[0045] Step S3, Calculation of vertical spring stiffness of gantry crane foundation piles

[0046] The geological survey data from each borehole point are summarized in Table 1. This invention calculates the theoretical pile foundation settlement based on the vertical bearing capacity of the gantry crane foundation piles, and then calculates the vertical spring stiffness of a single pile based on the settlement value and the vertical bearing capacity of the single pile to simulate the elastic support of the support pile and calculate the support pile settlement. This invention superimposes the additional stress generated by each pile on the stress calculation point within the horizontal influence range of the settlement calculation point, and uses the uniaxial compression layered summation method to calculate the soil layer settlement, taking into account the pile compression (se). The final settlement of the pile foundation is then calculated using the following formula:

[0047]

[0048] In the formula, s represents the final settlement of the pile foundation (mm); m represents the number of piles within the horizontal influence range of a circle with the settlement calculation point as the center and a radius of 0.6 times the pile length; n represents the number of calculated soil layers within the settlement calculation depth range; the number of layers should be combined with the soil properties, and the layer thickness should not exceed 0.3 times the calculation depth; σ zi This represents the sum of additional vertical stresses generated by each pile within the horizontal influence range at a point half the thickness of the i-th soil layer below the pile tip plane of the stress calculation point; the stress calculation point should be the pile center point closest to the settlement calculation point; Δz i E represents the calculated thickness of the i-th soil layer (m); si Let Q represent the compression modulus (MPa) of the i-th soil layer, using the compression modulus from the soil's own weight pressure to the soil's own weight pressure plus additional pressure; jThis represents the additional load (kN) at the top of pile j under the quasi-permanent combination of load effects (for composite pile foundations, the load shared by the soil under the pile cap should be deducted); when the basement depth exceeds 5m, the total load under the quasi-permanent combination of load effects is taken as the equivalent additional load considering rebound and recompression; l j A represents the length (m) of the j-th pile; ps α represents the cross-sectional area of ​​the pile; j This represents the ratio of the total end resistance of the j-th pile to the pile top load, approximately taken as the ratio of the ultimate total end resistance to the ultimate bearing capacity of a single pile; I p,i , and I s,ij E represents the influence coefficients of the pile tip resistance and pile side resistance of the j-th pile on the stress at half the thickness of the i-th calculated soil layer along the calculation axis, determined according to Appendix F of the "Pile Foundation Code"; c This represents the elastic modulus of the pile concrete; s e Indicates the calculation of pile compression; ξ e The coefficient of compression of the pile body is 1.0 for end-bearing piles; for friction piles, it is 2 / 3 when l / d ≤ 30 and 1 / 2 when l / d ≥ 50; linear interpolation is allowed for values ​​between the two. Ψ represents the empirical coefficient for calculating pile settlement, which is 1.0 when there is no local experience.

[0049] Calculate the depth Z for pile foundation settlement n This makes the Z-depth of the pile foundation settlement calculation point... n The additional stress caused by the pile, the additional stress caused by the earth pressure of the pile cap, and the soil self-weight stress satisfy the following relationship (2), and the settlement depth Z of the pile foundation is used as the calculation depth. n The calculated number of soil layers, n, is obtained.

[0050] σ z +σ zc =0.20σ c (2)

[0051] In the formula, σ z To calculate depth Z n Additional stress caused by piles; Z at the calculated depth n Additional stress σ caused by earth pressure on the pile cap zc , σ c The stress is the stress due to the soil's own weight.

[0052] Then, calculate the vertical spring stiffness based on the ratio of the ultimate vertical bearing capacity of a single pile to the settlement, as shown in the following formula.

[0053] In the formula, K represents the vertical spring stiffness; F represents the standard value of the vertical ultimate bearing capacity of a single pile; and S represents the Mindlin solution for pile settlement under the action of the standard value of the vertical ultimate bearing capacity of a single pile. Thus, the statistical table of pile settlement calculation for gantry crane foundations is obtained, as shown in Table 2. Analysis of Table 2 shows that the maximum settlement of temporary support pile M48, representing the maximum settlement, is 2.37 mm, which meets the specifications and construction requirements.

[0054] Table 2. Statistical Table of Vertical Spring Stiffness Calculation for Gantry Crane Foundation Piles

[0055]

[0056] Step S4, Determining the stiffness of the supporting beam

[0057] In this case, suitable materials for the support beams include double-section HM and HN steel systems, multi-section (double, triple, and quadruple) Bailey truss systems, and self-made H-shaped support steel beams. Considering the ease of construction and cost, the type of support beam with readily available materials and the lowest cost was selected. In this case, the Haishu side gantry crane track beam uses a 1.5m I-beam, and the Yinzhou side gantry crane track beam uses a double-section HN700 main crossbeam. The stiffness parameters of the support beams are shown in Table 3 below.

[0058] Table 3. Parameters of Moment of Inertia for Different Types of Supported Beams

[0059]

[0060]

[0061] Step S5, adjust the spacing s of individual piles

[0062] According to building technical specifications, the settlement of adjacent pile foundations within a range of 6 times the pile diameter must be considered, while settlement beyond 6 times the pile diameter can be disregarded. To reduce design complexity and facilitate the promotion of this invention, when the center-to-center distance does not exceed 3 times the pile diameter, only the influence of adjacent pile foundations needs to be considered.

[0063] Therefore, in this invention, only when the center-to-center spacing of a single pile does not exceed 3 times the pile diameter (630mm) (1.6m) is considered, the deformation of a single supporting pile is calculated under the conditions of "different spacing" and "different supporting beam stiffness" according to the structural analysis program.

[0064] In this case, the maximum allowable uneven settlement of the gantry crane during its travel is 10mm, and the maximum allowable settlement of the main structure's supporting foundation is 40mm. When the deformation of a single pile at the minimum pile spacing is less than the maximum allowable deformation of a single pile, the specifications of the supporting beam and the pile spacing that meets the condition of less than the maximum allowable deformation of a single pile are determined. When the deformation of a single pile at the minimum pile spacing is greater than the maximum allowable deformation of a single pile, the supporting beam is reselected according to the principle of lowest cost, and step S5 is repeated to determine the specifications of the supporting beam and the pile spacing that meets the condition of less than the maximum allowable deformation of a single pile, thus completing the pile foundation layout. Finally, with the supporting beam specifications that meet the requirements determined, the spacing of the steel pipe piles is further determined.

[0065] Step S6, Construction Selection

[0066] When driving steel pipe piles, a medium-frequency vibratory hammer (f≤1200Hz) is used; however, when extracting steel pipe piles, a high-frequency vibratory hammer (f≥2000Hz) is used.

[0067] Verification of Vibratory Hammer Design at Different Frequencies During Steel Pipe Pile Driving and Extraction:

[0068] The inventors statistically analyzed the vertical bearing capacity data of support piles driven by vibratory hammers of different frequencies, and also compiled data on the vertical displacement of steel pipe piles of the same specifications. 1. Analysis of the impact of drive-on support piles with vibratory hammers of different frequencies on the vertical displacement of the surrounding soil.

[0069] Statistical analysis of the vertical bearing capacity data of 20 steel pipe piles of similar specifications driven by medium-frequency and high-frequency vibratory hammers reveals that: the vertical bearing capacity of steel pipe piles driven by medium-frequency vibratory hammers is approximately 5% lower than the theoretical value; the vertical bearing capacity of steel pipe piles driven by high-frequency vibratory hammers is approximately 30% lower than the theoretical value. Specific data are shown in Table 4 below. Figure 3 As shown.

[0070] Table 4. Statistical Table of Bearing Capacity Deviation of Supported Piles Driven by Vibratory Hammers of Different Frequencies

[0071]

[0072]

[0073] 2. Analysis of the impact of vibratory hammer driving of support piles at different frequencies on the vertical displacement of the surrounding soil.

[0074] Based on statistics of the vertical displacement values ​​of the soil surface within a 15m radius of influence of a 1000Hz-2400Hz vibratory hammer at the pile center, it can be seen that: medium-frequency and high-frequency vibratory hammers have little impact on the vertical displacement of the soil; however, the vibration impact decreases significantly with increasing distance within a 4m range of the supporting pile center, as shown in Table 5. Figure 4 As shown.

[0075] Table 5. Analysis of the impact of vibratory hammer driving of support piles at different frequencies on the vertical displacement of the surrounding soil (m)

[0076]

[0077] 3. Analysis of the influence of vibratory hammers of different frequencies on the vertical acceleration of surface soil during the installation of support piles.

[0078] According to statistics on the vertical displacement acceleration values ​​of the ground surface within a 15m radius of influence of a 1000Hz-2400Hz vibratory hammer at the pile center, it can be seen that the vertical acceleration value generated by the medium-frequency vibratory hammer on the surrounding ground surface is about 60% greater than that of the high-frequency vibratory hammer. Within a 4m range of the center of the supporting pile, the vibration acceleration decreases significantly with increasing distance, as shown in Table 6. Figure 5 As shown.

[0079] Table 6. Analysis of the impact of vibratory hammer driving of support piles at different frequencies on the vertical displacement acceleration of the surrounding soil.

[0080]

[0081] 4. Analysis of the impact of vibratory hammers at different frequencies on the vertical displacement of the surrounding soil during the removal of support piles.

[0082] According to statistics on the vertical displacement values ​​of the surface within a 15m radius of influence of a 1000Hz-2400Hz vibratory hammer at the pile center, the vertical displacement influence of a medium-frequency vibratory hammer on the surrounding soil is 2 to 2.5 times that of a high-frequency vibratory hammer. Within a 4m range of the supporting pile center, the vibration influence decreases significantly with increasing distance, as shown in Table 7. Figure 6 As shown.

[0083] Table 7. Analysis of the impact of vibratory hammers at different frequencies on the vertical displacement of the surrounding soil during the removal of support piles.

[0084]

[0085] 5. Analysis of the impact of vibratory hammers at different frequencies on the vertical acceleration of the surrounding soil during the removal of support piles.

[0086] According to statistics on the vertical displacement acceleration values ​​of the ground surface within a 15m radius of influence of a 1000Hz-2400Hz vibratory hammer at the pile center, it can be seen that the vertical acceleration value generated by the medium-frequency vibratory hammer on the surrounding ground surface during pile extraction is about 1.5 to 2 times greater than that of the high-frequency vibratory hammer. Within a 4m range of the supporting pile center, the vibration acceleration decreases significantly with increasing distance, as shown in Table 8 and... Figure 6 As shown.

[0087] Table 8. Analysis of the impact of vibratory hammers at different frequencies on the vertical acceleration of the surrounding soil during the removal of support piles.

[0088]

[0089] In summary, the reason why the present invention adopts the aforementioned construction method is based on the experience and findings of the engineers of this invention:

[0090] (1) When driving the pile, if a high-frequency vibratory hammer is used, it will cause shear failure of the soil around the pile. At this time, the pile-soil resonance effect is greatly alleviated (it can be considered that part of the pile and soil have separated). However, the design bearing capacity of a single pile will be greatly reduced. The reduction is the largest for sandy soil, exceeding 50%, while the reduction is relatively smaller for cohesive soil, with a bearing capacity loss of close to 30%.

[0091] (2) The use of high-frequency vibratory hammers to remove steel pipe piles has significant advantages: a. High-frequency vibratory hammers damage the soil, causing the steel pipe piles to separate from the soil, which greatly weakens the pull-out bearing capacity of the steel pipe piles and facilitates pile extraction; b. The removed steel pipe piles carry less soil, which greatly alleviates the deep soil settlement caused by the collapse of the pile hole soil and has less impact on surrounding pipelines; c. High-frequency vibratory hammers have a higher vibration frequency, shorter wavelength of mechanical waves, and poorer propagation ability. The amplitude attenuation reaches 80% within a 10m working radius and 95% within a 20m working radius, thus greatly reducing the impact range of construction operations.

Claims

1. A method for arranging a temporary support system in a confined space, characterized in that... Includes the following steps: Step S1: Before the steel pipe pile driving construction, for existing shallow pipelines and / or shallow foundation buildings and structures, the driving construction area shall be avoided by horizontal avoidance in accordance with the construction safety distance requirements. Step S2: After horizontally avoiding the pile driving area, it is also necessary to avoid the deep pipeline in the vertical direction and ensure that the bottom of the steel pipe pile is not lower than the top elevation of the deep pipeline at a safe distance. Step S3, Determination of the stiffness of a single pile support First, steel pipe pile driving operations are carried out in the construction area. The additional stress generated by each pile in the direction of the settlement calculation point is superimposed by the horizontal plane of the settlement calculation point. Then, the settlement of the soil layer is calculated by the uniaxial compression layer summation method to obtain the final settlement s of the single pile foundation. The calculation method is shown in Equation (1). In the formula, s represents the final settlement of the pile foundation (mm); m represents the number of piles within the horizontal influence range of a circle with the settlement calculation point as the center and a radius of 0.6 times the pile length; n represents the number of calculated soil layers within the settlement calculation depth range; the number of layers should be combined with the soil properties, and the layer thickness should not exceed 0.3 times the calculation depth; σ zi It represents the sum of additional vertical stresses generated by each pile at the pile tip plane below the i-th layer of soil at 1 / 2 thickness within the horizontal influence range; The stress calculation point should be the pile center point closest to the settlement calculation point; Δz i E represents the calculated thickness of the i-th soil layer (m); si Let Q represent the compression modulus (MPa) of the i-th soil layer, using the compression modulus from the soil's own weight pressure to the soil's own weight pressure plus additional pressure; j Let l represent the additional load (kN) at the top of pile j under the quasi-permanent combination of load effects. When the basement depth exceeds 5m, the total load under the quasi-permanent combination of load effects is taken as the equivalent additional load considering rebound and recompression. j A represents the length (m) of the j-th pile; ps α represents the cross-sectional area of ​​the pile; j This represents the ratio of the total end resistance of the j-th pile to the pile top load, approximately taken as the ratio of the ultimate total end resistance to the ultimate bearing capacity of a single pile; I p,i , and I s,ij E represents the influence coefficients of the pile tip resistance and pile side resistance of the j-th pile on the stress at half the thickness of the i-th calculated soil layer along the calculation axis; c This represents the elastic modulus of the pile concrete; s e Indicates the calculation of pile compression; ξ e The coefficient of compression of the pile body is represented by 1.0 for end-bearing piles; for friction piles, it is 2 / 3 when l / d ≤ 30 and 1 / 2 when l / d ≥ 50; linear interpolation is used for values ​​between these two; Ψ represents the empirical coefficient for calculating pile foundation settlement, which is 1.0 when there is no local experience. Calculate the depth Z for pile foundation settlement n This makes the Z-depth of the pile foundation settlement calculation point... n The additional stress caused by the pile, the additional stress caused by the earth pressure of the pile cap, and the self-weight stress of the soil satisfy the following relationship (2), and the settlement depth Z of the pile foundation is used as the calculation depth. n The calculated number of soil layers, n, is obtained. s z +s zc =0.20σ c (2) In the formula, σ z To calculate depth Z n Additional stress caused by piles; Z at depth of calculation n Additional stress σ caused by earth pressure on the pile cap zc , σ c The stress is the stress due to the soil's own weight. Step S4, determine the stiffness of the support beam: based on the on-site construction conditions, select the support beam first according to the principle of lowest cost, and obtain the stiffness parameter data of the support beam; Step S5, Determination of single pile spacing s: Under the premise that the center-to-center spacing of single piles does not exceed 3 times the pile diameter, the deformation of the single pile support pile under different single pile spacings is calculated by adjusting the single pile spacing. Step S6: When the deformation of a single pile is less than the maximum allowable deformation of a single pile under the minimum single pile spacing, determine the specifications of the supporting beam under this condition and the single pile spacing that satisfies the condition of being less than the maximum allowable deformation of a single pile. When the deformation of a single pile under the minimum single pile spacing is greater than the maximum allowable deformation of a single pile, the support beam is reselected according to the principle of lowest cost, and step S5 is repeated to determine the specifications of the support beam and the single pile spacing that meets the condition of being less than the maximum allowable deformation of a single pile, thus completing the pile foundation layout.

2. The method for arranging a temporary support system in a confined space according to claim 1, characterized in that: The supporting beams include double-section HM600 steel, double-section HN700 steel, double-section 321 Bailey panels, triple-section 321 Bailey panels, quadruple-section 321 Bailey panels, self-made 1.5m supporting beams with B=600mm, self-made 2.0m supporting beams with B=300mm, or self-made 2.0m supporting beams with B=600mm.

3. The method for arranging a temporary support system in a confined space according to claim 1, characterized in that: The supporting beam is made of double-section HN700 steel.

4. The method for arranging a temporary support system in a confined space according to claim 1, characterized in that: The safe distance mentioned in step S2 is 1.0 meter.

5. A construction method for a temporary support system in a confined space, characterized in that: After completing the layout design of the temporary support system as described in claim 1, the pile foundation construction is carried out in the following manner: during the driving stage, according to the steel pipe pile spacing arrangement scheme, a medium-frequency vibratory hammer is used for driving construction, the medium frequency range being 900 to 1200 Hz; when the steel pipe piles are extracted, a high-frequency vibratory hammer is used for extraction construction, the high frequency being greater than 3000 Hz.

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