PROPOSED BADULLA, HALI ELA & ELLA INTEGRATED WATER SUPPLY SCHEME FIELD TRIP REPORT

PROPOSED BADULLA, HALI ELA & ELLA INTEGRATED WATER SUPPLY SCHEME
Figure 1 : Map of the field trip

A field trip was arranged by Uva Wellassa University of Sri Lanka, Department of Science and Technology, Degree program of Mineral Recourses and Technology on 10th January, 2014. The students who are following Mineral processing technology specialized area & water science and technology specialized area were participated for the visit. It was a one day field trip to Demodara, Haliella (GPS : 6.913056, 81.060556) area which is approximately 23 km from Uva Wellassa University. We left for trip on Friday 10 January, 2014 at 12:30pm and arrived back to University on same day at 7:30 pm. The main objectives of the trip were to study the Engineering geology and the application of geological data, surficial materials and ground water, proper location, planning, design, construction, operation, and maintenance of engineering structures, Engineering geology complements environmental geology or hydrogeology, bore hole, regional geology and geomorphological features of the area. Mr.T.Cooray lead the team in this event.

The Badulla –Haliela –Ella integrated water supply project has proposed a dam crossing the Badulu oya from Demodara. This Project is spread out of wide area to Haliela division stretching from Pinnarawa existing pumping station to Kithal Ella storage tank. The proposed and existing water supply schemes given in will be improved and integrated under this project.
The main objective of the project is to cater for the need of safe water supply facilities to Badulla, Haliela, Ella and Demodara demand centers. This is to fulfill the current and future needs of pipe borne water supply facilities of the beneficiaries in the area and enhance their health and living standards. About 15,000 families will be benefited from the project in the design horizon in Badulla, Haliela and Ella  areas.
Under this project the rock mass classification is carried on for study of the proposed site. Rock mass classification is the method of identify the most significant parameters influencing the behavior of a rock mass and provide a basis of understanding the characteristics of each rock mass class. This gain mainly two benefits as improving the quality of site investigations and providing quantitative information for design purposes.
On the 10th of January 2014 we have visited the place in Demodara where undergone geotechnical investigations of this project.

 TOPOGRAPHICAL OVER VIEW OF THE DAM PLACE

Figure 2 : Dam Location (6.913056, 81.060556)

The Badulla- Hali-ela- Ella integrated water supply project main purpose is give water to badulla district by build a dam across the badulu-oya. Their main targeted water supply cities are badulla, hali-ela and ella. So they have to choose the wright dam place in badulu oya. It is very important because, they have to supply water for three cities continuously all over the year. According to knowledge of Geo technology engineers, they are plain to build dam in domodara. They are plain to build 15 meters height dam across the badulu oya.
Before contracts the dam geologist should have to be investigating the dam place. Because they don’t know rock type of the place, rock direction, rock strength and morphological features which are early mentioned.
Badulu-oya flow along with badulla-colombo road and there are several paddy fields near the badulu-oya. Before constructing dam geologist want to consider many things about the place. They are, Definitely dam should be damage the paddy and some time it effect the Badulla-Colombo road also, they have to investigate the rock type and rock strength and weathering condition of the place. For that they tested the rock type and rock strength by using bore holes.

ACCESSIBILITY

 The area is well accessible through a well carpeted road. The drive to the area is approximately 1-1.5 hours from Uva Wellassa University.

VEGETATION

The area is vegetated and contains many types of crops for the summer.

DRAINAGE

The drainage is mostly dendritic to parallel and generally controlled by structure.

RAINFALL AND TEMPERATURE


We don’t receive any rainfall during the period of field trip, Temperature is almost average in between 18 Celsius to 24 Celsius.

DAM SITE INVESTIGATION CENTER

  • Investigations
    • Leakages
    • Fracture zones
    • Depth
    • Strength
      • Compressive strength
      • Rock mass
    • Discontinuities
      • Fault zone, shear zones
      • Fracture characteristics
      • Joints(axial, vertical) and the joint spaces
·         Using borehole investigations check the stability and the safety of the dam.
The rock type observations consider only for decide whether the rock could bear the water capacity and the ability of having discontinuities causing water leakages. If present calcnite, quartzite have to do further lab testing, because of their water solubility. In a cross section of a layer, the top part is the overburden or soil layer, and the other part is the bed rock.
For a dam construction, do not do a soil investigation using Standard Penetration Test(SPT) but for drilling use the SPT tube .the rock type identification also not needed very much. But the weathering grade is important, to clarify whether it is a highly weathered, weathered or fresh, according to the ASTM code they used.

When do borehole investigations make a drill hole and take a core run. By careful observations of the core run, geotechnical engineers identify the fractures and the related 
characteristics that effect to the safety of the dam. For a dam, usually make three drill holes, one at the middle of the river and the others on banks.

Bore hole test     

The work includes drilling boreholes, installation of casings and screens, provision of gravel packing, development of the boreholes; test pumping, obtaining rock and water samples, water Quality analysis; platform casting and hand pump installation.
Equipment and materials are drilling instrument, test pumping and headwork construction material. Test pumping equipment should be independent from the drilling rigs.

Drilling process in bore hole.

Hydraulic feed rotary boring machine was used for drilling work. A cutting tool was attached at the lower end of the drilling rod. Drilling was carried out by continuously rotating the drilling rod and pumping mud water through hollow rods into the bottom of the boreholes. The cutting was washed out to the ground surface by the water under circulation.
Overburden was removed by using Cassin bitt. (Tungsten carbide) and weathered rock was drilled by using diamond bitt.

Testing methods

Rock Quality Designation (RQD)


If  
RQD>75%   high quality rock mass and 
RQD<50%   low quality rock mass

Core Recovery (CR)

Have two types of CR, solid core recovery (SCR)  and  the total core recovery(TCR)
If   CR > 70%   accept for constructions.

BORE HOLE LOGGING

The investigation of samples taken from drilling is considered under this. For this, the main thing is recording. Each project should have to  maintaining a field book as a hard copy or an excel sheet as an soft copy including all the details, such as the date,time,weather condition, no of bore holes and all the dates and interpretations related to each and every core run in each borehole separately.
In each bore hole should have a log sheet with; site name, bore hole number(BH no),log box no, starting and the ending date, machine type,time,coordinations.This is very important and should keep record carefully because the decisions that make on the site are mainly depend on the logging observations.
Each core barrel is kept in a log box in a particular sequence with their length, and each box have a number. The sequence is start from the left top most corner keeping the upper part of the overburden, lie near the surface.
In each core run take observations of the colour,grain size,mineral type(if needed) , discontinuities, silt content(clay),soil strength for take discussions.
By observing the color of the drill core can take an idea of the weathering pattern, geological effects and the organic content of the sample.
Joint can behave as open joint, close joint. According to the joint type (joint separation) of the discontinuity can take an decision of the water penetration. If present iron oxide in the joint, could have water there. If the joint is very smooth, can say that there is high ability for water mobile. Furthermore investigations, take accounts on the joint roughness, joint angle, coal gauges-resulted from rock moving (can identify by small tractions).




DRILLING PROCESS

We observed drilling machines at 2.30p.m. That placed in the site area, few meter away from the project investigation center. At the top most part of the drilling machine have a tripod to hang the drilling hammer. The  hammer with 63.5kg weight  is use to press the rock by the SPT tube with 45cm length in order to take the sample of the cross section of layers.
As the cutter of the machine, use a drill bit;
o  
Diamond (100-125 carets) for rock cutting and for coarse boulders
Tungsten carbide for soil cutting

A diamonds Drill bit

The drill bit with its casing cut a core barrel according to the requirement and it comes out with drill fluid (water) along the mud rod. All this process is done using the hydraulic force resulted from the mechanical power of diesel engine in the drill machine. The rotation speed (rotations per minute) can change according to the level that going to drill by varying the hydraulic push. According to the requirement can break the core barrel by the way of touching the clutch of the machine.
The drill fluid helps to;
o   Mitigate the friction by lowering the heat
o   Bring out the core barrels
o   Reduce the soil collapsing

DISCUSSION

Geological engineer stated the Demodara dam site have lineaments along the dam axis according to the geological surveys which are done so far. There is an old land slide area near to the planed site. Because of the lineation near by the river it can turn direction and velocity. So best way to identify the lineation underneath rock structure that can be affect to dam by using bore hole mining.


And also the rock investigations there are charnokite, gneiss and marble rock boulders near the river. Though charnokite is a hard rock there are fractures and other discontinuities that can be weaken the dam. So the bore hole logging observations are needed in this case.



Figure 9 and 10 : Proposed dam site, valley and the elevation profile of the cross section of the valley


REFERENCES

1.    http://www.crdcecbsl.lk/Special%20Projects/Badulla_project_home.asp : IEE FOR THE PROPOSED BADULLA , HALI ELA & ELLA INTEGRATED WATER SUPPLY SCHEME
2.    http://www.crdcecbsl.lk/Special%20Projects/documents/Badulla-R-Ex.summary.pdf : PROJECT PROPONENT by NATIONAL WATER SUPPLY & DRAINAGE BOARD (NWS&DB)


By Chanaka Gayan Wickramasinghe