Nurly Gofar

Extreme rainfall characteristics for surface slope stability in the Malaysian Peninsular

This paper discusses the results of an investigation on the influence of rainfall intensity and duration on the suction distribution within a soil mass. A series of numerical analyses were conducted on an infinite slope model to simulate the responses of the slope consisting of typical soil types to various rainfall intensities and durations from selected locations in the Malaysian Peninsular. The study showed that the critical duration was governed by three major factors: the saturated permeability of the soil, the geographical location, and the depth of the slip plane. The critical rainfall duration for highly permeable soil was 1 day, while 30 days of antecedent rainfall were required for the stability analysis of a slope made of soil with low saturated permeability. The critical duration of antecedent rainfall in soils with intermediate saturated permeability was found to vary with the rainfall pattern. A chart is proposed to determine the critical duration, critical intensity and critical suction for each type of soil.

Effect of concrete waste particles on infiltration characteristics of soil

Demolition of old buildings to create space for new development resulted in the near surface soil (topsoil) to be mixed with particles derived mostly from concrete wastes. This condition could affect the infiltration capacity and surface runoff, therefore, storm-water management of the area. This paper presents results of study on the effect of concrete waste particles on the hydraulic properties and infiltration capacity of the topsoil. Laboratory tests were performed to compare the hydraulic properties of the topsoil and the mixture of topsoil and concrete particles. Laboratory infiltration column test was performed on the mixture to evaluate its infiltration capacity. Results from the laboratory tests indicated that the presence of particles from concrete waste decreased the water-holding capacity and permeability, thereby the infiltration capacity of the ground surface. The results were supported by numerical analysis performed using the same material and boundary conditions as the column test. Parametric study was performed on both the topsoil and the mixture to extend the results of infiltration test to different materials under different ranges of rainfall intensity. The parametric study showed that the presence of concrete particles increased the run-off and the effect increased as the rainfall intensity increased. Therefore, the increase in runoff coefficient should be considered for the storm-water management when the near surface soil is mixed with concrete waste.

THE EFFECT OF BLAST DESIGN IN A CONTROLLED BLASTING

The use of blasting operations in constructions nowadays is not rare anymore. The presence of hard materials during excavation works can disrupt the progress of the project since it cannot be excavated using the conventional excavators. Indirect excavation assessment is the best way to assess the best excavation method prior to the actual excavation works. Past experiences have shown that rippers are up to the mark for soft-rocks. Nevertheless, sometimes rippers fail to reach the desired productivity and will increase the cost and time of the project. As a solution, blasting operation is normally employed in most cases. The blasting operation must be monitored and controlled especially if it is carried out at sensitive area to avoid damage to property, buildings and injuries to people. , This study looks at 2 actual case studies of controlled blast at Seri Alam and Gelang Patah, Johor, Malaysia which have different geological material. Seri Alam is a granitic area and has a lot of boulders to be blasted while Gelang Patah site comprises of old alluvium. The results showed there are differences in the blast design especially on the spacing and burden at these sites in order to achieve the desired fragmentation and to control flyrock.

SURFACE AND GROUNDWATER CONTAMINATION DUE TO MINING OF TIN AND IRON– A CASE STUDY IN JOHOR, MALAYSIA

Active and abandoned mines in Kota Tinggi, Johor, have raised environmental concern over heavy metal contamination. Arsenopyrite in tailing and ore body could be the source for acid water generation and subsequent acid mine drainage processes. According to the hydrochemistry facies classification, groundwater has Na-K-Ca, HCO3 character with trend toward sulfatic, near mining area. Two water quality indices have been used for groundwater and surface water assessment, which reveal low heavy metal dissolution, both in tailing and working sites. According to Ficklin diagram, surface water lies in near neutralhigh metal content boundary, that shows relatively high dissolved heavy elements in mining area. When compared to the INTERIM IIA/IIB standard for supply water in Malaysia, it shows that Cu is higher than the limit and As is almost reaching the threshold level.