The Importance of Geological Knowledge - Report Example

Table of Contents Introduction…………………………………………………….…………………………..3 Need of Knowledge of Geology.....................………………...……………………….3 Geology of Site..........................................................................................................3 Geological Hazards............................................................................................…...4 Site Investigations....................................................................................................5 Methods of Site Investigations................................................................................5 Data of Site Investigations.......................................................................................6 References…............................................................................................................7 Introduction The essay gives a detailed discussion of the importance of geological knowledge of the site outlining the different methods and techniques which may be employed for the geological investigations of the site for two storey art gallery. Need to know the Geology of a site It is very important for a civil engineer to know the geology of the site on which a particular building is to be constructed because different types of soils and rocks are present at a particular location which may have altogether different properties from any other site therefore it is very important to know what type of rocks or soils are present at the site because this will dictate the type and nature of the foundation used for the building on that particular site. Geological considerations are most important when designing buildings on faults. The study of geology of the site helps to determine the alignments for linear designs and the best foundation and excavation characteristics. The study of geology of the site is also directly related to the economy of the design and construction as it helps to determine the best location for building to avoid costly foundations and dewatering requirements. During construction the problems faced in dewatering and shoring can also be solved only if the engineer has the sound knowledge of geology of the site. The knowledge of the geology of the site is equally important during the maintenance and operation phase of the building because certain problems of settlement are to be solved utilizing this knowledge. General Geology of the Site The general geology of the site can be described as coarse clay approaching fine sand which is quite similar to the London Clay, which is stiff bluish grey marine deposit famous for its fossil inclusions which suggests that the area was under warm tropical seas during the geological developmental era of the region. Traces of heavier sediments i.e. sands and gravels are also present. Geological Hazards The only geological hazard present at the site according to my observations is the erosion due to river flow because as the water flows with different velocities during the course of the year recession of the river is very much likely to occur. This problem can easily be solved by constructing embankments from hard rock to avoid erosion. The hazards like differential settlement are not likely to occur. The moisture conditions are also likely to change because of the river being near which can result in weakness of foundations and thus failure. In order to avoid this the foundations should be made deep to reach more consistent strata. Therefore the pore water pressure is a major consideration while deciding the nature and size of foundation because it may result in ultimate failure of the structure. The liquefaction of soil during earth quake is also governed by the pore water pressure of the soil. Site Investigation Site investigation describes the process of carrying out investigations on land to determine the geological properties of the soil and to collect suitable data for the purpose of risk assessment. The investigation is normally carried out in several stages. These stages range from desk study and simple visual inspection to full intrusive investigation using trial pits and boreholes etc and the sampling and analysis of materials. A wide range of techniques and methods for gathering site data are available however, it is essential that any site investigation is designed based upon the available conceptual site model and will produce sufficient quantity and quality of data which is required for risk assessment. Methods of Site Investigation According to the preliminary investigation of the site geology the following methods can be employed for the detailed study of the geology of the site: a. Wash-type Boring: In this method a light bit is used and by chopping, twisting and jetting action of the bit as circulating drilling fluid removes cuttings from the holes. It is difficult to obtain undisturbed samples in this method. Changes indicate rate of progress. b. Magnetic Measurement: To check the faults, bedrock, buried utilities or metallic trash this method is used. Highly sensitive proton magnetometer is used to measure the Earth’s magnetic field at closely spaced stations along a traverse. c. Rotary Drilling: Power rotation of the drilling bit removes cutting from hole as circulating fluid. Changes indicate the rate of progress. d. Refraction: It is based on time required for seismic waves to travel from source of emission to points in ground surface as measured by geophones. This is a very useful method to check the depth of bedrock. e. Test Pits: Excavations are made and both disturbed and undisturbed samples are obtained. f. Probing and Sounding: The resistance to the driving action of a steel rod into the soil dictates the type and strength of soil Data of Site Investigation The following data is required to be produced from the geological investigations of the site for the purpose of design: a. Type of soil b. Grain size of soil c. Information about the moisture content of the soil d. Depth of the bedrock e. Structure and texture of soil f. Bearing Capacity of soil g. Presence or absence of a fault-line Several types of foundations based on shape and materials can be constructed and the selection is done using the data based on above mentioned parameters. This data is employed to calculate the load bearing capacity of soil and its resistance against settlement and geological hazards already mentioned. References: David George Price (2009) Promoting Engineering Geology, Principles and Practices, Springer Richard E. Goodman (1993) Engineering Geology, Rock in Engineering Construction, J. Wiley and Sons F. G. Bell (2004) Engineering Geology and Construction, Spon Press Suping Peng, Jincai Zhang (2007), Engineering Geology for Underground Rocks, Springer Arthur Conway (1981), Engineering Hazards, Assessment Frequency and Control, Oyez Press. Read More