Calculation of the resistance of backfill to displacements of retaining walls

Abstract

The interaction of backfill with a retaining wall which is being displaced toward the backfill is most often described by a linear relation between the reaction pressure Pr (over and above the active pressure created by the weight) acting at a given contact point and the displacement of this point A p,=cA. (l)The modulus of subgrade reaction (Winkler model) or coefficient of compressive strength of the backfill is the proportionality factor [1-3]. It is well known that in this case the results of the calculations (e.g., the diagram of the reaction pressure) depend substantially on the adopted law of variation of the modulus of subgrade reaction (resistance) of the backfill with increase in depth and do not always agree with the data from measurements [2,3]. In [2] a refinement of the calculations is related, in partlcular, to an evaluation of the magnitude and character of the change in the compressive strength of the backfill with increase in depth on the basis of determining the size of the active compressible soil stratum. In [4,5] attention was called to the experimentally obtained dependence of the character of the change of C with depth on the type of wall displacement and the need to take into account this circumstance in calculations using the Winkler model. A nonlinear relation a=aM,which reflects better the behavior of the backfill than Eq. (I), was proposed and used in examples there.The indicated refinements are of practical interest and permit more reliable calculations. At the same time, a further development of calculations of the interaction between structures and backfill is related to their representation by fundamentally new models differing from those indicated above and more fully reflecting the properties and behavior of soils. First of all we need mention the model of an elastoplastic foundation.In this case the broadest possibilities are realized when solving the so-called mixed problem of the theory of elasticity and plasticity of soil, permitting a determination of stresses and strains within the design region having zones of both a prelimit (elastic) and limit (plastic) state of the soil in accord with the adopted yield (plasticity) condition [6,7]. The formulation of the mixed problem within the framework of the theory of plastic flow and the algorithm for its solution by the numerical finite element method (FEM) were presented earlier [7]. The qualitative and quantitative agreement of the results with data from instrumental measurements was established by solving mixed problems for experimental foundations loaded by flexible and rigid test plates [8,12].The examples given below were calculated according to the SUPZ-GP program* for solving mixed elastoplastic problems of plane strain on a BESM-6 computer and take into account the experience gained in using a similar progra M developed earlier [8]. The use of triangular (TFE) and rectangular (RFE) finite elements, separately and combined, is provided for in the SUPZ-GP program. The design region can be separated into RFE "automatically"...

Assessment of the Probability of Exceeding the Limiting Deformations of a Building Foundation

“…1.5 study, a numerical experiment was carried out and the values of failure the probability -the probability of exceeding permissible settlements for the range of the coefficient of variation E within 5 -35% (as allowed in scientific and normative literature: Ermolaev, N.N. Mikheev, V.V., 1976; Bugrov, A.K., 2003;Phoon K.K., 2008 etc. ), where investigated.…”