Browsing by Author "Welideniya, HS"

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item: Conference-Full-text
Design and fabrication of cable bolt for excavation in a fractured rock
(Department of Earth Resources Engineering, 2009-05) Dhanawardana, YLC; Siriwardana, HDPM; Henderson, SH; Kumara, HMCP; Indika, KAS; Dharmaratne, PGR; Welideniya, HS; Rohitha, LPS; Karunaratne, S
In fractured rock masses, large excavations have an unsupported stand-up times less than the minimum time required to support the roof after the excavation. Therefore, the principal objective in the design of a support system is to help the rock mass to support itself. The use of rock bolts is a very flexible supporting method that can be combined with wire mesh, shotcrete and concrete lining. During past years a wide variety of dowels and bolt types were developed but most of them failed within a short period and the cost were high. Advantages of cable strand supports have been well documented and include flexibility, strength, and ease of installation. Main objective of this project is to design rock bolts using discarded wire ropes or cables at a low cost. A detailed designing methodology was carried out to fabricate this bolt. The bolt consists of nearly 1.6m long cable and 16 cm of anchored part and cable tightening part. Outer diameter of bolt is 33 mm and inner diameter is 12 mm and used cable diameter is 5mm. Field data illustrated the amount of load measurements that the bolt can carry is 5 kN. Suggestions were made to improve the design, which will enhance bolt performance. Field tests carried out at Bogala Lanka Graphite Ltd proved that cable bolts are effective in Sri Lankan conditions.
item: Conference-Extended-Abstract
Design and fabrication of cable bolt for excavation in a fractured rock
(2009) Dhanawardana, YLC; Siriwardana, HDPM; Henderson, SH; Kumara, HMCP; Indika, KAS; Dharmaratne, PGR; Welideniya, HS; Rohitha, LPS
Most often in fractured rock masses, large excavations have an unsupported stand-up times less than the minimum time required to support the roof after the excavation. During past few years a wide variety of dowels and bolt types have been developed but most of them failed within a short period of time and the cost were high. Main objective of this research work was to design rock bolts using discarded cables at a low cost. The bolt consists of nearly 1.6m long cable and 16 cm of anchored part. Field data illustrated the amount of load that the bolt can carry as 5 KN. Suggestions were made to improve the design, which will enhance bolt performance. Field tests carried out at Bogala Graphite Lanka Ltd proved that cable bolts are effective in Sri Lankan conditions.
item: Conference-Abstract
Design and fabrication of cable bolt for excavation in a fractured rock
(2014-08-08) Dhanawardana, YLC; Siriwardana, HDPM; Henderson, SH; Kumara, HMCP; Indika, KAS; Dharmaratne, PGR; Welideniya, HS; Rohitha, LPS
In fractured rock masses, large excavations have an unsupported stand-up times Jess than the minimum time required to support the roof after the excavation. Therefore, the principal objective in the design of a support system is to help the rock mass to support itself. The use of rock bolts is a very flexible supporting method that can be combined with wire mesh, shotcrete and concrete lining. During past years a wide variety of dowels and bolt types were developed but most of them failed within a short period and the cost were high. Advantages of cable strand supports have been well documented and include flexibility, strength, and ease of installation. Main objective of this project is to design rock bolts using discarded wire ropes 01' cables at a low cost. A detailed designing methodology was carried out to fabricate this bolt. The bolt consists of nearly 1.6m long cable and 16 em of anchored part and cable tightening part. Outer diameter of bolt is 33 mm and inner diameter is 12 mm and used cable diameter is Smm. Field data illustrated the amount of load measurements that the bolt can carry is 5 kN, Suggestions were made to improve the design, which will enhance bolt performance. Field tests carried out at Bogala Lanka Graphite Ltd proved that cable bolts are effective in Sri Lankan conditions.
item: Conference-Full-text
Designing suitable mining method and processing plant for Kukurampola magnetite ore body
(Department of Earth Resources Engineering, 2006-10) Amarasekera, HM; Sajirupan, S; Senanayake, IP; Sirisoma, RHANC; Chaminda, SP; Rohitha, LPS; Welideniya, HS; Karunaratne, S; Dissanayake, DMDOK; Ratnayake, N; Chaminda, SP
Evaluation of mining methods for the exploitation of Kukurampola ore body is considered in this report. Minerals take millions of years to form, but exploitation takes only few decades. Therefore, mineral deposit is a wealth which must be used for the maximum benefit of the country. Iron is one of the most important metals in the world for many industries. Therefore, exploitation of iron ore is essential for the industrial development of a country. The Magnetite deposit in Kukurampola contains high purity Magnetite; hence it is a valuable resource need rational exploitation. Mining methods evaluated include open pit and underground, and based on geological, engineering, environmental and economical factors combination of both open pit and underground mining are considered as the most suitable mining method. Consequent to open pit mining underground mining will commence for future ore body development and exploitation. A processing method is designed to produce feed material for palletizing those will include crushing, grinding and magnetic separation. If ample deposits are found in the future, there's a possibility of constructing a palletizing plant which need ore reserves for more than 25 years. Also, occurrences of magnetite in the neighborhoods are identified for further expansion of mining operations Special consideration is given to minimize environmental impacts. Remedial methods are proposed in this report to minimize adverse environmental impacts.
item: Conference-Extended-Abstract
The effect of infill on shear behaviour of idealised joints under constant normal stiffness conditions (CNS)
(2007) Welideniya, HS
The shear behaviour rock joints infilled with graphite, bentonite and clayey sand under eNS conditions were studied through a comprehensive laboratory testing programme to assess its influence on rock mass stability. A range of infill thicknesses such as 1.5, 3, 6 and 9mm, initial normal stresses (O'no) of 0.56, 1.1 and 2.43 MPa and two idealized joint types with 9.5° (Type 1) and 18.5° (Type 2) asperity angles were used in testing (Indraratna, Welideniya and Brown. 2005). This paper describes analysis of test results leading to better understand the effect of mobilised and apparent friction angles on shear strength envelope.
item: Conference-Extended-Abstract
GIS application in foundation cost zonation
(2007) Welideniya, HS
Complex geological features are predominant in some low lying sedimentary terrain, which is the direct result of surface processes such as weathering, transportation, sedimentation transgression, regression etc. This complex sub surface geology is mostly seen in Dutch flood plains (polders) which belong to Quaternary Period of geological time scale. A research study on suitability of land for development in Sliedrecht, The Netherlands, having complex subterranean geology belonging to quaternary period was carried out by the author (Wclideniya H.S. 1996). This type of land was not much preferred for construction due to its complex subterranean geology, which is characteristic with low bearing capacity. The study was aimed at developing a methodology combining engineering geology and GIS to support urban planners in decision making
item: Conference-Full-text
Ground vibration and air blast overpressure assessment using scaled distance
(Department of Earth Resources Engineering, 2007-11) Sivarajan, V; Kumara, KLDS; Hearath, HMSD; Nanayakare, NWP; Welideniya, HS; Weerawarnakula, S; Karunaratne, S
In recent years there was a noticeable developmental activity, especially in industrial as well as construction sectors such as roads, harbours, condominiums etc. This has enhanced and developed aggregate industry and the use of modern technology for its effective operation. Blasting is being used extensively to supply rock aggregates for construction and also to drive tunnels and roads through rugged rocky terrains. There is growing concern on blasting effects on the environment such as dust, toxic gases, noise, fly rock and ground vibration. Worldwide the common allegations mainly focused on damages to residences. Present study was carried out to monitor air blast and ground vibration due to rock blasting. Southern Highway expressway was selected to monitor above effects due to high blast frequency available and the availability of the vast data base. Geological condition of the site, including rock type, drilling and explosive parameters, and distance between blasting and monitoring location, ground vibration and air blast over pressure were recorded. The data was used to develop site specific constants useful for blast programming. By using the site factors, the quantity of explosive per delay or the vibration at particular range of distance could be predicted.
item: Article-Full-text
Guidelines for industrial rock blasting
(2014-06-30) Welideniya, HS
Under all circumstances "Industrial Blasting" needs to be carried out without inflicting disastrous affects on the neighbourhood. If it is carried out considering engineering properties of rock mass being blasted and with the proper quantification of blastability of explosives blasting can be done without inflicting any adverse affects caused by ground vibrations, ecological damage and also maintaining air blast overpressure below human tolerance levels. It is widely recognized that two aspects such as structural damage and human response are the ones which merit particular attention in surface mine and construction blasting. Under such circumstances blasting has to be carried out in a well designed manner. The affect of engineering geological properties of rock mass in blast designs and the role of quarry factor in blasting are discussed in this paper. The paper also describes the importance of the establishment of site constants for quarries. These factors will facilitate the design of better bench blast geometries, determination of maximum instantaneous charge for required ground vibration which will affect least environmental damage/noise control thus leading to better blasting practices.
item: Article-Full-text
Guidelines for industrial rock blasting
(2005) Welideniya, HS
Under all circumstances “Industrial Blasting” needs to be carried out without inflicting disastrous affects on the neighbourhood. If it is carried out considering engineering properties of rock mass being blasted and with the proper quantification of blastability of explosives blasting can be done without inflicting any adverse affects caused by ground vibrations, ecological damage and also maintaining air blast overpressure below human tolerance levels. It is widely recognized that two aspects such as structural damage and human response are the ones which merit particular attention in surface mine and construction blasting. Under such circumstances blasting has to be carried out in a well designed manner. The affect of engineering geological properties of rock mass in blast designs and the role of quarry factor in blasting are discussed in this paper. The paper also describes the importance of the establishment of site constants for quarries. These factors will facilitate the design of better bench blast geometries, determination of maximum instantaneous charge for required ground vibration which will affect least environmental damage/noise control thus leading to better blasting practices.
item: Thesis-Abstract
Laboratory evaluation and modelling of shear strength of infilled joints under constant normal stiffness (CNS) condition
Welideniya, HS
Infill materials found in natural rock joints may cause a reduction in joint shear strength, influencing rock mass stability. The shear strength of rock mass, already reduced by these discontinuities, will further diminish if they are filled with sediments, thereby posing significant concerns for any construction or excavation carried out in rock. These concerns invite accurate quantification of the shear strength of infilled joints and proper understanding of the basic mechanics of discontinua and the principles involved in their shear deformation. The practical application of any models developed through such studies will be of immense help to mining, tunnelling, and all other underground construction works. The geotechnical research work carried out by the University of Wollongong in the late 90's included infilled joint modelling using hyperbolic techniques. A new shear strength model was developed in these studies for predicting unfilled and infilled joint strength based on the Fourier transform method, energy balance principle and the hyperbolic stress-strain simulation. Taking into account the field conditions frequently encountered, the diversity observed in joint shear response and the occasional inadequacy of data (for the estimation of Fourier coefficients and the hyperbolic constants), this study was undertaken to develop a semi-empirical methodology for predicting the shear strength of infilled joints. In this research study joint shear behaviour was studied under CNS and CNL conditions and also the effect of joint orientation and confinement. The study aimed to develop a methodology which includes joint surface characteristics, joint properties, and infill materials. A new model for predicting the shear strength of infilled joints based on a series of tests carried out on two types of model joint surfaces (with asperity angles of 9.5° and 18.5°) is presented. Graphite, bentonite and clayey sand were used as infill materials. All tests were carried out in a large-scale shear apparatus under constant normal stiffness (eNS) conditions. The results indicate that at low infill thickness to asperity height ratio (t/a), the combined effect of the basic friction angle (
item: Conference-Full-text
Quartzite mining and sand manufacturing
(Department of Earth Resources Engineering, 2006-10) Kalubowila, KDLSSP; Gomes, DGNM; Arundathie, KWDD; Dharmarathne, WGAD; Kumara, WAP; Welideniya, HS; Fernando, WLW; Karunaratne, S; Dissanayake, DMDOK; Ratnayake, N; Chaminda, SP
Manufactured sand is considered as an alternative to match the rising demand of river sand in the construction industry. The basic concept is to crush Quartzite, the source rock to produce sand. This report focuses on sand manufacturing from a quartzite deposit at Dampellessa in Kurunegala district in Sri Lanka. The deposit has to be mined in multiple benches of 10m height and 80° of maximum working angle. Blasting for rock loosening and subsequent ripping with dozers, excavators and hydraulic hammers is recommended as a mining method. The manufacturing process involves crushing of the aggregates after. which grinding and milling is simultaneously done by a specially designed perforated ball mill. Product is made on for customer specifications and suitable for concerting, plastering and as mortar.
item: Conference-Full-text
Tunnel design for fractured rocks and suitable support selection
(Department of Earth Resources Engineering, 2008-05) Senthilkumar, M; Senadhira, AMADM; Giriwaksan, S; Welideniya, HS; Dharmaratne, PGR; Karunaratne, S
This research focused on design of a tunnel in highly fractured rocks, and to propose suitable support classes, based on the study carried out at the Upper Kotmale Hydro Power project location. The necessity arises in order to cope up the unpredictable changes in geological patterns which highly influence the continuity of tunnel works. Present tunnelling method in fractured rocks need to be further evaluated to suit the engineering geological patterns and rock types of the area. The rock strength and the fracture intensity are assessed through field and laboratory works, including tunnel mapping and joint intensity surveys. The suitable support class selected based on Q-value system formulated by Nick Barton (Norway) in mid 70's.The data and the borehole samples obtained from site location facilitated to propose a proper support design, suitable to Sri Lankan geotechnical conditions. The variation in the rock mass from unweathered to highly weathered, sound to heavily fractured along a tunnel was accounted in selecting a suitable supporting method to avoid disastrous consequences and to provide a secure working environment. The results of the study were used to develop a model for tunnel design, and to propose modifications to the existing support classes in fractured rocks at Upper Kotmale Hydro Power Project. And it was understood Q-value evaluation could be more suitable than RMR, for Sri Lankan terrain.
item: Conference-Full-text
Ventilation of underground workings and improvement of comfort levels
(Department of Earth Resources Engineering, 2009-05) Hewage, SC; Rajapakse, RAAC; Rathnayake, RMD; Prasanna, EAP; Dissanayake, DMAK; Dharmaratne, PGR; Welideniya, HS; Rohitha, LPS; Karunaratne, S
Ventilation of underground mines is required to dilute and hazardous gases, control heat and provide oxygen for workers and machinery. Kahatagaha- Kolongaha mines, Dodamgaslanda was selected for the present study as it was remove restarted recently and therefore very little research has been done on air quantity and quality of the mine. The objectives of this research are to make a proposal to rectify the existing ventilation system and to upgrade the existing airflow system with modifications to the present system. A detailed ventilation survey was carried out by measuring the variations of airflow, pressure drop and humidity differences along four levels of the mine (i.e. 565ft, 805ft, and 965ft and 1132ft levels) and compared with the corresponding standard values which describe the permissible conditions to be met for working underground. The distributions of airflows, pressures and humidity in each level could be detailed on graphs and the areas where the additional air supplies were identified. It was proposed to install a dehumidifier to reduce the humidity level inside the mine. Suggestions were made to improve the present ventilation system by locating two booster fans in level 565 ft and 805 ft, which will enhance mine air quality increasing health and safety aspects of underground environment.
item: Conference-Full-text
Ventilation of underground workings and improvement of comfort levels
(2014-08-08) Hewage, SC; Rajapakse, RAAC; Rathnayake, RMD; Prasanna, EAP; Dissanayake, DMAK; Dharmaratne, PGR; Welideniya, HS; Rohitha, LPS
Ventilation of underground mines is required to dilute and remove hazardous gases, control heat and provide oxygen for workers and machinery. Kahatagaha- Kolongaha mines, Dodamgaslanda was selected for the present study as it was restarted recently and therefore very little research has been done on air quantity and quality of the mine. The objectives of this research are to make a proposal to rectify the existing ventilation system and to upgrade the existing airflow system with modifications to the present system. A detailed ventilation survey was carried out by measuring the variations of airflow, pressure drop and humidity differences along four levels of the mine (i.e. 565ft, 805ft, and 965ft and 1132ft levels) and compared with the corresponding standard values which describe the permissible conditions to be met for working underground. The distributions of airflows, pressures and humidity in each level could be detailed on graphs and the areas where the additional air supplies were identified. It was proposed to install a dehumidifier to reduce the humidity level inside the mine. Suggestions were made to improve the present ventilation system by locating two booster fans in level 565 ft and 805 ft, which will enhance mine air quality increasing health and safety aspects of underground environment.