LRFD Resistance Factor Calibration for Axially Loaded Drilled Shafts in the Las Vegas Valley

2016Research reportPDFTech ReportReport No. 515-13-803P515-13-803CalibrationGeotechnical engineeringLoad testsMonte Carlo methodSandy soilsSimulationCalichedeep foundationsdrilled shaftsresistance factorsreliabilityLRFDUnited StatesNevadaLas Vegas (Nevada)Nevada. Dept. of TransportationMotamed, RaminElfass, SherifStanton, KevinUniversity of Nevada. Dept. of Civil & Environmental EngineeringNevada. Dept. of TransportationUS Transportation CollectionResistance factors for LRFD of axially loaded drilled shafts in the Las Vegas Valley are calibrated using data from 41 field load tests. In addition to the traditional implementation of Monte Carlo (MC) simulations for calibration, a more robust technique is investigated in which nested MC simulations are employed to capture the uncertainty associated with the interpretation of material properties from in-situ test data. Measures are also taken to improve design procedures regarding cemented sandy soils colloquially referred to as caliche. While caliche is common in Las Vegas, its potential contribution to resistance is difficult to predict using typical site investigation data and there is currently no consensus among local engineers regarding how it should be considered in design. Thus, an approach for treating caliche is proposed and compared to three other potentially viable methods. Overall it is found that the proposed design approach produces the most accurate nominal axial capacity predictions and the nested MC simulations yield lower resistance factors than traditional calibration procedures