Abstract
The paper presents the case study of the recurrent slope movement in colluvium deposits at Doi Chang, Thailand. A thorough site investigation confirmed the slope movement rate corresponding to slow creep during dry season, while in the rainy season, its velocity remarkably increased. Despite frequent repair, the movement rate was sufficient to result in the recurrent damage of infrastructures like roads and buildings, causing economic loss and public concerns. Furthermore, surface mapping revealed that the hill's topography led to the concentration of flowing water in a particular area. This resulted in a high level of groundwater table, especially during the rainy season. The inclinometer installed in that area suggested an average movement rate of 20.5 mm/month in the wet season. In contrast, during the dry season, it was limited within 2 mm/month, indicating that the increase in the rate of slope movement in the colluvium deposit was primarily due to the rising groundwater table. Field and laboratory tests were conducted to determine the properties of the colluvium deposit. Landslide susceptibility assessment was performed using infinite slope model and later integrated with GIS to evaluate the factor of safety (FS) over a large area. The FS decreased below 1 when the groundwater level rose to 0.3 cm below the ground surface, and using GIS, based on infinite slope model, the potential risk zone were delineated.
Highlights
The exploration of landslide behaviour in the scientific community dates back to the first half of the twentieth century[1,2]
The settlement in Doi Chang is growing, but the locals reported the recurrent damage of the infrastructures like walls, buildings, and roads in the area
Colluvium materials consist of soil, and rock debris with a heterogeneous mixture of grain sizes varying from large boulders to clay particle at the base of hill slopes
Summary
The study area is located at Doi Chang village, Vavee sub-district, Mae Suai District, Chiang Rai province, Thailand. The settlement is concentrated mainly at the middle portion of the slope (Fig. 1), where the locals had been reporting recurrent damages to the infrastructures. 7% of the total houses were categorized under severe damage, 35% under slight damage, 13% under moderate damages, while 45% of the houses reported no damage at all. Such categorization of the buildings was done on the basis of the extent of visible c racks[16]. It was noticed that houses categorized under severe and moderate damages fall mainly within a specific geographic location. The flow lines indicate the direction of water flow which appeared to converge in the area where the major and moderate damages of the houses were reported
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