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Department Of Earth Science
EASC 106: GEOLOGICAL FIELD EXCURSIONS
A Technical report on the visit to five places in Accra
By:
NAME: OBIDAN SAMUEL
ID: 10948515
Group : one
Instructors: Dr. Prince Ofori Amponsah Dr. Miriam Selorm Sapah Dr. Joseph Thompson Offei
th
November, 2022.
TABLE OF CONTENT
Chapter one
1.0 INTRODUCTION
T his report is about a five days trip that the class embarked on to visit five places within Accra
and its geological affiliated environs. The field was organized from Tuesday 4th^ October, 2022 to 8 th^ October, 2022 for group 1. The class visited five places (AESL Weija, Twin Rock Quarry, Gud Heart Quarry and Construction Ltd, Seismic Station and the Accra beaches), which are geology related companies and some beaches in Accra. The class had a life time experience of the practical aspect of all that our lecturers have been teaching in the class. We studied the three main types of rocks, their formation and how we can use them. The class had the chance to know the job opportunities and how to set up your own business after reading geology. We also learnt on how to use the geologic tools for measuring strike, dip, dip angle and the direction and with the help of the lecturers, we were able to also know some geologic structures and how they were formed. During the excursion, I created a new idea from Gud Heart Quarry, which can serve as a source of new business and will help the society a well.
1.1 OBJECTIVES
- To know the identification, formation and the composition of the three main types of rocks on the field,
- The Class to know how to use the geologic tools,
- The job opportunities related to Geology,
- Educating student on how to set up their own business after reading geology,
- To add more on student’s experience on the field
Chapter two
2.0 DAILY ACTIVITIES
DAY ONE – AESL (LOC: WEIJA)
Architectural and Engineering Service Limited ( AESL)
T he Architectural & Engineering Services Limited (AES Ltd) is located in ten regions in Ghana but we visited one of the branches in Accra, Weija. AESL is a practicing professional group of Consulting Architects, Civil, Structural, Electrical and Mechanical Engineers, Land and Quantity Surveyors. The main aim of the company is to provide a quick and flexible response with innovative and imaginative building and engineering designs to meet the aspirations of their numerous clients. There are many departments in the company and each has different laboratories in which they perform different work to help solve a problem. These are the department or sectors in AESL; Architects, Quantity Surveyors, Structural Engineers, Electrical Engineers, Mechanical Engineers, Water Engineers and Geo-technical Engineers. Based on the program we are studying; we visited the Geo-technical Department where most of their work is related to Geology. In the Geo-technical Department, there are three labs that work together to provide accurate test on materials. They work on earth materials where they use the principles of soil mechanics and rock mechanics for the solution of its respective engineering problems. The three labs are Foundation lab, Road and Air-Field lab (or compression Lab) and the Tensile lab.
To determine the liquid limit of soil we use a mechanical liquid limit device called Casagrand e. Using a gauge or the handle of the grooving tool and the adjusting plate of the liquid limit device
(Casagrande) such that the cup falls exactly 10 mm for one revolution of the handle. Weigh about 120 grams of the soil sample passing the 425 μm IS sieve and then transfer it to the mixing dish. After that you will Mix the soil with distilled water to form a soft uniform paste and take portion of it into the cup of the casagrande, making sure it uniformly spread in all area of the cup, divide the soil in the cup by firmly running the grooving tool diametrically such that a sharp groove is formed. After that you perform from 40- 50 blows to determine whether the line between the soil is closed. If the groove close above 50 blows, then we have to add water to and blow it again. This test can be done 2-3 trails to achieve consistent consecutive closures of the line in the soil which shall be observed before taking the moisture content sample for calculation of the liquid limit. For the calculation, we will calculate the moisture content, W, for the accepted trial, expressed as a percentage of the oven-dried weight. We can now use the formula given to calculate the liquid limit of the soil using LL=W (N/25) ^ 0.12 where ‘LL’ is the Liquid Limit and N is the Number of drops of the cup required to close the
groove at the moisture content, W.
II. Plastic Limit Test
Sample No. 1 2 Mass of empty, clean can + lid (grams)
Mass of can, lid, and moist soil (grams)
Mass of can, lid, and dry soil (grams)
Mass of soil solids (grams) 4.67 5. Mass of water or moisture(grams)
Water content, w% 6.29 7. Therefore, here the plastic limit is, (6.29+7.65)/2 = 6. PLASTIC LIMIT = [(Weight of water) / (weight of oven – dry soil)] ×
III. PLASTICITY INDEX
The plasticity index of a soil is the numerical difference between its liquid limit and its plastic
limit, and is a dimensionless number. Both the liquid and plastic limits are moisture content. Plasticity Index = Liquid Limit - Plastic Limit PI =LL- PL. (PL=Plastic Limit and Liquid Limit)
SECTION 2: At the Compression Lab
Engineer Moses Nabil was the senior lab technician at the compression lab. He took us through the process and how they work with their machine. The Compression Lab is also called “Concrete Lab”. The main work at this lab is to test for materials at the site, mostly concrete.
They test for the Compressive strength of concrete, which is one of the main properties of a concrete.
Test procedure and how to use the machine
From the engineer, concrete take much time to gain 100% strength so the concrete cube should be cast for standard size and allowed to cure for 28 days. Three specimens of the same dimension are cast for testing in order to obtain accurate results. First of all, takeout the specimen from the curing tank and wipe out the excess water from the surface of the specimen. Take the dimension of the specimen to the nearest 0.2m, and clean the bearing surface of the testing machine to avoid problem or errors in the test. After that you will Place the specimen in the machine in such a way that the load shall be applied to the opposite sides of the cube cast. You will then align the specimen centrally on the base plate of the machine and rotate the movable portion gently with your hand so that it touches the top surface of the specimen. From there, you will apply the load gradually without shock and continuously at the rate of 140 kg/cm2/minute till the specimen fails. Finally, you will record the maximum load and note any unusual features in the type of failure After all the necessary procedures, you will then repeat the procedures for the other two cubes.
Fig 8: the concrete block fig 9: the mold for preparing the block
SECTION 3: At the Tensile Lab
This lab test is performed to determine the tensile strength, yield strength, and ductility of a
metallic material. First of all, the specimen is thoroughly cleaned and the gauge length is marked on the steel rod using the punching tool. The specimen is then placed on the testing machine by operating the handle in such a way that the specimen firmly fits at the base. The extensometer is then fixed on the specimen and the reading is set to zero and the load is then applied to utilize the right valve. The loading rate is increased gradually until the pointer moves backward and the specimen finally breaks. From engineer Moses the load just before the breaking is known as the ultimate load and the load at the instant of breaking is known as the breaking load. And the change in length of the rod can be obtained from the extensometer reading.
Fig 10: the TMT Bars testing machine used for determining the tensile strength
Metamorphic rocks are pre-existing rocks on the earth's surface that change in composition and density over a long period of time under the influence of pressure and heat. They can be either igneous or sedimentary rocks. They could even be formed from pre-existing metamorphic rocks. Different rocks have different compositions as they usually consist of one or more minerals. Some metamorphic rocks may have the same composition as other sedimentary or igneous rocks, but rocks are classified mainly based on how they were formed. There are two processes of metamorphic rock formation, these are Contact metamorphosis and regional metamorphosis. Gneiss: Gneiss is a metamorphic rock formed when granite metamorphosized at high temperature and pressure. The minerals found in the rock was Quartz, Garnet and Amphibole. The texture of the rock was coarse grain and the structures found are foliation, joints, cracks and bands.
Fig: 11. Gneiss
THESE ARE SOME OF THE MACHINERIES USED
- Front Loaders
- Excavators
- Quarry Truck
- Bulldozer
5. Powerscreen
Front Loader
Fig 13: Excavator
Quarry Truck
A quarry truck is a type of haul truck and it a key player in the equipment stock needed for effective quarrying. It helps to transport materials from the source location where the front loader is located to the processing location
Fig 14: Quarry truck
Bulldozer
A bulldozer is essentially just a high-capacity tractor with a large metal plate stationed on its front end. This gives the machine the capability of pushing large quantities of materials during quarrying process.
