Deep Foundation Pit Engineering Research Articles

Force Calculation of Mechanical Model of Pile-anchored Support Structure Based on Elastic Foundation Beam Method

With the widespread use of deep foundation pit engineering in engineering construction, the force calculation problem about deep foundation pit support engineering has become a common problem in today’s engineering construction process. In this paper, based on the elastic foundation beam method, a simplified mechanical model of pile-anchored structure is proposed, and a systematic and practical calculation method is proposed for the force and deformation calculation of deep foundation pit support structure. The method simplifies the support structure as a vertically placed elastic foundation beam, the support, anchor and geotechnical body are replaced by a spring system, the spring stiffness of geotechnical soil can be calculated by the deformation modulus of geotechnical soil, and a systematic calculation method is proposed for the dynamic characteristics of the construction and structure of the foundation pit project; Based on the monitoring data of a deep foundation pit project, the calculation method of the simplified mechanical model proposed in this paper is verified, and the theoretical calculation value is compared with the field monitoring results; Single factor analysis is carried out on the detailed parameters of pile-anchor supporting structure to study the influence of cable prestress, cable dip Angle, pile diameter, pile length and other related parameters on the deformation and stress characteristics of supporting structure. Then the orthogonal combination of all factors is carried out to propose the optimization design. The results show that the maximum settlement deformation of the calculated value is 23.437 mm, and the maximum settlement deformation of the monitored value is 26.517 mm, and the difference between them is small. The maximum bending moment is 1210 kN⋅m after 150 kN and 250 kN horizontal prestressing is added to the second- and third-layer anchors respectively. After optimization, the maximum bending moment of pile row is 336.87 kN⋅m, and the maximum horizontal displacement of pile body is 16.505 mm, which is reduced by 11.97% compared with the original design.

Study of Improved Grey BP (Back Propagation) Neural Network Combination Model for Predicting Deformation in Foundation Pits

Deep excavation engineering is a comprehensive discipline that involves multiple fields such as engineering geology, hydrogeology, and foundation engineering. With the improvement of the utilization rate of underground space, the demand for the construction of large-scale underground structural engineering is growing, making the excavation of underground soil become increasingly frequent, which also brings about the safety problems of deep foundation pit engineering and the surrounding environment. Prediction of foundation pit deformation is an important research direction with diverse historical developments, but it is also facing a series of difficulties and challenges. In order to solve these problems, this article proposes an improvement plan, establishes a prediction model based on the combination model of grey BP (back propagation) neural network, and verifies its effectiveness through experiments. The results show that the average error of the new model’s prediction of horizontal deformation is about 0.31, which is about 32% lower than the traditional model’s prediction error. The difference between the vertical deformation prediction and actual monitoring results is also controlled. The vertical deformation predicted by wavelet transform is 7% to 9% larger than the actual monitoring results, meeting the prediction requirements. Finally, this article explores the research on the prediction of foundation pit deformation in deep excavation engineering, An improved grey BP neural network combination model was proposed and its effectiveness was verified through experiments. This article has important reference value for the study of deformation prediction in deep excavation engineering.

BIM Model Design of Deep Foundation Pit Engineering Based on BP Network

Abstract It is of great significance to predict the multistage deformation of the foundation pit. A new neural network method is proposed in this paper. The disadvantages of the BP neural network multistage forecast method are discussed. A multistage recursive neural network model for foundation deformation prediction is established. They are taking a deep foundation pit project in the soft soil area as an example. The multistage deformation prediction method is verified in this paper. This new detection technique is feasible. This method can also be used for multistage forecasting.

Hydrogeological Parameter Estimation of Confined Aquifer within a Rectangular Shaped Drop Waterproof Curtain

For the dewatering of deep excavation, the existing man-made waterproof curtain has a significant influence on flow response in confined aquifers; the effect of the waterproof curtain must be considered when using the field data for hydrogeological parameter estimation. In this study, a closed-form analytical solution for constant discharge pumping in a confined aquifer within a rectangular-shaped drop waterproof curtain is obtained by making use of the image method coupled with the superpose principle. A straight-lined method is presented to determine the value of the hydraulic parameters of the confined aquifer and the application of the obtained results is illustrated by the usefulness of a field pumping test in Wuhan, China. The results show that the predicted drawdowns developed by the estimated parameters are in good agreement with the measured drawdown in the field. The proposed solution and parameter estimation are reliable and can provide important help for the design of dewatering in deep foundation pit engineering.

Research on Groundwater Control Technology in Construction Based on Foundation Pit Construction Condition

With the rapid development of national economy and the restriction of urban construction land, high-rise buildings are mostly concentrated in urban centers. The construction and development of high-rise buildings promote the rapid development of deep foundation pit engineering, and the number and scale of foundation pit engineering are increasing day by day. In urban construction, a large number of high-rise buildings appear, and with the need of subway engineering and civil air defence works, deep foundation pit engineering in buildings is very common. In order to ensure the safe construction of deep foundation pit, groundwater must be controlled. If the groundwater is mainly phreatic water, vadose water or confined water with low water pressure, it should be blocked mainly. The specific technology is to construct a water-stop curtain around the foundation pit to stop the groundwater outside the foundation pit. If the groundwater is confined water with high pressure, measures should be taken to remove the water in the pit to prevent the foundation pit from surging. By analyzing the relationship between deep foundation pit engineering and groundwater, this paper summarizes the control methods of groundwater in deep foundation pit engineering.

Prediction of Surface Subsidence of Deep Foundation Pit Based on Wavelet Analysis

Predicting surface settlement in deep foundation pit engineering plays a central role in the safety of foundation pit construction. Recently, static or dynamic methods are usually applied to predict ground settlement in deep foundation pit projects. In this work, we propose a model combining wavelet noise reduction and radial basis neural network (XW-RBF) to reduce noise interference in monitoring data. The results show that the XW-RBF model predicts an average relative error of 0.77 and a root average square error of 0.13. The prediction performance is better than the original data prediction results with noise structure and has higher prediction accuracy. The noise data caused by the interference of construction and the surrounding environment in the original data can be removed via the wavelet noise reduction method, with the discreteness of the original data reducing by 30%. More importantly, our results show that the XW-RBF model can reflect the law of data change to predict the future data trend with high credibility. The findings of this study indicate that the XW-RBF model could optimize the deep foundation pit settlement prediction model for high accuracy during the prediction, which inspires the potential application in deep foundation pit engineering.

The Role and Necessity of Drainage Construction in Deep Foundation Pit Engineering

The Role and Necessity of Drainage Construction in Deep Foundation Pit Engineering

Dynamic back analysis of soil deformation during the construction of deep cantilever foundation pits

Field monitoring of foundation pits alone cannot predict the future deformation of retaining structures. Numerical simulations can predict the deformation of foundation pits and the working state of retaining structures to avoid the risk of foundation pit damage in advance. Accurate inversion of the soil parameters used for simulation and prediction is a key step. The associated multivariable problem is transformed into a single-variable problem by using the interval influence coefficient. Soil layer weightings and excavation step weightings are introduced and exploited to optimize the calculation process, and the soil parameters are calculated through inversion based on the least squares method. Based on actual engineering, the excavation sequence is regarded as a progressive sequence for back analysis, and the parameters of each soil layer are calculated through dynamic calculations with the excavation process in a cycle comprising inversion, prediction, reinversion and reprediction. The soil parameters after inversion are used to predict the maximum value and the depth of the deep horizontal displacement of the retaining structure, which verified the feasibility of the back-analysis method. Compared with the results before inversion, after the final inversion, t the overall error of section 2 is reduced by 67.24%, the overall error of section 3 is reduced by 40.5%, and the overall error of section 4 is reduced by 35%. The prediction curves are all close to the monitoring displacement curves, which plays a good guiding role and ensures the safe construction of the foundation pit. A new effective idea is proposed for the inverse analysis of the composite formation parameters of the deep foundation pit engineering.

BIM Digital Shadow Technology and Risk Assessment Method of the Deep Foundation Pit’s Behavior for Zibo Light Rail

With the shortage of land resources, there has been a trend toward increasingly deep foundation pit engineering in urban areas. It is extremely important to reflect on the behavior and safety of deep foundation pits and conduct risk assessments in time. A nonhomologous and multi-indicator deep foundation pit risk assessment model was studied for nine types of nonhomologous on-site data monitored in the deep foundation pit. Based on the BIM (Building Information Modeling) technology, a family of monitored points was created that reflects the information on site from a deep foundation pit. The data visualization module was redeveloped by using Visual Studio 2019 to map the on-site data monitored to the components in the BIM model, which can visualize the data monitored in the BIM model of deep foundation pits. On this basis, the assessment of the safety level of deep foundation pits was realized in combination with a risk assessment model. Through the instance of the deep foundation pit of Zibo light rail, the analysis shows that the new visualization and risk assessment method can help construction workers locate dangerous units and formulate corresponding prevention and control measures better and faster.

Discussion on the Focus of Geotechnical Engineering Investigation of Deep Foundation Pit Engineering

Discussion on the Focus of Geotechnical Engineering Investigation of Deep Foundation Pit Engineering

Brief Discussion on Construction Technology and Safety Management Countermeasures of Deep Foundation Pit Engineering

Brief Discussion on Construction Technology and Safety Management Countermeasures of Deep Foundation Pit Engineering

Key Points of Geotechnical Engineering Investigation in Deep Foundation Pit Engineering

Key Points of Geotechnical Engineering Investigation in Deep Foundation Pit Engineering

Analysis on Supporting Construction Technology and Measures of Deep Foundation Pit Engineering for Housing Construction

Analysis on Supporting Construction Technology and Measures of Deep Foundation Pit Engineering for Housing Construction

Research on Monitoring Information Management of Deep Foundation Pit Engineering Based on BIM Technology

With the rapid development of construction industry, there are more and more deep and large foundation pit projects with complex architectural environment and geological conditions. Deformation monitoring in deep foundation pit as a basic element of engineering quality assurance is becoming more and more important. At present, the management and expression form of monitoring data in deep foundation pit still stays in the stage of two-dimensional form and curve expression, and it can not reflect the deformation of deep foundation pit in real, fast and effective way.Take the 3#, 4# high-rise residential and underground garage project of a college in Xi'an as an example. Based on Revit software, taking BIM technology and Revit API as the theoretical basis, and taking Microsoft Visual Studio 2012 and Autodesk Revit 2014 as the development platform, we use C# programming language to carry out the two development of information management module for deep foundation pit engineering monitoring. Combining BIM technology with monitoring data management of deep foundation pit, the information management mode of monitoring data of deep foundation pit is improved, which makes express expression of deep foundation pit construction monitoring more rapid and effective, and has guiding significance for safety construction of deep foundation pit engineering.

Numerical Simulation Analysis of Deep Foundation Pit Engineering Based on HS-Small Constitutive Modell

Numerical simulation has become one of the most important means of foundation pit engineering analysis, but there is a lack of numerical simulation of deep foundation pit engineering examples under the condition of adjacent buildings in Xi ’ an. In this paper, MIDAS GTS NX software is used to simulate the deep foundation pit engineering of Xi ’ an International Conference Center Phase II by using the Hardening Soil-Small constitutive model which is more suitable for foundation pit engineering. Combined with the measured data, the study on the characteristics of building settlement, the characteristics of surrounding surface settlement, the deformation characteristics of foundation pit retaining structure, the soil pressure at pile side and the variation characteristics of pile internal force is conducted under the condition of stepwise excavation-reduction of groundwater level of foundation pit. The results show that the top displacement of the retaining structure and surface settlement near the building are larger than those without load. The building settlement and surface settlement rate present the characteristics of medium-term slowdown. The lateral earth pressure and internal force of pile show different trends in free section and anchorage section, affected by building load. The simulation results of the constitutive parameters of HHS numerical simulation determined by parameter inversion are in good agreement with the measured data, which verifies the reliability of HHS constitutive model in the numerical simulation of foundation pit engineering in Xi ’ an area, and provides reference for the numerical simulation of similar engineering cases in relevant areas.

Analysis of Situ Test Results of Earth Pressure and Pile Internal Force under Pile-Anchor Support in a Deep Foundation Pit in Xi’an

At present, in deep foundation pit engineering, on the one hand, practice is ahead of theory, and on the other hand, theory can not correctly reflect the actual construction process and environmental effects. In order to further study the distribution and change law of earth pressure and internal force of pile body in deep foundation pit pile-anchor supporting system, field monitoring test of earth pressure and pile body reinforcement stress was carried out. The monitoring results show that before excavation, the distribution of earth pressure has a great relationship with the layering of the soil, and it is distributed in sections along the depth. Compared with the theoretical static earth pressure, the measured data of the upper depth is relatively small; after excavation, the overall earth pressure is distributed along the depth in a “z” shape under the non-limiting state. As the excavation progresses, the magnitude of the reduction of the earth pressure varies from place to place, and the magnitude of the decrease of the soil with better properties is not large; after the excavation, the stress and earth pressure of the pile reinforcement correspond to each other, and the distribution is also nonlinear. The existence of anchor tension has an obvious effect on improving the internal force of the pile. The selected earth pressure calculation methods have some discrepancies in the calculation of the earth pressure value of the project, and they need to be further improved. The research in this paper can provide reference and reference for the calculation of earth pressure and support design of pile-anchor supported foundation pit.

Optimization Design of Supporting Structure for Metro Deep Foundation Pit Engineering

Optimization Design of Supporting Structure for Metro Deep Foundation Pit Engineering

Analysis on Management Measures of Construction Deep Foundation Pit Engineering

Analysis on Management Measures of Construction Deep Foundation Pit Engineering

Mechanical properties of a new string capsule drainage anchor and its supporting effect in deep foundation pit

With the increase of the scale and depth of urban underground space construction in coastal soft soil area, the traditional anchoring technology has been difficult to meet the requirements of deep foundation pit excavation and support. This paper puts forward a new type of string capsule drainage anchor supporting structure, introduces its structure composition, analyzes its working mechanism and mechanical characteristics, the calculation formula of ultimate bearing capacity of small cylindrical shear failure between anchor and surrounding soil is given, finally, the supporting effect of the new structure in deep foundation pit engineering is simulated and analyzed by finite element software. It is concluded that the stress of the new type of anchor can be divided into three stages: static earth pressure, plastic zone development and plastic zone breaks through; the new anchor can quickly dissipate the pore water pressure in the surrounding soil, which is more conducive to the stability of foundation pit; the axial force distribution presents a “sawtooth” shape, and the axial force increases sharply in the expanding section; the supporting effect of the new anchor is more obvious than that of the traditional anchor, which can more effectively inhibit the horizontal displacement of the slope.

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