Engineering Commons^™

Early-Age Strength And Failure Characteristics Of 3d Printable Polymer Concrete: Numerical Modelling And Experimental Testing, Mohammad Amin Dehghani Najvani

Civil Engineering ETDs

The time-dependent rheological and early-age strength parameters of Polymer concrete (PC) were investigated. PC flow decreased, and the static yield stress and thixotropy increased as the specimen aged, while the dynamic yield stress remained unchanged. The study found that the Herschel-Bulkley model can accurately describe the PC’s rheological behavior over time. The change in cohesion strength and internal friction angle over time was observed using uniaxial unconfined compression and direct shear tests of fresh PC. A time-dependent MohrCoulomb failure criterion was established. Temperature analysis was used to determine the gel time and explain the evolution of the time-dependent early-age strength …

Modeling Of Asphalt Concrete For Cross-Anisotropic Visco-Elasticity And Heterogeneity, Zafrul Hakim Khan

Civil Engineering ETDs

Asphalt Concrete (AC) is a cross-anisotropic viscoelastic material. This study has developed a methodology to backcalculate the cross-anisotropic properties of the AC layer from the Falling Weight Deflectometer (FWD) sensor and pavement response data from embedded sensors inside a pavement section. This study has also developed a two-way coupled Multiscale Finite Element Model (MsFEM) with Phase Field Fracture (PFF) to study the microstructural heterogeneity and damage of the AC layer based on the actual field loadings. A Finite Difference Time Domain (FDTD) and Machine learning-based backcalculation algorithm were developed to determine the layer thickness and dielectric constant from air-coupled Ground …

Permeability And Porosity Of Loose Granular Salt, Evan J. Babcock

Civil Engineering ETDs

In this study, permeability and porosity measurements are made and reported for loose granular salt from the Waste Isolation Pilot Plant (WIPP). Measurements are made on a particularly wide range of particle sizes of this salt in a permeameter constructed large enough to fit and represent mixtures containing salt particles up to 25.4 cm in size. Salt samples with different particle size distributions are constructed and tested at varying levels of consolidation due to induced vibrations. Permeability measurements are made at a varying range of porosities for a given sample. Measurements are also compared with a predictive model for permeability …

Strength, Fracture Evolution, And Permeability Changes From Confined Brazilian Tests On Sandstone, Tyler Louis Hagengruber

Civil Engineering ETDs

This research reports on confined Brazilian strength tests and concurrent permeability testing on sandstone. The majority of the tests measured permeability during loading to failure in the confined extension region. Additional testing includes unloading and reloading cycles to detect the development of microcracks and the dependence of permeability on mixed stress conditions. Further testing characterizes fracture networks by observing porosity changes due to microcrack interactions before peak load. All tests involve 5 cm diameter disk-shaped, jacketed samples that are subjected to confining stresses while they are diametrically loaded. Specially designed end caps allow for gas flow measurements. The test configuration …

The Development Of A Novel Experiment On Confined, Flattened Brazilian Disks To Correlate Damage And Permeability In Brittle Geo-Materials, Samuel H. Boyce

Civil Engineering ETDs

This research develops a novel experiment using flattened Brazilian disks under confining pressure with concurrent permeability measurements and acoustic emission monitoring. The purpose of this work is to correlate damage and permeability in brittle geo-materials. Two series of tests are performed on concrete and one series on tuff, under a range of confining stresses between 2.76 and 13.79 MPa. Tests were continued beyond peak stress conditions, capturing data in the post-peak region. The acoustic emission data (cumulative energy and counts) are used to identify damage thresholds and track the progression of microscopic damage. This quantified damage is then correlated to …

Effects Of Coefficient Of Thermal Expansion On Unbonded Concrete Overlay Design And Performance, Gauhar Sabih

Civil Engineering ETDs

With the deterioration of highway pavements across the country, more emphasis is being laid on the rehabilitation of existing pavements. Unbonded concrete overlay (UBCO) is a cost-effective technique used to rehabilitate damaged concrete pavements. The design and performance of UBCO rely on various properties of concrete, of which coefficient of thermal expansion (CTE) is an important one. Concrete CTE has a direct impact on the design and performance of rigid pavements and overlays. CTE regulates the magnitude of curling and related stresses that impact the performance of overlays with regards to cracking, faulting and pavement roughness. Previous research revealed that …

Modeling And Simulation Of Damage In The Brazilian Indirect Tension Test Using The Finite-Discrete Element Method, Jeremiah C. Leyba

Civil Engineering ETDs

The Brazilian indirect tension test is used to investigate possible correlations between progressive damage and associated permeability changes. The test offers ease of replicability with a damage behavior known to lead to fracture openings as a tool for interpreting the indirect tensile strength of concrete and rocks. This behavior can lend insight into the nature of tensile damage and fracture progression in association with changes in permeability. The nature of these brittle materials is known to exhibit rapid failures in the Brazilian indirect tension test and require a method to retard the progression of damage for the possibility of acquiring …

Understanding Asphalt Concrete Aging Using Nanoindentation, Hasan M. Faisal

Civil Engineering ETDs

Asphalt concrete (AC) is created by mixing liquid asphalt binder with solid aggregates. When asphalt binder is mixed with aggregates, it creates a thin film (about 7-16 microns thick) around the aggregate surface. Fine aggregate (smaller than 0.075 mm size) get entrapped within the binder film or mixed with the binder, and create a phase called mastic. Both asphalt film and mastic play significant roles in aging of asphalt pavement. To this day, tests were performed mainly on the bulk liquid asphalt, but not on the film or mastic. In this study, for the first time, nanoindentation tests were done …

Development Of Design Equations For Drilled Shafts In Granular Dense Soils Using Dem Simulations, Sadia Faiza

Civil Engineering ETDs

Drilled shafts have proven to be cost-effective, excellent performing, deep foundation systems where large loads and lateral resistance are major factors. The available design methods that are recommended by FHWA (2010) for drilled shafts are mostly empirical and are developed based on generalized data which sometimes can be conservative for a particular soil. The main objective of this study is to develop a design methodology for estimating the side resistance of an axially loaded drilled shaft based on the current and the unique properties of the soil. The objective was met through using the discrete element method (DEM) to investigate …

Characterization And Modeling Of Asphalt Concrete For Dynamic Properties And Performances, A S M A. Rahman

Civil Engineering ETDs

The recently developed mechanistic-empirical pavement design guide (MEPDG, also known as Pavement M-E design method) uses the nationally calibrated, binder viscosity-based dynamic modulus predictive model for the design and analysis of asphalt pavements. In this study, this model is assessed for its appropriateness for asphalt-aggregate mixtures typically used in New Mexico. In essence, this study investigates the predictability issue of complex modulus of New Mexico mixes. A total of 54 Superpave mixes with different aggregate gradations, air voids, and binder grades were collected from the mixing plants and from the pavement construction sites. The loose asphalt mixtures were then compacted, …

Characterization Of Unknown Bridge Foundations, Saman Rashidyan

Civil Engineering ETDs

The National Bridge Inventory (NBI) recognized 86,133 bridges in the United States have no foundation data on record in 2003. It is evident that an unknown percentage of the 86,133 bridges identified by NBI with missing foundation data could also be highly vulnerable to scouring induced by water flow coupled with erodible soils. Conventional excavation, coring and boring excavations to identify unknown bridge foundation depths and types are deemed to be expensive, destructive, and limited in their application to the unknown foundation problem. Many surface and borehole nondestructive testing (NDT) technologies have been developed for this purpose. Three economical proven …

Practical Considerations In Determining Timber Pile Depth Using The Sonic Echo Method, Ali F. Jwary

Civil Engineering ETDs

The Federal Highway Administration indicates that about 85,000 bridges in the United States have no original contract documents with information about the type, depth, geometry and material of their foundations (FHWA, 2010). Furthermore, the National Bridge Inventory (NBI) provides information about 86,133 bridges nationwide that are rated as scour critical because of unknown foundation condition. In New Mexico, there are more than 281 bridges with unknown foundations, which are owned by the New Mexico Department of Transportation; 71 of these are timber bridges. These data indicate a serious problem that needs decisive action to assess the unknown bridge foundation characteristics …

Input Parameters In Discrete Element Modeling, Seyedali Yousefi

Civil Engineering ETDs

The discrete element method (DEM) is employed to study complex behaviors of particulate media. Input parameters may greatly affect the response of DEM models and should therefore be selected carefully. Scaling techniques are employed to enlarge prohibitively small time-steps. To study these techniques, dimensionless input parameters were defined. Responses of models in the dimensionless scale were invariant with choice of density, elastic modulus, and characteristic length if the dimensionless parameters were kept constant. Hence, density scaling is equivalent to use of a higher strain-rate, and stiffness scaling results in a higher strain-rate and an elevated stress state in the dimensionless …

A Plane Coordinate System For Bernalillo County, Karl V. Morin

Civil Engineering ETDs

The first purpose of this thesis is to frame an enabling act that could be submitted to legislature for adoption. Such an act would authorize the use of plane coordinate system, but not make it mandatory. Twenty-four states have passed laws establishing state coordinate systems.

A second purpose of this thesis is to provide practicing engineers with all the necessary information and explanatory material in one manuscript to permit them to apply the system to their work. An example is worked out in detail using local points known to local men and fully explained step by step.

In addition to …