scholarly journals Analysis of Seepage Characteristics of a Foundation Pit with Horizontal Waterproof Curtain in Highly Permeable Strata

Water ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1303
Author(s):  
Chenghua Shi ◽  
Xiaohe Sun ◽  
Shengli Liu ◽  
Chengyong Cao ◽  
Linghui Liu ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Theoretical Calculation ◽  
Calculation Method ◽  
Design Method ◽  
Water Pressure ◽  
Water Inflow ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit ◽  
Seepage Characteristics

At present, jet-grouted horizontal waterproof curtain reinforcement has become an essential method for deep foundation pit groundwater control. However, there is still a lack of an effective theoretical calculation method for horizontal waterproof curtain reinforcement, and there is little research on the seepage laws of foundation pits under different horizontal waterproof curtain conditions. Based on Darcy’s seepage theory, theoretical analysis models of deep foundation pit seepage were established considering the effect of a horizontal curtain in a highly permeable formation. Through the established models, the calculation method of the water inflow and the water pressure under the condition of a horizontal curtain was derived. Then through indoor tests, the reliability of the theoretical calculation method was verified. Furthermore, the established theoretical calculation method is used to analyze the influence of various factors on the water inflow and the water pressure, such as the ratio of hydraulic conductivity of the horizontal curtain to surrounding soil, thickness, and reinforcement position of the horizontal curtain. It is found that the hydraulic conductivity ratio has the most significant influence on the seepage characteristics of the foundation pit. Finally, the design method was applied to an example of the horizontal waterproof curtain of the foundation pit, which is located at Juyuanzhou Station in Fuzhou (China). The water inflow per unit area is 0.36 m3/d in the foundation pit, and this implies that the design method of the horizontal waterproof curtain applied for the excavation case is good and meets the requirements of design and safety.

scholarly journals Study on Flexural Bearing Capacity Calculation Method of Enclosure Pile with Partial Excision in Deep Foundation Pit

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Mingfeng Lei ◽  
Linghui Liu ◽  
Yuexiang Lin ◽  
Jin Li
Keyword(s):  
Flexural Strength ◽  
Bearing Capacity ◽  
Calculation Method ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Theoretical Derivation ◽  
Deep Foundation Pit ◽  
Practical Engineering ◽  
Capacity Calculation ◽  
Partial Excision

During deep foundation pit construction, the structural clearance intrusion, which is caused by the complex formation conditions and the inefficient drilling equipment, is usually detected due to the vertical deviation of piles. To meet construction requirements, pile parts intruding into the structural clearance are supposed to be excised. However, the sectional flexural strength of the pile is bound to decrease with partial excision, which would reduce the bearing capacity of the enclosing structure during construction. In this paper, a theoretical derivation of the normal sectional flexural strength of the partially excised circular pile is proposed. The derivation adopts the assumption of the plane section and steel ring equivalence and can be solved by the bisection method. Furthermore, the calculation method is applied to the pile evaluation of a practical engineering; also, the method is verified by the numerical method. The application results show that the excision of rebar and pile’s sectional area will cause a rapid linear decline in the sectional flexural strength. After excising 18 cm radial thickness of the circular pile (ϕ800 mm) and 6 longitudinal rebars, the sectional flexural strength of the pile decreases to 58% from the origin, which cannot meet the support requirement. The analysis indicates that pile reinforcements must be carried out to maintain the construction safety.

On Overloading Design Method for the Slope of Deep Foundation Pit with Layered Soil Braced by Soil Nail

2013 ◽  
Vol 438-439 ◽  
pp. 724-727
Author(s):  
Li Hua Li
Keyword(s):  
Design Method ◽  
Limit Equilibrium ◽  
Work Rate ◽  
Layered Soil ◽  
Plastic Limit ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit ◽  
Soil Nail ◽  
Limit Equilibrium Theory

Based on plastic limit equilibrium theory of soil, the suitable values of energy safety factor are discussed here from energy work rate, the new design method for vertical slope of deep foundation pit with layered soil braced by soil nail with even overloading on slope top is proposed and engineering example is given out.

scholarly journals Finite-Difference Numerical Simulation of Dewatering System in a Large Deep Foundation Pit at Taunsa Barrage, Pakistan

2019 ◽  
Vol 11 (3) ◽  
pp. 694 ◽  
Author(s):  
Ijaz Ahmad ◽  
Muhammad Tayyab ◽  
Muhammad Zaman ◽  
Muhammad Anjum ◽  
Xiaohua Dong
Keyword(s):  
Hydraulic Conductivity ◽  
Finite Difference ◽  
Three Dimensional ◽  
Rehabilitation Program ◽  
Diaphragm Wall ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit ◽  
Constant Head ◽  
Design Depth

This study investigates a large deep foundation pit of a hydraulic structure rehabilitation program across the Indus river, in the Punjab province of Pakistan. The total area of the construction site was 195,040 m2. Two methods, constant head permeability test and Kozeny–Carman equation, were used to determine the hydraulic conductivity of riverbed strata, and numerical simulations using the three-dimensional finite-difference method were carried out. The simulations first used hydraulic conductivity parameters obtained by laboratory tests, which were revised during model calibration. Subsequently, the calibrated model was simulated by different aquifer hydraulic conductivity values to analyze its impact on the dewatering system. The hydraulic barrier function of an underground diaphragm wall was evaluated at five different depths: 0, 3, 6, 9, and 18 m below the riverbed level. The model results indicated that the aquifer drawdown decreases with the increase in depth of the underground diaphragm wall. An optimal design depth for the design of the dewatering system may be attained when it increases to 9 m below the riverbed level.

Research on Seepage Characteristics of Deep Cut Canal under Dewatering Well

2013 ◽  
Vol 438-439 ◽  
pp. 588-592
Author(s):  
Kai Yun Yang ◽  
Xiang Yu Li ◽  
Lin Hao Li ◽  
Quan Long Li
Keyword(s):  
Finite Element ◽  
Element Model ◽  
Saturation Line ◽  
Deep Foundation ◽  
Seepage Field ◽  
Foundation Pit ◽  
Element Analysis ◽  
Deep Foundation Pit ◽  
Geological Conditions ◽  
Seepage Characteristics

In view of the problems of complex geological conditions with high underground water level, large permeability coefficient of soil and the presence of large seepage hazard of deep cut canal and deep foundation pit project of South-to-North Water Transfer Project, China, research on seepage characteristics of digging canals under dewatering well is carried out by finite element analysis, and the FORTRAN procedure is programmed. The three-dimensional finite element model of a digging canal is built, and the seepage field of the different conditions of the canal is simulated, the water head distribution, saturation line and leakages are obtained, and the rules and characteristics of steady seepage field under design impervious system are analyzed. The results indicate that the method can exactly determine the key overflow point and saturation line of canal, and well predict seepage field in canal. The results should be of guiding significance to design and construct retaining engineering in deep cut canal and deep foundation pit.

scholarly journals Numerical Simulation of Seepage and Deformation in Excavation of a Deep Foundation Pit under Water-Rich Fractured Intrusive Rock

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Changfeng Yuan ◽  
Zhenhui Hu ◽  
Zhen Zhu ◽  
Zijin Yuan ◽  
Yanxiang Fan ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Water Inrush ◽  
Risk Level ◽  
Silty Clay ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit

Water is one of the major risk sources in the excavation of deep-large foundation pits in a water-rich area. The presence of intrusive broken diorite porphyrite in the stratum aggravates the risk level of deep foundation pits. Based on a geological survey report and design documents of parameter information, MIDAS/GTS software was used to perform the numerical simulation of an engineering example of a deep foundation pit project of ultradeep and water-rich intrusion into the broken rock station of subway line 4 in a city. The simulation results show the characteristics of seepage path evolution, seepage aggregation areas and points, and the effect of seepage on the deformation of a deep foundation pit during the whole construction of this deep foundation pit. The results show that with the precipitation-excavation of the deep foundation pit, the pore water pressure at the bottom of the foundation pit follows a distribution of three “concave” shapes. High-permeability pressure zones are found around the foundation pit, intruding broken diorite porphyrite zones, and middle coarse sand zones. With further excavation of the foundation pit, the seepage pressure in the middle part of the foundation pit gradually decreases, and the two “concave” distributions in the middle gradually merge together. After excavation to the bottom of the pit, the pore water pressure at the bottom is distributed in two asymmetrical “concave” shapes, and the maximum peak of pore water pressure is found at the intrusion of fractured porphyrites prone to water inrush. The four corners of the foundation pit are prone to form seepage accumulation zones; therefore, suffosion and piping zones are formed. The surface settlement caused by excavation is found to be the largest along the longitudinal axis of the deep foundation pit, whereas the largest deformation is found near the foundation pit side in the horizontal axis direction of the foundation pit. With the excavation of the deep foundation pit, the diaphragm wall converges to the foundation pit with the maximum deformation reaching about 25 mm. After the first precipitation-excavation of the deep foundation pit to the silty clay and the bottom of the pit with the largest uplift, with further precipitation-excavation of the deep foundation pit, the uplift at the bottom of the deep foundation pit changes only slightly.

A Method of Calculation on the Deformation of Column Piles in Deep Foundation Pit

2013 ◽  
Vol 291-294 ◽  
pp. 1131-1134
Author(s):  
Lin Na Sun ◽  
Yan Liu ◽  
Li Ming Zhang
Keyword(s):  
Calculation Method ◽  
Bending Moment ◽  
Practical Case ◽  
Vertical Deformation ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit ◽  
Method Of Calculation ◽  
Overall Stability

During excavation of deep foundation pits, the effects of vertical deformation on column piles are often neglected while those uplifts may lead to destruction of internal supports. The factors leading to the column piles' vertical deformation mainly include basal uplift and vertical loads. In this paper, the causation and mechanism of the column piles' uplift are discussed. The influence of the additional bending moment due to the column piles' vertical deformation on the overall stability of the founda-tion pit is analyzed. A calculation method of the permissible value of vertical deformation is present¬ed. The method is verified by a practical case to be feasible.

scholarly journals Analysis of Lateral Displacement Law of Deep Foundation Pit Support in Soft Soil Based on Improved MSD Method

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Gang Lei ◽  
Xiaonan Gong
Keyword(s):  
Finite Element ◽  
Data Analysis ◽  
Calculation Method ◽  
Retaining Wall ◽  
Soft Soil ◽  
Analysis Method ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit ◽  
Data Analysis Method

Foundation pit envelope and foundation pit excavation solution design is a multidisciplinary problem that could be linked to a series of safety issues in the geotechnical engineering of an actual construction project. Moreover, the construction of large deep foundation pit in soft soil often faces greater risks and challenges as the support structure deforms more easily and unpredictably. In order to improve the deformation prediction of deep foundation pit engineering precision and efficiency and to ensure that the construction of deep foundation pit engineering is safe and efficient, in this article the traditional MSD (mobilizable strength design) theory research and analysis, combined with the Jinan formation characteristics of a tunnel in JInan, and new parameters were introduced to the original MSD method theory: the wall itself within the bending strain energy U and support compression elastic potential energy of V. A new law of conservation of energy is constructed, and finally, an optimized MSD method has been proposed, this method is shown in the article. Finally, the results of foundation pit deformation calculation were compared among the optimized MSD method, finite element calculation method, and field monitoring data analysis method, so as to demonstrate the reliability of the prediction system of optimized MSD method and finite element analysis method. The results show that, by optimizing the MSD calculation method, the horizontal displacement of the retaining wall varies depending on the excavation depth of the foundation pit and the form of internal support with the overall peak value of displacement between 0∼0.2% H (H being the excavation depth); the deformation of retaining wall increases gradually with the increase of excavation depth of the foundation pit, and the peak position of deformation gradually moves down with the excavation of foundation pit. The trend of these changes is consistent with the results of the finite element method and field data analysis method, proving that the optimized MSD method is reliable in predicting the deformation of the foundation pit under specific stratum conditions.

scholarly journals The application of land subsidence control technologies caused by deep foundation pit dewatering

2020 ◽  
Vol 382 ◽  
pp. 775-780
Author(s):  
Jinbao Liu
Keyword(s):  
Land Subsidence ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Integrated Design ◽  
Good Effect ◽  
Information Control ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit ◽  
Control Technologies

Abstract. In order to analyze land subsidence caused by the dewatering of a deep foundation pit in Shanghai, numerical analysis, field testing, automatic monitoring and other technologies are applied to research land subsidence control technologies, covering the whole process during the design, construction and operation of foundation pit dewatering systems. The key technologies are applied to a typical metro station foundation pit in Shanghai, such as the integrated design of foundation pit dewatering and a waterproof curtain, information control, groundwater artificial recharge, etc. The measured data of groundwater level, pore water pressure and land subsidence show a good effect on land subsidence prevention and control.

Mechanical Analysis of Enclosure Pile under Different Constraints

2011 ◽  
Vol 90-93 ◽  
pp. 485-489
Author(s):  
Li Guo ◽  
Peng Li He ◽  
Guang Jun Zhang
Keyword(s):  
Mechanical Analysis ◽  
Subway Station ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit ◽  
Retaining Structure ◽  
Cantilever Structure ◽  
Reinforcement Measures

The enclosure pile is extensively used as retaining structure in the foundation pit excavation. And it is always combined with other reinforcement measures. So it is unreasonable to a certain degree that the enclosure pile is analyzed as cantilever structure. Taken the deep foundation pit of a subway station in Hefei for instance, the effect of other reinforcement measures on restrained conditions of enclosure piles in the paper was taken into account. And the behavior of enclosure pile under various restrained conditions was analyzed. Based on that, some helpful suggestions for practical retaining structure of foundation pit were put forward.

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