Showing papers by "Rodrigo Salgado published in 2001"

Analysis of Cavity Expansion in Sand

Abstract: Cavity expansion analysis plays a significant role in modern soil mechanics. The analysis of many of the most important problems in the practice of geotechnical engineering (such as cone penetration testing, pile loading, or pressuremeter testing) rely to a large extent on cavity expansion analyses. Cavity expansion processes are of two basic types: expansion from a finite radius and expansion from zero initial radius. It is usual to use a different type of analysis for each of these problems. Analysis of the cavity creation problem yields only the limit pressure, but not necessarily information on the pressure-strain relationship during expansion. Analysis of expansion from an initially finite cavity radius gives a pressure-strain curve, but no information on the limit pressure. In this article, we present a simple numerical analysis that provides the solution to both problems simultaneously. The analysis takes full account of the flow rule and dependence of the friction angle on stress state, p...

Retaining Wall Model Test with Waste Foundry Sand Mixture Backfill

Abstract: This paper presents experimental data concerning the lateral earth pressures acting against a small-scale retaining wall, with a backfill consisting of waste foundry sand (WFS) mixtures. The instrumented retaining-wall facility at Dongeui College in Korea was used in the testing. Two different testing methods were employed in this study: the controlled-strain method and the natural-strain method. The lateral earth pressures on the wall depend on the backfilling sequence, the type and drainage characteristic of the WFS mixture, and the shear strength of the mixtures. The mixtures of Green WFS performed best, showing a decrease in the lateral earth pressures and an increase in cohesion with curing time. The measured thrust lateral earth pressure of WFS mixtures was less than that observed for common residual soils in Korea. The stability of the retaining wall with respect to overturning and sliding, calculated using the measured lateral earth pressures, increased substantially with curing time. Judging from the retaining wall model test, the backfilling of a 6-m high retaining wall can be completed in two days with two backfilling stages.

Seismic design of deep foundations

Abstract: Detailed investigations of pile foundations affected by earthquakes around the world since the 1960s indicate that pile foundations are susceptible to damage to such a degree that the serviceability and integrity of the superstructure may be affected. Although numerous cases of seismically damaged piles are reported, the detailed mechanisms causing the damage are not yet fully understood. As a consequence, an effective seismic design of pile foundations has not been yet established in practice. Many road bridge structures supported on piles exist in southern Indiana. This is a region where the risk of occurrence of a dangerous earthquake is high due to its proximity to two major seismic sources, the New Madrid Seismic Zone (NMSZ) and the Wabash Valley Fault System (WVFS). The present study is a first step towards the assessment of potential earthquake induced damage to pile foundations in southern Indiana. Credible earthquake magnitudes for each of the two potential seismic sources are assessed for a return period of 1000 years. SHAKE analyses are performed at nine selected sites in southwestern Indiana to estimate the potential of ground shaking and liquefaction susceptibility. The soil profile and soil properties at each site are obtained from the archives of the Indiana Department of Transportation. The amplitude of the rock outcrop motion is estimated using attenuation relationships appropriate to the region, and estimated values are compared with predictions from the USGS. SHAKE analyses are performed for two earthquake scenarios: a NMSZ earthquake and a WVFS earthquake. Two sets of input motions are considered for each scenario. The liquefaction potential at those nine sites is assessed based on the Seed et al. (1975) method. Data from a total of 59 real cases of earthquake-induced damage to piles have been gathered through an extensive literature survey. The collected and compiled data have been used to identify the causes and types of pile damage, and the severity of damage. Based on the survey, damage is usually located near the pile head, at the interfaces between soft and stiff layers, and between liquefiable and non-liquefiable layers. Large inertial loads from the superstructure can cause crushing of the head of concrete piles. Imposed deformations due to the response of the surrounding soil can produce small to large cracks on concrete piles depending on the soil profile. In contrast, large inertial loads, liquefaction and lateral spreading can cause wide cracks. Few cases of steel piles are found in the literature. Steel casing seems to improve the performance of concrete piles. Numerical simulations of a concrete pile at a selected road bridge site with and without steel casing are used to investigate the effect of steel casing on the performance of concrete piles. Results from this work suggest that major credible seismic events can generate accelerations high enough to produce damage to concrete piles in southern Indiana. The potential of liquefaction and lateral spreading increase the likelihood of damage.