In-Place Weathering of Late-Stage Volcanic Materials at Ka Loko Dam, Hawaii

Friday, April 15, 2016 – 12:00 – 01:30 pm, 3310 Yeh Center

David_Groholski

David R. Groholski, PhD, PE
Senior Engineer, Civil Engineering

Ka Loko Dam, in Kauai, Hawaii, failed suddenly and catastrophically on March 14, 2006.  The resulting broad “U”-shaped breach was marked by three distinct topographic benches.  The lowest bench was founded on a greasy, waxy, gel-like material produced by in-place weathering of late-stage volcanic materials.  Gravel-size pieces in the hydraulic fill of the embankment derived from these materials were also weathered in place.  Engineers and geologists generally assume that the strength, stiffness, and durability of bedrock, earth, and embankment materials will not vary over the operating life of a hydraulic fill dam.  However, bedrock materials can progressively weather into soil constituents over “geologic time.”  In the case of Ka Loko, late-stage volcanic materials substantially weathered in-place over approximately 115 years.  Prolonged exposure to seepage of anoxic water completely weathered the bedrock to saprolite, including weak, sensitive, fine, spherical halloysite clay.

Please view the flyer and bio attached for further details: 16-03-22 – David Groholski

Seismic Response of a High Plasticity, Diatomaceous Naturally Cemented Soft Clay Deposit

Moday, April 4, 2016 – 15:00 – 16:00 pm, B218 Newmark Civil Engineering Laboratory

Xavier Vera

Xavier Vera-Grunauer, PhD
Director of the Engineering Institute at the UCSG and CEO of Geoestudios

High plasticity deltaic estuarine clays (non-liquefiable NEHRP F sites) are the predominant soils in Guayaquil City in Ecuador. A new geotechnical characterization scheme for these soils was proposed based on geological studies, historical data of geotechnical and insitu explorations. Accordingly, some correlations were developed between geotechnical parameters and seismic response properties to characterize the Guayaquil soil deposits for dynamic analyses. Based on the calculated elastic and inelastic responses of these soils, a seismic zonation for the city was proposed. In addition, a detailed procedure for estimating a design site response spectrum for Guayaquil City’s prevalent soil conditions was developed. The experimental results and numerical procedures presented in this research provide a framework for understanding the mechanical behavior of the estuarine-deltaic, high plasticity, diatomaceous, naturally cemented clay and provide key information for the design of engineered systems in Guayaquil and for cities worldwide, with similar geomorphological, seismic, and geotechnical characteristics.

Please view the flyer and bio attached for further details: GESO Guest Speaker – Dr. Xavier Vera

Experiences in large slope stability problems under complex geology

Friday, March 4, 2016 – 12:00 – 1:00 pm, 3310 Yeh Student Center

Camilo Marulanda, Ph.D.
Technical Manager, INGETEC

This presentation presents a brief summary of the origin of metamorphic rocks, specially schist and the presence of shear or gouge zones in metamorphic rocks, as defects that induce weakness characteristics to the rock mass and that depart substantially from the traditionally evaluation of joints and discontinuities, turning eventually into failure surfaces that govern the stability conditions of surface works. The effect these weak zones inflict into the metamorphic rock mass, especially to schist, causing significant slope stability problems, is illustrated through three case histories. The presence of such defects in the rock mass, detected and analyzed by means of exploratory holes drilled from the surface, can be hardly anticipated during the design stage as far as location, dip direction and geotechnical characteristics, given their erratic alignment within the rock mass, and their disguise during the drilling processes when the clay infill is washed away by the drill water, making their recognition and readiness for lab test sampling even more difficult. Special care of these geologic features, often present in metamorphic rocks, must be taken through: 1) direct exploration –such as galleries–, 2) the elaboration and interpretation of adequate geological models and corresponding sensitivity analyses of shear strength parameters of the established failure surfaces and 3) sound decision making and implementation of stabilization measures based on engineering judgment.

Please view the flyer and bio attached for further details: GESO Guest Speaker – Camilo Marulanda