Measurement of Vibration and Noise During the Installation of Rammed Aggregate Piers

The objective of the study was to record and evaluate ground vibration and noise generated during the installation of rammed aggregate piers (RAPs). Summarized are ground vibration and noise induced by the ramming equipment (i.e. the hydraulic break hammer and rammer) during the installation of forty-five RAPs at a single site. Data were collected during the entire installation process for each pier, which allowed for the measurement of ground vibration and noise levels for periods when the ramming equipment was positioned at different depths within the RAP. Measurements were also taken at different horizontal distances from the ramming equipment and RAP being installed. The entire data set consists of over 160 ground vibration measurements and over 260 noise measurements. Peak ground velocities measured during the study ranged between approximately 0.5 and 15 millimeters per second for horizontal distances ranging between 1.5 and 10.5 meters. Corresponding vibration frequencies ranged between approximately 20 and 60 Hz. Measured noise levels ranged between approximately 82 and 111 dBA for measurement locations between approximately 1.5 and 10.5 meters from the hammer. Overall, these measured ground vibrations and noise levels are moderate in nature and below those typically generated during pile driving

Teaching consolidation: Case study of preloading with vertical drains

This paper describes a ground improvement case study where preloading and prefabricated vertical drains (PVDs) were used to accelerate foundation settlements. The case study is used in a classroom setting with the learning objective of introducing engineering students to methods for estimating settlement of shallow foundations on compressible soils. The project site was developed for a corporate retail chain planning to open a new facility in San Luis Obispo, California. Up to 2.5 meters of fill were needed across much of the site to raise foundations and improvements above the flood elevation. Loads from the fill and the structure were expected to cause total and differential settlements that exceeded the allowable values established by the retailer. To mitigate settlement, the geotechnical engineer developed a preloading plan. Although the soil conditions were complex (e.g., interlayering, dipping strata, variable compressibility), the preloading plan was successful in achieving the desired settlement within 3 months, and subsequent site performance has been exemplary. This case study has been used for several years within a quarter-long shallow foundation design course to teach settlement performance. Learning outcomes from the assignment are summarized in the paper. Students are given the subsurface information and test results originally acquired by the geotechnical engineer. The students, working in teams, try to estimate how much primary consolidation settlement will occur due to the fill plus the preload, and the PVD spacing needed to achieve 90% of that settlement in 3 months. The assignment and relevant data are included herein along with the grading policy. The project culminates with the geotechnical engineer of record presenting in class the results of site monitoring during preloading and consolidation. These results include settlements across the 16,908 m2 site, which were tracked up to three times a week at 20 locations. This project affords students a case study experience that is rich in the “messy” details of a complex and local (i.e. familiar) geotechnical project. Included is a discussion of lessons learned by the instructors who have taught several iterations of this case study

Earthquake Input Motions for Physical Model Tests

The results from several dynamic centrifuge experiments are presented in this paper; the experiments were performed as part of a study to assess the influence of local site conditions on earthquake ground motions. Medium dense dry sand and saturated soft clay models were subjected to the accelerogram recorded at Santa Cruz during the 1989 Loma Prieta Earthquake. Scaled versions of the input motion were used to shake the soil models; in addition, different time steps were used in order to study the effects of frequency content of the input motion. The results confirm that the characteristics of the input motion and the soil model combine to have important effects on soil response. This fact must be recognized when selecting input motions for physical model tests

Earthquake Input Motions and Seismic Site Response in a Centrifuge Test Examining SFSI Effects

This paper describes the ground motion selection process and reports observed seismic site response and SFSI effects during a dynamic centrifuge test (Test-1). The centrifuge test is the first in a series of tests examining the effects of SFSI in dense urban environments. The objective of Test-1 is to examine SFSI effects for two structures that are located a significant distance apart and essentially isolated. The model structures represent a three-story building founded on spread footings and a nine-story structure founded on a threestory basement. The structures are sited on a dry, dense bed of Nevada Sand. The centrifuge model is subjected to a series of shaking events that represent near-fault and “ordinary” ground motions at a site in Los Angeles. Results show that site periods degrade as ground motion intensity increases with more pronounced degradation observed for near-fault ground motions as compared with ordinary ground motions. Additionally, the results indicate the importance of kinematic effects of embedded structures when considering SFSI effects

Seismic Performance Assessment in Dense Urban Environments: Evaluation of Nonlinear Building-Foundation Systems Using Centrifuge Tests

In dense urban areas, buildings are generally constructed in clusters, forming city blocks. New buildings are designed assuming their response is independent of adjacent buildings, which ignores potentially important structure-soil-structure-interaction (SSSI) effects. Although a few studies have revealed the significance of SSSI effects, validated simulation and design tools do not exist. In this paper, we present the results from the first in a series of centrifuge tests intended to investigate SSSI effects. Results herein are focused on the design and measured response of two model building-foundation systems placed on dense dry Nevada sand and tested at 55-g. The two models represent prototypical nine-story and three-story special moment resisting frame buildings, with the former structure supported by a three-level basement-mat and the later on isolated spread footings. Nonlinear response-history simulations are performed to aid in the design of the models, with particular attention to reproducing prototype building periods and nonlinear characteristics. Yielding of the model buildings is achieved using custom-designed fuses placed strategically throughout the superstructures. At present, the two models are placed as far apart as possible to characterize soil-structure interaction on individual buildings; subsequent experiments will move the structures in near proximity, allowing direct experimental assessment of structuresoil- structure-interaction

AC 2011-811: GRADUATE STUDENTS MENTORING UNDERGRADU- ATE RESEARCHERS ON A LARGE-SCALE EXPERIMENTAL RESEARCH PROJECT -A CASE STUDY Graduate Students Mentoring Undergraduate Researchers on a Large-Scale Experimental Research Project -A Case Study

Abstract The paper describes our strategies and experiences in recruiting, training, advising, and mentoring five undergraduate student researchers for a large-scale experimental research project. Specific discussions focus on the development of student learning outcomes and the establishment of a recruiting program. For this project, graduate student leaders served as the primary mentors to the undergraduate researchers. In the paper, we discuss how the graduate students prepared for their roles as research mentors. The principal investigators worked with the graduate student leaders to provide advice and training on topics such as teamwork, project management, communication, feedback, and student learning. Details of this approach are described in the paper. The paper also includes a discussion of the methods used to assess the undergraduate students' project experiences. Examples are provided of different work products prepared by the undergraduates. Also provided are the results of a post-employment assessment survey, which was developed by the graduate student leaders and a principal investigator. The survey results indicate that the undergraduate student research experiences have been challenging and rewarding. The survey results also provide valuable feedback for the graduate student leaders. At the mid-point of the project, the graduate students are using the feedback to develop specific recommendations for managing the research project and mentoring undergraduates in the future. The recommendations are summarized in the paper

Identifying and Overcoming Barriers to Integrating Sustainability across the Curriculum at a Teaching-Oriented University

This research collects and analyzes student and faculty knowledge and perceptions toward sustainability education at a predominately undergraduate, teaching-oriented university. In-depth, qualitative methods distinguish low- and high-knowledge student and faculty cohorts, identify perceived barriers to sustainability education in each cohort, and recognize strategies to overcome the barriers identified by each cohort. Data collected from recorded and transcribed semi-structured interviews of student and faculty subjects underwent analysis via repeated readings to uncover key themes. Results required developing metrics for student and faculty sustainability knowledge and attitudes across disciplines, determining discipline-specific gaps in sustainability knowledge and differences in attitudes, and relating implementation barriers to general or specific knowledge gaps and attitudes. Findings identified low and high levels of sustainability knowledge within the student and faculty subject population and revealed barriers in pursuing interdisciplinary sustainability curricula across disciplines and among both students and faculty at the study university. Overall, higher sustainability knowledge participants tend to identify barriers related to institutional accountability while lower sustainability knowledge participants tend to identify barriers related to personal responsibility. Distributing barriers and solutions along a continuum from personal responsibility to educational institution responsibility reveals more recognition of barriers at the personal level and more solutions proposed at the institutional level. This result may reflect a common tendency to deny personal responsibility when addressing sustainability challenges