Construction Of Deep Excavations Research Articles

Advances in Design and Construction of Deep Excavations and Foundations in Sri Lanka

Advances in Design and Construction of Deep Excavations and Foundations in Sri Lanka

Estimate the impact of deep excavation construction in high-rise buildings on neighboring structures

The estimation of diaphragm wall displacements and soil movement around the deep excavation of a high-rise building during the construction of basement floors plays a crucial role in limiting risks that may cause damages to human lives and property during the construction process. This study proposes the use of Finite Element Analysis (FEA) to accurately predict the behavior of soil and diaphragm walls in deep excavations of high-rise buildings. The model is based on advanced soil models and considers the interaction between diaphragm walls and soil, enabling the prediction of adverse impacts during the construction process, as well as negative effects on adjacent buildings. Additionally, the study will analyze and highlight the primary parameters that negatively impact the excavation process and neighboring constructions.

A nonlinear optimization method for calibration of large‐scale deep cement mixing in very soft clay deep excavation

AbstractThis work proposes a novel technique to conduct back‐analysis of lateral displacement of deep cement mixing (DCM) columns in deep excavation construction. For the first time, we propose a process to investigate both soil and underground structure end‐to‐end automatically. The novel technique is a complex combination of three crucial factors: (1) a nature‐inspired optimization algorithm (O), (2) a three‐dimensional PLAXIS Geotechnical Engineering software (P) and (3) a modern Python language programming (P), hereinafter called the a nature‐inspired optimization algorithm (O), a three‐dimensional PLAXIS Geotechnical Engineering software (P) and a modern Python language programming (P) (OPP) technique. The novel meta‐heuristic algorithm simulated the co‐evolved partnership behavior of shrimps and goby fishes, termed Shrimp and Goby Association (SGA), which plays an important role in complex analyses. A series of exams to determine the SGA's performance is conducted on 38 benchmark test functions (IEEE Congress on Evolutionary Computation 2017 and 2019) and three real‐world engineering design problems to showcase its applicability. The metaheuristic and PLAXIS 3D analysis work well together, which makes the back‐analysis technique powerfully to determinate stiffness parameters instead of the traditional approaches. Based on the optimized parameters, the lateral deflection of DCM and soil are well predicted for excavation. This study proposes a technique to estimate efficiently the stiffness parameter for very soft soil. As a consequence of the optimization process, an equation to determine the stiffness parameter of DCM columns from laboratory test is also proposed. Based on the obtained results, this research provides a comprehensive methodology for predicting risk, enhancing safety, saving time and money, and effectively designing and constructing underground structures.

Displacement Monitoring of Subway Tracks and Tunnels According to Adjacent Construction

In the Republic of Korea, large-scale deep excavation construction is being conducted adjacent to structures owing to overpopulation in urban areas. Securing the safety of earth-retaining and underground structures is crucial for adjacent excavation work in urban areas. Accordingly, an automated measurement system is used to monitor the behaviors of subway tunnels and track structures; however, the utilization of its results is extremely low. Existing techniques evaluate the safety of track and tunnel structures based on the measured maximum values. This study introduces an evaluation technique for improving behavior monitoring in subway tunnels and track structures. A substantial amount of long-term measurement data on subway tunnels and track deformation was quantitatively evaluated using the Gaussian probability density function. In addition, the results from the same location where the tunnel convergence meter (TL) and track bed settlement (RM) sensors were located were compared. The comparison results revealed a difference in the vertical displacement of the tunnel and track structure owing to adjacent excavation work. A technique to analyze the continuous behavior of the tunnel was presented by numerically analyzing the tunnel measurement results as input data. In addition, they emphasized the need for simultaneous monitoring of tracks and tunnels.

Monitoring the construction of a deep energy-from-waste bunker in soft clay and peat

This paper describes the monitoring of the construction of a deep underground waste storage bunker for the PROTOS energy-from-waste facility in Chester, UK. A key element of the construction process was a 12 m deep excavation in soft clays and peats which was supported by a complex ‘combi-wall’ cofferdam comprising alternate tube and sheet piles, a reinforced concrete (RC) capping beam and two levels of internal bracing. The permanent bunker RC structure was constructed within the excavation using a bottom-up approach. The primary aim of this monitoring programme was to assess the performance of the composite support system through measured cofferdam wall deflections, bracing member loads, and site and bunker water levels. An additional objective of the monitoring was to provide the site team with real-time feedback to inform the construction process. Interpretation of the monitored data allows for a quantitative assessment of the influence of various construction activities on the responses of the support system. The monitored behaviour shows that the high stiffness and embedment depth of the supporting structure, combined with careful control of groundwater levels, significantly reduced risks associated with deep excavation construction in challenging ground conditions.

Risk assessment of deep excavation construction based on combined weighting and nonlinear FAHP

Deep excavation construction safety has become a challenging and crucial aspect of modern infrastructure engineering, and its risk assessment is frequently carried out using the Fuzzy Analytic Hierarchy Process (FAHP). However, when using FAHP to evaluate the risks of deep excavation construction, the results of the weightings obtained through subjective weighting are heavily influenced by the subjective factors of the evaluators. In addition, using linear operators to calculate the risk level can easily cause a weakening effect on the influence of prominent risk factors, resulting in poor rationality of the evaluation results. To address these problems, this paper constructs a deep excavation construction risk evaluation model based on combined weighting and nonlinear FAHP. The WBS-RBS method is used to guide the construction of the risk evaluation index system for deep excavation construction. The combined weighting values of subjective and objective weightings are calculated through the game theory combined weighting method. The fuzzy relation matrix is constructed using the membership degree vector obtained from the expert evaluation method. Nonlinear operators are introduced for comprehensive calculation. According to the maximum membership degree principle, the final risk level of the excavation construction is obtained. The newly constructed model is applied to the risk analysis of the deep excavation construction of the Rongmin Science and Innovation Park project in Xi’an. The evaluation result for the excavation construction risk is N= [0.3125, 0.3229, 0.1939, 0.0854, 0.0854], and according to the maximum membership degree principle, the risk level of the excavation is classified as Level 2, which is a relatively low risk. Based on the deep excavation construction of the Rongmin Science and Innovation Park project, this paper discusses the differences between the new model and the traditional FAHP evaluation method, further verifies the reliability of the new model, optimizes the construction plan based on the evaluation results, avoids risks, and determines its guiding significance.

A Numerical Study on the Influence of Anchored Diaphragm Walls on Adjacent Buildings during Deep Excavation Construction

The aim of this numerical study is to investigate the impact of anchored diaphragm walls on adjacent buildings during deep excavation construction, considering five typical geological conditions in big cities of Vietnam. To achieve this, the behavior of anchored diaphragm walls systems is simulated using the Plaxis 2D program. By conducting these analyses, the study seeks to provide important insights into the behavior of anchored diaphragm walls and their effects on nearby buildings during deep excavation construction.

Extension AHP-Based Assessment of Safety Risk Levels in Subway Deep Excavation Construction

Extension AHP-Based Assessment of Safety Risk Levels in Subway Deep Excavation Construction

Semantic IFC Data Model for Automatic Safety Risk Identification in Deep Excavation Projects

Safety risk identification throughout deep excavation construction is an information-intensive task, involving construction information scattered in project planning documentation and dynamic information obtained from different field sensors. However, inefficient information integration and exchange have been an important obstacle to the development of automatic safety risk identification in actual applications. This research aims to achieve the requirements for information integration and exchange by developing a semantic industry foundation classes (IFC) data model based on a central database of Building Information Modeling (BIM) in dynamic deep excavation process. Construction information required for risk identification in dynamic deep excavation is analyzed. The relationships among construction information are identified based on the semantic IFC data model, involved relationships (i.e., logical relationships and constraints among risk events, risk factors, construction parameters, and construction phases), and BIM elements. Furthermore, an automatic safety risk identification approach is presented based on the semantic data model, and it is tested through a construction risk identification prototype established under the BIM environment. Results illustrate the effectiveness of the BIM-based central database in accelerating automatic safety risk identification by linking BIM elements and required construction information corresponding to the dynamic construction process.

Numerical analysis on zone-divided deep excavation in soft clays using a new small strain elasto–plastic constitutive model

Accurate prediction of displacements associated with deep excavations is essential to ensure safety and stability of the excavation and to prevent any damage and distress to the adjoining infrastructures. This paper presents a numerical approach for prediction of ground displacements related to a zone-divided deep excavation construction executed in Shanghai soft clays based on a new elasto–plastic constitutive model (small-strain Shanghai model) that incorporates small strain stiffness. This model can describe the mechanical properties and structural and over-consolidated characteristics of natural clays. The model is implemented into a finite element analysis software. Numerical analysis on the deep excavation in Shanghai using zone-divided method is conducted. A comparison between monitored and simulated results of horizontal displacements along the diaphragm wall, the settlements in the surroundings, and the effects on the adjoining metro tunnel due to excavation construction is carried out. Special attention is paid to the stiffness degradation of representative elements in the ground. The simulated displacements show a good agreement with the monitored data. Overall, this study provides an integrated solution for predicting displacements related to deep excavation in soft clays.

Design and Construction of Deep Excavations

Design and Construction of Deep Excavations

Fiber Bragg Grating (FBG) based magnetic extensometer for ground settlement monitoring

Monitoring for sub-surface settlement in deep excavation construction and tunneling works will provide an early indication of potential settlement or sinkhole formation at the ground surface. Currently, rod and magnetic extensometers may be used to monitor sub-surface settlement, with the latter most commonly used. In this paper, a novel Fiber Bragg Grating (FBG) based extensometer is proposed working on the magnetostatic interaction between a ring magnet and a disc magnet. The proposed FBG extensometer can be automated for continuous monitoring, as compared with the commonly used magnetic extensometer which monitors manually at prescribed intervals. Multiple units of FBG extensometer can be connected together and easily installed in a deep borehole. The number of FBG extensometer used is not limited by the borehole size, as compared with the rod extensometer where a maximum of 3 tips per borehole is typically specified. The proposed extensometer with current instrumentation gives a measurement range of 80 mm with a measurement resolution of 0.65 mm/με.

Time-domain analyses for pile deformation induced by adjacent excavation considering influences of viscoelastic mechanism

The construction of deep excavation in crowded urban cities requires effective measures to strictly control the displacements of the disturbed soil induced by excavation, in which the time behavior of excavation-soil-pile interaction mechanism obviously exists in soft clays. Many previous analytical studies for pile deformation caused by adjacent excavation are mainly based on the instantaneous behavior and provide little attention on the viscoelastic properties of surrounding soils during excavation. This paper introduces a two-stage time-domain method to predict the viscoelastic interaction between deep excavation and adjacent pile, focusing on additional stress of soil and structural deformation due to excavation-induced soil unloading. Firstly, the Mindlin’s time-domain solution based on Boltzmann viscoelastic model is derived to efficiently predict the additional stress of surrounding soils at the position of adjacent pile in viscoelastic foundation. Secondly, the Pasternak’s two-parameter foundation model is employed for the time-domain deformation response of adjacent pile caused by excavation unloading stress, which accounts for rheological effects in viscoelastic soil. The accuracy of the two-stage time-domain method is then verified by comparisons with numerical simulation and good agreements are obtained. Finally, the parametric analyses are performed to estimate the influences of correlative coefficients in the Boltzmann viscoelastic model and paramount factors of pile on the deformation responses. In general, the two-stage time-domain method proposed in this study provides an effective insight into the excavation-soil-pile interaction considering influences of viscoelastic mechanism, which can serve as an alternative approach for conservatively estimating pile deformation tendency over time in the preliminary design of deep excavation.

Method of thermal detection of leakages in construction of deep excavation: A real case study in Poland

The thermal method is nowadays the only one that allows precise location of leaks in a shorings of a planned deep excavation, still before this excavation is made. It also allows to determine the leak intensity. As a consequence, it enables precise and early repair work, especially sealing. It allows to prevent or significantly reduce the serious consequences and losses resulting from a leaky excavation shoring. The paper presents the first in Poland case of the thermal detection of leaks in the excavation shoring at a construction site. This method has proven very effective in solving this complicated problem. The leaks were many and occurred in the diaphragm wall as well as under its lower edge. The depth of their occurrence reached over forty meters. The substrate‘s geology was highly heterogeneous. The method produced accurate details about the locations and intensity of the leaks.

Building Deformation Prediction Based on Ground Surface Settlements of Metro-Station Deep Excavation

Building deformations are not only closely related to the distance from the building to metro-station excavation but also related to the relative positions of the building and metro-station excavation. Building deformations can be predicted using ground surface settlement profiles. Based on typical geological parameters of Nanjing metro-station excavation, ground surface settlements were numerically simulated by auxiliary planes perpendicular and parallel to the excavation and by angled auxiliary planes at the excavation corner. Results show that the ground surface settlement profiles in auxiliary planes are closely related to the relative positions of the auxiliary planes and the metro-station excavation. Partitioning of ground surface settlements was proposed according to the three types of ground surface settlement profiles; furthermore, bending deformation and torsional deformation regularities of surrounding buildings were analyzed, and an estimation method for building settlements was developed. Finally, field-monitored settlement data of 21 buildings in different zones were compared with the estimated settlement data, and the application of the settlement estimation method to different types of foundations was analyzed. The results of this study can serve as reference for metro-station deep excavation construction and protection of surrounding buildings.

Design and construction of deep excavations in Shanghai, China

With rapid infrastructure construction and urban redevelopment, there has been an increasing demand for utilisation of underground spaces, which gives rise to a large number of excavation projects. In the past decade, a series of new trends have emerged on excavation engineering in Shanghai, China. As available ground resources in congested urban areas are scarce, excavations become much larger and deeper than before. More excavations have to be carried out in close proximity to existing buildings, tunnels, utilities and other structures. Any severe damages to the nearby utilities probably lead to economic losses and complicated conflicts among owners, tenants, utility customers and the public. As a consequence, it is of great concern not only to ensure the safety of the excavation itself but also to mitigate adverse excavation-induced influences on the adjacent environment. This paper presents recent developments in practical design and construction techniques of controlling excavation-induced deformations in Shanghai. Commonly used techniques including the top-down construction method, ground improvement, the zoned excavation method and the underpinning technique are described and discussed. Relevant instrumented case histories on excavations in different types of urban environment are reported as well.

Analysis of Deep Foundation Pit Construction Monitoring in a Metro Station in Jinan City

In order to study the deformation law of adjacent building structures, surface settlement, displacement of supporting piles, axial force and variation of water level during different excavation stages of deep excavation construction, the deep foundation pit project in the M1 line of the Jinan Metro was used as the background, and the data from field measurement of excavation and support were analyzed. The results show that the horizontal displacement of the pile presented a pronounced “bow” shape with the excavation of the foundation pit. The maximum horizontal displacement of the pile appeared at one third of the top of the pile, with a maximum of 31.98 mm. The maximum value of monitored axial force was 3100 kN, which was much less than the control value of 6847 kN. The maximum axial force appeared on the second steel support. The axial force of the first reinforced concrete support rapidly increased with the time. It was considered that the initial bearing capacity of the concrete was low, so the axial force of the concrete support was smaller than the steel support. The strength and load-bearing capacity of concrete increased in the later period, which resulted in a rapid increase in axial force. At the same time, during the process of setting up or dismantling the support, the attention should be paid to the axial force change of the adjacent support to prevent the danger caused by the abrupt change of the axial force. The maximum settlement value of the building appeared at the two corners far from the foundation pit, with the value of 4.3 mm. When the constructions were 34 m away from the deep foundation pit, the impact of dewatering on the building was greater than that of the foundation pit excavation, and he effect of the dewatering on the variational soil texture in this area was different. The maximum angular variation of adjacent constructions was 1/16,050, which was less than the 1/5000 of the minimum angular variation. The foundation pit structure and building were in a safe state, and the layout of the supporting structure was reasonable.

Finite element study of deep excavation construction processes

Excavations for deep basements in urban areas present complex design questions, e.g. related to the selection of retaining systems and the specification of construction processes. Consideration must be given to the design of structural systems to support the excavation and the mitigation of any impact that the construction might have on any nearby infrastructure. The finite element analysis is routinely used (in design and research) for the analysis of this type of complex soil-structure interaction problem. Care is needed to ensure that representations of the construction processes, soil and structural behaviour are incorporated in the finite element model at an appropriate level of detail. This paper addresses the implementation of construction procedures in a finite element analysis of a deep excavation in Shanghai. Initially, an analysis is developed to model the construction processes actually employed in the project. The results of this model compare favourably with data measured during construction. The model is then developed to investigate the influence of certain aspects of the construction processes on the computed results. The results indicate the following: (i) the construction sequence for the floor slabs does not have a significant influence on the computed deformations in the retaining walls or the nearby ground at the end of construction; (ii) earth beams (used as temporary supports) are effective in reducing the computed wall and ground movements, and (iii) neglecting the presence of openings in the floor slabs may lead to unconservative calculations of the retaining wall and ground movements.

A risk assessment method of deep excavation based on Bayesian analysis and expert elicitation

In project management, it is an important approach that the deep excavation safety risk (DESR) is synthetically assessed based on experiential information provided by experts. This information is usually obtained from multiple sources and is incomplete. Therefore, the problem of synthesizing multiple sources and uncertainty information is of great significance for the assessment and control of DESR. This paper presents a risk assessment and decision approach for deep excavation construction based on Bayesian analysis. First, the expressions of a likelihood function used to describe and synthesize uncertain information obtained from expert panel is constructed, and a discretization interval division method of occurrence probability and consequences of an unwanted event is proposed based on the current risk code in China. Then, the discrete model of synthesizing information of expert estimates is constructed, and a comparative analysis of expert-elicited results and formula deduction are utilized to evaluate the advantages of this model under some hypothetical scenarios. On that basis, the index system of DESR is established and the weight of each index is calculated by the method of analytic hierarchy process. The risk matrix, deviation degree and risk acceptance criteria are developed to determine the whole risk level. Finally, the proposed method is verified by analyzing a typical deep excavation of Beijing Metro. The results demonstrate the feasibility of this method and its application potential.

The deformation of retaining piles and ground surface under various support systems during deep excavation

BackgroundSince the high-rise buildings and deep underground structures dramatically increases in urban area, the decent design and construction of deep excavations is essential before these structures are actually built up. The building area is very susceptible to the changes of their geo-environment, and even minor insecurity of a deep excavation may lead to a catastrophic failure of structures and deformation of the ground. Therefore, the adverse influence of deep excavation on the surrounding environment should be monitored and controlled stringently.ResultsBased on the real case of deep excavation in Xuzhou, China, a FDM numerical model, which was accomplished by FLAC-3D, was developed to evaluate the deformation of retaining piles and ground surface under various excavation support systems. The original pile-anchor support system was simulated as well as the proposed quincunx double-row piles support system. For the original support system, the deformations were discussed by comparing the numerical results with monitoring data. For the proposed support system, orthogonal tests were designed to evaluate the influence of multiple factors on the effectiveness of excavation support. The optimum solution for the proposed support system was obtained through orthogonal tests.ConclusionResults show that the pile space is the primary factor for the excavation-induced deformations, which can be reflected by the lateral displacement of retaining piles and the settlement around the excavation, while the row space has insignificant influence on the deformations. The conclusions of this paper can contribute to the design of similar projects and avoid excessive deformation of the ground during excavation in the future.