Foundation Pit Research Articles

Risk Analysis and Evaluation Model Based on Internal Support Structure in Deep Foundation Pit Engineering

Risk Analysis and Evaluation Model Based on Internal Support Structure in Deep Foundation Pit Engineering

Study on the Influence of Deep Foundation Pit Construction on the Pile Foundation of Adjacent Existing Stations

Study on the Influence of Deep Foundation Pit Construction on the Pile Foundation of Adjacent Existing Stations

A Precise Analysis of the Behavior of Pit Side Tunnels Caused by Deep Excavation

As urbanization gathers pace, projects involving adjacent subway tunnels are increasing, thereby amplifying the need for robust tunnel protection measures. Currently, there exists a notable lack of precise analyses on the three‐dimensional (3D) deformation laws and mechanisms of tunnels affected by adjacent deep excavation. Moreover, the influence patterns of retaining wall stiffness and deep excavation depth on the 3D deformation of pit‐side tunnels remain unclear. The purpose of this research is to bridge the existing disparity by adopting the hypoplastic model, which effectively captures soil stiffness that is dependent on soil state, strain, and stress path, even at small strains, as well as soil strength, based on reported centrifuge model tests. This approach facilitates a comprehensive, precise numerical analysis of the interaction between deep excavation and preexisting tunnels located outside the retaining wall. The analysis sheds light on the deformation mechanisms and trends of pit‐side tunnels not solely confined to the longitudinal axis but extending to the transverse plane as well, while systematically examining the influence of varying excavation depths and retaining wall stiffness on key tunnel parameters, including longitudinal deformation, diameter changes, bending strains, and soil pressure distributions around the tunnels. The study reveals that if the tunnel situated outside the retaining structure lies beneath the foundation pit’s base, deep excavation only slightly deforms the tunnel. However, when the tunnel outside the retaining structure is positioned above the pit’s base, its deformation progressively intensifies with deeper excavation, but the growth rate has a decreasing trend. An enhancement in the stiffness of the retaining wall results in a notable decrease in the deformation exhibited by the adjacent tunnels. The findings contribute to a deeper understanding of the complex responses of pit‐side tunnels to excavation activities, ultimately facilitating the design and construction of safer and more resilient urban subway infrastructure.

Study on the influence of deep foundation pit excavation on the deformation of adjacent viaduct pile foundation

Study on the influence of deep foundation pit excavation on the deformation of adjacent viaduct pile foundation

Study on the influence of deep foundation pit excavation on the deformation of adjacent viaduct pile foundation

Study on the influence of deep foundation pit excavation on the deformation of adjacent viaduct pile foundation

Analysis and Practicality of a Plate Wall and Prestressed Steel Struts in the Interstage Backfill Construction of Deep Foundation Pits

Analysis and Practicality of a Plate Wall and Prestressed Steel Struts in the Interstage Backfill Construction of Deep Foundation Pits

Evaluation of the Additional Stress on Adjacent Tunnel Shafts Induced by Foundation Pit Excavation

Evaluation of the Additional Stress on Adjacent Tunnel Shafts Induced by Foundation Pit Excavation

临近地铁超深基坑施工管控技术

临近地铁超深基坑施工管控技术

Case Study on the Mutual Influence of Simultaneous Construction of Adjacent Deep Foundation Pit with Cover‐Excavation Reverse Method

Case Study on the Mutual Influence of Simultaneous Construction of Adjacent Deep Foundation Pit with Cover‐Excavation Reverse Method

Study on the Stress and Deformation Laws and Work Principles of the Pull-pile Supporting Structure in a Deep Foundation Pit

Study on the Stress and Deformation Laws and Work Principles of the Pull-pile Supporting Structure in a Deep Foundation Pit

Case Analysis of Water Gushing in a Deep Foundation Pit Caused by Local Defects.

Water gushing is a common engineering geological disaster in the process of foundation pit construction. Its successful judgment directly affects the safety of engineering construction. Taking the case of water gushing at the bottom of the foundation pitas as a research object, the mechanism and treatment of water gushing in foundation pits, the stability against water gushing, and its influencing factors are analyzed with a field investigation, field testing, and theoretical calculation. The calculation formula for the safety factor and critical thickness of the foundation pit against surges, considering the influence of multiple factors, is deduced. The influence of the height of the confined water level, the thickness of the water-resisting layer, the shear strength of the soil mass, the reinforcement depth of the soil mass in the pit, and the diameter of the bearing pile in the pit on the safety factor of the foundation pit surge are expounded. In addition, measures such as the reinforcement of the soil mass in the passive area in the pit, the increase in the thickness of the water-resisting layer, and the reduction in the confined water level are proposed to improve the anti-surge stability of the foundation pit. A new monitoring method is proposed for characterizing uplift deformation at the bottom of the pit without affecting normal construction. The research results show that: (1) the minimum safety factor against surges, considering multiple factors, is 1.455, and the critical thickness is 5.87 m, which is in line with specifications. (2) Measures such as reinforcing the soil in the passive zone of the pit, increasing the thickness of the water-insulating layer, and lowering the bearing pressure level are used to improve the stability of the pit against surges. (3) The pit, obtained by the pit bottom counter-pressure, pumping water out of the pit, and the timely construction of the pit bottom bedding to block the program, exhibits a measured maximum bottom plate pressure of 115.189 kPa, and the deformation corresponding to the method proposed in this paper is 1.406 mm, which is better disposed in the field. The research results provide a reference basis for the judgment of anti-surge stability of foundation pits and similar engineering applications.

Retracted: Deformation Detection Model of High-Rise Building Foundation Pit Support Structure Based on Neural Network and Wireless Communication

Retracted: Deformation Detection Model of High-Rise Building Foundation Pit Support Structure Based on Neural Network and Wireless Communication

The Role of Steel Pile Sheets in Building Base Reinforcement

<p class="Abstract" style="text-align: justify;"><span lang="EN-GB" style="mso-ansi-language: EN-GB;">Structures supporting the slopes of the foundation pit were installed in a densely built-up city area. Geological studies had been carried out, and based on the conclusion, the design of reinforcing the pit was prepared for the first time along the outer perimeter with interlocked steel piles. Due to the insufficient length (12 m) of the steel pile sheets, additional column constructions were used, which created a spatial supporting frame of the pit, ensuring the stability of the pit’s slopes.</span></p>

Stability Analysis of Super-Large Special-Shaped Deep Excavation in Coastal Water-Rich Region Considering Spatial Variability of Ground Parameters

The excavation of a super-large foundation pit is a greatly risky project in coastal water-rich silt strata, and it is of great significance to establish a numerical model to analyze and predict the stability of the foundation pit retaining its structure for safe construction. Based on a geological investigation report and key node monitoring data, the model parameters have been modified. Subsequently, the random field theory and numerical analysis were employed to proceed with deterministic analysis and uncertainty analysis, respectively. Using the uniform distribution method, Gaussian distribution method and the covariance matrix method to generate a random field model, finite difference software was applied to analyze the impact of spatial variability of cohesion and the internal friction angle on structural deformation. The study shows that the overall distribution of axial force is small on both sides and large in the center, and the axial force is larger near the shaped region. Due to the principle of “lever”, there is a tendency for the horizontal displacement of surrounding piles to partially rebound from the pit when the bearing platform pit is excavated. The spatial variability of the internal friction angle and cohesion has an important influence on the numerical value of the enclosure structure and surface deformation, and the variation pattern is basically unchanged.

THE ROLE OF THE UMAYYAD MOSQUE OF DAMASCUS IN CONCEIV-ING THE PAVILION OF NIẒĀM AL-MULK IN ISFAHAN

The excavations carried out in the South domed hall of the Friday Mosque of Isfahan brought to light several features of this structure's building stage. Three pits were retrieved in the centre of the hall, which once was occupied by the pillars of the grid of the ʿAbbasid mosque’s hypostyle in 9th century. These were identified as probable foundation pits for the building of a domed space arranged as that of the Umayyad Mosque of Damascus during the Saljuq period. This possible connection was analysed from different perspectives using different data (archaeological, epigraphical, art, and historical data) and provide different conclusions. A comparison between the archaeological data and the epigraphical record may highlight the possible liaison between the two buildings. This paper discusses some results of the 1970s excavations to prove how unlikely a layout such as Damascus could ever be adopted in Isfahan. Nevertheless, proven by the epigraphical record, the presence of the pits discovered by the IsMEO mission and the interest shown by Malik Shāh for Syria plead for a connection between the two mosques. Such connection could highlight the role the Damascene prototype could play in conceiving the pavilion the vizir Niẓām al-Mulk in Isfahan demanded.

Numerical and theoretical analysis on soil arching effect of prefabricated piles as deep foundation pit supports

This study presents a detailed investigation into the soil arching effects within deep foundation pits (DFPs), focusing on their mechanical behavior and implications for structural design. Through rigorous 3D finite element modeling and parameter sensitivity analyses, the research explores the formation, geometric characteristics, and spatial distribution of soil arching phenomena. The investigation encompasses the influence of key parameters such as elastic modulus, cohesion, and internal friction angle on the soil arching effect. The findings reveal that soil arching within DFPs exhibits distinct spatial characteristics, with the prominent arch axis shifting as excavation depth progresses. Optimal soil arching is observed when the pile spacing approximates three times the pile diameter, enhancing soil retention and minimizing deformation risks. Sensitivity analyses highlight the significant impact of soil parameters on soil arching behavior, underscoring the critical role of cohesive forces and internal friction angles in shaping arching characteristics. By elucidating the interplay between soil parameters and soil arching effects, the research provides insights for optimizing pile spacing and structural stability.

Research on the Applicability of Integrated Earth Lifting Machine for 500KV Transmission and Substation Project in Highland Area

In the power construction project, the tower foundation deep pit operation is a fundamental and important process, because of its operation point of the geological foundation structure complex and changeable, large amount of work, many dangerous factors and difficult to observe and identify, the construction is easy to cause safety accidents. State Grid Gansu Power Company has developed a set of intelligent equipment for deep foundation pit operation which is easy to operate, safe, reliable and complete in function, relying on the equipment to actively and timely discover the danger and early warning, and automatically take effective measures to strengthen the protection of personnel, crack the problem of safe operation of deep foundation pit and prevent the occurrence of infrastructure safety accidents. Since this project is located in the plateau area of Tibet, it is intended to study the applicability of the integrated deep foundation pit operation intelligent machine in the plateau area through this project. This project adopts "integrated deep pit operation intelligent machine"; this equipment is specially designed for a series of problems encountered in deep pits and other limited spaces, it integrates a number of practical functions: electric lifting, real-time gas detection, intelligent air supply, automatic sound and light alarm, emergency rescue, differential hanging point, soft ladder hanging point, lighting power, etc. It aims to protect the lives of construction personnel, improve the safety and reliability of construction, enhance construction efficiency, and is a kind of equipment with convenient transportation, installation and operation, diversified and integrated functions and intelligent control.

A Study on the Influence of Dewatering in the Excavation of Adjacent Tunnels under Lateral Soil Effects

The dewatering of foundation pits leads to changes in the water level and effective stress within the surrounding strata. When existing tunnels are present within the dewatering influence zone, the impact of dewatering on these tunnels cannot be ignored. The Vlasov foundation beam model was used to simulate the interaction between the tunnel and the soil, and the key parameters of the model were precisely investigated. In addition, the constraining effect of the lateral soil on the tunnel was also considered. By integrating the principles of effective stress and Dupuit’s assumption, in this work we calculated the additional load on the tunnel caused by foundation pit dewatering, which was then applied to determine the tunnel stress and deformation induced by dewatering. The accuracy of this approach is validated through comparative analysis with finite element results. Furthermore, the relationships between the permeability coefficient (kt), the spacing (d) between the tunnel and the dewatering well, the water level drop (sw), and tunnel stress and deformation were further studied. The key findings are summarized as follows. Firstly, accounting for lateral soil effects enhances computational accuracy. Secondly, an increase in soil kt leads to a greater tunnel settlement with relatively minor changes in bending moments. Thirdly, as d increases, both tunnel settlements and bending moments decrease. Additionally, as the water level dropped from 10 m to 30 m, the maximum additional stress on the tunnel increased by 94.50%, and the settlement increased by 127.43%. Consequently, it is essential to pay close attention to the tunnel segment nearest to the water level.

Development and application of an integrated system of dewatering and recharge for the deep foundation pit

A large amount of pumping in the deep foundation pit will reduce the groundwater level and lead to surface cracking, building settlement, ground collapse and spring water cut-off. And the groundwater recharge is a good control measure. An integrated system of dewatering and recharge for the deep foundation pit is developed, and it is mainly composed of a pumping system, an assembled water tank, a variable frequency pressure system, a cleaning and filtering system, a recharge pressure tank, a recharge well system and a central control system. This system can realize intelligent automatic control according to the monitoring data. It does not require staff to operate on site and can be remotely adjusted by computer or mobile phone. Taking a subway station under construction in Jinan as the background, the single well recharge test and the multiple wells recharge test were carried out. It can be found that with the increase of recharge pressure, the recharge volume gradually increases, but the increasing trend is smaller and smaller. The relationship between the groundwater level and the recharge volume is a logarithmic function. Blindly increasing recharge wells may not improve the overall reinjection volume, and the relationship between the number of recharge wells, the diameter of reinjection pipes and the maximum recharge capacity of the variable frequency pressure system needs to be comprehensively considered.

ANN deformation prediction model for deep foundation pit with considering the influence of rainfall

Deep foundation pits involving complex soil–water-structure interactions are often at a high risk of failure under heavy rainfall. Predicted deformation is an important index for early risk warning. In the study, an ANN model is proposed based on the Wave Transform (WT), Copula method, Convolutional Neural Network (CNN) and Long Short-Term Memory Neural Network (LSTM). The total deformation was firstly decomposed into low and high frequency components with WT. The CNN and LSTM were then used for prediction of the two components with rolling training and prediction. The input variables of the CNN and LSTM were determined and optimized based on the correlations analysis of Copula method of the two components with different random variables, especially with the rainfall. And finally, the predicted total deformation was obtained by adding the two prediction components. A deep foundation pit in Chengdu, China was taken as a case study, of which the horizontal deformation curves at different measuring points shows three types of developed trend, as unstable, less stable, and stable types. The predictions of the deformations of different development types by the proposed ANN model show high accuracies with a few input variables and can accurately prompt risk warning in advance.