Pls diagnose a landslide investigation at 2017 Biliran landslide. Make an introduction to the problem and field investigations methods.

 

Introduction

Geologist claims that open pit mining in the island of Biliran is to be blamed for the landslides during the onslaught of Tropical Depression Urduja.

            Geologists that it was not mining but rather other factors were identified to have contributed to the occurrence of the landslides as follows:

1. Intensely weathered, fractured and altered volcanic rocks with clayey materials underlying the areas;
2. Continuous heavy rainfall brought about by Typhoon Urduja which loosened the topsoil with boulders and uprooted the trees;
3. Slope gradients of approximately more than 45% which is considered Very High based on established MGB Landslide Susceptibility Rating parameter;
4. Presence of points of weaknesses along roadcuts, riverbank portions and sloping mountainous areas; and
5. Unstable grounds due to road development, farming and poor drainage systems.

Geologists have not come across any ongoing or remnants of previous open pit mining/quarrying activity within the vicinities of the landslide areas that may have contributed to such occurrence of landslides. The landslides, however, mostly occurred on vegetated areas where coconuts and fruit bearing trees are present.

Methodology

In the primary phases and after the field works and providing different maps, nine following factors Altitude classes, slope, aspect, rainfall, lithology, land use, distance from road, distance from fault and distance from hydrographic network, were determined as primary effective factors on landslides occurrence.

Also, landslides distribution map of the area with doing field works and GPS recording is derived.After this phase all of the maps with using GIS techniques need to analyzed. Then, each of the primary effective factor maps has been crossed with landslides distribution map. With doing this work, is determined that two factors, aspect and distance from hydrographic network are not effective on landslides occurrence of the area.

Landslide is a phenomenon of mass movement of terrain. ... The behavior of the landslide is usually measured by extensometer, inclinometer or GPS (global positioning system). These equipments are measuring some points or along the lines; it is difficult to measure the whole landslide