Excavation Case Research Articles

Dynamic response and regular analysis of adjacent buildings under blasting construction across foundation pits of subway stations

To study the impact of cross-pit blasting on nearby buildings, a numerical model was used based on the case of a subway station excavation. The analysis focused on the vibration response patterns at monitoring points, considering different lengths, widths, depths, and positions of the adjacent foundation pit (AFP) and varying blasting foundation pit (BFP) depths. Additionally, a data-driven method was adopted to improve numerical calculation efficiency under multiple scenarios. In this method, leave-one-out cross-validation is used to enhance the accuracy of the XGBoost vibration reduction prediction model, and the model's hyperparameters are optimized using Bayesian algorithms. Furthermore, employing the established LOO-BO-XGBoost model in combination with the physical equations for charge control, the data-physical hybrid dynamic design method for cross-pit blasting charge is developed. The results indicate that, among the size parameters of the AFP, depth has the greatest impact on peak particle velocity (PPV), followed by length and width. When the size of the AFP is the same, the closer it is to the building, the more significant its vibration reduction effect. The deeper the excavation of the BFP, the lesser the impact of the blasting on the building. The LOO-BO-XGBoost model outperforms the XGBoost and ANN models, achieving higher accuracy (training dataset: R² = 0.93, RMSE = 0.023; testing dataset: R² = 0.90, RMSE = 0.021). Subsequently, the data-physical hybrid dynamic design method optimizes the charge in the cross-pit blasting case. As the AFP is excavated from 11 m to 15 m, the single-hole charge is increased from 9 kg to 10 kg according to this method. And the measured PPV still meets the requirements. Therefore, considering the vibration reduction effect of the AFP, it is important to expedite construction and reduce time costs. The research method proposed in this paper can serve as a valuable guide for similar projects.

Direct Field Curve Fitting Method to Determine Hardening Soil Parameter for Geotechnical Projects

Abstract In a wide archipelago country like Indonesia, transporting soil samples for laboratory tests are quite a bit of challenge in terms of cost and time as those need to be transported for weeks to nearest big cities. In-situ tests and correlation methods can be used as an alternative solution for preliminary or detailed design beside having on site laboratory. Correlating in-situ test results to hardening soil parameter (e.g. E 50) is common but it is not clear how those should be adjusted for Plaxis input. Two deep excavation projects and a lateral pile load test are used to see the performance of direct field curve fitting method utilizing SPT correlation to HS parameter. From the analysis, using E 50=4000N for clay soils and E 50=2800N for sand soils as upper bound parameters produce the best results with lesser discrepancy with the field measurements compared to calculations with lower bound parameters. For the deep excavation cases (Case 1 and Case 2), calculated lateral displacement results using upper bound parameters overestimates inclinometers measurement for less than 1.5 cm for both cases. For the case of lateral pile load test (Case 3), calculation using upper bound parameters succeed to capture a high detail of unloading-reloading curves similar to the actual measurement. This method can be used as a technique to design geotechnical projects and it proposes a framework for future research regarding a new possibility to establish various E 50 correlations.

A case study of the response of support structure and stratum deformation caused by deep foundation pit excavation in soft area

Investigating the spatial distribution and evolution patterns of deformations during foundation pit excavation is crucial for safeguarding the surrounding environment. This study focuses on a deep excavation case in Nanjing and discusses the strata deformation and the response of the retaining structure through the excavation phase, informed by on-site monitoring data. A three-dimensional finite element model of the excavation was developed, with comparisons between predicted values and on-site deformation monitoring data underscoring the accuracy of the numerical simulation results. This analysis delved into the deformation spatial distribution within the retaining structure and ground surface settlement throughout the excavation. Moreover, the three-dimensional deformation patterns of the diaphragm wall at various excavation depths were scrutinized, mapping the evolution pattern and spatial distribution of ground surface settlement around the foundation pit across different excavation stages. The findings reveal a pronounced spatial effect in both the diaphragm wall deformation and ground movements behind the wall, with the greatest deformation manifesting near the symmetric plane of the excavation center and markedly less deformation near the excavation corners. Furthermore, the deformation scope broadens with increasing excavation depth. These research outcomes aim to furnish a substantive reference for practical engineering implementations.

경남내륙지역 목관·목곽묘의 구조적 특징과 축조양상

This study examined the wooden gasket tombs and wooden chamber tombs in Gyeongnam Inland areas from two main perspectives. It summarizes recent excavation cases to review the structural characteristics of these tombs and infers the construction style and burial methods through the example of the Jeongjang-ri Tomb No. Ⅲ-86. Firstly, the wooden gasket tombs consist of ① burial area (tomb pit), ② wooden gasket, ③ backfill soil, ④ topsoil, ⑤ wooden fence, and ⑥ mound, which are not significantly different from those found in the Yeongnam region. However, the wooden gasket tomb at Jangchon-ri B-25 is a unique half-cut chamber type. What is particularly noteworthy is that the lower part of the tomb pit is excavated about 10° eastward from the top, where the wooden gasket is placed. Additionally, the wooden gasket tomb at Dohang-ri #48 lacks backfill soil and exhibits a distinctive structure with retaining walls. The structure of the wooden chamber tombs consists of ① burial area (tomb pit), ② wooden chamber, ② wooden gasket, ③ pedestal, ④ backfill soil, ⑤ topsoil, ⑥ capstone, and ⑦ outer wall. There are various types of wooden chamber tombs, including single-chamber style, double-chamber style, and compound chamber style. Among them, the wooden chamber tombs in Jeongjang-ri is notably distinct because it has separate compartments on both walls for the relics among the double-chamber style tombs that have both the inner and outer walls and the single-chamber style tombs. Additionally, the floor surface is excavated to install a pedestal, and two to five wooden planks are placed across it. And it is clear that the inside and outside are installed on the wooden board. Second, the architectural features and burial styles have been reconstructed by inferring the procedure of construction based on the structural features of the Jeongjang-ri Tomb No. Ⅲ-86. The assumed procedure is as follows: Excavation of the ① burial area and ② tomb pit and installation of the pedestal → Installation of horizontal wooden planks and longitudinal planks → ④ Installation of inner and outer walls and backfilling → ⑤ Placement of body and artifacts → ⑥ Closing and sealing of the wooden gasket and mound construction. Therefore, the Jeongjang-ri Tomb No. Ⅲ-86, among others, holds significance as it provides an opportunity to comprehensively reconstruct the structural characteristics and construction processes of wooden chamber tombs in the Gyeongnam Inland region.

A spatiotemporal feature fusion-based deep learning framework for synchronous prediction of excavation stability

Under rapid urbanization, analyzing and perceiving synchronous excavation stability is essential to generate valuable and foresightful information in identifying and mitigating potential risks in deep excavations. Although the existing forecasting methods can achieve high accuracy in the safety state perception of deep excavations, it is prone to lack proper consideration of the monitoring item’s fusion and cause error and uncertainty via the single-parameter risk evaluation. To address it, this paper proposes a spatiotemporal feature fusion-based deep learning (FFDL) framework to implement the feature fusion-based data analysis and time-series forecasting on the factor of safety (FS) on behalf of excavation stability, and global sensitivity analysis. The fusion indicators and proposed FFDL framework are validated through a comprehensive case study encompassing 100 typical metro station constructions. The feature fusion-based data analysis results confirm the statistical significance of fusion indicators, contributing to establishing a high-quality spatiotemporal sequential database. As for the real-time prediction, the Bayesian optimization CNN-LSTM model provides a reliable prediction of excavation stability and the relative errors in the training and testing datasets do not exceed 1% and 3% in construction duration. It also enhances the predictive accuracy and outperforms the existing models LSTM, GRU, BiLSTM, and CNN-LSTM, reaching an average improvement of 38%, 32%, and 32% in RMSE, MAE, and MAPE, respectively. Furthermore, the proposed model has an excellent generalization performance in accurately predicting the excavation stability of the other ten excavation cases with an average relative error of 5.37%. In short, this work contributes to not only providing a new perspective in risk management by integrating feature fusion-based indicators and excavation stability but also verifying the applicability of the proposed framework.

Deterministic and probabilistic analysis of great-depth braced excavations: A 32 m excavation case study in Paris

The Fort d’Issy-Vanves-Clamart (FIVC) braced excavation in France is analyzed to provide insights into the geotechnical serviceability assessment of excavations at great depth within deterministic and probabilistic frameworks. The FIVC excavation is excavated at 32 m below the ground surface in Parisian sedimentary basin and a plane-strain finite element analysis is implemented to examine the wall deflections and ground surface settlements. A stochastic finite element method based on the polynomial chaos Kriging metamodel (MSFEM) is then proposed for the probabilistic analyses. Comparisons with field measurements and former studies are carried out. Several academic cases are then conducted to investigate the great-depth excavation stability regarding the maximum horizontal wall deflection and maximum ground surface settlement. The results indicate that the proposed MSFEM is effective for probabilistic analyses and can provide useful insights for the excavation design and construction. A sensitivity analysis for seven considered random parameters is then implemented. The soil friction angle at the excavation bottom layer is the most significant one for design. The soil-wall interaction effects on the excavation stability are also given.

Multi-status Bayesian network for analyzing collapse risk of excavation construction

In response to the need for effective collapse risk analysis in engineering projects, a decision support approach is presented. It is rooted in multi-status Bayesian network (MSBN) and fuzzy set theory, encompassing MSBN construction, risk analysis, and management. This research addresses the causative correlation between influential factors and excavation collapse, considering the inherent uncertainty and fuzziness of the project. To enhance the reliability of evaluation results, an expert confidence index, integrating judgment ability, subjective reliability, and risk preference, is introduced. The approach is applied to an excavation case study, demonstrating its viability and capacity. Furthermore, it offers actionable insights for decision-makers to proactively mitigate accident probabilities. Notably, sensitivity analysis identifies critical risk factors. This research contributes to the field of engineering project risk assessment and management. It serves as a foundation for future research and development, guiding the way for improved strategies and decision support systems.

Study on the Performance of Twin Shield Tunnel Excavation below Existing Multi-Arch Culvert Bridge in Close Vicinity

Various adjacent construction projects are inevitably encountered during the large-scale construction of urban underground transportation. The case of a twin shield tunnel excavated below an existing multi-arch culvert bridge in close vicinity has not yet been thoroughly studied. A case of a shield tunnel excavation below an existing multi-arch culvert bridge in Foshan is presented. First, a fully coupled three-dimensional model incorporating fluid and solid interactions was established to simulate the twin shield tunnel excavation below the existing multi-arch culvert bridge in close vicinity. Subsequently, the numerical model was validated using the modified Peck empirical formula. Finally, the influence of different foundation reinforcement deformation moduli, tunnel excavation face support pressures and grouting pressures on ground deformation was discussed. The results indicate that the area most significantly affected by the excavation of the tunnel passing underneath is not within the section of the multi-arch culvert bridge after applying the foundation reinforcement design. The area most significantly impacted is concentrated as the shield tunnel commences excavation and advances beneath the location corresponding to the 1-hole of the steel corrugated pipe. The range of influence of the ground disturbance extends approximately 7 m in front of the excavation face before the tunnel passed through. The range of ground disturbance decreases to 4–6 m in front of the excavation face after the tunnel passed through. The excavation face support pressure and grouting pressure have a minor impact on the settlement of the multi-arch culvert bridge under this reinforcement design. The results provide useful references for the reinforcement design for tunnel excavation adjacent to existing structures.

Prediction of geological composition using recurrent neural networks and shield tunnel boring machine data

ABSTRACT Tunnel Boring Machines (TBMs) are large-scale excavation tools used commonly in transportation tunnel construction. While tunnelling, TBMs generate data at large scales, often at levels difficult to parse using traditional statistical techniques. Utilising this data can be highly beneficial to obtain a better understanding of TBM excavation conditions, and such understanding can be applied to machine and technique selection. This paper presents a novel method for sequential estimation of geological composition using advanced machine learning algorithms and the data collected from TBMs. In this approach, we use Recurrent Neural Networks and Long Short-Term Memory (RNN-LSTM) models as a hybrid machine learning algorithm for processing sequential and time-series data. The results from an excavation case study demonstrate that the proposed method is an effective approach for sequential estimation of geological composition as encountered by TBM during operation. It is worth noting that TBM data captures the signature of the ground, and the developed model in this study was successful in predicting the ground geological composition even without using the borehole data.

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 Influence of Geological Conditions in the Hangzhou Bay Area on the Deformation Behavior of Deep Excavations

The deformation behavior of deep excavations is affected by many factors, among which the geological conditions are greatly affected. Hangzhou Bay is affected by marine siltation and river alluvium, and the geological conditions within the urban area of Hangzhou are quite different. In this paper, the geological and deformation data of 79 deep excavation cases in the Hangzhou urban area were collected, and the statistical analysis showed that the deformation control of excavations in the silt area was poor. The average maximum lateral wall displacement of deep excavations of the Hangzhou urban area was 0.41%H (H was the depth of the excavation), the average value of the alluvial area was 0.22%H, and the average value of the silted area was 0.55%H. The influence of geological conditions, wall type, and construction period on the deformation of excavations was compared, and the deformation behavior of excavations in the silted area was clearly affected by various factors.

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.

Shape optimization of the spillway approach channel of Baleh Hydropower Project based on numerical simulation

Baleh Hydropower Project has a protruding headland between the spillway inlet and the power intake structure. Based on the results of the model tests, the velocity gradient near the protruding headland under high flow conditions is large and an unstable vortex occurs. To address the unfavorable flow problems of the original spillway approach channel, this paper simulates the original spillway approach channel using a three-dimensional turbulence numerical model and verifies it with the model tests, and provides numerical simulation results for two optimized cases: excavation and backfilling. The calculation results show that both backfilling and excavation optimization cases improve the right side flow pattern, the unstable vortex disappears, and the flow between the approach channel and the spillway inlet is smoother than the original design. Comparing the two optimized cases, the average flow velocity in the upstream section of the approach channel of the excavation case is reduced, but the flow velocity near the right bank of the approach channel close to the spillway gate bay inlet becomes larger, and the average flow velocity of the excavation modified case is more unevenly distributed.

Method for estimating three-dimensional effects on braced excavation in clay

The maximum lateral wall movements are usually estimated by two-dimensional finite element analysis. However, three-dimensional effects due to the higher stiffness at the corner will result in smaller wall movements than that under plane strain conditions. This paper proposed a method to quantize the three-dimensional effects. The limitations of quantifying the three-dimensional effects by the current method were presented by analyzing an excavation case. A comprehensive parametric study was carried out to explore the effects of soil condition, support system stiffness, and the excavation geometry on the three-dimensional effects of excavation. The finite-element simulation results were represented by the plane strain ratio (PSR), and an empirical equation for PSR prediction was proposed considering soil condition, support system stiffness, excavation geometry, and distance from the excavation corner. The proposed equation was verified against case data reported in the literature, and the overall agreement was satisfactory. This equation offers a more reliable way to quantify the three-dimensional effects of rectangular excavation with internal struts in clay.

One-Dimensional Reverse Consolidation Model for Basal Soil from Deep Excavation Based on the Continuous Drainage Boundary

Excavation-induced unloading effects and dewatering-induced groundwater seepage inevitably result in basal soil reverse consolidation in deep excavation. However, this reverse consolidation process is rarely considered because most previous analytical methods were developed based on total stress analyses. This study proposes a one-dimensional reverse consolidation model for basal soil of deep excavation. Based on the consolidation theory proposed by Terzaghi, governing equations of soil reverse consolidation caused by excavation and dewatering were separately established. The continuous drainage boundary was introduced to describe the construction processes. The reverse consolidation responses of basal soil were obtained by superimposing analytical solutions of the excess pore-water pressures that resulted from excavation and dewatering. The proposed model was verified by existing solutions and a well-documented excavation case history. Moreover, the reverse consolidation characteristics of basal soil were investigated by parametric analyses. Results indicate that the excavation-induced variations in pore-water pressure decreased with increasing excavation depth. The final pore-water pressure and effective stress were predominantly affected by excavation duration rather than interval distribution. In addition, a smaller coefficient of consolidation led to lower pore-water pressure and greater effective stress at a given excavation depth.

Model test and numerical simulation of a new prefabricated double-row piles retaining system in silty clay ground

This paper introduces a new prefabricated recyclable double-row piles retaining system for excavations in silty clay ground. Laboratory model test and numerical simulation are conducted to study the system behavior upon excavation. The horizontal displacement (δh), Von Mises stress (σM), strain (ε), ground surface settlement (δv), and earth pressure are systematically investigated. Furthermore, the monitoring data of 13 excavation cases supported by double-row piles retaining system are presented and discussed. The experimental results can basically match the numerical results, and the maximum σM, maximum bending moment (Mmax), maximum horizontal displacement (δhm) of structural members are all less than the tolerance limits. The ground surface settlement model of double-row piles retaining system consists of three zones, i.e., rebound influence zone, primary influence zone and secondary influence zone. The δhm values are 0.07%–1.42% of the excavation depth (He). The maximum ground surface settlement (δvm) is generally less than δhm. The ratio of δvm/δhm varies between 0.09 and 0.76, with an average value of 0.5. The observed earth pressure on the retained side of front pile (paf) is about 0.53–0.57 γH below the excavation surface. Above the excavation surface, paf decreases dramatically when getting closer to the ground surface.

Methodology for selecting measurement points that optimize information gain for model updating

Information collected through sensor measurements has the potential to improve knowledge of complex-system behavior, leading to better decisions related to system management. In this situation, and particularly when using digital twins, the quality of sensor data determines the improvement that sensors have on decision-making. The choice of the monitoring system, including sensor types and their configuration, is typically made using engineering judgement alone. As the price of sensor devices is usually low, large sensor networks have been implemented. As sensors are often used to monitor at high frequencies over long periods, very large data sets are collected. However, model predictions of system behavior are often influenced by only a few parameters. Informative data sets are thus difficult to extract as they are often hidden amid redundant and other types of irrelevant data when updating key parameter values. This study presents a methodology for selecting informative measurements within large data sets for a given model-updating task. By selecting the smallest set that maximizes the information gain, data sets can be significantly refined, leading to increased data-interpretation efficiency. Results of an excavation case study show that the information gains with refined measurement sets that are much smaller than the entire data set are better than using the data set prior to refinement for the same probability of identification, while the computational time of model updating is significantly reduced. This methodology thus supports engineers for significant data filtering to improve model-updating performance.

A probabilistic deep reinforcement learning approach for optimal monitoring of a building adjacent to deep excavation

AbstractDuring a deep excavation project, monitoring the structural health of the adjacent buildings is crucial to ensure safety. Therefore, this study proposes a novel probabilistic deep reinforcement learning (PDRL) framework to optimize the monitoring plan to minimize the cost and excavation‐induced risk. First, a Bayesian‐bi‐directional general regression neural network is built as a probabilistic model to describe the relationship between the ground settlement of the foundation pit and the safety state of the adjacent building, along with the actions in a dynamic manner. Subsequently, a double deep Q‐network method, which can capture the realistic features of the excavation management problem, is trained to form a closed decision loop for continuous learning of monitoring strategies. Finally, the proposed PDRL approach is applied to a real‐world deep excavation case in No. 14 Shanghai Metro. This approach can estimate the time‐variant probability of damage occurrence and maintenance actions and update the state of the adjacent building. According to the strategy proposed via PDRL, monitoring of the adjacent buildings begins in the middle stage rather than on the first day of the excavation project if there is full confidence in the quality of the monitoring data. When the uncertainty level of data rises, the starting day might shift to an earlier date. It is worth noting that the proposed PDRL method is adequately robust to address the uncertainties embedded in the environment and model, thus contributing to optimizing the monitoring plan for achieving cost‐effectiveness and risk mitigation.

Two- and Three-dimensional Numerical Back-analysis of Deep Excavation Case Studies from Budapest, Hungary

In this paper, the numerical back analyses of four, typical, monitored deep excavations completed in Budapest are presented. The typical excavation solution in Budapest city center, down to 15–18 m excavation depth, is a diaphragm wall embedded in the clay bedrock and supported by prestressed anchors embedded in the sedimentary soils above the clay. In these case studies this solution is analyzed with traditional Winkler type and more complex PLAXIS 2D and 3D finite element models. The focus of the study was to compare the measured wall deformations with the calculated ones derived by the listed methods. As the clay bedrock is a deterministic layer for the wall behavior, several different FEM models were prepared to analyze the appropriateness of the potential constitutive models for its proper characterization. As a conclusion, practical proposals were made for practitioners for future excavations.

Analysis of observed performance of a deep excavation straddled by shallowly buried pressurized pipelines and underneath traversed by planned tunnels

The objective of this paper is to analyze the observed performance of a deep excavation facing severe restrictions from underground facilities or structures in Suzhou, China. The first source of the restrictions comes from two shallowly buried pressurized pipelines that straddle the excavation at an intersection angle of about 81°. The pipelines need to be well protected at the site during the construction to ensure the normal life of the local resident. The second source of the restrictions arises from the twin tunnels that are planned to be constructed beneath the excavation in the future for Suzhou Metro Line 14. The planned tunnels will be constructed using a tunnel boring machine, which necessitates the reservation of favorable conditions by the present excavation project. Because of these restrictions, the form of the excavation support system becomes complicated, and the performance of the excavation will inevitably differ from that of the common excavations. Based on a thorough analysis of the extensive field performance data collected by means of settlement points and inclinometers located within and adjacent to the excavation, the characteristics of the ground surface settlements, lateral ground movements, ground water table variations, vertical and lateral displacements atop diaphragm walls, vertical displacements atop lattice column, axial forces in concrete strut, and vertical and lateral pipeline deformations are captured. Despite the discontinuity of the peripheral retaining wall and the shortened wall height on the discontinuous sides, the ground and structural deformations are well controlled by the specially designed excavation support system. The pipelines are slightly uplifted by the suspension system, with the maximum vertical pipeline displacement being lower by an order of magnitude than the commonly observed maximum pipeline settlements in the literature. The existing empirical envelops are found to be site-specific in applicability, and are recommended to incorporate the field observations of this unusual deep braced excavation case history.