CN112926111B - Suspension type curtain foundation pit seepage calculation method based on improved resistance coefficient method - Google Patents
Suspension type curtain foundation pit seepage calculation method based on improved resistance coefficient method Download PDFInfo
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- CN112926111B CN112926111B CN202110099492.4A CN202110099492A CN112926111B CN 112926111 B CN112926111 B CN 112926111B CN 202110099492 A CN202110099492 A CN 202110099492A CN 112926111 B CN112926111 B CN 112926111B
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Abstract
The invention discloses a hanging curtain foundation pit seepage calculation method based on an improved resistance coefficient method. The invention corrects the improved resistance coefficient method of the gate dam on the basis of analyzing the difference between the foundation pit of the suspended curtain and the seepage field of the gate dam, provides a segmentation mode of the seepage section of the foundation pit of the suspended curtain under the condition of pressure-bearing water, deduces a new equivalent resistance coefficient calculation formula considering the horizontal confluence section of the special section of the foundation pit, expands the equivalent resistance coefficient calculation formula to the condition of the anisotropy of the aquifer, and realizes quantitative calculation of the water inflow of the foundation pit of the suspended curtain and the water level drop depth outside the pit. According to the invention, the complicated seepage path is divided into simple basic sections, so that the scale effect of the foundation pit is effectively described, the problems of complex seepage field and difficulty in calculation caused by the hanging type curtain are solved, a method basis is provided for the precipitation optimization design of the hanging type curtain pressure-bearing water foundation pit, and the method has the characteristics of flexible segmentation, simplicity in calculation and high precision, and has great application value.
Description
Technical Field
The invention relates to the technical field of hydrogeology, in particular to a hanging curtain foundation pit seepage calculation method based on an improved resistance coefficient method.
Background
With the rapid development of cities, the demands of urban underground space are continuously increased, and the scale and depth of foundation pits are also continuously increased. In order to prevent the underground water from affecting the foundation pit construction and simultaneously control the influence of precipitation on the surrounding environment, a foundation pit underground water control scheme combining precipitation and curtains is generally adopted. Considering factors such as construction difficulty, economic benefits and the like, a scheme of combining a suspension curtain with precipitation in a pit is a main trend of underground water control of foundation pit engineering.
In the suspended curtain precipitation mode, the aquifer is partially isolated and partially communicated, underground water flows around the curtain to form a three-dimensional flow state, and due to the complexity of the seepage mode, no unified analytical calculation method exists at present, so that precipitation design is carried out by referring to a numerical method calculation result, but the numerical method calculation process is complicated and is inconvenient to be directly used by most engineering technicians. For this reason, many students have conducted studies on a method of calculating a suspension type curtain analysis. However, due to the scale effect of the suspended curtain precipitation, geometrical parameters such as curtain depth, foundation pit area, aquifer thickness, foundation pit depth and the like have different degrees of influence on the precipitation effect. The introduction of these variables tends to make the mathematical model quite complex and difficult to solve, so that many studies tend to ignore the influence of some factors and have limited applicable conditions.
For the complex seepage problem of underground buildings, the improved resistance coefficient method is used for completing the head loss calculation of each segment by dividing the whole seepage segment into a plurality of simple basic segments, so as to obtain a head curve and flow. The method has the characteristics of simple calculation and high precision, is popularized in the gate dam seepage calculation, but the research in the foundation pit seepage calculation is still less. The method is characterized in that an improved resistance coefficient method originally belongs to a two-dimensional flow method of a section, a formula of the method is based on the condition that the width of the water section of a sluice gate is unchanged, a foundation pit dewatering process belongs to a more complex three-dimensional flow problem, ground water on a plane is collected towards the center, the width of the water section is smaller when the ground water is closer to the center of the foundation pit, and the hydraulic gradient is larger. For more complex anisotropic formations, the original method is more difficult to characterize the errors and effects it brings. Therefore, although the improved resistance coefficient method has the advantages of simplicity, convenience and flexibility in the seepage problem of the gate dam, the improvement and correction are needed when the seepage problem of the foundation pit under the action of the curtain is caused.
Disclosure of Invention
The invention aims to provide a simple and practical deep foundation pit seepage calculation method under the action of a suspended waterproof curtain, aiming at the defects of the prior art, so as to be applied to calculation of water inflow and descending depth of actual engineering.
The invention provides a hanging curtain foundation pit seepage calculation method based on an improved resistance coefficient method, which comprises the following specific implementation steps:
s1, determining a precipitation influence radius R according to survey design data, and determining an equivalent circle radius R of a foundation pit 0 Initial head H of groundwater 0 Safety water level H of foundation pit D Horizontal permeability coefficient K of aquifer r Vertical permeability coefficient K of aquifer z Subtracting the total thickness M of the aquifer from the total thickness M of the aquifer of the foundation pit part, and subtracting the curtain depth d' of the foundation pit part from the curtain depth w of the aquifer of the curtain entering the aquifer d;
s2, dividing the foundation pit aquifer into four sections through an equal water head line passing through corner points on two sides of the curtain on the vertical section, wherein the four sections comprise a horizontal converging section, a first inner vertical section, a horizontal section and a second inner vertical section;
s3, calculating the resistance coefficient xi of the horizontal confluence section in S2 according to the geometric parameters of each section of the foundation pit aquifer in S1 1 Resistance coefficient ζ of the first inner vertical segment 2 Horizontal levelDrag coefficient of segment ζ 3 And a drag coefficient ζ of the second inner vertical segment 4 ；
S4, according to each sectional resistance coefficient of S3, the initial water head H of the groundwater 0 Safety water level H of foundation pit D Calculating curtain outside water level H by anisotropic correction coefficient alpha A ；
S5, according to each sectional resistance coefficient of S3, the initial water head H of the groundwater 0 Safety water level H of foundation pit D Equivalent radius r of foundation pit 0 Horizontal permeability coefficient K of aquifer r And calculating the water inflow quantity Q of the foundation pit by using the anisotropic correction coefficient alpha.
Compared with the prior art, the invention has the following beneficial effects: according to the invention, after the site water level is known and the foundation pit safety water level is determined, the calculation of the water head and the water inflow on the outer side of the foundation pit can be simultaneously realized, so that the change trend of the water head and the water inflow on the outer side of the pit under different curtain depths is obtained, and a guiding basis is provided for the design of foundation pit precipitation. The method is simple and flexible, has higher precision and has great application value.
Drawings
FIG. 1 is a flow chart of a method for calculating seepage of a foundation pit of a suspended curtain based on an improved resistance coefficient method;
FIG. 2 is a schematic illustration of a foundation pit section according to the related art of the invention;
fig. 3 is a schematic diagram of a horizontal bus section and a horizontal section plane flow network according to the related art of the invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. Referring to fig. 1, the invention provides a suspension curtain foundation pit seepage calculation method based on an improved resistance coefficient method, which considers the influence of three-dimensional flow of underground water on the basis of the original improved resistance coefficient method, provides a new basic section 'horizontal confluence section' formula, and considers the anisotropy of the permeability coefficient of an aquifer.
The foundation pit calculated by the method is positioned in Wuhan city, and the excavation area of the foundation pit is about 65000m 2 The circumference of the foundation pit is 1005m. The field region belongs to the class I field of the Yangtze river, and the Yangtze river is laminated into a typical binary structure, namely, the upper part is mainly made of cohesive soil, and the middle part is made of soft soil and silt; the lower part is a fine and middle coarse sand and pebble layer. The excavation depth of the foundation pit is 14.4-15.8 m, and the foundation pit is excavated through the relative water-resisting layer of the relative cohesive soil. The initial water level of the field area is 17.35m, and the minimum water level drop depth in the foundation pit is required to be 9.88m, and the method comprises the following specific steps:
s1, determining a precipitation influence radius R according to survey design data, and determining an equivalent circle radius R of a foundation pit 0 Initial head H of groundwater 0 Safety water level H of foundation pit D Horizontal permeability coefficient K of aquifer r Vertical permeability coefficient K of aquifer z Subtracting the total thickness M of the aquifer from the total thickness M of the aquifer of the foundation pit part, and subtracting the curtain depth d' of the foundation pit part from the curtain depth w of the aquifer of the curtain entering the aquifer d;
in the embodiment, the precipitation influence radius R is 388.2m, and the equivalent circle radius R of the foundation pit 0 =148.2m; the initial water head of the underground water is H 0 =17.35 m; the water level is controlled to be 1m below the maximum excavation depth, and the safety water level H of the foundation pit D ＝7.47m；
Generalizing the multilayer aqueous layer to one layer, the total thickness m=52.8m; horizontal permeability coefficient K of aquifer r =14.2m/d; vertical permeability coefficient K of aquifer z =9.5 m/d; the foundation pit enters an aquifer for 0.5M, and the aquifer thickness M' of the foundation pit part is subtracted by 52.3M;
the curtain enters the aquifer to a depth d=31.7m; the foundation pit enters an aquifer for 0.5m, and the curtain depth d' =31.2m of the foundation pit part is subtracted; curtain thickness w=1m;
s2, dividing a foundation pit aquifer into four sections through an equal water head line passing through corner points on two sides of a curtain on a vertical section, wherein the four sections comprise a horizontal converging section (1), a first inner vertical section (2), a horizontal section (3) and a second inner vertical section (4), as shown in fig. 2 and 3;
s3, calculating the resistance coefficient xi of the horizontal converging section (1) in S2 according to the geometric parameters of each section of the foundation pit aquifer in S1 1 Resistance coefficient ζ of the first inner vertical segment (2) 2 Resistance coefficient ζ of horizontal segment (3) 3 And a drag coefficient ζ of the second inner vertical segment (4) 4 The formulas are as follows:
s4, according to each sectional resistance coefficient of the step S3, the initial water head H of the groundwater 0 Safety water level H of foundation pit D Calculating curtain outside water level H by anisotropic correction coefficient alpha A ；
From the horizontal permeability coefficient K of the aquifer r Vertical permeability coefficient K of aquifer z The anisotropic correction coefficient α is calculated as follows:
the outside water level H of the curtain A The following formula is calculated:
s5, according to each sectional resistance coefficient of the step S3, the initial water head H of the groundwater 0 Safety water level H of foundation pit D Equivalent radius r of foundation pit 0 Horizontal permeability coefficient K of aquifer r And calculating the water inflow quantity Q of the foundation pit by using the anisotropic correction coefficient alpha, wherein the water inflow quantity Q of the foundation pit is represented by the following formula:
while the present invention has been described with reference to the above-described embodiments, it is to be understood that the same is not limited to the above-described embodiments, but rather that the same is intended to be illustrative only, and that many modifications may be made by one of ordinary skill in the art without departing from the spirit of the invention and scope of the appended claims.
Claims (1)
1. The method for calculating the seepage of the foundation pit of the suspension curtain based on the improved resistance coefficient method is characterized by comprising the following steps of:
s1, determining a precipitation influence radius R according to survey design data, and determining an equivalent circle radius R of a foundation pit 0 Initial head H of groundwater 0 Safety water level H of foundation pit D Horizontal permeability coefficient K of aquifer r Vertical permeability coefficient K of aquifer z Subtracting the total thickness M of the aquifer from the total thickness M of the aquifer of the foundation pit part, and subtracting the curtain depth d' of the foundation pit part from the curtain depth w of the aquifer of the curtain entering the aquifer d;
s2, dividing the foundation pit aquifer into four sections through an equal water head line passing through corner points on two sides of the curtain on the vertical section, wherein the four sections comprise a horizontal converging section, a first inner vertical section, a horizontal section and a second inner vertical section;
s3, calculating the resistance coefficient xi of the horizontal confluence section in S2 according to the geometric parameters of each section of the foundation pit aquifer in S1 1 Resistance coefficient ζ of the first inner vertical segment 2 Drag coefficient ζ of horizontal segment 3 And a drag coefficient ζ of the second inner vertical segment 4 ；
S4, according to each sectional resistance coefficient of S3, the initial water head H of the groundwater 0 Safety water level H of foundation pit D Calculating curtain outside water level H by anisotropic correction coefficient alpha A ；
S5, according to each sectional resistance coefficient of S3, the initial water head H of the groundwater 0 Safety water level H of foundation pit D Equivalent radius r of foundation pit 0 Horizontal permeability coefficient K of aquifer r Calculating the water inflow Q of the foundation pit by using the anisotropic correction coefficient alpha;
in the S3, the resistance coefficient xi of the horizontal confluence section 1 Resistance coefficient ζ of the first inner vertical segment 2 Drag coefficient ζ of horizontal segment 3 And a drag coefficient ζ of the second inner vertical segment 4 The calculation formulas of (a) are respectively as follows:
wherein R is the influence radius of precipitation, R 0 The equivalent radius of the foundation pit is d is the depth of the curtain entering the aquifer, M is the total thickness of the aquifer, M 'is the thickness of the aquifer subtracted from the foundation pit part, d' is the depth of the curtain subtracted from the foundation pit part, and w is the thickness of the curtain;
the anisotropic correction coefficient alpha has the following calculation formula:
wherein: k (K) r For the horizontal permeability coefficient of the aquifer, K z is Vertical permeability coefficient of aquifer;
in the step S4, outside the curtainSide water level H A The calculation formula of (2) is as follows:
wherein: zeta type toy 1 Is the resistance coefficient of the horizontal confluence section, xi 2 Is the resistance coefficient of the first inner vertical section, ζ 3 Is the resistance coefficient of the horizontal section, xi 4 Resistance coefficient of the second inner vertical section, H 0 Is the initial water head of the groundwater, H D The safety water level of the foundation pit is ensured, and alpha is an anisotropic correction coefficient;
in the step S5, a foundation pit water inflow Q calculation formula is as follows:
wherein, xi 1 Is the resistance coefficient of the horizontal confluence section, xi 2 Is the resistance coefficient of the first inner vertical section, ζ 3 Is the resistance coefficient of the horizontal section, xi 4 Resistance coefficient of the second inner vertical section, H 0 Is the initial water head of the groundwater, H D For the safe water level of the foundation pit, alpha is an anisotropic correction coefficient, K r Is the horizontal permeability coefficient of the aquifer, r 0 Is the equivalent circle radius of the foundation pit.
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| CN113505549B (en) * | 2021-07-22 | 2023-05-19 | 西南交通大学 | Groundwater level simulation method in foundation pit dewatering process in tidal environment |
| CN114741924B (en) * | 2022-04-12 | 2023-02-07 | 西南交通大学 | Engineering rapid calculation method for water guiding and draining capacity of underground building deeply buried in pressure-bearing water-containing layer |
| CN114528786B (en) * | 2022-04-24 | 2022-07-08 | 中铁城建集团有限公司 | Method and system for calculating two-dimensional steady-state seepage field of foundation pit under suspension type retaining wall support |
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| CN108549774A (en) * | 2018-04-17 | 2018-09-18 | 中南大学 | Heterogeneous artesian aquifer suspended cutoff foundation pit determines water level and draws water method for determination of amount |
| CN111027127A (en) * | 2019-12-27 | 2020-04-17 | 深圳市工勘岩土集团有限公司 | Method for calculating constant water head water inflow of foundation pit |
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| CN109868833B (en) * | 2019-03-06 | 2020-12-22 | 中国地质大学（武汉） | Control method for precipitation of deep foundation pit of binary structure stratum |
| CN110055989B (en) * | 2019-05-10 | 2020-06-30 | 中南大学 | Method for determining water pumping amount of suspended curtain confined water foundation pit based on three-dimensional depth reduction |
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| CN108549774A (en) * | 2018-04-17 | 2018-09-18 | 中南大学 | Heterogeneous artesian aquifer suspended cutoff foundation pit determines water level and draws water method for determination of amount |
| CN111027127A (en) * | 2019-12-27 | 2020-04-17 | 深圳市工勘岩土集团有限公司 | Method for calculating constant water head water inflow of foundation pit |
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