The Effect of Targeted Field Investigation on the Reliability of Earth-Retaining Structures in Passive State: A Random Field Approach

Abstract

In one of their recent works, the authors examined parametrically the effect of targeted field investigation on reducing statistical uncertainty in active state analysis of earth retaining structures based on 2165 different cases for each of the sliding and overturning modes of failure. This analysis indicates that the optimal sampling location is always adjacent to the wall, while a sampling domain length equal to the whole height of the wall is suggested to be considered. The present paper deals with the “symmetrical” problem of soil under the passive state of stresses. Working in a similar manner, 1879 passive state cases have been considered (also for each of the sliding and overturning modes of failure) in a Random Finite Element Method (RFEM) analysis framework, where soil properties are modeled as random fields while measurements are modeled by sampling from different points of the field domain. The “actual” resultant earth passive pressure force (or moment) exerted by the random soil on the retaining wall is compared against the respective “predicted” one calculated using the soil property values sampled from the random field. Failure is considered to have occurred when the derived “actual” force is smaller than the respective “predicted” force. This analysis clearly indicates that the passive state constitutes a different problem, where the optimal sampling distance from the wall is half the wall height. Regarding the depth of exploration, it was again found to be the entire wall height. In addition, the present analysis shows that, the benefit from a targeted field investigation is much greater than the benefit gained using statistical methods for obtaining cautious estimates for the various soil properties; the latter refers to the “characteristic value”, a concept commonly used in the Limit State analysis framework of Eurocode 7.

The Effect of Targeted Field Investigation on the Reliability of Earth-Retaining Structures in Active State

“…This came as a surprise, as someone would expect the optimal location to lie on or in the close vicinity of Rankine's 45 • + φ /2 failure plane passing through the lower point of the wall. Actually, based on authors' findings [30], this is the case for the passive state. Regarding Rankine's earth pressure theory, it is reminded that there is not a single failure plane, but rather an infinite number of such planes, parallel to the one mentioned above encompassing all of the others [31].…”

Comparing Eurocode 8-5 and AASHTO methods for earth pressure analysis against centrifuge tests, finite elements, and the Generalized Coefficients of Earth Pressure

“…mrearth2d (freely available at http://www.engmath.dal.ca/rfem) is intended solely for the analysis of simple retaining walls (smooth or rough, non-battered walls with zero backfill inclination). A detailed description of the program can be found in [28][29][30][31]. Focusing on our deterministic analysis subject, the readers should skip the material referring to random fields, while it is noted that the horizontal pseudo-static function has been added by the authors (the vertical pseudo-static action just affects the unit weight of soil).…”

The Effect of Targeted Field Investigation on the Reliability of Axially Loaded Piles: A Random Field Approach

“…Soil heterogeneity is an important component in designing geotechnical engineering structures, where the proper soil parameter values need to be determined directly in the laboratory based on undisturbed samples or indirectly based on in-situ tests (usually continuous probing tests such as, the Cone Penetration Test (CPT) or the Standard Penetration Test (SPT)). Recent studies have shown that that the reliability of geotechnical engineering structures is greatly affected by the location and the number of sampling points [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. This sampling-related uncertainty is commonly known as statistical uncertainty.…”