ISERME - 2018

Permanent URI for this collectionhttp://192.248.9.226/handle/123/14734

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International Symposium on Earth Resources Management & Environment 2018 [Pre Text]
(2018-08) Abeysinghe, AMKB
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Noise and vibration control in crusher plant activities to enhance health and safety of workers
(Department of Earth Resources Engineering, 2018-08) Thiruchittampalam, S; Kinoj, A; Ekanayake, EMCK; Vithurshan, S; Hemalal, PVA; Samaradivakara, GVI; Rohitha, LPS; Chaminda, SP; Abeysinghe, AMKB; Samaradivakara, GVI
Fulfillment of human needs necessitates activities that have their positive and negative aspects. Crusher plant operation is not an exception. One of the major concerns related to these activities is its impact on worker health and safety. Although noise and vibration related legislation focus on reduction at the source, provision of personal protective equipment is considered as an effective method of control. The focus of this study was to look for control strategy for noise and foot transmitted vibration hazards related to fixed machineries in crusher plants. Six crusher plant sites were selected based on their varying production capacity for the study. Accordingly, selected sites were visited to carry out area noise and wholebody vibration surveys. Plant arrangement, details of crusher units, prevailing meteorological conditions and ground conditions were also recorded. Daily exposure levels were determined and sound and whole-body vibration contour maps were developed based on Control of Noise and Vibration at Work Regulations Act 2005. Relationship of areas of hazardous zones w i t h production capacity was determined using statistical tools and the level of worker awareness was studied through one to one interviews. Cost effective controls are recommended by studying the best practices.
item: Conference-Abstract
Geochemical approach of phosphate mineral exploration in lake sediments around Eppawala phosphate deposit, Sri Lanka
(Department of Earth Resources Engineering, 2018-08) Dushyantha, NP; Hemalal, PVA; Jayawardena, CL; Ratnayake, AS; Ratnayake, NP; Abeysinghe, AMKB; Samaradivakara, GVI
Mineral exploration is a stochastic process of finding and locating commercially viable mineral resources. In this regard, lake sediment is an important material in exploration as it contains three distinct types of minerals i.e. allogenic or detrital minerals (minerals brought into the lake from outside of the lake), endogenic minerals (minerals originated within the lake) and authigenic minerals (minerals formed during the diagenetic alteration of sediments). Koon-wewa, Ihalahalmillawewa and Kiralogama-wewa are three lakes connected with a man-made water canal, namely Jaya-Ganga flowing across the Eppawala Phosphate Deposit (EPD). Kiralogama-wewa is located downstream of the EPD whereas other two lakes are located upstream. Thus, lake sediments in the downstream lake could be influenced by the phosphate-bearing minerals derived from the EPD. The bulk chemical analyses of surface lake sediments showed that average P2O5 concentrations were 0.80% and 0.45% in downstream and upstream, respectively. Further, in downstream, P2O5 significantly and positively correlated with AI2O3, CaO, Fe203, K2O and MnO whereas no such correlations were observed in upstream sediments. Presence of calcium-iron-aluminum phosphate minerals such as fluorapatite, crandallite, millisite and strengite in downstream sediments, revealed via mineralogical analyses, delineated the above correlations. Moreover, high Chemical Index of Alteration (CIA) values were observed in the downstream sediments which indicate intense chemical weathering conditions in the source area. It is justified by the presence of weathering products of the EPD such as crandallite and millisite in the downstream sediments. Grain size analyses displayed a dominant silt fraction in both upstream and downstream areas. Textural analyses in downstream revealed the relative proximity of the source and nature of the material deposition through solid suspension. Presence of fluorapatite (detrital mineral) in downstream is corrobarated the conclusion in textural analyses. Four representative core samples were obtained from both the upstream and downstream lakes. In upstream core samples, P2O5 concentrations varied from 0.03% to 1.81% whereas P2O5 concentrations in downstream core samples varied f r om 0.26% to 2.22%. Continuous sediment supply via Jaya-Ganga can also improve the fertilizing capacity of downstream lake sediments, eventually; becoming a commercially viable phosphate mineral resource.
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UAV application for blast design and fragmentation analysis
(Department of Earth Resources Engineering, 2018-08) Miranda, V; Bhatawdekar, RM; Leitei, F; Gupte, A; Sobral, R; Edy, TM; Pradhan, GK; Abeysinghe, AMKB; Samaradivakara, GVI
With the advancement of various techonlogies during last two decades, processing power of computers and software development, accuracy in Geographical Positioning System (GPS), photogrammetry with high resolution digital camera, cloud computing, application of Unmanned Aerial Vehicle (UAV) in mining application is providing benefits. Blasting is one of the critical operation in any excavation system in mining, was dependent on conventional methods of analysis till new technologies made in-roads in last few decades period. Digitised Terrain Models (DTM) are developed based on images captured of mine terrain and mine faces(as a part of pre-blast and post-blast situations). With mobile phone application vis-a-vis App based, real charge per hole, 2D/3D view of borehole patterns, geometric paramters, real coordinates of blast location and boreholes and presence of water in individual borehole can be recorded. For measurement of blast fragmentation, UAV is flown on blasted muckpile with video recording of images. Blast fragmentation photographs are analysed using image analysis software. Photographs are useful to calculate blasted rock volume. This paper describes two case studies. In one of aggregate (granite) quarry in Malaysia, with the help of UAV aerial phographs were obtained to identify rock types and geological structures which improved blast design. In another case study, in photgrapghs of blasted muckpile are taken manually in limestone quarry. Results of blast fragmentation prediction by software Vs image analysis are discussed in this paper.
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Optimizing the specific charge for limestone blasting at Aruwakkalu limestone quarry
(Department of Earth Resources Engineering, 2018-08) Mendis, HCVS; Wimalagunasekara, KR; Jinadasa, MLS; Hemalal, PVA; Dharmaratne, PGR; Chaminda, SP; Abeysinghe, AMKB; Samaradivakara, GVI
The largest open pit limestone mine in Sri Lanka operated by Siam City Cement Lanka Limited is located at Aruwakkalu, Puttalam. The red soil overburden is directly excavated and low grade and high grade limestone layers are drilled and blasted. Specific charge plays a vital role in open pit blast design as it affects many operational costs in mining activities. An optimum specific charge with proper fragmentation not only reduces costs but also reduces undesirable effects like ground vibration, fly rock and air blast over pressure [1]. When optimizing the specific charge, it was decided to change the charging method by creating air decks and evaluate the fragmentation of the blasted material, because it was often difficult to accomplish several elements of improvement simultaneously. Fragment size directly affects the downstream operations like loading, transporting and crushing [2]. Two computer softwares, 'JKSimBlast' and 'Split-Desktop' were used to analyse fragmentation of material where the 'JKSimBlast' was used to simulate and analyze the modelled blasts while the 'Split-Desktop' was used to analyze the blasted material. The analysis of data by the software and cost analysis reveal that top column air deck charging method would save the cost of blasting by about 11% and the Specific Charge value is reduced by 19%, resulting in reasonable fragmentation and size distribution.
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Applicability of a neural network model for forecasting ground vibrations in opencast mining
(Department of Earth Resources Engineering, 2018-08) Dassanayake, SM; Dushyantha, NP; Jayawardena, CL; Abeysinghe, AMKB; Samaradivakara, GVI
Ground vibration and air-blast over pressure are two significant undesirables, among many environmental risks, in open-pit mining . Gaining control over the ground vibrations generated by rock blasts had been difficult mainly due to the complexities involved with local geology and properties of the blast. Accordingly, existing empirical equations are only capable of making vague approximations on the vibration frequencies based on site-specific parameters and attenuation factor. Therefore, the available models cannot be generalized to different geo-mining environments to obtain sufficiently reliable forecasts for ground vibration and airblast overpressure. Hence, this study attempts to employ an Artificial Neural Network (ANN) based feed-forward back-propagation algorithm to train a model, using a supervised learning technique to forecast possible ground v i b r a t i on frequencies. The main in-put parameters included in the model are noise level, number of boreholes per single blast, depth and diameter of a borehole, charge per hole, number of delays of the Electric Detonators (ED) in a single blast, burden and spacing. Airblast overpressure and the ground vibration levels will be the output by ANN model. The model was validated using 50 datasets, which were obtained from a quarry site. After adequate training, the model can determine Peak Particle Velocity (PPV) and frequency of Ground Vibrations (GV) for new input parameters with a statistically significant confidence level.
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A review of prediction of blast performance using computational techniques
(Department of Earth Resources Engineering, 2018-08) Bhatawdekari, RM; Danial, JA; Edy, TM; Abeysinghe, AMKB; Samaradivakara, GVI
In hard rock excavation, drilling and blasting is commonly used for loosening rock. Optimum rock fragmentation due to blasting is desirable for downstream operation productuivity. Environmental impacts due to blasting consist of flyrock, ground vibration, air over pressure (AOp). Blast performance depends upon mainly 3 factors consisting of rock mass properties, blast design and explosives system utilised. Mean fragment size is commonly used for rock fragmentation analysis. During 1960-80, blast performance was evaluated using empirical methods. With advancement of computing power during the last two decades, various computentional techniques have been developed for predicting fly rock distance, peak particle velocity, air over pressure with various input paramters based on set of blasts. Technique involves training and testing blast data and comparing results with different computentional algorithm. Various computetntional techniques consisting of Artifical bee algorithem (ABC), Artifical Neural Network (ANN) , Fuzzy Interface System (FIS), GA Genetique algorithm (GA), Imperialist Competitive Alorithm (ICA), Particle Swarm Optimization (PSO), Supoort Vector Machine( SVM) for predicting blast performance are reviewed. Presently, various computentional techniques are ustilsed by researchers. This paper further discusses h ow these techniques can be implemented at operating mines by mining engineers, blasting team for predicting blast performance.
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Applicability of pre-heating techniques for recovery of minerals from rocks
(Department of Earth Resources Engineering, 2018-08) Dasanayake, RB; Jatheesan, N; Nissanka, NACM; Samaradivakara, GVI; Abeysinghe, AMKB; Rohitha, LPS; Abeysinghe, AMKB; Samaradivakara, GVI
In mineral processing industry, liberating of minerals is the most important involvement because it can enhance the purity of the mineral. However, if we can initiate micro-cracks in rock pieces in advance to these operations, it would be more economically viable. Hence, there is a trend i n the world to investigate less energy-consuming methods for propagating micro cracks within rock grains. Previous studies show that preheating techniques such as heating in muffle furnace, microwave preheating can enhance micro-cracks propagation in rocks and samples. Microwaves have several advantages over standard heat application methods namely that they heat only "responsive" phases. Microwaves also heat considerably faster than conventional heating methods as the heating on radiation and conduction heat transfer mechanisms. Therefore, in this scientific investigation, we applied microwave pre-heating technique to liberate Garnet from Garnet Biotite Gneiss for which samples were collected from Boulder Mix Pvt. Ltd quarry in Meepe. To create a weak zone i n between graphite and its gangui rock in graphite bearing rocks which were collected from Bogala Mines in Aruggammana have also tested. Industrial price of garnet vary w i t h the particle size. In general, higher the particle size, higher w i l l be the value. Hence, the recovery of Garnet in this study was considered focused on industry needed particle size which is less than 850 |xm. The analysis revealed that there is a possibility to produce low cost garnet sand which is cheaper than i n the international market with high purity, by means of microwave technology,. Also it is proved that creating a weak zone along the grain boundary of graphite and its gangue rock is possible w i t h microwave pre-heating.
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Production of high quality iron pellets by changing the composition and firing conditions
(Department of Earth Resources Engineering, 2018-08) Wisumperuma, KB; Hewawasam, HPSS; Weerakoon, WMBMB; Rohitha, LPS; Guluwita, SP; Abeysinghe, AMKB; Samaradivakara, GVI
There are no Iron ore mininhg activities and very few Iron extraction activities in Sri Lanka due to high electricity consumption and non availability of proper survey results of those ore deposits. Main components need for Iron melting are Iron ore. Limestone and Coke. The Hematite (Fe203.XH20) percentage in Dela Iron ore is 88.71%, Si02 percentage is 7.18% and AI2O3 percentage is 1.07%. Blast furnace is the most suitable method to extract Iron in Sri Lanka considering the cost and the necessary resources. Cupola furnace has the same mechanism of the blast furnace which has been used for laboratory scale Iron melting . By changing the composition and firing condition, high quality pellets were produced. While extracting Iron, huge amount slag formation is the main draw back in Iron making. By comparing degree of magnetism, degree of reduction, apparent porosity, apparent specific gravity, bulk density and water absorption, high quality pellets were produced. The optirruzed carbon percentage for pelletizing with optimized in duration temperature were determined using above tests. Physical, chemical errors and further improvement of this procedure have been discussed in this research.
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Increasing the thermal conductivity of rubber by using natural graphite as an additive
(Department of Earth Resources Engineering, 2018-08) Lasantha, MML; Liyanage, LWA; Gunasekara, HMSU; Jayasinghe, AP; Abeysinghe, AMKB; Samaradivakara, GVI
In liquid form, natural rubber is also known as latex (raw rubber) and the purified form of natural rubber is the polyisoprene, which can be used i n many applications and products through the process of vulcanization. Rubber making process can be divided into four stages such as compounding, mixing, shaping and vulcanizing. In compounding stage, many additives such as vulcanizing agents, accelerators, activators, retarders, fillers and anti-degradants usually are added to improve properties of natural rubber. Two main reasons were expected by adding natural graphite as an additive such as improve thermal properties i n rubber and less energy to cure the rubber products. Natural graphite is produced at Bogala Mines which has +99 carbon percentage and 40-micron particle size. Raw natural rubber has very low thermal conductivity such that rubber with a good thermal conductivity can withstand high temperatures without undergoing reversion or property changes. Therefore, this study focuses on the improving the thermal conductivity of rubber by using natural graphite as an additive. Three master batches were prepared on a laboratory two-roll mill by mixing 40-micron natural graphite (5PPHR (Parts per Hundred Rubber), lOPPHR and 15PPHR) with latex (raw rubber). Prepared three samples were sent to a laboratory in India to test the thermal conductivity by using Hot Disk TPS (Transient Plane Source). A l l the results were compared with corresponding control sample (OPPHR) which describes the behavior of thermal conductivity of three samples corresponding to the control sample. Test results showed that all three samples have higher thermal conductivity, compared to the control sample (2.60%, 1.33% and 1.93% respectively) and the thermal conductivity of 5PPHR sample was increased with time than other two samples. Further studies can be done to improve the thermal conductivity of rubber by functionalization of carbon w i t h different groups like oxygen, carboxyl, amine, amide and fluorine which can drastically change the surface properties of graphite or graphene instead of raw natural graphite as an additive.
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Possibility of producing manufactured sand from quartzite rocks at Rajawaka off Balangoda
(Department of Earth Resources Engineering, 2018-08) Priyankara, WMD; Pavithra, P; Suwimal, WMW; Weerawarnakula, S; Abeysinghe, AMKB; Samaradivakara, GVI
Demand for construction sand rapidly increases due to speedy development projects going on all over the country. Until the recent past the sand requirement was fulfilled mainly by river sand. However due to scarcity of river sand and restriction of river sand mining due to negative environment effects, increased attention was received to find suitable alternatives. Inaddition to sea sand mining possibility of producing manufacture sand from suitable rocks, recycled aggregates and crush waste glass were carried out by many research groups.This study was carried out to find the suitability of large scale quartzite rocks occur at Rajawaka off Balangoda area for producing manufactured sand in the industrial scale. Sieve analysis, cube tests and slump tests carried out showed that manufactured sand produced from quartzite rocks of the area reach required strength for concrete.
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Impurities in Eppawala rock phosphate and removal methods
(Department of Earth Resources Engineering, 2018-08) Weerasooriya, HMJC; Waisundara, WMLB; Lakmal, KPT; Hemalal, PVA; Rohitha, LPS; Ratnayaka, NP; Abeysinghe, AMKB; Samaradivakara, GVI
Apatite mined f r om Eppawala (Eppawala Rock Phosphate - ERP) cannot be directly used as a fertilizer for armual crops such as paddy and vegetables because of its low water solubility. It is difficult to manufacture water soluble phosphate fertilizers from ERP due to its stable chemical formation and impurities in ERP. This study focuses on impurities i n ERP and methods of their removal. Removing the impurities in ERP will help to produce water soluble phosphate fertilizers for annual crops. Literature shows high contents of Fe203, AI2O3 and chlorine as impurities i n ERP. This investigation helped us to reduce combined Fe203 and AI2O3 content from 12.36% to 6.42% i n test 1 of this study and to 4.61% i n test 2 by using froth floatation technique. Acceptable level of combined Fe203 and AI2O3 content for the production of water soluble phosphate fertilizer is less than 5%. Therefore, the concentrate of test 2 is suitable for the production process, but high chlorine content in the concentrate w i l l create difficulties in the formation of water soluble phosphate fertilizers.
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Evaluation of seasonal groundwater quantity and quality variation in Malwathu Oya Basin
(Department of Earth Resources Engineering, 2018-08) Rohanson, KR; Rahulan, Y; Thavaganesh, S; Chaminda, SP; Abeysinghe, AMKB; Jayawardena, CL; Abeysinghe, AMKB; Samaradivakara, GVI
Malwathu Oya is located in Anuradhapura district which has water quality and scarcity problem for drinking purpose. Samples were collected from selected locations which included upstream and downstream of Malwathu Oya basin. The samples were analyzed for conductivity, pH , turbidity , calcium, magnesium, fluoride, chloride and arsenic. Only shallow regolith aquifers are considered for the study. The quality variation of the area shows a considerable variation from southwest monsoon to second inter monsoon period. In general, water quality of the area is inacceptable limitd of drinking water for most of the basic parameters. With the seasonal changes, fluoride and chloride content is higher than permissible limits in some areas.
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Experimental optimization of biocement formation: alternative countermeasure for surface erosion of cut slope
(Department of Earth Resources Engineering, 2018-08) Gowthamani, S; Nakashima, K; Ebina, K; Kawasaki, S; Abeysinghe, AMKB; Samaradivakara, GVI
The research w o r k aims to assess the feasibility of i n t r o d u c i n g the microbial induced carbonate p r e c i p i t a t i on (MICP) as an alternative technique for surface stabilization of the cut slopes by augmenting potential indigenous ureolytic bacteria. A set of column solidification tests was conducted on embankment soil (Hokkaido expressway, Japan) to optimize the performance of bacteria regarding bacterial population of culture solution (optical density (OD600) from 1 to 6), and concentration of Ca^* and urea i n cementation solution (0.5 m o l / L and 1 mol/L) at the temperature of 20°C. The UCS of treated samples was estimated using needle penetrometer, and the microstructure of the treated specimens was observed using scanning electron microscope (SEM). The results reveal that the UCS of the specimen increases w i t h increasing ODeoo w i t h o u t any clogging w i t h i n the samples. Treating the soil using 1 m o l / L concentrated (Ca2+ and urea) cementation solution and bacterial culture w i t h ODeoo of 6 results the highest UCS of 7.5 MPa while achieving relatively a homogeneous solidification along the column profile. The micrographs of the treated specimen confirms that the rombohedral calcium carbonate crystals formed w i t h i n the pores of soil matrix, w h i c h has effectively bonded the adjacent soil particles, and contributed to enhance the strength significantly at the o p t i m i z e d treatment condition.
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A study on environmental issues due to the development of nuwaraeliya baduua road
(Department of Earth Resources Engineering, 2018-08) Adikarii, AMHV; Pitawala, HMTGA; Abeysinghe, AMKB; Samaradivakara, GVI
Special emphasis has been given on road construction by the National Highways Sector Project (NHSP) of Sri Lanka i n order to bring socio-economic upliftment. However, construction and developments of roads of the country create many environment issues. Rehabilitation and improvement of the NuwaraEliya - Badulla road which r un through the hilly area were established in 2010. Construction length of the road was considered to identify the environmental impacts. Slope instability, hydrological conditions, soil erosion and blasting effects were studied. Disturbance of the natural drainage systems and making deep cuts and fills across already fragile slopes were identified as the main causes. Highly unstable slopes are identified in the Dabalawelahinna area. Dougolla Oya and Gregory Lake are the hilly affected water bodies of the area. Area around the rock quarry has been affected due to blasting vibration and high air blast over pressure. Since the vibration of back side of the quarry is high, landslides can be occurred in future. The life style of species live in Hakgala strict nature reserve has been disturbed due to noise and vibration. Prior to the construction of roads in hilly areas, special attention should be paid, specially on the morphological and geological conditions
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A preliminary investigation on isolation and identification of marine bacteria for biocementation in nearshore environments
(Department of Earth Resources Engineering, 2018-08) Nayanthara, PGN; Dassanayake, ABN; Nakashima, K; Kawasaki, S; Abeysinghe, AMKB; Samaradivakara, GVI
Microbial Induced Carbonate Precipitation (MICP) is a widely explored technique that involves utilizing bacterially produced carbonate biominerals for improving the engineering properties of soils. When this novel approach is used in cementing sandy soils in nearshore areas, it is necessary to identify suitable bacterial strains which are resistant to high saline dynamic marine environments. Thus, current study was carried out to isolate and identify ureolytic bacteria from Sri Lankan beach sand and to check their suitability for use in MICP. To accomplish this, bacterial strains were isolated from beach sand samples and urease activity was determined. MICP capability was evaluated by cultivating the species on agar plates containing CaCh and urea. Based on these results, four isolates having high feasibility to induce bacterially precipitated calcium carbonates were selected and identified by 16S rDNA gene sequencing. Two strains were identified as belonging to Halomonas sp. and other two to Sulfitobacter sp. and OceanobaciUus sp. genera. Further analysis was done to determine the bacterial cell growth of isolates at different temperatures and concluded that all four isolates have a more stable growth at temperature close to 30°C. Isolates were evaluated for their biosafety and found to be non pathogenic. However, detailed analysis on biomineralization by the selected isolates and their biological behaviour is recommended prior to any large scale applications.
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Assessment of environmental impacts resulting from ground vibrations due to piling activities and railway transport
(Department of Earth Resources Engineering, 2018-08) Piyarathna, HDAM; Godagama, GWADC; Maduranga, THT; Hemalal, PVA; Samaradivakara, GVI; Samaradivakara, GVI; Dharmaratne, PGR; Abeysinghe, AMKB; Samaradivakara, GVI
With the development of the country's economy, industrial activities close to urbanized areas have inceased tremendously. These activities are sources of ground vibrations impacting on human life. Resulting annoyance conditions near residential areas and possible human response to ground vibrations have been investigated in this study. Ground vibration have been monitored at precast pile driving sites and at a location close to Panadura-Moratuwa railway line using an A4-channel seismograph. Human perception and disturbance conditions associated with each location is discussed with the criteria given in British Standards. According to the ground vibrations levels measured at the piling site, up to 55 m distance from pile driving locations perceptible level of ground vibrations have been occurred thus caving annoyance to occupants. Zone with adverse comments, extends up to 37 m from the pile and adverse comment possible zone extend up to 50 m from the pile when using pile diver and piles with given specifications. According to ground vibration levels near the railway track, occupants in residential areas will experience annoyance as residential area contains ground vibrations in perceptible amount. Up to 27 m distance from the railway track, ground vibrations levels were measured up to a level of making complaints regarding annoyance made by train.The trench already existed near the railway track (parallel to the rail way track) is capable of reducing ground vibration levels up to 40%.
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Analysis of physical and mineralogical properties of aggregate on strength and durability of asphalt concrete
(Department of Earth Resources Engineering, 2018-08) Lakshan, LPS; De Silva, SHSN; Kapilaratne, RDMCLB; Chaminda, SP; Jayawardena, CL; Abeysinghe, AMKB; Samaradivakara, GVI
Asphalt is made by mixing aggregates, filler and binder materials together according to pre-determined ratios. Out of the total asphalt weight, 94% to 95% consists of aggregate. It is not surprising that the performance of asphalt concrete mixtures is influenced by the properties of their aggregate blends, such as gradation, shape (angularity and elongation), texture (roughness) and mineralogy. In asphalt concrete, numerous studies have related gradation, shape, and texture of the aggregate to durability , workability , shear resistance, tensile strength, stiffness, fatigue response, rutting susceptibility, and optimum binder content of the mixtures. However, a few has described about the influence of mineralogy on characteristics of asphalt. This research has been carried on to make an effort to fill that gap between the aggregate mineralogical properties and the characteristics of asphalt concrete. Under the research, a number of representative aggregate samples were collected from different quarry sites which are currently used in the process of manufacturing asphalt all over the country. The samples were subjected to a series of tests in order to determine both physical and mineralogical properties. Marshall stability and flow values of the asphalt mixtures were determined to assess the properties of asphalt made using the collected aggregates. Finally, using test results, an analysis was conducted followed by the conclusions made using the test results, a set of recommendations were proposed.
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Review of rock mass classification of tropically weathered rock
(Department of Earth Resources Engineering, 2018-08) Wedage, W; Bhatawdekar, RM; Silva, G; Batagalla, S; Madawala, S; Edy, TM; Abeysinghe, AMKB; Samaradivakara, GVI
In tropical climate, limestone is frequnetly exposed to rain water which when absorbed by limestone forms carbonic acid. This further enhances process of dissolution resulting in change in geomechanical properties of limestone. With various geological discontiuties such as faults, folds, joints, water flows through these cavities. The weathering process along these cracks or cavities takes place at faster rate. In this paper, two case studies are reviewed. Rock mass is classified based onlithology , degree of hardness, degree of weathering, % of cavities. Rock Quality Designation (RQD)% and nature of joints. I n another case study on limestone deposist f r om Thailand is classified based o n Geological Strength Index (GSI) which enhances blast design. Limestone deposit at Aruwakkalu based on rock structure can be classified as (i) heavily cracked, frequent weak joints, weakly cemented layers (ii) T h i n , well-cemented layers w i t h tight joints (iii) Massive intact rock. This limestone deposit is also classified as bedding plane dipping in to face, bedding plane dipping into cut and other cases. Existing system of rock mass classification at Sri Lanka is reviwed with case studies. Thus for Aruwakkalu limestone deposit, rock mass can be classified based on type of rock structure, Blastability Index (BI), RQD%, degree of weathering and degree of hardness. Average powder factor of 0.15 kg/1 can be correlated with BI.
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Identification of soil/rock interface using GPR technique for soil nail wall design
(Department of Earth Resources Engineering, 2018-08) Narangoda, SRAIB; Isuranga, SNAMTK; Jeneeshaa, A; Abeysinghe, AMKB; Premasiri, HMR; Samaradivakara, GVI; Abeysinghe, AMKB; Samaradivakara, GVI
Soil nailing is one of the common slope stabilization techniques which has been used in Sri Lanka during the past decade. Due to the advantages of this method, its applications are growing rapidly around the landslide hazard areas in Sri Lanka. Applications of subsurface investigation methods which are used to identify soil/rock interface are limited due to steepness of the slope areas. Since lesser information available about the bed rock geometry, this leads to generate a low cost effective design for soil nailing. The aim of this research is to demonstrate applicability of GPR for optimizing soil nail length. The study area is located near the Nursing Training School Kandy, that has been proposed to be stabilized by using soil nailing technique. GPR readings were taken on the pre-determined traverse lines. Soil/Rock interface identification was done by using survey results together with their interpretation, and geological cross section was produced. GPR imaging indicated that the bed rock level variation at this location is from 15 m to 18 m. It was identified that design length of the soil nail is shorter than depth to the bed rock on the slope with the aid of the diagram. Therefore, it was identified that soil nail length cannot be optimized for the location. The scope of the GPR survey was to find the depth to the bed rock. By using that, length of the soil nail can be optimized and soil nailing process can be performed more efficiently. However, the depth to bed rock level on the slope has to be less than the design length of the soil nail to optimize the soil nail length by means of this technique. This research illustrates the benefits of using GPR to provide understanding about the soil/rock interface in a slope area for the optimization of soil nail length.

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