Geotechnical research in the Department of Civil Engineering covers:
- earthquake-induced soil liquefaction
- seismic response analysis of high rises
- deep foundations (driven piles and drilled shafts)
- risk-based geo-structure designs
- expansive soil foundation designs
In the past decade, the strong earthquake seems increasingly frequent. Civil Engineering Professor Nien-Yin Chang has devoted three decades in trying to unlock the mysteries of earthquake—induced ground liquefaction, when ground loses all its strength and flows like a heavy liquid, and its effects on building performance. It was found that saturated sandy soils can liquefy with fines content of up to 30 percent.
Many high-rise buildings populated some big urban areas in the World. A doctoral dissertation was completed in 2009 on the seismic responses of high-rises on piles, in which performance of high-rises were assessed using finite element analysis and analysis results compared with the measured seismic responses of an actual high rise. It was concluded that comprehensive analyses were required for assessing high-rise building seismic responses during the design stage, instead of relying completely on IBC seismic design code. Deep foundations (piles and drilled shafts) provide support for structures built in the areas with problem soils/rocks near surface.
More than one dozen graduate students are researching the effectiveness of deep foundations as structure supports. Many have also researched the problem of expansive clay (or swelling, or traditionally called bentonite soils) for their damaging effects on building and roadways. Annually the cost of such damage totals billions of dollars and the appropriate solutions are greatly needed.
Our geotechnical research covers experimental, analytical and numerical research in geotechnical and soil-structure interaction problems under static and seismic loads, probability and risk-based research in geotechnical problems, seismic responses of various structures, expansive soil foundation designs and deep foundation problems, as outlined in more details as follows:
- Dynamic properties of soils
- Earthquake-induced soil liquefaction
- Numerical approach to: dynamic soil-structure interaction (SSI) effects in composite dams, highway bridges, and high rises
- Seismic responses of MSE walls
- Ground motion amplification through soft soils
- Seismic soil-structure interaction in high rises and dams
- Deep foundations on heavily over-consolidated clays
- Soil-pile-structure interaction
- Influence of anomalies on drilled shaft foundations
Probability and Risk-Based Designs
- State-specific resistance factors for LRFD driven pile designs
- Statistical and probabilistic approaches to geotechnical problems
Transportation Facilities and Winter Road-Way Maintenance
- Winter snow and ice management: environmentally sensitive winter roadway sanding and deicing, management cost of sanding, cost of sanding on vehicular damage
- Cost of sanding
- Traffic barrier impact performance
- Expansive soil mechanics, properties and foundation designs
- Soil-pile-structure Interaction of high Rises under Earthquake Shakings
- Seismic Responses of MSE Retaining Walls
- Finite Element Analysis of driven piles and drilled shafts
- Seismic Soil-Concrete Interaction in Composite Section of Folsam Main Dam
Nien-Yin (N.Y.) Chang, Professor
Geotechnical Earthquake Engineering
Office: North Classroom 3019A
- BS in Civil Engineering from the National Chun-Hsing University in 1965
- MS in Structural Engineering for the National Taiwan University in 1967
- PhD in Geotechnical Engineering from Ohio State University in 1976
N.Y. (short for Nien-Yin) likes to teach, research and serve others. He loves people, and he loves sharing. He is always looking to improve his technical/scientific knowledge.
Philosophy on Research
“Publish or perish” is a general rule in the academic profession. When I joined CU, very few people were writing proposals. However, I continued to submit proposals for external funding. My first three proposals were funded by the National Science Foundation. Subsequently, the research funding agencies expanded to cover U.S. Army Corps of Engineers, Department of Energy, Federal Highway Administration, NIOSH, Colorado Department of Transportation and industry with research topics included: oil shale and spent shale mechanics, expansive soils, resilient modulus of soils, geotechnical earthquake engineering, earthquake–induced soil liquefaction, soil-pile–structure interaction of high rises under strong earthquake shaking, resistance factors for driven pile foundation designs, mechanical behavior of municipal solid wastes, etc.
Many papers and research reports were published on the wide range of topics. Several times I received the outstanding research awards at CU Denver.
Future Research Plan
My future plan after ending my tour of duty as the interim dean of the college, besides continuing my traditional engineering interest, is to expand my teaching and research interest into biomaterial testing and characterization and implementation of the bio-constitutive relationship into finite element codes for the numerical analysis of the bio-beings, like human bodies, etc.
North Classroom (NC1805) is designated as Geotechnical and Structural laboratory, which houses many pieces of the state-of-the art equipment used in both teaching and research. The major feature of this lab is its capability in testing both soils and rocks for their dynamic properties critical for assessing the seismic responses of structures and materials. High school students in Colorado generally named it earthquake alb, because they experienced many earthquake demonstrations in the past two-plus decades. Major equipment includes: five hydraulic-electric closed-loop universal testing machines with capacities ranging from 20 to 1,000 kips and digital controller (one of them with axial and torsional capabilities), resonant column apparatus, triaxial apparatus for testing the permeability of low permeable soils using flow pump, and many triaxial test apparatuses for both soil and rock testing are available besides the apparatuses for routine soil testing. Also facilitated are the apparatuses for expansive (or swelling, or bentonite) soils tests, which are used in evaluating the swelling characteristics of bentonite soils for assessing their swell potential and swell pressure, directly associated to the expansive soil damage to structures and roadways.
To meet the demand I have offered many undergraduate and graduate courses as shown in my cv. The list of courses related to my research areas include:
- Advanced Soil Mechanics
- Engineering Properties of Soils
- Seismic Resistance Design of Embankment Dams
- Expansive Soil Foundation Design and Forensic Investigation
- Shear Strength and Stability
- Dynamics of Soils and Foundations
- Earthquake-induced Ground Failures
- LRFD Designs of Geo-structures and Foundations
For complete, up-to-date course descriptions, visit the CU Denver academic catalog and search for the course numbers listed above.