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CONTENTS
Volume 40, Number 5, March10 2025
 

Abstract
The traffic congestion in many cities in China especially during the peak hours has led to the building of new subways. The development of public transportation can reduce the use of private vehicles, thereby reducing road traffic congestion. In this paper, a case study in Chongqing City including a big tunnel section with a diameter of 26 m will be shown. In addition, two small tunnel sections laying orthogonal with the main tunnel (big section) will also be studied. Wind ventilation is located between the two small tunnels have also been excavated. To investigate the deformation characteristics of such dense excavation procedures 3D FEM model has been built. The numerical simulation resulting data with the site monitored determined points has been compared. However, the comparison shows good agreement. Moreover, according to some sections of the big tunnel which includes a dense urban area with the above structures, a raft building with different piles diameter as a foundation support has been considered. Based on the numerical simulation as an effective tool, huge data has been generated to investigate the extension of the spreading of the influenced zone due to the excavation of three types of tunnels: the first is the big tunnel section with a diameter of 26 m. The second is a tunnel section with 13 m. While, the final tunnel case is twin tunnels, each tunnel has a diameter of 13 m. These tunnel cases have been studied and the interaction between (different piles diameter + raft) systems and different tunnel diameters has also been investigated. The influenced area has been proposed according to each tunnel case. However, the results show that 'R' ratio which represents the pile settlement after the excavation divided by the pile settlement before the excavation has much more difference in comparison with the extension area of the disturbanc

Key Words
big tunnel section; dense urban areas; extension of the disturbance; influenced zone

Address
Lojain Suliman and Changbao Jiang: National Joint Engineering Research Center of Geohazards Prevention in the Reservoir Areas (Chongqing), Chongqing 400045, China
Xinrong Liu: State key laboratory of coal mine disaster dynamics and control, China
2College of Civil Engineering, Chongqing University, Chongqing 400045, China;
State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China;
National Joint Engineering Research Center of Geohazards Prevention in the Reservoir Areas (Chongqing),
Chongqing 400045, China
Xiaohan Zhou, Yuxuan Chen and Lei Fang: State key laboratory of coal mine disaster dynamics and control, China
2College of Civil Engineering, Chongqing University, Chongqing 400045, China;
State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China

Abstract
Optimal use of construction materials takes center stage in engineering problems so much so that new techniques are daily proposed. Application of shell footings with various geometries are good cases in point in the novel system of foundation engineering. This study aims to present a numerical simulation of laboratory model tests by FLAC 3D software, developing an understanding of the behavior of shell strip footing located at the adjacent of unreinforced and geotextile-reinforced slopes. In this regard, bearing capacity and settlement of the shell foundations by considering contributory factors, notably apex angles, distances of the footings from the crest of the slope namely "edge distance", slope angle, stiffness of the footing core in shell footings, and reinforcement status were studied. The results indicated that the ultimate bearing capacity of foundations increases with decrease of apex angle and increase of footings edge distance. It was also observed that the core in shell footings plays a key role in stress transfer though the foundation depth so that dense soil among the others brought about the highest bearing capacity. At the end, the applicability and interpretation of the obtained results for prototype model were discussed.

Key Words
bearing capacity; numerical modelling; reinforced soils; shell footings; slopes

Address
Gholamhosein Tavakoli Mehrjardi, Masoud Khoshnevisan and Elham Sattari: Department of Civil Engineering, Faculty of Engineering, Kharazmi University, Tehran, Iran

Abstract
In geotechnical engineering, the limit equilibrium technique is known as a widely used method in slope stability analyses. There are many different methods in the literature for this technique to be used in slope stability analyses. Among these methods, the Morgenstern-Price method provides more realistic results compared to other methods since it considers equilibrium conditions of both force and moment and thus provides solutions. Therefore, this study integrates the Morgenstern-Price (M-P) method with the Jaya optimization algorithm to determine critical failure surfaces and safety factors in slope stability analysis. Since finding the minimum safety factor and the associated critical failure surface is essentially an optimization problem, Jaya algorithm, which is one of the many algorithms for solving this optimization problem and also works faster and reaches the result in a shorter time due to its simple structure, was used. For the purpose of examining the performance and currency of this optimization method, two case studies are analyzed and compared with existing optimization methods. The results demonstrate that the Jaya algorithm achieves comparable or improved performance in identifying critical failure surfaces while maintaining computational efficiency.

Key Words
critical failure surface; jaya optimization; morgenstern-price method; safety factor; slope stability

Address
Emel Turker: Department of Civil Engineering, Karadeniz Technical University, 61080, Trabzon, Türkiye

Abstract
In this paper, a finite element formulation for the impact-induced waves in a variable cross-section rod that collides with a rigid mass is provided. The rod has either fixed, free, or deformable support conditions. The analysis is based on St. Venant's contact theory. The effects of boundary conditions, mass ratios, and geometrical shape of the rod upon stress wave propagation, contact force, displacement, and velocity are thoroughly analyzed by illustrative examples. The proposed finite element formulation considers the rod and the struck mass as one system during the contact period to eliminate the discontinuity at the arrival of the impact wave to the contact end, which gives accurate results. Excellent agreement is found between the finite element results and analytical solution using the mode superposition method for the fixed support boundary condition. The results show that the presented formulation can be used to model many systems with variable cross-section rods that are subjected to longitudinal impact. For instance, it can be used as a basis for modeling nanostructures under impact loads, as benchmark templates for crack detection, and for validating approximate analytical solutions.

Key Words
conical rod; finite element analysis; longitudinal impact; stress wave propagation; superposition method

Address
Ragab M. Etiwa and Hesham A. Elkaranshawy: Department of Engineering Mathematics and Physics, Engineering Mechanics Division, Alexandria University,
Alexandria, Egypt

Abstract
The soil-squeezing effect induced during the construction of secant piles can significantly affect the surrounding strata and existing structures. Managing the deformation caused by secant pile construction is crucial to mitigate adverse effects. While much has been studied on the effects of secant pile construction on surrounding soil, few studies focus specifically on the deformation of high-speed railway bridge foundations in these contexts. This study integrates on-site measurements with numerical analysis. It investigates the deformation effects of secant pile construction on surrounding strata and adjacent highspeed railway bridge foundations. A finite element model was developed. The model was used to validate the feasibility of the calculation method for cylindrical cavity expansion and the equivalent simplification of three secant piles in simulating the soil - squeezing effect during construction. Based on these findings, an additional finite element model was created to assess the deformation of high-speed railway bridge piles resulting from the construction of secant piles. The model's computations considered scenarios involving secant piles constructed on single-side and on double-sides (both symmetrically and asymmetrically) of the bridge pier. This article provides insights into the impact of secant pile construction on adjacent bridge piles and offers recommendations for mitigating deformation.

Key Words
cylindrical cavity expansion; high-speed railway; numerical analysis; secant piles; soil-squeezing effect

Address
Changdan Wang, Bingjun Wang, Shunhua Zhou and Jinglong Wang: Shanghai Key Laboratory of Rail Infrastructure Durability and System Safety, Tongji University, Shanghai 201804, China
Xiaolong Li: Shanghai Donghua Local Railway Development Co., Ltd., Shanghai 200071, China
Jingjing Xu: China Railway 24th Bureau Group Co., Ltd., Shanghai 200070, China

Abstract
Urban development often necessitates underground construction activities such as basement excavations and tunneling, in close proximity to existing pile foundations supporting high-rise structures. This study investigates the combined effects of basement excavation followed by tunneling on single pile foundation in stiff clay using three-dimensional coupled consolidation numerical modelling. To ensure realistic soil behaviour, an advanced hypoplastic constitutive model for clay was employed, incorporating small-strain stiffness, and stress dependent dilatancy of soil. This research focuses on the response of single piles subjected to sequential basement excavation and tunnelling activities. A parametric study was conducted, analyzing three different basement excavation depths and three tunnel positions relative to the pile. These combinations include scenarios where the formation levels and tunnel depths are near the pile shaft (SeSt case), near the pile toe (TeTt case), and below the pile toe (BeBt case). In each scenario, the tunnel excavation was simulated after the basement excavation. The results reveal that tunnelling following basement excavation induces significant pile settlement and alters axial load redistribution along the pile, primarily due to stress release and degradation of soil stiffness. Among the three scenarios, the BeBt case exhibited the maximum pile settlement of 63.1 mm, equivalent to 7.9% of the pile diameter. The TeTt case recorded the highest induced bending moment of 328 kNm, accounting for 43.7% of the bending capacity of the pile. Additionally, the BeBt scenario resulted in the greatest deflection at the pile toe due to basement excavation. These findings provide critical insights for practitioners in assessing pile performance during sequential excavation and tunneling activities.

Key Words
parametric study; pile; sequential excavation and tunnelling; settlement

Address
Naeem Mangi: School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, China;
Department of Civil Engineering, Quaid-e-Awam University of Engineering, Science & Technology, Sindh, Pakistan
Qian Su: School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, China;
Sichuan College of Architectural Technology, Deyang, 618000, China
Zongyu Zhang and Aibo Luo: School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, China
Yanfei Pei: School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, China;
Key Laboratory of High-Speed Railway Engineering of Ministry of Education, Southwest Jiaotong University,
Chengdu, Sichuan 610031, China




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