Graduation Semester and Year

2017

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Civil Engineering

Department

Civil Engineering

First Advisor

Anand Puppala

Abstract

A novel cone penetration test device, the P-cone, has been developed to assist in deep foundation design and this P-cone device combines features of CPTU cone sounding technologies with capabilities to perform bidirectional loading at a given soil depth condition. Using two independent systems, the P cone measures shear stress versus movements of cone shaft and stress versus penetration of the cone tip at desired depths. The P-cone can also improve the penetration depth and offer a potential application for the in situ consolidation test. Laboratory experiments of the P-cone device were successful beyond the expectation. P-cone Tests performed on three large compaction-unsaturated clayey silt specimens showed that the movements necessary to fully mobilize the shaft shear resistance and tip resistance were close to 0.2 mm and 2.0 mm, respectively. The comparison of the measurements and the equivalent pile-head load-movement curve constructions show an average difference of 15% between the positive and negative shaft resistance of soil when being sheared. An average adjustment coefficient of 1.2 was proposed for the constructed equivalent pile-head load-movement curves. The investigation of soil failures along the cone shaft and below the cone tip showed that the soil areas sheared surrounding the cone shaft were twice cone diameters and the shear failures of soil took place at interface between the cone wall and soil. The shear failures of soil below the cone tip did not occur though the movements of the cone tip ranged from 100 through 185% cone diameter. The investigation of soil deformation around the jack indicated that the expansion of the jack did not create tension areas for all tests and thus the effects of the tension areas created by the jack expansion can be ignored for the equivalent pile-head load-movement curve construction from the bidirectional load test results. The modelling of the axial compression and bidirectional load tests on P-cone showed the influence zones surrounding the P-cone shaft and below the P-cone tip caused by the P-cone installation of about four and thirteen times diameter of P-cone, respectively. It is likely that the dimension of soil chamber used for P-cone tests is not large enough to eliminate completely the effect of the boundary conditions.

Keywords

Novel cone penetration test device (P-Cone), Deep foundation design, Bearing capacity

Disciplines

Civil and Environmental Engineering | Civil Engineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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