F o r e w o r d 01 this indian standard part i was

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Unformatted text preview: Indian Standard (Part I) was adopted by the Indian Standards Institution on 5 October 1981, after the draft finalized by the Foundation Engineering Sectional Committee had been approved by the Civil Engineering Division Council. 0.2 Raft foundation is a substructure supporting an arrangement of columns or walls in a row or rows and transmitting the loads to the soil by means of a continuous slab with or without depressions or openings. Such types of foundations are found useful where soil has low bearing capacity. This standard was first published in 1965 and revised in 1973. In this revision, besides making its contents up-to-date, guidelines have been given to choose particular type of methods in particular situations and giving reference to finite difference method which will be covered at a later stage. 0.3 This edition 3.1 incorporates Amendment No. 1 (December 1988). Side bar indicates modification of the text as the result of incorporation of the amendment. 0.4 For the purpose of deciding whether a particular requirement of this standard is complied with, the final value, observed or calculated, expressing the result of a test, shall be rounded off in accordance with IS : 2-1960*. The number of significant places retained in the rounded off value should be same as that of the specified value in this standard. 1. SCOPE 1.1 This standard (Part I) covers the design of raft foundation based on conventional method (for rigid foundation) and simplified methods (flexible foundation) for residential and industrial buildings, store-houses, silos, storage tanks, etc, which have mainly vertical and evenly distributed loads. *Rules for rounding off numerical values ( revised ). 3 IS : 2950 (Part I) - 1981 2. TERMINOLOGY 2.1 For the purpose of this standard, the definitions of terms given in IS : 2809-1972* shall apply. 3. NECESSARY INFORMATION 3.1 For satisfactory design and construction of a raft foundation, the following information is necessary: a) Site Plan — Site plan showing the location of the proposed as well as neighbouring structure. b) Building plan and vertical cross-sections showing different floor levels, ducts and openings, etc, layout of load bearing walls, columns, shear walls, etc. c) Loading conditions preferably shown on a schematic plan indicating design combination of loads transmitted to the foundation. d) Environmental Factors — Information relating to geologic history of the area, seismicity of the region, hydrological information indicating ground water conditions and its seasonal variations, climatic factors like vulnerability of the site to sudden flooding by surface run-off, erosion, etc. e) Geotechnical Information — Giving subsurface profile with stratification details ( see IS : 1892-1979† ), engineering properties of the founding strata, namely, index properties, effective shear parameters determined under appropriate drainage conditions, compressibility characteristics, swelling properties, results of field tests like static and dynamic penetration tests, pressure meter tests, etc. f ) Modulus of Elasticity and Modulus of Subgrade Reaction — Appendix A enumerates the methods of determination of modulus of elasticity ( Es ) and Poisson’s ratio ( µ ). The modulus of subgrade reaction ( k ) may be determined in accordance with Appendix B. g) Limiting values of the angular distortion and differential settlement, the superstructure can withstand ( see IS : 19041987‡ ). h) A review of the performance of a similar structure, if any, in the locality. *Glossary of terms and symbols relating to soil engineering ( first revision ). †Code of practice for subsurface investigations for foundations ( first revision )....
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