 Sandeep Javeri, Assistant Professor, Department of Civil Engineering from Valchin Institute of Technology, Sholapur. In today's session we are going to discuss types of dam which is a part of basic civil engineering. The learning outcomes at the end of this session students will be able to explain the different types of dam. Now the types of dams are depends upon different types of material to be used in the construction of dam. It may be earthen dam, it may be masonry dam, it may be concrete dam and rockfill dam. Some dams are classified depending upon the various forces acting on the dam and how that forces is resisted by the dam whether that forces are resisted by arch action or by self-made of the dam. So here we are going to discuss few types of dam. These are gravity dam, arch dam and rockfill dam. Now let us consider gravity dam. Now in the gravity dam what are the various forces acting on the dam that is forces due to water pressure, wear pressure, shield pressure and uplift pressure. These are resisted by the weight of the dam itself. So you can see in this figure the various forces acting on the dam. So this is a force due to the water pressure, there is a force due to the uplift pressure, then there is a force due to the tail water. So these are the forces which are acting on the dam. Other forces are shield pressure, then wear pressure and earthquake forces these are acting on a dam. So such kind of forces is resisted by the gravity dam by its weight only. So that is why in India the most of the dams are gravity dam. It requires strong base that is strong foundation. Now let us consider the advantage of gravity dam. As we know the gravity dam is strong and stable than earthen dam because in case of earthen dam we are going to use natural soil material and the drawback of the earthen dam is there is a seepage of water and that water seepage of water that should be controlled by a proper drainage system. In case of gravity dam the dam is resting on a strong foundation while in case of earthen dam it can rest on soft soil also. So gravity dam is more strong and stable than earthen dam. Also it requires very less maintenance, it may be constructed of masonry or concrete material, it can be constructed for greater height. So due to increase in height in case of gravity dam we can increase the storage capacity of the dam also. Now let us consider arch dam. Now arch dam is covered in plant and it carries major part of its water load horizontally by arch action and some part of load is carried by cantilever action. You can see here this is a arch dam and this is the upstream side of the dam and these are the internal gates which is provided inside the dam and through that the water is coming from the upstream side to the downstream side. So here the in case of arch dam due to arch action the load is transferred to the side abatements which are present here and some part of the load is going to be carried by means of cantilever action. One of the important thing is that in case of arch dam the length of dam we can reduce. So the construction cost is going to be reduced. Now let us see some advantages of arch dam. It is suitable for George's where the length is small in proportion to height. For a given height the cross sectional area of arch dam is less as compared to gravity dam. As the thickness of the wall which is provided for arch dam is small so the cross sectional area is going to be reduced. So it also helps to achieve the economy in construction of dam. Uplift pressure is small as compared to gravity dam due to narrow base width. So in case of gravity dam the second important force which is acting on a dam is the uplift pressure. So in case of arch dam the uplift pressure is small. Uplift pressure is a pressure which is exerted on the base of the dam through the foundation due to presence of water and which due to seepage of water within the foundation. So we have to minimize that uplift pressure. For that we have to construct some trench or wall inside the foundation to overcome the seepage of water within the foundation. Rock fill dam. So rock fill dam is a flexible than gravity dam and less flexible than earthen dam. Foundation requirement is more rigid than earthen dams which is constructed in all types of foundation. Impervious membrane is provided to achieve water tightness. So rock fill dam we can construct by using a available material near the dam site. So you can see here this is a photograph of rock fill dam. It has a impervious foundation. Now this top portion is called crest. On the upstream face you can see the water level and here on the upstream face a concrete face is provided. This is to be provided to avoid or to prevent the entry of water within the body of the dam. If the water is allowed within the body of the dam it will cause decreasing strength of the joints motor joints which is provided for the construction of rock fill dam. Hence it will deteriorate the material and this will reduce the strength of the dam. For that purpose the upstream face is provided with a concrete surface. The advantages of rock fill dam are it is cheaper than concrete dam. As we know the rocky material is used for the construction of dam. So the cost is less as compared to concrete dam. It constructs rapidly if proper rock is available. If the size of the rock available is well defined then we can construct it rapidly. It is very useful in seismic regions as they provide higher resistance to seismic forces because of their flexible character. So this is one of the important advantage of rock fill dam. Now you are supposed to pause the video and answer these questions. These are the answers. As we know rock fill dam can be constructed for any type of foundation. So this statement is true and the second statement is concerned with the height of that. The height of the cross for the given height the cross section area of the arch dam is more as compared to ground dam. So this statement is false because for a particular height the cross section area of arch dam is going to be reduced due to the small thickness as compared to the gravity dam. So the cross section area is going to be reduced. So second statement here is false. Now these are the references that we are going to use for creation of this video. Thank you.