Recent cee_ucla_geotechnical items

Sea Level Rise effects on Earthquake-induced Soil Liquefaction at NHERI Computational Conference

Fri, 30 Jan 2026 00:00:00 +0000

Existing codes for performing probabilistic liquefaction hazard analysis (PLHA) are decoupled as first a probabilistic seismic hazard analysis (PSHA) is required to obtain a hazard curve.

Drawbacks of this method are it only accounts for the influence of magnitude on liquefaction because it uses a small number of magnitudes and selection of the magnitudes requires judgment. Our approach integrates the liquefaction uncertainty into the hazard calculation by performing a PLHA for every event in the PSHA. We adopt the UCERF3 source model, which uses over a million events. For each event, ground motion at the site is a random variable that is used to compute cyclic stress ratio (CSR). Cyclic resistance ratio (CRR) is also a random variable obtained from a liquefaction triggering model. Because CSR and CRR are log normally distributed, we can use a closed-form solution to obtain a distribution for factor of safety (FoS). The rate of the event is then multiplied...

Sea Level Rise and its effects of earthquake-induced soil liquefaction at Le Val Lund Lecture on Lifeline Infrastructure and Community Resilience

Fri, 30 Jan 2026 00:00:00 +0000

Global sea levels are expected to increase up to five meters by the year 2150. Due to elevation differences, ocean dynamics, and the uneven redistribution of water from global ice melting, California will experience 1.25:1 of relative amounts of sea level rise (SLR). Ocean fluctuations such as storm surge and spring tides, as well as higher marine water levels can periodically elevate coastal groundwater. These fluctuations pose multiple interrelated coastal hazards, including groundwater salinization, contaminant mobilization and infrastructure damage. Specifically in California, over 2.5M people live along the coast making it the most populated coastline in the continental US. This densely populated area is also a critical infrastructure hub that serves not only California but other US states. The state has vital energy and water facilities, transportation lifelines, shipping ports, and countless residences – all under threat from rising sea levels. One meter of SLR could...

Sea Level Rise Effects on Earthquake-induced Soil Liquefaction at SSA 2025

Fri, 30 Jan 2026 00:00:00 +0000

Global sea levels are expected to increase up to five meters by the year 2150. Higher marine water levels as well as ocean fluctuations will also raise unconfined coastal groundwater levels. These fluctuations pose multiple interrelated coastal hazards. Currently, there has been minimal attention paid to the effects of sea level rise on groundwater, specifically how rising groundwater levels interact with hazards such as earthquake-induced soil liquefaction. We propose to use a probabilistic liquefaction hazard assessment (PLHA) to obtain annual rates of nonexceedance of factor of safety of liquefaction. Our approach integrates the liquefaction uncertainty into the hazard calculation by performing a PLHA for every event in the PSHA. Existing codes for performing probabilistic liquefaction hazard analysis (PLHA) are decoupled as first a probabilistic seismic hazard analysis (PSHA) is required to obtain a hazard curve. Drawbacks of this method are it only accounts for the influence...

Sea Level Rise Effects on Earthquake-induced Soil Liquefaction at ISGSR 2025

Fri, 30 Jan 2026 00:00:00 +0000

Global sea levels are expected to increase up to five meters by the year 2150 (Fox-Kemper

et al., 2021). Ocean water level fluctuations will cause an increase in coastal

groundwater in addition to extreme water levels from storm surge and spring tides. These

fluctuations pose multiple interrelated coastal hazards, including beach erosion and infrastructure

damage. Currently, there has been minimal attention paid to the effects of sea level rise on groundwater,

specifically how rising groundwater levels interact with other hazards, such as earthquake-induced

soil liquefaction. In collaboration with the California Geologic Survey, the United States

Geologic Survey, and the California Seismic Safety Commission, we attempt to

quantify the effects of sea level rise on earthquake-induced liquefaction.

We propose to use a probabilistic liquefaction hazard assessment

(PLHA) (Kramer and Mayfield, 2007)...

Laboratory investigation of the pre- and post-cyclic volume change properties of Sherman Island peat

Wed, 10 Apr 2013 00:00:00 +0000

We investigate through laboratory testing the volume change characteristics of peaty organic soil from Sherman Island, California under static conditions (consolidation, secondary compression) and post-cyclic conditions. Incremental consolidation tests indicate the material to be highly compressible (C_c = 3.9, C_r = 0.4) and prone to substantial ageing from secondary compression (C_a/C_c = 0.05 following virgin compression). Strain-controlled cyclic triaxial testing of the peat finds the generation of cyclic pore pressures for cyclic shear strain levels beyond approximately 0.5-1.0%, with the largest residual pore pressure ratios r_ur (cyclic residual pore pressure normalized by pre-cyclic consolidation stress) being approximately 0.2-0.4. Post cyclic volume change occurs from pore pressure dissipation and secondary compression. The level of post-cyclic secondary compression increases with r_ur. Many of these phenomena...

Estimating Undrained Strength of Clays from Direct Shear Testing at Fast Displacement Rates

Wed, 10 Apr 2013 00:00:00 +0000

When the direct shear test is performed in accordance with ASTM guidelines, the measured shear stresses at failure estimate drained strength parameters. We investigate the possibility of estimating undrained strength using direct shear testing at variable shear displacement rates on specimens composed of various combinations of kaolinite and bentonite. Even at fast displacement rates, constant volume conditions are not achieved in the direct shear device because of changes in specimen height that are large relative to allowable ASTM thresholds for constant volume simple shear testing. However, undrained strengths established by constant volume simple shear testing at slow strain rates are well approximated by direct shear tests conducted at fast shear displacement rates (time to failure < t₅₀/8, where t₅₀=time to 50% consolidation in a conventional oedometer test). Because of the simplicity of direct shear testing, such estimates of undrained...

Full Scale Cyclic Large Deflection Testing of Foundation Support Systems for Highway Bridges. Part I: Drilled Shaft Foundations

Wed, 13 Feb 2008 00:00:00 +0000

This research involved analysis and field testing of several foundation support components for highway bridges. Two classes of components were tested - cast-in-drilled-hole (CIDH) reinforced concrete piles (drilled shafts) and an abutment backwall. The emphasis of this document (Part I of the full report) is CIDH shafts.

CIDH shafts are among the most common support structures in highway construction. Typically, drilled shafts have simple, prismatic geometries; yet, they display a complex, inelastic response under applied loading. The two major factors that affect their behavior are the interaction between the shaft and surrounding soil media, and the material inelasticity of the shaft itself. In this report we document the results of two single shaft tests and one shaft group test. All specimens are two-feet diameter reinforced concrete drilled shafts that extend approximately 24ft below ground line. The single shaft specimens include one in a flagpole configuration...

Full Scale Cyclic Testing of Foundation Support Systems for Highway Bridges. Part II: Abutment Backwalls

Wed, 6 Feb 2008 00:00:00 +0000

This research involved analysis and field testing of numerous foundation support components for highway bridges. Two classes of components were tested - cast-in-drilled-hole (CIDH) reinforced concrete piles (drilled shafts) and an abutment backwall. The emphasis of this document (Part II of the full report) is abutment backwall elements.

The backwall test specimen was backfilled to a height of 5.5 up from the base of the wall with well-compacted silty sand backfill material (SE 30). The wall is displaced perpendicular to its longitudinal axis. Wing walls are constructed with low-friction interfaces to simulate 2D conditions. The backfill extends below the base of the wall to ensure that the failure surface occurs entirely within the sand backfill soil, which was confirmed following testing. The specimen was constructed and tested under boundary conditions in which the wall was displaced laterally into the backfill and not allowed to displace vertically.

A maximum...