Award Date

8-1-2015

Degree Type

Thesis

Degree Name

Master of Science in Engineering (MSE)

Department

Civil and Environmental Engineering

First Committee Member

Barbara Luke

Second Committee Member

William Savage

Third Committee Member

Haroon Stephen

Fourth Committee Member

Wanda Taylor

Number of Pages

206

Abstract

The Nevada Department of Transportation design standards for deep foundations, particularly drilled shafts, in the Las Vegas Valley (LVV) may be overly conservative due to the challenges in characterizing strong but difficult-to-sample sediment strata, such as dense gravel, heavily cemented sediments, and mixed materials, which occur commonly in the LVV. Consequently, there is a need for investigating methods to assess the shear behavior of sediments that occur in the LVV in situ in working ranges of stress/strain, with the end goal of improving abilities to predict the capacity of drilled shafts in the LVV. To this end, global correlations of readily measured in situ tests – specifically, Standard Penetration Testing (SPT), shear wave velocity (VS) testing, and pressuremeter testing (PMT), with laboratory-measured shear parameters of sediments are reviewed to evaluate their applicability in the LVV. Direct measurements of shear wave velocity are conducted using downhole testing at a site in the LVV known to have cementation and dense gravels. Local LVV datasets of aforementioned in situ tests and laboratory tests used to determine shear strength parameters are obtained from local consultants and government entities and are analyzed to detect possible relationships between in situ tests and shear parameters (such as friction angle, cohesion, undrained shear strength) beneficial for deep foundation design . Despite the high sediment heterogeneity across the LVV, variations in testing procedures, and lack of laboratory data, results show that readily measured in situ test data can be valuable for deep foundation design in the LVV when complemented with each other and laboratory data. In the datasets analyzed, blow counts are highly variable. Some local data show weak trends of increasing friction angle and cohesion with increasing blow count. Comparisons of blow counts with VS did not yield any useful correlations. Neither seismic velocities nor N60 is more informative than the other, but when complemented with each other they provide valuable insight regarding stiffness and relative density of sediments and their variability with respect to depth. Most correlations from other sites considered in this study are not representative of the shear behavior of the local sediments that were studied. Local VS profiles correspond better with local reference profiles than with others studied.

Keywords

cemented sediments; deep foundation design; Las Vegas Valley; sediment heterogeneity; shear wave velocity; standard penetration testing

Disciplines

Civil Engineering

Language

English


Share

COinS