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Conventional design and construction procedures of the drilled shafts (bored piles) are mainly developed for homogenous soils in the absence of highly cemented layers. However, the presence of competent and cementitious layers such as caliche deposits in soil profile can affect the resistance and settlement of pile foundations. This study concerns with the uncertainties on the resistance estimation of axially loaded drilled shafts in interaction with caliche layers The prime objective is to calibrate the side shear and end bearing resistance factors of axially loaded drilled shafts based on the soil characteristics of Nevada. The load-settlement responses of axially loaded drilled shafts installed as single piles are evaluated based on the 40 available databases of full-scale bi-directional Osterberg static load tests performed in the Southern Nevada valley. The side shear and end bearing resistance of drilled shafts are separately determined by analyzing upward and downward load-displacement components of the bidirectional Osterberg tests. To measure the drilled shafts’ resistances up to their failure capacity, extrapolations are conducted by incorporating polynomial, cubic spline, and exponential functions to achieve the best extrapolation fit using MATLAB. Furthermore, finite element back analysis is incorporated for extrapolations to include the geotechnical properties of homogeneous soil along with characteristics of caliche and drilled shafts to achieve outcomes with more accuracy on the measured resistances. Additionally, the resistance values of drilled shafts are predicted using the SHAFT program. The design procedure is conducted following the strength I limit state criteria of the Load and Resistance Factor Design (LRFD) approach. Resistance factors of axially loaded drilled shafts in the soil containing caliche deposits is calibrated by performing Monte Carlo (MC) simulation. Side shear and end bearing resistance of drilled shafts are calibrated and categorized if the extrapolation on measured values was conducted by MATLAB and FEM back analysis prior to commencing the calibration. The calibrated side shear resistance factors by MC based on the type of the performed MATLAB and FEM extrapolations are ∅Side=0.318 and ∅Side=0.365, respectively. The developed end bearing resistance factors using MC approach according to the extrapolations by MATLAB and FEM are determined as ∅Tip=0.242 and ∅ Tip=0.225. The developed resistance factors in this research by conducting MC simulations concerns with the presence of competent caliche layers in LRFD design procedure of axially loaded drilled shafts in Nevada soil and can be applied to other soil profiles with comparable geotechnical characteristics.

Liquefaction is a hazardous seismic-based phenomenon, which causes an abrupt decrease in soil strength properties and can result in the massive destruction of the built environment. This research presents a novel approach to reduce the risk of soil liquefaction using jet-grouted micropiles in clean sands. The saturated soil profile of the study project mainly contains clean sands, which are suitable to more reliably employ simplified soil liquefaction analyses. The grouting is conducted using 420 micropiles to increase the existing soil properties. The effect of jet grouting on reducing the potential of liquefaction is assessed using the results of the cone penetration test (CPT) and the standard penetration test (SPT), which were conducted before and after jet grouting by implementing micropiles in the project sites. According to three CPT-based liquefaction analyses, the Juang method predicts the most effective improvement range of the factor of safety in the clean sand. The Boulanger and Idriss, and Eurocode methods show comparable evaluations. Results of the SPT-based analyses show the most considerable increase of the factor of safety following the Boulanger and Idriss, and NCEER approaches in the SP soil. CPT- and SPT-based analyses confirm the effectiveness of jet grouting by micropiles on enhancing soil properties and reducing the risk of liquefaction.

One of the main concerns in the design of bridge structures is evaluating the resistance capacity of foundation settings. Full-scale reinforced concrete piles are commonly used as a traditional method in the design of deep foundations; however, the use of micropiles as an alternative method can facilitate the process of the bridge construction by addressing the concerns such as different properties of the soil layers and site restrictions. The objective is to introduce an alternative solution in that the geometry of the construction area, such as limited overhead access areas, or the existed structures in the adjacent of the project would not affect the efficiency of deep foundations. In this regard, the battered (inclined) piles are applicable based on the geometry criteria. Moreover, applying micropiles is a preferred method in soil remedial practices along with the maintenance procedure of existing foundations. This study deals with the effect of applying micropiles on soil stabilization by enhancing the bearing capacity of the existing soil layers. Variations in soil properties using 9 drilled boreholes before and after implementation of micropiles are addressed. The results of the standard penetration test (SPT) prior to and after the installation of micropiles prove the considerable effect of micropiles on enhancing the soil properties.