Engineering Analysis of Foundation Slab Settlement and Deformation for a High-Rise Building on a Nonuniform Rock Bed

Abstract

According to [1,2], no analysis of bed deformation need be performed for buildings erected on rock. However, in accordance with accepted normative documents on the design of high-rise buildings and those under development, analysis of bed settlement should be carried out even if rock lies under the bottom of the slab. In addition, for high-rise buildings under elevated load levels on the bed, such an analysis is necessary, in part, for a more reliable determination of the bed foundation modulus curve and, consequently, for a more accurate calculation of the forces arising in the foundation slab and aboveground structures.An engineering procedure is being developed at the Gersevanov Research Institute to analyze bed deformations under foundations on a natural bed, constructed in accordance with schematizations proposed and adopted in normative documents [1, 2, 4, and others]. Without using finite-element programs, the procedure [5, 6] allows, during determination of settlement, effective consideration of the shape of slabs in plan view, the pressure distribution under their bottom side and the depth of their placement, as well as information on the geological aspects of the bed and soil properties, which is incorporated into the analysis in the form in which it appears in geological engineering survey reports.Earlier, within the scope of [5, 6, and others], two extreme schematizations of the interaction between the foundation and bed were used, allowing bed settlement to be estimated without analyzing deformations of the building structure and the slab, and the foundation modulus curve, which is requiredThe development of a Gersevanov Institute procedure is given for analyzing bed settlement under a slab foundation, with consideration of the foundation shape, uneven load, and bed nonuniformity. In the proposed procedure alternative, which has been adapted for the analysis of foundation slabs on a nonuniform rock bed, the load distribution under the slab bottom is taken from the results of a finite-element analysis of a building structure on a base assumed to be absolutely inelastic. Implementation of the analytical procedure is shown using the example of calculating the settlement and deformation of a high-rise building slab, for which a "weakened" area was identified in the bed during surveys. Stochastic simulation of additional "columns" of geological engineering boreholes is carried out to estimate the impact of insufficiently complete information on the properties of the rock mass. The impact of bed nonuniformity on the results of analyzing settlement, slab tilt, and forces within the slab are analyzed.