Application of remote sensing and GIS techniques for exploring construction material from inaccessible terrains; case study in Eastern Province of Sri Lanka

Demand for construction materials in the North and Eastern provinces of Sri Lanka has risen significantly due to accelerated construction work in progress to restore the destroyed infrastructures during the civil war. Ground surveying methods to locate quarries within this area are not applicable due to security reasons and the larger area to be covered. Thus a Remote Sensing method is suitable for this task. This study introduces a methodology to locate suitable quarries and sand mines for constructions in the Eastern province. LANDSAT ETM+ images were used for classification. Feasible rocks and sand deposits for quarry operations were located using Multicriteria Analysis (AHP).The highly suitable rock quarries and sand deposits were considered in closest facility analysis. The results showed that the integration of Remote Sensing (RS) and Geographic Information System (GIS) can serve as an effective tool in demarcating suitable sites for construction material and this methodology can also be applied for projects of similar nature

Spatial and temporal variation of runoff trend in Sri Lanka during the past decades

Inconsistency of seasonal monsoon weather patterns during the past several decades have a major influence on surface water management system in the in Sri Lanka. The present study aim is to analyze the changes in the inter-annual and intra-annual spatial and temporal variation of surface water flow in Sri Lanka to understand the surface runoff variation under the past climatic change. The spatially distributed hydrological model was calibrated and validated for four different discharge gauge stations in four basins and employed to simulate the natural surface runoff over the period 1975 - 2005 at daily time interval for 39 river basins. The rank-based, non-parametric Mann-Kendall statistical test was used for trend detection due to its robustness for non-normally distributed and censored data. The results confirm that seasonal runoff changes in basins completely located in dry zone are higher and mainly it is limited to 2nd inter and northeast monsoons. Basins located in the west and east show a significant increasing trend in mean annual runoff volume due to precipitation increase in the southwest monsoon to the west and northeast monsoon to the east. However, river basins located in northwest show general decreasing trend in mean annual runoff volume as inter-monsoon precipitation gets reduced. This study concludes that wet zone basins get wetter while leaving the dry zone drier during the past decades along with climate change

Effect of physical and mineralogical properties of aggregates on strength and durability of asphalt concrete

Asphalt is a mixture of aggregates, binder and filler. The performance of an asphalt matrix mainly depends on the characteristics of its constituents along with the quality of construction process. As 94-95 percent of the total weight of asphalt matrix consists of aggregates, the performance of the mixture is greatly affected and influenced by the properties of aggregates. In the local asphalt industry, aggregates used to produce asphalt concrete, are tested and approved for the application only by evaluating physical parameters such as LAAV, AIV, and shape tests. In this research, mineralogical properties of aggregates have been systematically analysed along with the respective physical and asphalt properties. Crushed aggregates and lump samples were collected from a number of metal quarries and asphalt plants, representing rock types from three major geological complexes; Wanni, Highland and Vijayan of Sri Lanka. Tests were carried out to evaluate physical and mineralogical properties of aggregate and Marshall stability and flow values of asphalt mixture. The suitability of aggregates for asphalt pavement construction were discussed using the test results. Findings of the research proposes to consider the collective influence of both physical and mineralogical properties of aggregates when selecting competent materials for asphalt concrete manufacture

Assessment of seasonal impacts on groundwater quantity and quality in upstream of Malwathu Oya Basin

Malwathu Oya Basin which covers 2350km2 located in Anuradhapura district is considerably populated and the safety and the available quantity of water is crucial for the people. Water samples were collected from selected locations during South- West monsoon period, Second Inter monsoon period and North-East monsoon period from September 2016 to March 2017. The samples were analysed for pH, turbidity, conductivity, fluoride, chloride, magnesium and calcium as basic drinking water quality parameters. Only the shallow regolith aquifers are considered for the study. The groundwater quality variation of the area shows a considerable variation from dry season to rainy season in general water quality of the area, and is in acceptable limit for most of the basic parameters. With the seasonal changes Fluoride and Chloride content is higher than permissible limits in some areas

Fluctuations in groundwater level and corresponding earth resistivity changes

The earth resistivity at a known location was frequently measured, through resistivity sounding. Resistivity of subsurface layers could be influenced by the permeability, porosity, transmissivity, composition etc., where moisture content was the concern of this study. ABEM-Terrameter SAS 1000 instrument was used for surveying and data were interpreted using “IPI2-win” software. A borehole was established to reveal accurate subsurface stratification information and monitor the groundwater level, at the surveying location. Groundwater level was recorded through a datalogger in the borehole, at each 12 hour interval. The precipitation data of the area were obtained from the meteorological department to understand the wet & dry seasonal characteristics. Attempts were made to identify the changes in apperant resistivity data in response to the changing groundwater levels/moisture content and the accuracy of corresponding layer thicknesses, computed through resistivity data

Slope Stability Analysis and Design of Open Pit Mine Slopes for Limestone Mine at Aruwakkalu, Puttalam, Sri Lanka

The largest open pit limestone mine in Sri Lanka which belongs to Holcim Lanka Limited is located at Aruwakkalu, Puttalam. The sub-surface of this site is comprised of an overburden of average thickness 24 m followed by a 9 m thick low grade limestone layer and a high grade limestone layer at the bottom which extends even below the seawater level.The overburden which is currently being excavated in five benches of near vertical cuts becomes unstable during the rainy season, which is a significant safety issue on this site. In this scientific investigation, the physical properties of each layer of material are determined by laboratory testing, in order to design optimum bench heights and slope angles for this open cast mine. Direct shear tests are carried out on undisturbed soil samples collected from the overburden, whereas rock-triaxial tests are carried out on the samples collected from low-grade and high-grade limestone layers, in order to determine design parameters: cohesion(c) and friction angle(ϕ) of these materials. The stability analysis is carried out by means of “SLOPE/W” software. The analysis of data for a three layer model reveals that the possible failures are confined to the overburden based on the outcome of this study. The overburden mine slopes could be optimized to three berms of each 8 m height, 6 m wide and of 700 slopes, having a sufficient safety factor which will enhance the safety and productivity of the future mining operations on this site