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Page 1 CHAPTER – 10 FOUNDATIONS Every structure consists of two parts. (1) Foundation and (2) Super structure. The lowest artificially prepared parts of the structure which are in direct contact with the ground and which transmit the loads of the structure to the ground are known as Foundation or Substructure. The solid ground on which the foundation rest is called the “foundation bed” or foundation soil and it ultimately bears the load and interacts with the foundations of buildings. 10.1 Objects of foundations: Foundations are provided for the following purposes 1) To distribute the total load coming on the structure on large area. 2) To support the structure 3) To give enough stability to the structures against various distributing forces such as wind, rain etc. 4) To prepare a level surface for concreting and masonry work. The general inspection of site of work serves as a good for determine the type of foundation, to be adopted for the proposed work and in addition, it helps in getting the data w.r.to the following items. i) Behavior of ground due to variations in depth of water table ii) Disposal of storm water at site iii) Nature of soil by visual examination iv) Movement of ground due to any reason etc. Page 2 CHAPTER – 10 FOUNDATIONS Every structure consists of two parts. (1) Foundation and (2) Super structure. The lowest artificially prepared parts of the structure which are in direct contact with the ground and which transmit the loads of the structure to the ground are known as Foundation or Substructure. The solid ground on which the foundation rest is called the “foundation bed” or foundation soil and it ultimately bears the load and interacts with the foundations of buildings. 10.1 Objects of foundations: Foundations are provided for the following purposes 1) To distribute the total load coming on the structure on large area. 2) To support the structure 3) To give enough stability to the structures against various distributing forces such as wind, rain etc. 4) To prepare a level surface for concreting and masonry work. The general inspection of site of work serves as a good for determine the type of foundation, to be adopted for the proposed work and in addition, it helps in getting the data w.r.to the following items. i) Behavior of ground due to variations in depth of water table ii) Disposal of storm water at site iii) Nature of soil by visual examination iv) Movement of ground due to any reason etc. Foundations 10.2 Bearing capacity: The ability of the foundation material, weather soil or rock to carry loads safely. Methods of determine the bearing capacity of soil: The bearing capacity of soil is determined by any one of the following methods (i) Method of loading (ii) Method of dropping a weight I. Method of loading Procedure to carry out the test: 1. A square pit of required size is excavated upto 5 times the side of steel plate to be used. At the centre of pit, square hole is dig, which is same ratio to that of breadth to depth of pit. 2. The bottom of the hole is made level 3. The steel plate is put up in the hole and then platform is prepared as shown in fig 10.1. Fig 10.1 Method of loading Page 3 CHAPTER – 10 FOUNDATIONS Every structure consists of two parts. (1) Foundation and (2) Super structure. The lowest artificially prepared parts of the structure which are in direct contact with the ground and which transmit the loads of the structure to the ground are known as Foundation or Substructure. The solid ground on which the foundation rest is called the “foundation bed” or foundation soil and it ultimately bears the load and interacts with the foundations of buildings. 10.1 Objects of foundations: Foundations are provided for the following purposes 1) To distribute the total load coming on the structure on large area. 2) To support the structure 3) To give enough stability to the structures against various distributing forces such as wind, rain etc. 4) To prepare a level surface for concreting and masonry work. The general inspection of site of work serves as a good for determine the type of foundation, to be adopted for the proposed work and in addition, it helps in getting the data w.r.to the following items. i) Behavior of ground due to variations in depth of water table ii) Disposal of storm water at site iii) Nature of soil by visual examination iv) Movement of ground due to any reason etc. Foundations 10.2 Bearing capacity: The ability of the foundation material, weather soil or rock to carry loads safely. Methods of determine the bearing capacity of soil: The bearing capacity of soil is determined by any one of the following methods (i) Method of loading (ii) Method of dropping a weight I. Method of loading Procedure to carry out the test: 1. A square pit of required size is excavated upto 5 times the side of steel plate to be used. At the centre of pit, square hole is dig, which is same ratio to that of breadth to depth of pit. 2. The bottom of the hole is made level 3. The steel plate is put up in the hole and then platform is prepared as shown in fig 10.1. Fig 10.1 Method of loading 4. The amount of initial load is decided according to the type of the soil to be tested 5. A level is planted to note the setting of steel plate w.r.to the permanent benchmark. 6. The load is to be kept on platform till the settlement of the ground ceases or stops 7. The load is increased by a suitable amount, usually 0.5 tonnes and the procedure is continued 8. The recording of results is carried out in the following proforma. Date and time of taking reading Load Increase in settlement Total settlement Remarks 0.5 tonne 1.0 tonne a b c - a1 b1 c1 a a+b a+b+c - a+b+c+a1 a+b+c+a1+b1 a+b+c+a1+b1+c1 settlement ceases settlement ceases 9. The settlement of the ground will be fairly is proportion to the load upto a certain limit, when the bearing power of soil exceeded, the settlement will be out of the proportion. 10. The bearing capacity and safe bearing capacity of soil are calculated by using the following Page 4 CHAPTER – 10 FOUNDATIONS Every structure consists of two parts. (1) Foundation and (2) Super structure. The lowest artificially prepared parts of the structure which are in direct contact with the ground and which transmit the loads of the structure to the ground are known as Foundation or Substructure. The solid ground on which the foundation rest is called the “foundation bed” or foundation soil and it ultimately bears the load and interacts with the foundations of buildings. 10.1 Objects of foundations: Foundations are provided for the following purposes 1) To distribute the total load coming on the structure on large area. 2) To support the structure 3) To give enough stability to the structures against various distributing forces such as wind, rain etc. 4) To prepare a level surface for concreting and masonry work. The general inspection of site of work serves as a good for determine the type of foundation, to be adopted for the proposed work and in addition, it helps in getting the data w.r.to the following items. i) Behavior of ground due to variations in depth of water table ii) Disposal of storm water at site iii) Nature of soil by visual examination iv) Movement of ground due to any reason etc. Foundations 10.2 Bearing capacity: The ability of the foundation material, weather soil or rock to carry loads safely. Methods of determine the bearing capacity of soil: The bearing capacity of soil is determined by any one of the following methods (i) Method of loading (ii) Method of dropping a weight I. Method of loading Procedure to carry out the test: 1. A square pit of required size is excavated upto 5 times the side of steel plate to be used. At the centre of pit, square hole is dig, which is same ratio to that of breadth to depth of pit. 2. The bottom of the hole is made level 3. The steel plate is put up in the hole and then platform is prepared as shown in fig 10.1. Fig 10.1 Method of loading 4. The amount of initial load is decided according to the type of the soil to be tested 5. A level is planted to note the setting of steel plate w.r.to the permanent benchmark. 6. The load is to be kept on platform till the settlement of the ground ceases or stops 7. The load is increased by a suitable amount, usually 0.5 tonnes and the procedure is continued 8. The recording of results is carried out in the following proforma. Date and time of taking reading Load Increase in settlement Total settlement Remarks 0.5 tonne 1.0 tonne a b c - a1 b1 c1 a a+b a+b+c - a+b+c+a1 a+b+c+a1+b1 a+b+c+a1+b1+c1 settlement ceases settlement ceases 9. The settlement of the ground will be fairly is proportion to the load upto a certain limit, when the bearing power of soil exceeded, the settlement will be out of the proportion. 10. The bearing capacity and safe bearing capacity of soil are calculated by using the following Foundations Bearing capacity of soil in tones/m 2 Maximum load = -------------------------------- Area of steel plate Safe bearing capacity of soil in tones/m 2 Bearing capacity of soil = --------------------------------------- Factor of safety Note: 1) This method can also be used for confirming the known bearing power of a soil 2) The loading should applied without shock 3) Dial gauges or deflect meters to record the settlement instead of level & staff for the accuracy upto 0.02mm 4) The zero corrections should be deducted from the observed settlement to get actual settlements zero correction is the settlement due to adjustment of soil particles under the action of loading 5) The bearing capacity of sandy soil and gravelly soil is affected to the extent of 50% by presence of water table. Water should be pumped out before placing the steel plate 6) The results obtained by this method are fairly accurate and reliable. Page 5 CHAPTER – 10 FOUNDATIONS Every structure consists of two parts. (1) Foundation and (2) Super structure. The lowest artificially prepared parts of the structure which are in direct contact with the ground and which transmit the loads of the structure to the ground are known as Foundation or Substructure. The solid ground on which the foundation rest is called the “foundation bed” or foundation soil and it ultimately bears the load and interacts with the foundations of buildings. 10.1 Objects of foundations: Foundations are provided for the following purposes 1) To distribute the total load coming on the structure on large area. 2) To support the structure 3) To give enough stability to the structures against various distributing forces such as wind, rain etc. 4) To prepare a level surface for concreting and masonry work. The general inspection of site of work serves as a good for determine the type of foundation, to be adopted for the proposed work and in addition, it helps in getting the data w.r.to the following items. i) Behavior of ground due to variations in depth of water table ii) Disposal of storm water at site iii) Nature of soil by visual examination iv) Movement of ground due to any reason etc. Foundations 10.2 Bearing capacity: The ability of the foundation material, weather soil or rock to carry loads safely. Methods of determine the bearing capacity of soil: The bearing capacity of soil is determined by any one of the following methods (i) Method of loading (ii) Method of dropping a weight I. Method of loading Procedure to carry out the test: 1. A square pit of required size is excavated upto 5 times the side of steel plate to be used. At the centre of pit, square hole is dig, which is same ratio to that of breadth to depth of pit. 2. The bottom of the hole is made level 3. The steel plate is put up in the hole and then platform is prepared as shown in fig 10.1. Fig 10.1 Method of loading 4. The amount of initial load is decided according to the type of the soil to be tested 5. A level is planted to note the setting of steel plate w.r.to the permanent benchmark. 6. The load is to be kept on platform till the settlement of the ground ceases or stops 7. The load is increased by a suitable amount, usually 0.5 tonnes and the procedure is continued 8. The recording of results is carried out in the following proforma. Date and time of taking reading Load Increase in settlement Total settlement Remarks 0.5 tonne 1.0 tonne a b c - a1 b1 c1 a a+b a+b+c - a+b+c+a1 a+b+c+a1+b1 a+b+c+a1+b1+c1 settlement ceases settlement ceases 9. The settlement of the ground will be fairly is proportion to the load upto a certain limit, when the bearing power of soil exceeded, the settlement will be out of the proportion. 10. The bearing capacity and safe bearing capacity of soil are calculated by using the following Foundations Bearing capacity of soil in tones/m 2 Maximum load = -------------------------------- Area of steel plate Safe bearing capacity of soil in tones/m 2 Bearing capacity of soil = --------------------------------------- Factor of safety Note: 1) This method can also be used for confirming the known bearing power of a soil 2) The loading should applied without shock 3) Dial gauges or deflect meters to record the settlement instead of level & staff for the accuracy upto 0.02mm 4) The zero corrections should be deducted from the observed settlement to get actual settlements zero correction is the settlement due to adjustment of soil particles under the action of loading 5) The bearing capacity of sandy soil and gravelly soil is affected to the extent of 50% by presence of water table. Water should be pumped out before placing the steel plate 6) The results obtained by this method are fairly accurate and reliable. II. Method of dropping a weight: In this method, a substance of known weight is dropped from a known height as shown in 10.2. The depth of impression made by the weight on the soil is noted. Then the bearing capacity of the soil is worked out as follows. Fig 10.2 Method of Dropping Weight Ultimate resistance of soil w x h R= ------------- d where R – Resistance of soil A – cross section area of the substance h - Height w - weight of substanceRead More
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