Karst-Induced Geoharzards in Kenya’s Coastal Region: A Case Study of Vipingo Coral Limestone Quarry

Abstract

As the human population grows, the demand for space to settle and infrastructure development puts a strain on land resources hence people move to occupy areas of difficult terrain such as mountainous regions and karst environments. The trends in anthropogenic activities mean that there will be increased human interaction with the perilous terrain and consequently geohazards associated with them. Studies on geohazards in Kenya have focused mostly on landslides in mountainous regions but not much has been reported on geohazards that are common in areas of carbonate rocks such as coral limestone. Vipingo coral limestone quarry, a coastal quarry, is taken as a case study as a number of hazardous situations have been encountered during mining. This paper outlines the karst features, their formation processes in the coralline limestone rock mass, and the resultant geohazards. Field visits made to the quarry complemented with previous exploration reports enabled the collection of field data on rock mass characteristics, karst features, and potential hazardous sites were mapped out. Karstification is evident in traces of pores and fissures filled with soil in the upper layers of the rock. Cavities, voids, and caves occur randomly in the rock mass and are the genesis of incidents such as bench collapse, sagging of overlying rock slaps leading to sinkholes. The rock mass is weak and prone to slope failures. Suggestions have been fronted for geohazard mitigation and further research work for the scientific community. Thus, this work constitutes an important knowledge base for infrastructure development and any other quarries around the area, and for those who are settled around this karst environment in order to preempt geo-accidents.

Slope stability analysis at soapstone mining sites in Nyamarambe, Kisii County, Kenya

“…Therefore, it is significant to reduce and optimize the slope angles and heights. Undercutting excavation of soapstone rocks as shown in Figure 5 (I) should be avoided and adapt the top-down approach to slope excavations (Atieno & Moses, 2021) [3] .…”

“…This means that the stability conditions of the slopes can be maintained at their equilibrium by slope optimization analysis. Excavated slopes with greater slope heights require less steep angles to maintain the stability of slopes and safety in mining operations (Atieno & Moses, 2021) [3] .…”