Model of Probabilistic Analysis of Pile Capacity Based on the Extrapolation of Load-Settlement Curves
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SOIL MECHANICS MODEL OF PROBABILISTIC ANALYSIS OF PILE CAPACITY BASED ON THE EXTRAPOLATION OF LOAD-SETTLEMENT CURVES
UDC 624.131.524.4 >
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M. C' osic' ,1* N.Susic' ,1 R. Folic' ,2 and B. Folic' 3 1
Institute for Testing of Materials IMS, Belgrade, Serbia; 2University of Novi Sad, Novi Sad, Serbia; 3University of Belgrade, Innovation Center, Belgrade, Serbia, *Corresponding author Email: [email protected].
This paper formulates a mathematical model using the extrapolation of load-settlement curves with a rational function for analyzing the capacity of piles obtained from the static load test (SLT). In preliminary analyses, the extrapolation was based on the application of a number of mathematical functions that were gradually eliminated by iterative selection and filtering. The solution was obtained by extrapolation with a rational function. Using a rational function in the extrapolation of the load-settlement curve, a clearly identifiable part is obtained in which the asymptote is vertical, indicating the reached limit state of capacity in the soil and/or in the pile. The probabilistic analysis showed that no unique value for pile capacity was obtained, and that the spectrum of capacity values depends on the probability of occurrence of the corresponding event.
Introduction Identifying the bearing capacity of piles represents a complex problem in geotechnics. There is a large number of tests to assess the capacity of piles. The most reliable test is the static load test (SLT). Even after the application of SLT, some dilemma still exists about the analysis and determination of the limit capacity of the pile. The quality of solution for the bearing capacity is in direct correlation with this when applying a global safety factor or which is obtained for characteristic and calculated capacity, if partial safety factors are applied according to EN 1997-1:2004 [1]. In order to clearly define the procedures for conducting SLT for pile capacity, the regulation stipulates the pile testing method. The most detailed and reliable are the US ASTM D1143 [2] regulations, where there are clearly defined procedures, rules, and systems for testing quality. After the conducted SLT, a load-settlement curve is constructed using the linear interpolation of discrete values of load and settlement. Using mathematical methods, the limit capacity of the pile is determined. Solutions with different quality levels are obtained depending on the applied methods. The most commonly used methods for determining the bearing capacity of piles using the SLT method are: Van der Veen [3], Mazurkiewicz [4], Decourt [5], ChinKondner [6], and the like. The following methods are also widely used: hyperbolic extrapolation method [7], regression analysis based on the least square support vector machine (LSSVM) [8], as well as support vector machine (SVM) learning based on artificial intelligence for prediction of the limit bearing capacity of piles [9]. Prediction of the pile's bearing capacity (establishing the pile capacity before conducting S
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