A Geotechnical Investigation of 2017 Chattogram Landslides

Md. Azijul Islam,Mohammad Shariful Islam,Abhijeet Acharjee Jeet

doi:10.3390/geosciences11080337

Md. Azijul Islam, Mohammad Shariful Islam + Show 1 more

Open Access

https://doi.org/10.3390/geosciences11080337

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Abstract

In this study, an attempt is made to uncover and discuss the geo-environmental characteristics, triggers, and consequences of a landslide disaster in the Chattogram Hill Tracts (CHT) region of Bangladesh. The hilly areas are composed of Tertiary and Quaternary sediments which have been folded, faulted, uplifted and, then deeply dissected by rivers and other water bodies. This paper presents a case study on the geotechnical investigation and numerical modeling of the landslides of 13 June 2017. A field visit and soil sample collection, followed by laboratory testing were conducted at the landslide-afflicted areas. The study revealed that the soil type was an important factor behind landslides, while high precipitation, hill cutting, deforestation, and unplanned human settlements act as contributing factors behind the landslide disaster. Extensive analysis of the geotechnical facts has been carried out, and an attempt is made to pinpoint the cause. A finite element modeling was conducted using PLAXIS 2D to investigate the failure mechanism. The numerical modeling results have suggested that most of the hill slopes were susceptible to failure after heavy rainfall. A conclusion is drawn that the landslides were triggered by incessant rainfall infiltrating into the subsoil, which led to a notable increase in its degree of saturation and a simultaneous reduction in suction and shear strength of the soil.

Highlights

The natural phenomenon of landslides is common and a major cause of casualties and damage to public and private property around the world
Result and Discussion The5.a2n. aRlyessuislt raensduDltsisschusoswionthat the factor of safety (FS) for all six landslide slopes (Table 2; FiguTrhee2a)nisallyessiss trheasunlt1s.4s.hAowcctohradtinthgetfoacatoprreovf isoaufestyst(uFdSy),faonr aFlSl sliexslsatnhdasnlid1.e4silsopes (Taquestionbalbele2;fFoirgduarme 2s)ainsdlesslsotpheasna1n.d4. aAncFcoSrldeisnsgthtoana 1p.r0eivsiouunssasfteud[3y6,]a. nThFeS olebstsaitnheadn F1.S4 is quesindicatestiothnaatbsloemfoer odfatmhse aslnodpeslsowpeesreansudpapnoFsSedletsos ftahial n(S1-.10, iSs-3u,nSs-a4f,ea[n3d6]S
Excessive rainfall infiltrates into the soil and can make clay very soft

Summary

Introduction

The natural phenomenon of landslides is common and a major cause of casualties and damage to public and private property around the world. Different types of geotechnical investigations and numerical analyses have been conducted for understanding the landslide phenomenon. The triggering factors for landslides include changes in slope geometry, excessive rainfall, infiltration of rainwater, and lack of a proper drainage system [1,2]. There are different methods available to investigate the landslide susceptibility and stability of slopes. Conventional slope stability analysis includes the ordinary method of slices, Bishop method of slices, kinematic analysis, limit equilibrium analysis, etc. The complex nature of the problem has led to limitations in classic geotechnical engineering methods for stability assessments. Numerical analysis has become more useful to investigate the landslide risk. A researcher developed a methodology through numerical analysis which can identify the rainfall-induced landslide-prone areas [8]

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