Analysis Of Deep Excavation Research Articles

Numerical investigation of the effects of compressibility of gassy groundwater (CGG) on the performance of deep excavations in Shanghai soft deposits

Although compressibility is a critical aspect of groundwater, research on this factor has been primarily limited to laboratory tests and theoretical analyses. Thus, the effects of this property on engineering applications, such as deep excavations, are unclear. In this study, a numerical model combined with the hydro-mechanical coupled method is established to analyze the impact of the compressibility of gassy groundwater (CGG) on the performance of deep excavations in Shanghai deposits, which are characterized by a typical composition of multi-aquifer–aquitard. A reasonable agreement between the numerical results and the measured data of three projects of deep excavations is achieved, verifying the established model's applicability. The results suggest that the deformation behavior of excavations increases significantly with the increase in CGGs. The impact of CGGs on excavation deformations can be attributed to the variation of the stress level inside the excavation and the pore water pressure outside the excavation. Furthermore, an equivalent CGG in the analyses of deep excavation involving dewatering-only in Shanghai soft deposits is suggested as a high value ranging from 1 × 10−7 m2/kN to 1 × 10−6 m2/kN, providing an available reference for the analyses of deep excavations in Shanghai while considering the effect of CGGs.

Development of Plane Strain Ratio for Soil Nailing Wall in Clay

Deep excavation analysis, the numerical modelling is now often utilized. Deep excavation is, in fact, a three-dimensional issue. Two-dimensional analysis is still often used for practical purposes. For deformation analysis, plane strain ratio (PSR) is an option to acquire three-dimensional behaviour from two-dimensional analysis. For braced excavations, PSR is well established, but it is yet unknown how to construct retaining walls using soil nails. The aim of this paper is to propose the PSR chart for a soil nailing wall used as a retaining structure in clayey soil with an asymmetrical layout. The excavation case history is adopted for this study. Later, the length (L) and width (B) of the excavated area were varied as part of three-dimensional parametric research to create a soil nailing wall PSR chart.

The Effect of Incorporating Vertical Spatial Variability on the Probabilistic Analysis of a Deep Excavation: A Case Study

This study explores the impact of including the vertical spatial variability in effective stress friction angle of clay on the probabilistic analysis of deep excavations. The proposed methodology is demonstrated and verified by conducting random finite element modeling (RFEM) of an instrumented deep excavation project situated in Ankara, Turkey. The excavation has a depth of 20 meters and is supported by six levels of pre-stressed ground anchors. To simulate the vertical spatial variability of effective stress friction angle in the clay, Monte Carlo simulation method and the random field theory are employed. The simulated parameters are then inserted into the finite element model via Python programming language to analyze the probabilistic distribution of lateral deflections and bending moments in the drilled shaft wall. The results obtained from the Monte Carlo simulations reveal that the incorporation and selected value of spatial variability significantly impacts the resulting lateral movements, bending moments, and the probability of failure of the system.

Establishment of Localized Utilization Parameters for Numerical Simulation Analysis Applied to Deep Excavations

The aim of this study was to apply deep excavation behavior prediction models in the geotechnical field to establish localized soil parameters for gravel layers. Common software tools, including PLAXIS and SoilWorks, were used extensively. Monitoring data from deep excavation cases related to gravel layers in the Xindian area of Taiwan were collected. In the background analysis, the deformation of the retaining walls was used instead of parameters typically used in deep excavation analysis. This was performed to provide the ideal range recommendations for the input parameters when conducting a numerical simulation analysis of the Xindian District stratum or similar strata. The assessment results show that when setting the fifth layer of gravel to SPT-N = 100, PLAXIS suggested a soil elastic modulus range of 7840 N to 9800 N per square meter (kN/m2), while SoilWorks recommended a range of 2450 N to 3430 N per square meter (kN/m2). These ranges allow for a reasonable estimation of the maximum wall deformation during the final excavation stage. Based on the research findings, it is recommended that when conducting an excavation analysis in gravel layers in the Xindian area of Taiwan or in similar strata, engineers should refer to the abovementioned recommended ranges when selecting the soil elastic modulus for different software programs. This will enhance the accuracy of the deformation predictions during the final excavation stage.

Dynamic and Static Analysis of Deep Excavation of Poligon Station in İzmir Metro Line

In this paper, the deep excavation stages of Poligon Station which is the located along the Üçyol–Fahrettin Altay subway line was modeled numerically. Although some parts of the metro line were constructed, some parts of metro line are currently under construction in İzmir. The Poligon Station is carried out with a surrounding diaphragm wall and top-down construction method. The foundation mat and four slabs of the station building are used as support elements. The excavation depth of the station is 18 meters. The soil properties of the numerical model were obtained engineering boreholes and laboratory tests. Lateral soil displacements were measured with inclinometers installed in the nearby soil layers. Displacements which were measured from inclinometers and obtained from numerical modeling were compared. Beside the static analysis, the Poligon station of the metro line was analyzed with a model earthquake. 16.12.1977 İzmir Earthquake (Ms=5.5, amax=0.21g) was used as a model earthquake for dynamic analyses. In addition, effects of changing the properties of the soil on computed results were numerically investigated using the software Plaxis.

Numerical Analysis of Deep Excavation

Because of limited knowledge on experience on deep excavation analysis in Sudan, this study aimed to study numerical models for modeling deep excavation and adjacent buildings or public facilities near by the excavation. A series of parametric studies were conducted to evaluate the effect of wall stiffness and strut stiffness. The numerical analysis results showed that the increase of retaining wall stiffness or strut stiffness to reduce wall deformation is certainly effective, however does not have linear relationship. Last, based on the numerical results, the evaluation of adjacent building damage related to settlement induced by excavation and suggestions protection of adjacent buildings before and during excavation were discussed.

A comprehensive FE study for design of anchored wall systems for deep excavations

Anchored wall system is one of the common methods used for deep excavation stabilization adjacent to sensitive structures in urban areas. A key aspect of the stability analysis of deep excavations is the amount of deformations occurring on the facing wall and the adjacent structures. In this research, a large number of parametric studies considering all aspects of soil-structure interaction is carried out for different excavation geometries to find the optimal design, and the outcome is shown in the form of design tables and charts. Also, by a GA-PSO algorithm and using the large database obtained from the numerical simulations, a simple equation is developed that can predict the deflections caused by deep excavations. The results of the proposed equation demonstrate high accuracy and marked consistency with the algorithm results, numerical analysis outcome, and real cases data.

Efficiency of Nondeterministic Methods in Reliability Analysis of Deep Excavations: Case Study of the Soheil Project

Abstract Geotechnical engineers deal with uncertainties in different projects. These uncertainties can be captured using nondeterministic approaches. Although during the last two decades numerous p...

Impacts of the plane strain ratio on excavations in soft alluvium deposits

Due to tool, time and budget limitations, 2-dimensional analyses of deep excavation are often adopted for engineering practice; thus, the 3-dimensional behaviour is ignored. Because conducting 3-dimensional analyses is very time-consuming and costly, the “plane strain ratio (PSR)” indicator is defined to assist in understanding the 3-dimensional behaviour of deep excavations via the results of 2-dimensional analyses. However, previous works of the impacts on PSR have focused on only the excavation geometry and distance from the excavation corner. In this paper, additional factors that may affect the PSR for excavations in both drained and undrained materials are examined, and it is concluded that not only excavation geometry and distance to the corner but also the ratio of the wall embedded depth to the excavation depth and the wall thickness have comparatively significant influences compared to other factors, whether excavating drained or undrained materials. Lastly, multiple regression is used to modify the value of the PSR from empirical PSR charts for sand and clay considering the impacts of these abovementioned factors.

SDMT-Based Numerical Analyses of Deep Excavation in Soft Soil

AbstractThe paper explores the application of conventional (DMT) and seismic (SDMT) dilatometer tests to an important case of deep excavation design. The work presents finite-element analyses simul...

Reliability analysis of deep excavations by RS and MCS methods: case study

In recent years, uncertainty inherent in geotechnical properties has caught great attention of researchers and engineers; thus, reliability analyses and non-deterministic methods have been applied widely. This paper presents the reliability analysis of a case study on deep excavation in a cemented coarse-grained alluvium adopting random set (RS) and Monte Carlo simulation (MCS) methods to tackle the inherent uncertainty associated with soil properties. The horizontal displacement of the excavated wall and safety factor of stability were adopted as a basis for assessing the system response. Pertinent codes were written by employing RS and generating random numbers of probability distribution functions in FLAC2D finite difference program. Introducing RS code into the numerical analysis process drastically reduced the computational effort required for this method. It was found that in cases of deep excavations with low target probability of failure, RS presents satisfactory performance and thus is preferable to MCS, while MCS can be employed as a beneficial tool for stability analysis and some special cases of deformation analysis in excavation problems. The results are presented and compared in terms of sampling procedure, as well as statistical moments, probability of occurrence and most likely values at every stage of construction.

Analysis of a deep excavation in diaphragm walls, on surrounding buildings

The article presents the results of deep excavation analysis performed using the finite element method as well as impact of diaphragm walls construction on the surrounding objects. First part of the article concerns on theoretical background, methodology and data used in program. The second part is focused on the design model, results of analysis and impact of the deep excavation on surrounding buildings. The design task was performed in Midas GTS NX software, which is modeling platform used to design ground conditions as well as structures cooperating with the soil. Presented content is part of Author’s master thesis.

Underground excavation behaviour in Bangkok using three-dimensional finite element method

This study provides evidence that three-dimensional finite element modelling can be effectively applied for deep excavation analysis in Bangkok. The Bangkok subsoils were modelled using the hardening soil model and their parameters were calibrated against the results of laboratory and field tests. A study of a MRT station excavation was initially used to validate the model. The predicted wall movements and surface settlements were compared with the instrument data and two-dimensional analysis from a previous study. Another deep excavation project was selected asan independent study. The result shows that the model can be confidently used for deep excavation analysis.

Experimental and theoretical investigation on the stability of deep excavations against confined aquifers in Shanghai, China

Urban development often requires deep excavations, such as for deep basements, cut-and-cover tunnels, and underground transportation systems. Pressure from a confined aquifer can cause a sudden failure of a deep excavation and have disastrous effects on the surrounding buildings. In this study, a series of centrifugal model tests were conducted on different aquitards in Shanghai to investigate the failure process and types. Two types of failure were identified from the centrifugal model tests: local failure (sand piping and sand boiling) and general upheaval. An approach to the stability analysis of deep excavation against a confined aquifer was developed. To increase the reliability of the analytical approach, the calculated results were compared with the experimental results. The results showed good agreement.

Evaluation of Hypoplastic Clay Model for Deep Excavation Modelling

AbstractThis paper presents an evaluation of the Hypoplastic Clay constitutive model for finite element analysis of deep excavations and displacements induced by excavations in the influence zone. A detailed description and formulation of the Hypoplastic Clay soil model is included. A parametric case study of a deep excavation executed in Pliocene clays is presented. FE analysis was performed using several soil models (Mohr-Coulomb, Modified Mohr-Coulomb, Drucker-Prager, Modified Cam-Clay, Hypoplastic Clay) and the results were compared to in-situ displacements measurements taken during construction. Final conclusions concerning the suitability of the Hypoplastic Clay model for deep excavation modelling in terms of accurate determination of horizontal displacements of the excavation wall, the uplift of the bottom of excavation, and, most importantly, vertical displacements of the terrain in the vicinity of the excavation are presented.

Reply to the discussion by Conti R., De Sanctis L. and Viggiani G.M.B. on ‘Influence of diaphragm wall installation on the numerical analysis of deep excavation’ by Burlon S., Mroueh H. & Shahrour I.

The authors thank the discussers R.Conti, L.De Sanctis and G.M.B.Viggiani for their interest to the paper entitled ‘Influence of diaphragm wall installation on the numerical analysis of deep excavation’ and for providing the opportunity to submit additional information to clarify some issues. The authors broadly agree with the comments which deal with three main aspects of the paper: presence of water and type of analysis, constitutive modelling and numerical strategies. The present reply addresses some additional issues that the discussers find not clear on the original paper submitted by the writers. Copyright © 2013 John Wiley & Sons, Ltd.

Discussion of ‘Influence of diaphragm wall installation on the numerical analysis of deep excavation’, by Burlon S., Mroueh H. & I. Shahrour

Discussion of ‘Influence of diaphragm wall installation on the numerical analysis of deep excavation’, by Burlon S., Mroueh H. & I. Shahrour

Influence of diaphragm wall installation on the numerical analysis of deep excavation

SUMMARYThis paper presents a numerical analysis of the influence of initial stress state on the response of deep excavation supported by retaining wall. Indeed, the influence of diaphragm wall installation prior to excavation works may affect the soil response and lateral wall deflection induced by excavation process. The first part of this paper gives a short review of the numerical methods aimed to reproduce the retaining wall installation. Numerical analysis of a deep excavation in two‐dimensional and three‐dimensional conditions is then performed according to the methods previously presented. In three‐dimensional conditions, diaphragm wall installation is performed considering a sequence of panels, described by their number and length. Results of three‐dimensional calculations confirm that stress state is disturbed by wall installation, which has a sensitive effect on the ground response induced by soil excavation. It is also noted that these results are not easily reproduced in two‐dimensional conditions. Copyright © 2012 John Wiley & Sons, Ltd.

Application of the Hardening Soil model in deep excavation analysis

The Mohr–Coulomb model (MC) is commonly used in deep excavation analysis for its simplicity. However, it has shortcomings that may produce unrealistic soil behaviour. The Hardening Soil model (HS) is an advanced soil model that is able to generate more realistic soil response in terms of non-linearity, stress dependency and inelasticity. This article highlights some of the shortcomings of the MC model and presents a simplified approach to determine the HS parameters for drained and undrained analysis of deep excavations. Three case studies were back-analysed to validate the application of the HS model for practical excavation analysis. The HS model suffers the same problems as the MC model in using effective stress parameters c′ and φ′ to determine the undrained shear strength.

Three-dimensional numerical analysis of deep excavations with cross walls

Previous plane strain analysis of a case history has shown that cross walls in an excavation can effectively reduce movements induced by deep excavation. This study performed three-dimensional numerical analyses for 4 deep excavation cases with different installations of cross walls, including different excavation depths, cross wall intervals and cross wall depths. Both the observed and computed wall deflections for the 4 cases were compared with those of the same excavations that were assumed with no cross walls installed to demonstrate the effectiveness of cross walls in reducing lateral wall deflections. The results show that the cross wall also had a corner effect similar to that of the diaphragm wall. The deflection of the diaphragm wall was smallest at the location of the cross wall installed and then increased with the increasing distance from the cross wall, up to the midpoint between two cross walls. Many factors such as in situ soil properties, diaphragm wall properties, construction procedure, cross wall depth and so on may affect the amount of reduction in lateral wall deflections due to the installation of cross walls. Under the same condition, the amount of reduction was highly dependent on the depth of cross walls, distance to the cross walls and the cross wall interval.