Reduction of liquefaction hazards by deep soil mixing

One of the most promising technologies for site improvement involves deep soil mixing (DSM), whereby cements and hardening agents are mixed in situ with native soil to increase strength and stiffness properties. this method proved to be effective in stabilizing potentially liquefiable soil at several sites during the Kole earthquake, including the Oriental Hotel, where partial coverage by DSM columns was successful not in controlling lateral spread but in preventing liquefaction. Analytical results compare very favorably with twoo separate sets of centrifuge test data. The analytical model correctly predicts the observed behavior of DSM-reinforced soil at the Oriental Hotel during the Kobe earthquake. DSM is effective in reducing liquefaction potential because it provides reinforcement to restrict shear strain in the soil mass. The proposed analytical approach correctly accounts for observed perfomance and provides a means of assessing the appropriate DSM grid dimensions for effective site improvement. (AU)

Gis assessment of water supply damage from the northridge earthquake

The 1994 Northridge earthquake results in the most extensive damage to a US water supply system since the 1906 San Francisco earthquake. Three major transmission systems, which provide over three-quarters of the City of Los Angeles, were disrupted. los Angeles Department od Water and Power (LADWP) and Metropolitan Water District (MWD) trunk lines (nominal pipe diameter >600 mm) were damaged at 74 locations, and the LADWP distribution system required repairs at 1013 locations. The widespread disruption provides a unique opportunity to evaluate the geographic variability of the damage, the most vulnerable pipelines, and the relationship among damage, transient motion, and permanent ground deformation. (AU)

Los Angeles water pipeline system response to the 1994 Northridge earthquake

Damage caused by the 1994 Northridge earthquake (Mw=6.7) to transmisin, trunk, and distribution pipelines operated by the Los Angeles Department of Water and Power and the Metropolitan Water District is summarized. The locations of trunk line [pipeline diameter>/610mm (24in.)] repairs are discussed relative to earthquake intensity, and the repair rate (repairs/km) is evaluated according to pipe composition. Repairs in both the trunk and distribution pipelines are summarized according to pipe composition and size. A simplified analytical model for assessing the potential damage to buried pipelines from traveling ground, wave effects is proposed. The model utilizes measured or estimated values of peak particle velocity, which affects ground strain, and predominant period, which affects wavelength, to develop pipeline seismic response diagrams that correctly predict damage to modern steel trunk lines during the 1994 Northridge and 1985 Michoacan earthquakes.(AU)

Centrifuge modeling of seismically - induced lateral deformation during liquefaction and its effect on a pile foundation

A cooperative project is reported between teams at Renssealaer Polytechnic Institute (RPI) and Cornell University to investigate the effects of lateral spreading on pile foundations. Centrifuge tests of lateral spreading and the corresponding permanent bending moments measured in instrumented model piles conducted at RPI, are used to study the problem and verify and calibrate Cornell University's computer program B-STRUCT. Individual piles and pile groups are investigated in a variety of pile and soil configurations. The paper reports in detail the results of Model 1, corresponding to the simulation of reinforced concrete piles that were deformed by lateral spread under the NFCH building in Niigata during the 1964 earthquake.(AU)

Feasibility study of replacement procedures and earthquake perfomance related to gas transmission pipelines

A detailed and systematic review of the seismic perfomance of gas transmission lines prior to the 1994 Northridge earthquake shows that all repairs in pipelines affected by traveling ground waves occurred in areas which experienced seismic intensities of MMI>/ VIII. A review of gas transmission line perfomance during the 1994 Northridge earthquake discloses a similar pattern of seismic response. Approximately 91

of all pipeline damage caused by traveling ground waves in the 1994 event occurred in areas with MMI>/VIII. The earthquake-related damage has been predominantly in the form of ruptures at oxy-acetylene girth welds. The potential for damage in such welds appears to increase considerably for seismic intensities equal to and greater than MM VIII.(AU)

The Northridge, California earthquake of january 17, 1994 : Perfomance of gas transmission pipelines

On January 17,. 1994 at 4:31 a.m., a magnitude 6.6 earthquake struck the Los Angeles metropolitan area. Epicentered in the San Fernando Valley town of Northridge, California, the earthquake caused serious damage to buildings and sections of elevated freeways; ignited at least one hundred fires as it ruptured gas pipelines; and disrupted water supply systems. As a consequence, 57 people died, another 1,500 were seriously injured, and 22,000 were left homeless. Over 3,000 buildings, most of which were residential structures, were declared unsafe for reentry due to earthquake damage. Los Angeles, a city which has extensively prepared itself for earthquakes, found that it had experienced the most destructive event since the 1906 San Francisco earthquake. Direct economic losses are estimated currently at over $20 billion. This reconnaissance report provides a perfomance analysis of gas transmission lines, both during this earthquake and during previous earthquakes, in Southern California.(AU)

Evaluation of pile response to liquefaction-induced lateral spread

This paper presents the results of a comprehensive analytical study of pile foundation response to lateral spread. Analyses were perfomed with the computer code B-STRUCT, which has been shown to provide results which compare favorably with field observations of pile deformation under ground failure conditions. Analytical results are combined to develop dimensionless plots which allow for the determination of failure mechanisms on the basis of relative stiffness and applied axial load. For the first time, these results show quantitatively how the behavior of deep foundations changes as the ground alters its force-diaplacement characteristics from a soil-like to a fluid-like medium. Dimensionless plots also are developed to determine surface soil displacement required to induce the formation of a plastic hinge under excessive bending conditions.(AU)

Time history analysis of seismic serviceability of a water supply system

A new method is presented for estimating the time-dependent serviceability of water networks damaged during earthquakes. The method accounts for the uncertainty in seismic ground motion, soil conditions, current system damage state, required water demand and the finite supply of water in reservoirs and tanks. The analysis is based on the Monte-Carlo simulation method and involves a large number of hydraulic analyses of a water supply system in various damage states. The hydraulic analysis uses an algorithm that eliminates the portions of the network experiencing negative pressures. A computer code with graphic capabilities, GISALLE, developed at Cornell University is modified for calculating the time-dependent seismic serviceability measures. The Auxiliary Water Supply Syatem in San Francisco and an earthquake of the similar intensity as the 1989 Loma Prieta earthquake are used to demonstrate the proposed mothod of analysis.(AU)

Earthquake perfomance of gas transmission pipelines

Over 61 years of earthquake perfomance of steel transmission pipelines operated by the Southrn California Gas Company are reviewed. The seismic record includes 11 major earthquakes with ML >= 5.8 and epicenters within the transmission system. An evaluation is made of the most vulnerable types of piping, failure mechanisms, break statistics, threshold seismic intensity to cause failure, and damage induced by permanent ground displacement. The database assembled represents one of the most comprehensive and detailed records of seismic response in a large, complex gas transmission system.(AU)

Earthquake vulnerability assessment of A 40-inch cruce oil pipeline in the Central United States

A 40-inch diameter crude oil pepiline runs from St James, Louisiana. to a terminal near Patoka, Illinois over a distance of 635 miles. This pipelines delivers more that 1.000.000 barrels of crude oil per day, primarilyfrom gulf of Mexico wells and overseas sources, to refineries in the Midwest, The pipeline passes in close proximity to the New madrid Seismic Zone, which is located principally in northeast Arkansas and southeast Missouri. A general assessment of the vulnerability of the 40-inch pipeline to seismic hazards such as liquefaction (lateralspreading and flow slides), landslides (i.e., slope instability), and ground shaking effects (above-ground facilities)was recently conducted. The effects of two levels of earthquakes were evaluated, one with a recurrence interval of 100 years and the other having an intensity equal to the 1811-12 New Madrid earthquake sequence (AU)

Site response and soil liquefaction in San Francisco during the Loma Prieta earthquake

During the 1989 Loma Prieta earthquake, liquefaction in San Francisco occurred at four principal locations: the Marina, foot of market, south of market, and mission creek areas. The result of soil investigations in these areas are presented, and used to characterize the subsurface conditions. Digitized strong motion records at several rock sites in the vicinity of these areas are used in conjunction with response analyses, using equivalent linear procedures, to evaluate site amplification at each location and its relationship with soil liquefaction. The role of Holocene bay mud is explored with respect to its influence on peak acceleration and predominant period of ground motion. Special attention is directed to the Mission Creek area where liquefaction in 1906 and 1989 pccurred at the same locations in the eastern portions of the old creek bed, but not in its western part. Since liquefaction in the western part during the 1906 earthquake was responsible for catastrophic water main rupture and building collapse, the absence here of liquefaction in 1989 is of considerable interest. Explanations are given for this intriguing behavior.(AU)

Post - liquefaction consolidation and lifeline damage in the Marina district after the 1989 Loma Prieta earthquake

The relationship between settlements caused by post-liquefaction consolidation and damage to buried lifeline systems is discussed. Settlement strains of submerged fill are used to evaluate the pattern of observed settlements. Vertical strains predicted with existing simplified procedures show good general agreement with observations, provided that the presence of nonliquefiable soils are accounted for properly. It appears that the postliquefaction consolidation of hydraulic fill in the Marina was influenced by layers of fine-grained sediments. The resolution in delineating subsurface conditions with cone penetration test (CPT) measurements is shown to be an important factor in estimating the magnitude and extent of post-liquefaction consolidation in the hydraulic fill.(AU)

A new method to estimate earthquake liquefaction damage to buried lifelines

A new method that relates soil movement to buried lifeline damage state has been developed and applied during a Federal Emergency Management Agency-sponsored study to evaluate the impacts of lifeline proximity during earthquakes. The method considers landslides and liquefaction as a continum of ground displacement; it uses similar analysis methods for estimating the impacts of such motions on buried lifelines. For landslides, a critical acceleration parameter is used to estimate the lifeline damage state, which is also related to a displacement scaling parameter. Similary, a Liquefaction Severity Index (LSI) parameter is used to estimate the lifeline damage state for lateral spread or liquefactions conditions. The LSI can also be related to a displacement scaling parameter. The relationship of the LSI parameter to the earthquake intensity and lifeline damage state is new and is based on empirical data and expert judgement.(AU)

Seismic serviceability of water supply systems

Several measures are developed for evaluating the serviceability of water supply systems following seismic events. These seismic serviceability measures are random variables that depend on uncertain parameters such as seismic intensity, system damage state, and water demand. The determination of the proposed serviceability measures involves hydraulic analyses of water supply systems in various damage states. Commercially available softwares for hydraulic analysis are configured for intact networks and can not be used reliably for heavily damaged and leaking systems.(AU)