Azman Kassim

Tree Water Uptake And Suction Distribution On Tropical Residual Soil Slope

This paper present an exploration of soil matric suction effected by water uptake via tree root at toe of slope on various condition between wet condition (high rainfall) and dry condition (prolonged no rainfall). Matric suction generated by active root tree has substantial influence soil moisture content on residual soil slope. A field monitoring was carried out to collect matric suction data at slope in two conditions; with a tree located at toe of slope and absent of a tree. The installations of instruments particularly at slope with tree at toe were placed within vicinity of the tree with certain depths and distances. The matric suction data from field monitoring was influence by the rainfall events that lead to the instability of soils slope. Analysis of soil matric suction distribution pattern indicates that the highest matric suction value was at shallower depth and proximity of tree. The matric suction profiles obtained from field monitoring are applied as an input data to develop soil matric suction contour. The effect of transpiration driven by active root zone generated matric suction on soil at vicinity of tree may create dry soil to increase soil shear strength.

Influence of relict joints on permeability of residual soil

Weathering process of granitic material results in the formation of relict joint in lateritic layer of the weathering profile. The number and arrangements of the relict joints affects the permeability of the residual soil which invariably affects water flow and suction distribution in the residual soil. Although the permeability of residual soil without a relict joint can be determined using standard permeability test, it is difficult to be measured when a relict joint is incorporated due to limitation of size and area of the standard equipment. Hence, modified permeability test equipment is introduced in this study. Two arrangement of the relict joint in the equipment were considered. In the first arrangement one relict joint with various spacing were tested while the orientation and spacing of the relict joint were tested using two relict joints in the second arrangement. The results obtained shows that the permeability of the residual soil due to one and two relict joint varies by two orders of magnitude. Therefore, the number and spacing of relict joints modified the permeability of residual soil.