Construction Method for Ultra-wide and Special-shaped Subway Station in Water-rich Sand Stratum

Abstract

The present invention discloses a construction method for an extra-wide and special-shaped subway station in a water-rich sand layer, including: construction of retaining piles for the extra-wide and special-shaped subway station; construction of dewatering wells for the extra-wide and special-shaped subway station; establishing a foundation pit excavation model for the pile-anchor support system of the extra-wide and special-shaped subway station; partial excavation of the special-shaped foundation pit; calculating the construction rhythm of each construction process in the rectangular foundation pit part; dividing the construction sections of the rectangular foundation pit part and calculating the construction period; optimizing the construction period of the rectangular foundation pit part by using the equal-rhythm asynchronous flow method; constructing the first layer of soil at the rectangular foundation pit by adopting the method of leaving a platform in the center and excavating with slopes on both sides; carrying out shotcrete and prestressed anchor cable construction for the first layer of soil, and simultaneously excavating the soil at the second section of the first layer; after undergoing operations such as purlin installation, tensioning, and grouting, excavating the soil at the first section of the second layer, and sequentially carrying out the following flow operations. The method obtains parameters such as the safe excavation length and depth by establishing a foundation pit excavation model for the pile-anchor support system of the extra-wide and special-shaped subway station, ensuring the safety of foundation pit construction.

Description

Technical Field

[0001] The present invention belongs to the technical field of subway construction, and particularly relates to a construction method for an extra-wide special-shaped subway station in a water-rich sand layer. Background Art

[0002] At present, most stations in China are standard-width stations with a width of about 19 - 23m, and the construction technology and construction quality control are mature. However, through literature review, the research on the pile-anchor support system foundation pit of extra-wide (50m) special-shaped subway stations in water-rich sand layer areas is still blank, and there is no rapid construction technology method formed yet.

[0003] For example, the patent application document with the Chinese invention patent application number CN202210062709.9 discloses a construction method for an open-cut foundation pit of a subway station in a water-rich sand layer without dewatering, including the following steps: 1) According to the soil conditions, groundwater conditions, and the size of the foundation pit excavation site surveyed, set up pile foundations and determine the design elevations of the first internal support and multiple internal supports during the excavation process from top to bottom; 2) Dig out the sand in the foundation pit from the ground surface down to the design elevation of the first internal support, and install multiple parallel reinforced concrete supports between the two opposite inner walls of the foundation pit, and multiple reinforced concrete supports are all connected to the inner wall of the foundation pit; 3) Continue to dig out the sand in the foundation pit, and complete the installation of multiple internal supports in sequence when reaching the design elevation of each internal support. Multiple internal supports are all located directly below the reinforced concrete supports; 4) At the same time as step 3), excavate the foundation pit to below the groundwater level line. First, use a grab to dig out the sand, then use a dredger to suck out the mortar, and re-inject the water precipitated from the slurry back into the foundation pit; 5) Continue to excavate until the excavation depth is 0.1m higher than the design elevation of the foundation pit, stop sucking out the slurry and injecting water, suck out the floating mud and spread a 50cm thick gravel cushion layer, and then pour a 1.5m thick concrete bottom layer. After pouring, cure for 7 - 14 days to complete the construction of the foundation pit.

[0004] This existing technology uses a conventional construction method for construction, and cannot achieve the safe construction of an extra-wide (50m) special-shaped subway station in a water-rich sand layer area.

[0005] Based on the above technical problems existing in the prior art, the present invention proposes a construction method for an extra-wide special-shaped subway station in a water-rich sand layer. Summary of the Invention

[0006] The purpose of the present invention is to provide a construction method for an extra-wide special-shaped subway station in a water-rich sand layer in view of the deficiencies of the prior art, including:

[0007] Step 1, construction of the retaining piles of the extra-wide special-shaped subway station;

[0008] Step 2, construction of the dewatering wells of the extra-wide special-shaped subway station;

[0009] Step 3, establishing a foundation pit excavation model for the pile-anchor support system of an ultra-wide special-shaped subway station;

[0010] Step 4: Use Revit software to three-dimensionalize the plane design of the transition interface where the vertical plane structure of the retaining pile support system intersects with the oblique plane structure of the slope support system; add multiple different safety slopes at the intersection of the vertical plane and the oblique plane, and form multiple safe transition interfaces between the vertical and oblique planes to ensure the system safety between different support structures;

[0011] Step 5, partial excavation of special-shaped foundation pit;

[0012] Step 6, calculating the construction rhythm of each construction process of the rectangular foundation pit;

[0013] Step 7, divide the rectangular foundation pit into construction sections, and calculate the construction period using the large difference method, construction rhythm, and construction step distance;

[0014] Step 8, using the equal rhythm asynchronous flow method to optimize the construction period of the rectangular foundation pit part, taking 2 days as the time interval of each construction process, matching the operation logarithm of all construction processes with the construction time of each construction section of the earthwork project, and converting all work into equal rhythm asynchronous flow construction optimization calculation to obtain the optimized construction period;

[0015] Step 9: Use the method of leaving a platform in the center and excavating the slopes on both sides to construct the first layer and the first section of 25m of earthwork at the rectangular foundation pit;

[0016] Step 10, performing spray anchor and prestressed anchor cable construction on the first layer of earthwork, and simultaneously excavating the earthwork at the second section of the first layer;

[0017] Step 11, after strengthening by surrounding purlins, tensioning, grouting, etc., excavate the first section of the second layer of earthwork, and carry out the next section of water flow operation in turn.

[0018] Furthermore, in step 1, a rotary drilling rig is used to perform hole skipping construction at intervals.

[0019] Furthermore, in step 2, a reverse circulation drilling rig and mud wall construction are used to drill sandless concrete pipe wells, wherein the drainage wells are arranged irregularly along the irregular sloping top surface of the foundation pit.

[0020] Furthermore, step 3 includes: using MIDAS / GTS software to input the design parameters of foundation pit length, extra width and depth, setting the width of the impact on the surrounding soil and buildings to 3-5 times the excavation depth, and the impact depth to 2-4 times the excavation depth, and using equal parameters to set the simulation range. When excavating earthwork, the layer height is not more than 3 meters, the segment length is not more than 25 meters, and the support system is implemented synchronously. When excavating the foundation pit, the time for spray anchor closure is controlled within 12 hours.

[0021] Further, step 3 also includes: determining the construction sequence and step distance of the foundation pit excavation for the three support systems of the anchor cables of the retaining piles in the water-rich sand layer, the steel supports of the retaining piles, and the slope anchors.

[0022] Further, in step 3, in the foundation pit excavation model, for 3 / 4 of the area of the foundation pit, the support form of retaining piles with anchor cables is adopted, and for 1 / 4 of the area of the foundation pit, the support form of irregular slope spraying with wire mesh and anchor support is adopted.

[0023] Further, in step 6:

[0024] According to the time parameters and space parameters of the flow construction, in the construction processes of earthwork construction, anchor cable construction, shotcrete with anchor construction, and steel structure construction, based on the on-site construction practice, obtain the time parameters of each construction process, and set the number of construction sections M, the number of construction processes N, the flow step distance K, and the flow rhythm t.

[0025] Further, in step 7: Calculate the construction period by using the time parameters of the construction processes obtained through the construction practice of earthwork, anchor cables, shotcrete with anchors, and steel structures, and obtain the cumulative series of the flow rhythms of each construction process; subtract the cumulative series by dislocation and take the maximum value of the positive values; calculate the total construction period: T = ∑K + ∑t + ∑G, where G is the time interval between two construction processes.

[0026] Further, in step 8: Combining the on-site construction conditions, analyze the construction indexes of earthwork construction machinery, anchor cable machinery, anchor machines, concrete spraying machines, and steel support erection. On the basis of obtaining the analysis data, with the core of maximizing earthwork construction, calculate the flow construction parameters according to the appropriate flow rhythm and flow step distance. Set the greatest common divisor of the flow rhythms t of the earthwork construction, anchor cable construction, shotcrete with anchor construction, and steel structure construction processes as the flow step distance K; increase the number of professional teams in multiples for each construction process. Among them, the total number of professional teams is N, and change the non-uniform rhythm flow construction into uniform rhythm flow construction to optimize the construction period.

[0027] The beneficial effects of the present invention are:

[0028] 1. For the construction method of the extra-wide and irregular-shaped subway station in the water-rich sand layer of the present invention, by establishing a foundation pit excavation model of the pile-anchor support system for the extra-wide and irregular-shaped subway station, parameters such as the safe excavation length and depth are obtained to ensure the safety of the foundation pit construction;

[0029] 2. For the construction method of the extra-wide and irregular-shaped subway station in the water-rich sand layer of the present invention, the plane design drawing of the transition interface where the vertical plane structure of the retaining pile support system intersects with the inclined plane structure of the slope support system is three-dimensionalized, realizing the combination of multiple slope ratios at the intersection of the slope structure and the retaining pile structure, ensuring the safety during the foundation pit excavation;

[0030] 3. The construction method of the ultra-wide special-shaped subway station in the water-rich sand layer of the present invention determines the daily work efficiency of each construction process, calculates the total construction period by using the large difference method, takes 2 days as the time interval of each construction process, matches the operation logarithm of all construction processes with the construction time of each construction section of the earthwork project, and transforms the work into equal-rhythm asynchronous flow construction optimization calculation, thereby realizing the optimization of the construction period. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of a part of the foundation pit area in an embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0033] Example

[0034] The construction method of the water-rich sand layer ultra-wide special-shaped subway station comprises:

[0035] Step 1: Construction of extra-wide special-shaped subway station retaining piles:

[0036] Use rotary drilling rigs to perform hole skipping at intervals;

[0037] Step 2: Construction of ultra-wide special-shaped subway station drainage wells:

[0038] Using reverse circulation drilling rigs, mud wall construction, and sandless concrete pipe wells;

[0039] Step 3: Use MIDAS / GTS software to establish the foundation pit excavation model of the pile-anchor support system for ultra-wide special-shaped subway stations:

[0040] Input the design parameters such as foundation pit length, extra width, depth, etc., set the width of the impact on the surrounding soil and buildings to be 3-5 times the excavation depth, and the impact depth to be 2-4 times the excavation depth. Set the simulation range with other parameters, and it is concluded that when excavating earthwork, the layer height should not exceed 3 meters, and the segment length should not exceed 25 meters. The support system is implemented synchronously. When excavating the foundation pit, the time of spray anchor closure is controlled within 12 hours.

[0041] Step 4: Revit software was used to establish the structural analysis mode of the transition interface node of the multi-support system of the special-shaped enclosure structure, and the parameter design correction of the joint between the soil nail and the pile anchor support under the combination of multiple slopes was performed:

[0042] For example, in actual construction, the slope cutting line and the toe line of the foundation pit are the same line, which means vertical excavation is required. However, in reality, vertical excavation cannot be achieved. Therefore, the position of the slope cutting line is changed to a slope excavation form. The modal analysis of the transition interface node structure is carried out using Revit software to form a combined method with multiple slope ratios, and the slope ratio is changed in sections to ensure the stability of the foundation pit slope structure. The node data processing of the multi-slope ratio change at the junction of the retaining pile and the slope system is deepened using Revit software, and the designed slope and support parameters are corrected to ensure the safe construction of the weakest part of the support system.

[0043] Step 5, as Figure 1 shown, excavate Figure 1 the right irregular foundation pit parts in areas 4, 5, and 7. Excavate with slopes in areas 4, 5, and 7, with each layer not exceeding 3m of the excavation depth simulated by MIDAS, and the length of each excavation section not exceeding 25m of the excavation length simulated by MIDAS. Install anchor rods and spray shotcrete within 6 hours after the excavation is completed.

[0044] Step 6, calculate the construction rhythm of each construction process in the rectangular foundation pit part:

[0045] According to the time parameters and space parameters of the flow construction, for construction processes such as earthwork construction, cable anchor construction, shotcrete construction, and steel structure construction, through on-site construction practice, obtain the time parameters of each construction process, and set the number of construction sections M, the number of construction processes N, the flow step distance K, and the flow rhythm t.

[0046] Step 7, divide the construction sections in the rectangular foundation pit part. Use the large difference method, construction rhythm, and construction step distance to calculate the construction period. Calculate the construction period based on the time parameters of the earthwork, cable anchor, shotcrete, and steel structure construction processes obtained through construction practice, and obtain the cumulative series of the flow rhythms of each construction process; subtract them staggeredly and take the maximum positive value; calculate the total construction period: T = ∑K + ∑t + ∑G, where G is the time interval between two construction processes. In this embodiment, the time interval is 0.

[0047] Step 8, optimize the construction period of the rectangular foundation pit part using the equal-rhythm asynchronous flow method:

[0048] Combined with the on-site construction conditions, analyze the construction indicators of earthwork construction machinery, cable anchor machinery, anchor rod machines, concrete spraying machines, and steel support erection. On this basis, with maximizing earthwork construction as the core, calculate the flow construction parameters according to a certain flow rhythm and flow step distance.

[0049] Set the greatest common divisor of the flow rhythms t of the earthwork construction, cable anchor construction, shotcrete construction, and steel structure construction processes as the flow step distance K; increase the number of professional pairs in each construction process by multiples. Among them, the total number of professional teams is N, and change the unequal-rhythm flow construction to equal-rhythm flow construction to optimize the construction period.

[0050] Step 9, as Figure 1 shown, the center is left with a platform, and the first layer of 25 m of soil in areas 1, 2, 6, and 3 of the rectangular foundation pit is excavated by the method of slope excavation on both sides. Each layer is 3 m; after the first layer of the first section of soil is completed, shotcrete, cable bolts, waling, tensioning, grouting and other processes are carried out within 12 h;

[0051] Step 10, when carrying out shotcrete and prestressed cable bolt construction for the first layer of soil, the soil at the second section of the first layer is excavated synchronously;

[0052] Step 11, after the waling, tensioning, grouting, etc. are completed, the soil of the first section of the second layer is excavated, and the next downstream operation is carried out in sequence. For the first layer, horizontal excavation and support construction are carried out according to the construction section numbers of 1, 2, 3, 4, 5, 6... For the second layer, it lags behind the first layer by 2 construction section numbers, and excavation and support construction are carried out vertically.

[0053] In the above embodiment, the ultra-wide special shape refers to that the foundation pit of the subway station is irregular in shape, and the average width is 30 - 60 m;

[0054] In step 7 of the above embodiment, the construction process of the rectangular standard section is: four construction processes of soil, shotcrete, cable bolts, and steel structure, and the areas realized in Figure 1 are: 1, 2, 3, 6; calculate the total construction quantities of soil, shotcrete, cable bolts, and steel structure in the rectangular standard section, divide it into two vertical construction layers and 7 horizontal construction section numbers, determine the construction quantities of each construction process in each construction section, select a construction team for each of the four construction processes of soil, shotcrete, cable bolts, and steel structure in the rectangular standard section to form a complete team with fixed personnel and equipment, and each construction process is constructed by this complete team. Each construction process works continuously for 5 days, and the daily average construction quantity is calculated as the daily work efficiency of this process;

[0055] For example: Each layer is divided into 7 construction sections:

[0056] Construction process 1 (soil): One construction section is constructed in 2 days;

[0057] Construction process 2 (shotcrete): One construction section is constructed in 2 days;

[0058] Construction process 3 (cable bolts): One construction section is constructed in 6 days;

[0059] Construction process 4 (steel structure): One construction section is constructed in 2 days;

[0060] The total construction period is calculated using the large difference method:

[0061] Then the cumulative series of the flow rhythms of each construction process is:

[0062] Construction process 1: 2, 4, 6, 8, 10, 12, 14;

[0063] Construction process 2: 2, 4, 6, 8, 10, 12, 14;

[0064] Construction process 3: 6, 12, 18, 24, 30, 36, 42;

[0065] Construction process 4: 2, 4, 6, 8, 10, 12, 14;

[0066] Subtract the staggered sequences and take the maximum positive value as the flow step distance;

[0067] Construction process 1 - Construction process 2 = (2, 4, 6, 8, 10, 12, 14) - (2, 4, 6, 8, 10, 12, 14)

[0068] = 2. Similarly, Construction process 2 - Construction process 3 = 2, Construction process 3 - Construction process 4 = 30;

[0069] Calculation of the total construction period:

[0070] T = sum of flow step distances + sum of the last 7 segments of the construction process = (2 + 2 + 30) + 14 = 48 days;

[0071] 48 days is the construction period before optimization.

[0072] The present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims.

Claims

1. A construction method for an ultra-wide special-shaped subway station in a water-rich sand layer, characterized in that, include: Step 1: Construction of super-wide special-shaped subway station retaining piles; Step 2: Construction of ultra-wide special-shaped subway station drainage wells; Step 3, establishing a foundation pit excavation model for the pile-anchor support system of an ultra-wide special-shaped subway station; Step 4: Use Revit software to three-dimensionalize the plane design of the transition interface where the vertical plane structure of the retaining pile support system intersects with the oblique plane structure of the slope support system; add multiple different safety slopes at the intersection of the vertical plane and the oblique plane, and form multiple safe transition interfaces between the vertical and oblique planes to ensure the system safety between different support structures; Step 5, partial excavation of special-shaped foundation pit; Step 6, calculating the construction rhythm of each construction process of the rectangular foundation pit; Step 7, divide the rectangular foundation pit into construction sections, and calculate the construction period using the large difference method, construction rhythm, and construction step distance; Step 8, using the equal rhythm asynchronous flow method to optimize the construction period of the rectangular foundation pit part, taking 2 days as the time interval of each construction process, matching the number of work teams of all construction processes with the construction time of each construction section of the earthwork project, and converting all work into equal rhythm asynchronous flow construction optimization calculation to obtain the optimized construction period; Step 9: Use the method of leaving a platform in the center and excavating the slopes on both sides to construct the first layer and the first section of 25m of earthwork at the rectangular foundation pit; Step 10, performing spray anchor and prestressed anchor cable construction on the first layer of earthwork, and simultaneously excavating the earthwork at the second section of the first layer; Step 11, after strengthening by surrounding purlins, tensioning, grouting, etc., excavate the first section of the second layer of earthwork, and carry out the next section of water flow operation in turn.

2. The construction method of the extra-wide special-shaped subway station in the water-rich sand layer according to claim 1, wherein In step 1, a rotary drilling rig is used to perform hole skipping construction at intervals.

3. The construction method of the extra-wide special-shaped subway station in the water-rich sand layer according to claim 1, characterized in that In step 2, a reverse circulation drill is used to construct a mud wall and drill sandless concrete pipe wells, wherein the drainage wells are arranged irregularly along the irregular sloping top surface of the foundation pit.

4. The construction method of an extra-wide special-shaped subway station in a water-rich sand layer according to claim 1, characterized in that, Step 3 includes: using MIDAS / GTS software to input the design parameters of foundation pit length, extra width and depth, setting the width of the impact on the surrounding soil and buildings to 3-5 times the excavation depth, and the impact depth to 2-4 times the excavation depth, and using equal parameters to set the simulation range. When excavating earthwork, the layer height is not more than 3 meters, the segment length is not more than 25 meters, and the support system is implemented synchronously. When excavating the foundation pit, the time for spray anchor closure is controlled within 12 hours.

5. The construction method of an extra-wide special-shaped subway station in a water-rich sand layer according to claim 1, characterized in that In step 6: According to the time parameters and space parameters of flow construction, in accordance with the earthwork construction, anchor cable construction, shotcrete construction and steel structure construction processes, based on on-site construction practice, the time parameters of each construction process are obtained, and the number of construction sections M, the number of construction processes N, the flow step K and the flow beat t are set.

6. The construction method of the extra-wide special-shaped subway station in the water-rich sand layer according to claim 5, characterized in that In step 7: calculate the construction period by obtaining the construction process time parameters of earthwork, anchor cables, sprayed anchors and steel structures through construction practice, and obtain the cumulative series of the flow rhythm of each construction process; subtract the cumulative series in an offset manner and take the maximum positive value; calculate the total construction period: T=∑K+∑t+∑G, where G is the time interval between two construction processes.

7. The construction method of the extra-wide special-shaped subway station in the water-rich sand layer according to claim 1 or 6, characterized in that In Step 8: Considering the on-site construction conditions, analyze the construction indicators of earthwork construction machinery, cable anchor machinery, anchor rod machines, concrete shotcreters, and steel support erection. Based on the obtained analysis data, with maximizing earthwork construction as the core, calculate the construction parameters of flow construction according to a certain flow rhythm and flow step distance. Set the greatest common divisor of the flow rhythms t of the earthwork construction, cable anchor construction, shotcrete and anchor construction, and steel structure construction processes as the flow step distance K; increase the number of work teams in each construction process by multiples. Among them, the total number of work teams is N, and transform the unequal-rhythm flow construction into equal-rhythm flow construction to optimize the construction period.

8. The construction method of an extra-wide special-shaped subway station in a water-rich sand layer according to claim 1, characterized in that Step 3 also includes: determining the construction sequence and step distance of the foundation pit excavation for the three support systems of the water-rich sand layer retaining pile cable anchor, retaining pile steel support, and slope-cut anchor.

9. The construction method of the extra-wide special-shaped subway station in the water-rich sand layer according to claim 1, characterized in that, In Step 3, in the foundation pit excavation model, the support form of retaining piles combined with cable anchors is adopted for 3 / 4 of the area of the foundation pit, and the support form of irregular slope-cut shotcrete with wire mesh combined with anchor support is adopted for 1 / 4 of the area of the foundation pit.

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