 I am here to have a discussion with you on topic soil investigation. Learning outcomes of today's session. At the end of the session, students will be able to explain soil investigation and its importance in the design of foundations. What is soil investigation? Dear friends, soil investigation is a methodology used to carry out physical testing on site to understand the ground conditions for geotechnical design. What for this geotechnical design is required? For design of foundations, design of retaining walls or soil improvement, etc. Here you can see a soil investigation being carried out. In the photograph, you can see the soil investigation. Now, little in depth, we will see what is soil investigation. See soil investigation is an essential part of the design and construction of a proposed structural system. Like buildings, dams, roads, highways and many other civil engineering projects are there. So this is an essential part of the design and construction of civil engineering structures. Now soils, what is done under soil investigation? Soils are identified, observed and recovered during the soil investigation of a proposed site. Now, again, making estimates and judgments based on information from a limited set of observations and from field and laboratory test data that will have profound effects on the performance and cost of structures constructed at a site is soil investigation. Remember, okay? Followed, making estimates and judgments based on information from a limited set of observations. How these observations are obtained from field and laboratory test data, okay? Here you can see the photographs of geotechnical investigation being carried out. Now let us see the objectives of soil investigation. What are the objectives? Number one, to evaluate the general suitability of the site for the proposed project. This is the first objective, first and the foremost, right? To evaluate the general suitability of the site for the proposed project. Then second, to enable and adequate and economical design to be made, get adequate and economical design for foundations, etc. Then to disclose and make provision for difficulties that may arise during construction due to ground and other local conditions. Followed, so these are the objectives of soil investigation. Now there are different stages involved in soil investigation. Generally, soil investigation has three components, remember. The first component is done prior to design. The second one during design process and the third one during construction, okay? The first component which is prior to design is more extensive and is conducted in phases. That we will see today, okay? So phase one of this first component, okay? What it is called? This phase is called sometimes desk study. It involves collection of available information which is that site plan, type, size and importance of the structure, loading conditions, previous geotechnical reports, maps, including topographical maps, aerial photographs, steel photographs, satellite imagery, geological maps and newspaper clippings, okay? Collection of all this data is called desk study. Then maps giving geology, counters and elevations, climate, land use, aerial photographs, regional seismicity, hydrology can be utilized from the internet. This data is available on net, okay? So that is also used in phase one. Now phase two of site investigation includes site visit, okay? So it is also called preliminary reconnaissance or a site visit is to provide general picture of the topography and geology of the site, right? So geotechnical engineer will visit the site, okay? And while visiting site, he will take utmost care of gathering important information from the site, okay? Now there are certain visit notes of geotechnical engineer. What they include, what they should include, photographs of the site and its neighborhood. Access to the site for workers and equipments, sketches of all fences, utility posts, driveways, walkways, drainage system and so on, okay? All these must be included in the notes of the geotechnical engineer from the site visit. Also, utility services that are available such as water and electricity, sketches of topography including all existing structures, right? The state of any existing building at the site or nearby. Engineers notes should also include exterior and interior cracks, any noticeable tilt, etc. Then geological features from any exposed area such as a road cut. Occasionally few boreholes may be dug to explore the site, okay? In order to boreholes if required at this particular stage may be taken. Now phase 3, detailed soil exploration. The objectives of detailed soil exploration are to determine the geological structure which should include the thickness, sequence and extent of the soil strata. To determine the ground water conditions, to obtain disturbed and undisturbed samples for laboratory tests, to conduct in situ tests. So all these are objectives of detailed soil exploration and this comes under phase 3 of soil investigation. Phase 4 of soil investigation includes laboratory testing. So the samples which are collected, those will be tested in the laboratory, right? So objectives of laboratory tests are to classify the soils. Then to determine soil strength, failure stresses and strengths, stress strand response, permeability, compactability, settlement parameters and many other things. So here you can see photograph of soil mechanics laboratory, okay? So laboratory testing is important phase and it comes under phase 4 of this soil investigation. And last phase, okay, is preparing a report, okay, soil investigation prior to design we are studying and last phase of that is preparing a report, detailed report which will contain clear description of the soils at the site, methods of exploration, soil stratigraphy, in situ and laboratory test methods and results and the location of the ground water. So information or explanations of any unusual soil, water bearing stratum, any soil and ground water conditions such as forced susceptibility or water logged areas that may be troublesome during construction. So all these details will be included and a prepare a report will be prepared, right? That will be presented, right, to the design engineer, geotechnical engineering laboratory of WIT gives consultancy to society, right, government, semi-government organizations and also private organizations. So here you are in a position to see large number of reports, right, those can be referred. Also when Google link is given here, you can refer to this particular link for a sample geotechnical report, right, a sample report. Now dear friends, let us stop while here, we will pause the video. Here are two questions for you. Write down their answers, ok. First question is what is soil investigation in the context of design of foundations? Is the first question and next is what are the objectives of soil investigation for design of foundations? Come on, write down the answers neatly. Here are the answers. First question, its answer. Soil investigation is a methodology used to carry out physical testing on site to understand the ground conditions for geotechnical design, maybe for foundation design, maybe retaining wall for soil improvement or any other soil investigation, right. Then second answer, objectives of soil investigation are to evaluate general suitability of the site for the proposed project. To enable and adequate and economical design to be made and to disclose and make provision for difficulties that may arise during construction due to ground and other local conditions. So, these are the answers. Hope you have written correctly. These are the references for today's session. Go through these. Thank you.