Ishola Valere Loic Chango

Bio: Ishola Valere Loic Chango is an academic researcher from Harbin Institute of Technology. The author has contributed to research in topics: Pile & Geogrid. The author has an hindex of 1, co-authored 1 publications receiving 5 citations.

Dynamic Response Analysis of Geogrid Reinforced Embankment Supported by CFG Pile Structure During a High-Speed Train Operation

Abstract: The performance of railroad structure has a tremendous influence on the safety and stable operation of high-speed trains. Strong vibrations and the degradation rate of the track are the main factors affecting the transport safety of a railroad built over a weak soil. Geogrid reinforced embankment supported by pile structure is a new efficient construction technique used to ensure the stability and enhance the performance of the railroad system; but only a few studies are oriented to its behavior under train operation. This paper investigates the dynamic response of geogrid reinforced embankment supported by cement fly-ash gravel pile structure during a high-speed train operation. The establishment of a realistic simulation model for railroad subjected to a moving train load, is an important first step towards the reliable design of geogrid reinforced embankment supported by pile structure. Thus, a 3D nonlinear FEM has been established to simulate the instrumented Harbin-Dalian railway test section. Each train carriage was modeled as a transient dynamic load through a user-defined Dload subroutine. The developed model was successfully validated by the dynamic response recorded from the field test section. The improvement of the railroad structure by the CFG piles and geogrids contributed significantly to the reduction of the vibration in the structure, which attenuates 1.2 times faster with the structure depth, even under overload conditions. Moreover, the phenomenon of resonance observed when the train reaches speeds of 100 and 260 km/h were annihilated. The analysis of the stress distribution within the embankment revealed that a dynamic arch is formed in the embankment at 2 m from the ground. The stress onto the pile was 16 times greater than that acted on the soil and the tensile stress developed in the geogrid was high at the piles edge below. In addition, the coupling effect of geogrid with various tensile strengths and the piles with different strength grades indicated that the combination of a high-strength pile and geogrid significantly reduces the displacement gap due to the variation of train speed. As a result, the vibrations of the track were almost constant during the train operation; thus, ensuring comfort to passengers and reducing the risk of derailment.

Numerical and Statistical Evaluation of the Performance of Carbon Fiber-Reinforced Polymers as Tunnel Lining Reinforcement during Subway Operation

Abstract: Ground vibrations during train operations have become a serious problem in recent years. Local residents often feel disturbed by the vibrations emanating from the railroad line. This inconvenience is particularly pronounced in loose areas traversed by subways. However, improving the mechanical properties of tunnels has been the subject of several studies. Among these works, the widely discussed fiber-reinforced polymer (FRP) is considered as a material that can be incorporated into the tunnel structure to increase stiffness, durability, and corrosion resistance. However, the function of FRP in the interaction between the soil and the tunnel during operation has scarcely been studied. In this study, the effectiveness of carbon fiber-reinforced polymers (CFRP) as reinforcement of tunnel lining on ground vibration is investigated. For this purpose, a nonlinear 3D finite element model was developed based on a subway section in Shanghai to simulate the dynamic behavior of the system. The moving subway load was modeled as a transient dynamic load via a DLOAD subroutine, in which the rail irregularities are taken into account. The numerical model was efficiently validated by field tests. Then, the efficiency of using CFRP as concrete reinforcement of the tunnel lining during the subway operation was investigated. In addition, a statistical analysis of the ground dynamic response depending on the CFRP bars properties is presented, evaluated, and discussed.

Analysis of Load Transfer in Geosynthetic-Reinforced Pile-Supported Embankments

Abstract: Geosynthetic-reinforced pile-supported embankments (GRPSEs) have proven to be an effective and economical technique to address the problems posed during the construction of embankments on soft soil or other special soils. A numerical study has been conducted to investigate the soil arching effect of GRPSEs including load transfer on pile and soil. Numerical results show a significant correlation between the height of embankment, the pile spacing and the tensile stiffness of geogrid. An empirical model considering these factors based on a theoretical model is presented, which can reasonably calculate the vertical stress on the cushion and the foundation soil. The study on internal stress distribution in soil arching is also helpful for understanding the behavior of this embankment structure.

Finite-Element Simulation of Instrumented Asphalt Pavement Response under Moving Vehicular Load

Abstract: Understanding the structural behavior of layered asphalt pavements subjected to dynamic moving wheel loads is a crucial requirement for the future design of more-durable pavement structures...

CFG Pile Composite Foundation: Its Engineering Applications and Research Advances

Abstract: Problematic soils exist almost everywhere on the globe. State-of-the-art solutions to make civil engineering infrastructures built on them are still highly sought. The CFG (cement-fly ash-gravel) pile composite foundation system has been widely used in buildings, highways, railways, and bridge transition sections owing to its proven engineering characteristics in soft ground treatment. This paper discusses about the development and achievements of its engineering applications, along with possible future research directions. The remarkable evolution took place in the past to address projects’ strict differential and postconstruction settlement control requirements including embedding the geosynthetic layer into the load transfer platform and combining it with rigid slabs, as seen implemented in few CFG pile-supported embankments. It was also observed that the interaction of the existing CFG pile composite foundation with an adjacent new foundation pit excavation inevitably presents a complex soil-structure interaction mechanism among the fundamental components—the retaining wall, mat, piles, cushion, and soil.

Improved methods to prevent railway embankment failure and subgrade degradation: A review

Abstract: Railway transportation is one of the most advantageous modes of transportation because of its high capacity, which obviates the increasing demand for conveying passengers and cargo. However, high initial costs and ongoing maintenance costs (partially resulting from the degradation of the subgrade and embankments) are drawbacks. Besides, railway subgrade soil experiences a high impact load and alternate drying-wetting and freeze-thawing cycles. In order to counter these problems, various kinds of soil improvement have been employed to improve the engineering properties of soils and minimise embankment and subgrade degradation. Chemical, mechanical, and geosynthetic techniques are currently being used to improve railway embankments. Some methods, such as columnar systems and deep mixing, fortify embankment foundations or subsoil, while others (e.g. chemical binders) can be used as mixed material to stabilise embankments and subgrade soil to a shallow depth. Hence, this review paper first discusses the correlation between railway track elements, failures, and the degradation of embankments in railway networks, and then compares the soil stabilisation techniques from multiple aspects.