ON DYNAMIC BEARING CAPACITY OF SHALLOW FOUNDATIONS

Abstract

vith the limits cad linitattcne of the csrrcnt state of knouledde on the aociamic design of shallow foundations the present day practices to to treat the dynento problem as an equivalent pssudostatic cat and then to detc:rtine tho bearinG capacity. One of such approach in paoudostatio case is to treat the dynamic loading as an equivalent problem of eccentric loading. In the present investigation the later approach has been followed and the scope of the stud* has been limited accordingly. In the present study a new cethod for settlement computation in case of •oeentrictfly loaded tooting hem been evolved based on the dsformatioahl characteristics of the sat-soil. It io felt that this cethod will be suitable both for homogeneous and layered substrata (Alluvial deposits). It is also considered that this will be suitable for a fairly accurate s.ttlewt prediction in the eorkiuc ,road ranjs. The method conuiots of the following two etc est (1) Jetimatinj the increase is vertical stress in various legere for a considerable depth in the subotrat,% in.cdiately below the foundation. (it) Zstiaatihc the strains In the individual layers by knc.vinb; the 'h' value at different depths and uorkivZ out the settlement by knowing the oorree-poading le;,er thicknesses. Vy a knowledge of dittersntv4 settlement, tilt can oleo be worked out The above sothod can be extended to work out the ultimsts bearina capacity 1t. c sbe of soils p0000saiog non-] antar street strain propertied. I'or ver,ifto3tiono of the validity of the aruggeet*4 aetbod, the load-aettic=ent plots obts.tned for various a/D ratios were coapared with the actual plate load test datt of Data (1969)• It was observed that the settlment and tilt prediction by this method and the above teat results compared fairly well in the working load rants. Similar comparison with the Saran's (1969) nethod were also made and close coo eSlance of results wore obseved.. It Is felt flat the suggested method being dimple and straightforward 4dU. roust the needs of the do$itjn offices ,. The other poondoctatic approaches available for earthquake, loading, bavc alto been discus:ed. A critical anti-notion of the ltaitatsonc of the niat1n6 and proposed uethod to determine the dymtic hiring capacity of shallow to. Lima have Loan prloentcd. J.)hloreat possible approaches for a realistic design have ciao been postulated.