4th International Conference on Structural Health Monitoring and Engineering Structures (SHM&ES 2025)

Table of Contents

1. Underground Engineering

   1. Frontmatter

   2. Study the Behavior of Flexible Pipes Considering the Dilatancy Effect of Sand

      Giang Vu-Thi-Thuy, Trang Do-Nhu

      Abstract

      The mechanical behavior of flexible pipes buried in sandy soils is significantly influenced by the dilatancy of sand—a critical factor in pipe–soil interaction that governs load transfer mechanisms and soil deformation behavior. This study investigates the role of dilatancy in soil behavior and pipe deformation under. This paper examines the behavior of backfill material, specifically sand, in both elastic and plastic states, and explores how dilation influences pipe load and deformation. A computational analysis integrating traditional methods, such as Iowa’s equation, with stress-dilatancy theory and critical state soil mechanics is presented. The results highlight the importance of accounting for dilatancy in design models and suggest future research directions in pipeline–soil interaction.

   3. Properties of CDM Columns from Unconfined Compression Test: A Case Study in Ho Chi Minh City

      Khac Tan Da Nguyen, Trong Nghia Le, Minh Trung Nguyen, Trung Kien Nguyen, Le Dai Thanh Hoang

      Abstract

      In recent years, cement deep mixing (CDM) columns have been widely adopted as a ground improvement solution for enhancing the stability of excavation bases in the basement construction of high-rise buildings on soft soils in Ho Chi Minh City. This technique plays a vital role in improving the mechanical characteristics of soft soils, including unit weight, shear strength, and elastic modulus. A total of 580 CDM samples were collected by core drilling from 65 in-situ CDM columns. Unconfined compression tests were carried out to determine the unconfined compressive strength q_u, elastic modulus E₅₀, and unit weight γ_CDM of the CDM columns. The study aims to assess the critical engineering properties of CDM columns, with emphasis on q_u and E₅₀, in the context of deep excavation for basement construction. This study investigates the correlation between the unit weight of natural soil and that of CDM columns, evaluates the E₅₀/q_u ratio. The findings of this study provide a practical framework for engineers to assess potential risks and enhance the reliability of design and construction practices for multi-basement structures with excavation bases reinforced by CDM columns.

   4. A Comprehensive Review of Load Distribution in Piled Raft Foundations: Effects of Pile Number and Spacing on Pile–Raft Interaction

      Vo Van Dau, Vo Phan, Le Ngoc Tan, Tran Van Tuan, Pham Huu Ha Giang

      Abstract

      This study provides a comprehensive review of load distribution behavior in piled raft foundations, with emphasis on the effects of pile number (n) and pile spacing (S) on the interaction between the raft and pile system. Results from analytical models, numerical simulations, and physical model experiments are synthesized to assess how these geometric parameters influence the proportion of vertical load carried by the raft and the piles. A consistent trend is observed: increasing the number of piles leads to a decrease in the load share carried by the raft (P_r/P_t) and a corresponding increase in the load carried by the piles (P_c/P_t). This indicates that, as pile density increases, the pile system gradually assumes a dominant role in supporting vertical loads. Conversely, increasing the pile spacing from 2.5D to 5D results in a higher raft load share for the same number of piles. This trend is more pronounced in configurations with fewer piles, where reduced interaction between widely spaced piles requires the raft to absorb a greater portion of the load. Comparative results also reveal that modern approaches, particularly physical modeling, finite element modeling (FEM), and advanced analytical methods, exhibit higher sensitivity to geometric variations and better capture the nonlinear nature of pile–raft interaction than simplified linear models. The convergence of results across different methods demonstrates the reliability of these approaches and their potential for improving foundation design practices. This review highlights the need to incorporate interaction effects into design guidelines to ensure accurate modeling of load sharing in piled raft systems.

   5. Investigating Natural Frequencies of Sand Soil Ground for Predicting Landslide Based on Field Tests

      Quynh Le-Bao, Toan Pham-Bao, An Huynh-Thai, Nhi Ngo-Kieu

      Abstract

      To predicting the landslide ability of sandy soil around the riverbank area, a field test for the vibration propagation of the ground surface at different positions from a fixed vibration excitation was performed near the river. While the current standards for ground vibration focus on predicting the vibration amplitude, this paper studies the frequency content. By analyzing the vibration response in all three directions under impact loads that are susceptible to resonance, the natural frequencies were extracted to evaluate the characteristics of the ground. Then, a novel indication for landslide is presented based on the appearance of natural frequencies in each vibration direction. The effectiveness and suitability of this evidence based on the transmission capacity and matched vibration model. It is showed that the vibration response of the ground weakens not only with a decrease in frequency when stiffness of soil reduce but also with an increase in the number of frequencies when soil layers lose cohesion. This study provides reference for disaster prevention agencies and for construction planning along river areas.

   6. Displacement Analysis of CDM Retaining Walls with CDM Bottom-Enhanced Stability in Soft Ground Excavation in Ho Chi Minh City

      Thanh Nhan Pham, Minh Trung Nguyen, Khac Tan Da Nguyen, Trong Nghia Le, Trung Kien Nguyen, Ha Dang Nguyen

      Abstract

      The use of Cement Deep Mixing (CDM) columns has become increasingly common in the construction of deep excavations in soft soil conditions. CDM columns are employed both to improve the ground within the excavation area and to serve as retaining walls in construction projects involving one or more basement levels. The horizontal displacement of CDM walls serves as an important indicator of the stability of the excavation and the safety of adjacent structures. This study investigates the horizontal displacement behavior of CDM walls by varying the CDM replacement ratio in the improved zone. The analysis is conducted through a comparison between numerical results obtained using the finite element method and field data from 32 monitoring points. Based on this comparison, the study evaluates the influence of CDM replacement ratio on the displacement pattern of CDM walls in deep excavation projects.

   7. An Undrained Cyclic Behavior of Reinforced Liquified Stabilized Soil Cured Outdoor

      Hung Khac Le, Hieu Minh Dao, Phuong Nguyen Ngoc

      Abstract

      Liquefied Stabilized Soil (LSS), a cement-stabilized soil pre-mixed in Japan, is a common application for excavated soil. This study examined the LSS behavior under cyclic loading using Consolidated-Undrained triaxial cyclic testing with cyclic deviator stress of amplitude variation on 10 kg/m³ fiber content cured 28 days outdoor. Following test results, both indoor and outdoor curing do not cause liquefaction. The existence of a critical stress level in cases of outdoor curing between 0.6 and 0.72 of stress ratio SR, which is higher compared to indoor curing. The results also conclude that at low cycle stress levels, LSS cured outdoor exhibits improved elasticity, while at high stress levels, strain softening increases. This is due to outdoor cement-hydration. In addition, LSS cured outdoor under high cyclic stress has higher stiffness degradation, strain energy dissipation, and inelasticity accumulation than indoor LSS.

   8. Performance of Piles Socketed in Weathered Rock

      Huu Nghia Bui, Thai Trung Le, Nhu Y. Nguyen, Hoang Nghi Le, Dang Khoa Nguyen, Van Qui Lai

      Abstract

      The paper presents a novel study on the performance of axially loaded piles socketed in rock. The finite element commercial software Plaxis is applied to simulate the axially loaded piles. The Hoke-Brown model is adapted to capture the behavior of Rock. The paper’s obtained results are verified with field test results. An agreement between the analysis results and the field test results is obtained. These results can be an effective tool for practical engineering in designing the resistance of axially loaded piles socketed in rock.

   9. A Novel Approach to Multi-objective Topology Optimization of Pile Foundations: The MOMPA Algorithm

      Truong Vu-Huu, Thanh Cuong-Le

      Abstract

      This paper explores the application of the Multi-Objective Marine Predator Algorithm (MOMPA) to a real-world engineering challenge: the topology optimization of the pile foundation of a Mooring Dolphin at Hai Linh LNG port in Vietnam. MOMPA, inspired by the hunting tactics of marine predators, is well-suited for solving problems involving multiple competing objectives. The study aims to reduce the overall weight of the pile foundation while ensuring that structural displacement remains within safe limits. This research demonstrates MOMPA’s ability to deliver practical, cost-effective design solutions for complex marine structures by optimizing the piles’ topology and cross-sectional properties. The findings suggest that MOMPA is a promising tool for enhancing the efficiency and safety of civil engineering designs.

   10. Influence of Earthquake Frequency Content on Soil Liquefaction

       Van-Quang Nguyen, Trong-Kien Nguyen, Tan Hung Nguyen, Usman Pervaiz

       Abstract

       This study aims to identify earthquake intensity measures (IMs) that have a reasonable correlation with pore water pressure (PWP). Moreover, the effect of earthquake frequency contents on site response is also investigated. To this end, the centrifuge model test (RPI2) soil profile used in the LEAP-2017 project and twenty input ground motions are employed to conduct effective stress analyses utilizing the one-dimensional (1D) site response analysis (SRA) program. The stress-based simulation model is first validated with centrifuge test results. Afterwards, two sets of analyses are carried out: (1) the analyses with twenty recorded motions to determine the optimal IM for PWP, (2) the analysis with scaled motion to examine the effect of earthquake frequency content. The numerical results show that peak ground acceleration (PGA), characteristic intensity (I_c), acceleration that accounts for up to 95% of the arias intensity (A₉₅), root-mean-square of acceleration (A_rms), and sustained maximum velocity (SMV) are the IMs that yield the most advantageous and accurate predictions for PWP. In contrast, PWP exhibits a weak correlation with the predominant period (T_p), mean period (T_m), PGV_max/PGA_max, and maximum displacement. In comparison to low-frequency (LF) ground motions, high-frequency (HF) ground motions tend to generate more significant site responses and lead to increased pore water pressure (PWP) in near-surface soil layers. HF motions lead to higher levels of spectral acceleration at the short-period and lower levels at the long-period.

   11. The Effectiveness of Applying High-Strength Geotextile on Top of Timber Piles for Foundation Reinforcement

       Phu-Huan Vo Nguyen

       Abstract

       Currently, timber piles are a widely used material in Southern Vietnam for reinforcing weak soil foundations prior to construction. However, Vietnam has not yet established any standards or guidelines for the design and calculation of this method, with most applications relying on empirical knowledge. In practical construction, a sand layer is typically placed on top of cừ tràm to enhance its performance, but there has been no specific research conducted on this practice. In this study, based on the results of static load testing on timber piles foundations, the authors evaluate the method using finite element analysis for comparison. Furthermore, the study proposes an enhancement to the efficiency of timber piles by incorporating a layer of high-strength geotextile above the timber piles. This research provides valuable insights for optimizing timber piles-based foundation reinforcement methods and suggests a practical approach for improving construction efficiency on weak soil.

   12. The Effectiveness of the DMM Method in Ground Improvement for Stability During Soil Treatment

       Phu-Huan Vo Nguyen

       Abstract

       Ground improvement in southern Vietnam has been extensively studied and implemented in various port projects, with the deep mixing method (DMM) emerging as a relatively new technique applied in a few ongoing projects. In addition to enhancing slope stability, reducing settlement is also a primary objective of soft ground improvement. This research aims to evaluate the effectiveness of the DMM approach. Field mowing and data analysis were conducted to assess the method’s performance and verify the quality of DMM piles combined with surface treatment. A full-scale test was performed using a surcharge applied to the design load, enabling the verification of both elastic and long-term settlement. For comparison, a site utilizing the preloading method with prefabricated vertical drains (PVD) was also studied. The findings revealed that DMM piles significantly reduced vertical settlement and lateral movements by up to 95% compared to the PVD method. Additionally, the incorporation of surface treatment further decreased the stress concentration ratio due to an enhanced arching effect.

   13. Predicting Liquefied Soil Settlement Using Boosting-Based Machine Learning Models

       Trung Hieu Tran, Van Than Tran, Thanh Danh Tran

       Abstract

       Soil liquefaction-induced settlement is a critical issue in geotechnical engineering due to its potential to cause severe structural damage. Traditional prediction methods often lack accuracy and adaptability when handling complex, nonlinear relationships in soil behavior. In this study, we explore the effectiveness of five boosting-based machine learning models—AdaBoost, Gradient Boosting Machine (GBM), XGBoost, LightGBM, and CatBoost—for predicting post-liquefaction settlement based on geotechnical input parameters. A real-world dataset containing key soil properties and corresponding settlement measurements was used for training and evaluation. The performance of the models was assessed using multiple metrics, including Mean Absolute Error (MAE), Mean Squared Error (MSE), Root Mean Squared Error (RMSE), and the coefficient of determination (R²). Among the models, CatBoost demonstrated the highest prediction accuracy with an R² score of 0.9705 on the testing set, outperforming both traditional regression techniques and other ensemble models. The findings confirm the potential of boosting algorithms, particularly CatBoost, in accurately modeling complex soil behavior, offering a valuable tool for engineers in liquefaction risk assessment and mitigation planning.