PART 1 DEALS WITH THE DYNAMIC ASPECTS OF THE SUBJECT: MATHEMATICAL ANALYSIS OF SYSTEMS SUBJECTED TO INDEPENDENT VIBRATIONS BY MEANS OF MATHEMATICAL MODELS. THE ANALYTICAL SYSTEMS USED ARE NON-LINEAR SYSTEMS, HYDRODYNAMICS AND NUMERICAL METHODS. PART 2 EXAMINES SEISMIC MOVEMENTS, THE DYNAMIC BEHAVIOUR OF STRUCTURES AND THE BASIC CONCEPTS OF THE SEISMIC DESIGN OF STRUCTURES.

Fundamentals of earthquake engineering

O ne of the few research texts authored by those with occupational therapy expertise, this book offers a vast amount of information to the beginning researcher or to professionals interested in reviewing studies with a more critical eye. The book proceeus in a logical fashion beginning with the philosophy of research. The how-to's of designing a study and collecting data are presented, and the final chapters deal with analysis and interpretation of data. In Pan I, the authors define research as a form of knowledge that is \"logical, understandable, confirmable and useful\" (p. 5). DePoy and Gitlin also point out that research provides the scientific evidence necessary to generate a professional body of knowledge. The naturalistic approach to research, designed to uncover phenomena via inductive reasoning, is presented in a positive light. The reader becomes aware of the basic theoretical differences between this approach and the somewhat less controversial experimental approach and is given examples of each. The authors discuss that, although these approaches vary in theory, they may be combined to proVide an integrated approach to research. In Part II, the specifics of structuring research projects are addressed. Which framework (experimental, naturalistic, or a combination) is used depends on the question the researcher wants to answer. The authors also discuss the importance and mechanics of performing a thorough literature review and methods to categorize research designs. The remainder of Pan II is devored to further explanation of the naturalistic and experimental approaches. Examples to illustrate the continuum of designs in each of these approaches are given and several methods 1O combine these designs are proposed. In Part Ill, DePoy and Gitlin delve into selection of appropriate populations and sample sizes. They talk aboLlt nor only what population to include, but also what population to exclude to provide the most stable foundation for a research project. Data-gathering techniques are examined in depth for borh the naturalistic and experimental designs, and several methods for performing statistical analysis are presented. Analysis techniques for naturalistic methodologies are included also. Some basic tips for metamorphosing the information proVided from data analysis into a written text that is clear and concise are outlined in the remaining chapters. The authors also make the pOint that information gleaned from research, no matter how relevant, is nor of use to the profession unless it is disseminated to others. In the last chapter, the authors share their personal research experiences. The reader is left with some perceptions of performing research in a practice-oriented profession. The entry-level researcher, or the clinician wishing to upgrade his knowledge of what constitutes a strong study, will find this book of great interest. The authors have tackled a rather esoreric subject and tied it into a clinician's frame of reference. This text was also written to be included in research curriculums. The Student will find all of the necessary teaching information, as well as examples of the theories presented. Some interesting features of this text include its logical organization. Each chapter contains a summary of the information presented so that the reader can review at a glance. Several of the chapters that present the steps necessary to carry out a study have mental exercises the reader can perform to tesl his knowledge. A wonderful gJossary, bibliography, and thorough index make this an appropriate reference book for the clinician. Theories, strategies, and methodologies are presented with tables and illustrations that are clear to those nor familiar with basic research ideas. One area that could be strengthened is the authors' use of clinical examples. The examples provided in the text are sometimes vague and difficult for the reader to relate to the tenets they are used to reinforce. In addition, many examples appear to be drawn from the authors' social work experience, rather than from their occupational therapy expertise. The book does, however, contain several pertinent references to studies encompassing the occupational therapy range. Several of these studies were also done by the authors, lending further credence to their opinions. For the most part, the authors present the information in an easily understandable style. The beginning of the text, with its explanations of the theory of research and the philosophies of several approaches, may be difficult reading for some. But overall, this text does what it was written to do: give the reader interested in research a thorough background in theory and methodology. The authors seek to demystify the research process for those in the health and human services fields, and the reader is left with a sense that research is not JUSt for those with specialized training, but that direct patient care proViders also can possess the necessary skills and knowledge to make a significant contribution to their profession's body of knowledge. Joanne Merante Baird, MA. OTRIL

Introduction to research.

Soils that exhibit nonassociated flow may, according to stability postulates by Drucker and by Hill, become unstable when exposed to certain stress paths inside the failure surface. Series of conventional triaxial tests on fully saturated and on partly saturated specimens were performed under drained and undrained conditions to study the regions of stable and unstable behavior. For specimens that compress and have degrees of saturation higher than critical, undrained conditions lead to effective stress paths directed within the region of potential instability, and instability was observed provided the yield surface opens up in the outward direction of the hydrostatic axis. Thus, instability occurs inside the failure surface. Instability is not synonymous with failure, although both may lead to catastrophic events. The location of the instability line is discussed. Examples of a shallow submarine slope and a nearly fully saturated steeper slope representing a tailings dam, which both should remain stable a...

Closure of "Static Instability and Liquefaction of Loose Fine Sandy Slopes"

金浩鎭著 「韓國政治體制論」(서울 : 博英社, 1990)

A gigantic rapid landslide claiming over 1,000 fatalities was triggered by rainfalls and a small nearby earthquake in the Leyte Island, Philippines in 2006. The disaster presented the necessity of a new modeling technology for disaster risk preparedness which simulates initiation and motion. This paper presents a new computer simulation integrating the initiation process triggered by rainfalls and/or earthquakes and the development process to a rapid motion due to strength reduction and the entrainment of deposits in the runout path. This simulation model LS-RAPID was developed from the geotechnical model for the motion of landslides (Sassa 1988) and its improved simulation model (Sassa et al. 2004b) and new knowledge obtained from a new dynamic loading ring shear apparatus (Sassa et al. 2004a). The examination of performance of each process in a simple imaginary slope addressed that the simulation model well simulated the process of progressive failure, and development to a rapid landslide. The initiation process was compared to conventional limit equilibrium stability analyses by changing pore pressure ratio. The simulation model started to move in a smaller pore pressure ratio than the limit equilibrium stability analyses because of progressive failure. However, when a larger shear deformation is set as the threshold for the start of strength reduction, the onset of landslide motion by the simulation agrees with the cases where the factor of safety estimated by the limit equilibrium stability analyses equals to a unity. The field investigation and the undrained dynamic loading ring shear tests on the 2006 Leyte landslide suggested that this landslide was triggered by the combined effect of pore water pressure due to rains and a very small earthquake. The application of this simulation model could well reproduce the initiation and the rapid long runout motion of the Leyte landslide.

An integrated model simulating the initiation and motion of earthquake and rain induced rapid landslides and its application to the 2006 Leyte landslide

This paper analyses the dominant mechanisms of slope failures and identifies potential obstacles to landslide-hazard reduction at the Iva Valley area, Enugu, Nigeria. The landscape is replete with landslide scars and gullies of varied sizes and the slope deposits comprise unconsolidated, friable sands inter-bedded with thin units of montmorillonitic claystone. Forty-three landslide events were identified in the study area with most being shallow, short run-out movements with slip-surface depth <2 m. The study found the landslides mainly occur in the beginning of rainy season characterized by short duration, high intensity rainfall. An integrated approach comprising field mapping, laboratory tests and numerical analyses reveals that the barren nature of the slopes prior to the outset of rainy season, high rainfall intensity, erosion, overgrazing, soil characteristics and the site’s unique lithologic sequence are the main causes of instability. Shearing tests under several conditions showed that the soils strongly strain-soften until low steady-state strength is achieved. A computer code, based on this strength reduction technique, used input parameters obtained from the field and laboratory studies to simulate a landslide with similar structure, travel distance and distribution area. It is noted that urbanization has gradually increased the vulnerability of the society’s poor to landslide hazards as they now erect unplanned residence (tents and blocks) on the slopes. This work is part of a regional study aimed at finding ways of protecting the vulnerable by generating data that could be used to build future landslide susceptibility map.

The analysis of rainfall-induced slope failures at Iva Valley area of Enugu State, Nigeria

Loess caves, a special kind of geo-hazard on loess plateau, northwestern China

Landslides in Nigeria occur in various forms and vary in mode, scale and frequency. The variations appear to be significantly controlled by geologic setting, hence the need to study in detail the distinctive features that differentiate landslides in sedimentary environments from those on metamorphic localities. The aim is to understand the actual features impacted on the landslides by geology, from which future predictions of occurrence and identification of instability could be based. The recognition of features that are characteristic of certain geologic setting may be a major step in early warning development in Nigeria. To achieve the objectives detailed mapping of the study area was carried out using topographic maps, aerial photographs and multiple field surveys. The landslides on the sedimentary terrain were mainly shallow, low-volume movements, material slumps and short runout slides some of which activated on slopes that followed the dip of strata, along wavy shear surfaces controlled by impermeable bedding planes. Runoff-triggered movements caused by erosion of channel bed and banks and failures caused by sediment bulking of runoff with material eroded from headwater slopes are also common on the sedimentary terrain. In comparison, the landslides on the metamorphic terrain were complex translational and rotational movements and mudslides on steep slopes sometimes involving a combination of slide and flow with curved headscarps and slickensided shear surfaces. The looseness of slope materials and their relatively low strength parameters account for the dominance of landslides on the sedimentary zone.

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The geotechnical characteristics of landslides on the sedimentary and metamorphic terrains of South-East Nigeria, West Africa

Three silica sand samples—well graded, intermediately graded, and narrowly graded—having different uniformity coefficients, were constituted to allow the investigation of the influence of particle size distribution on their mechanical behavior. Using a ring shear apparatus, samples were tested under a wide range of laboratory conditions. Results of the tests clearly indicate that, for specimens confined under identical stress conditions, well-graded specimens have higher values of peak and steady state strengths than the rest of the specimens. A relationship between uniformity coefficient and shear strengths shows that the higher the uniformity coefficient, the higher the shear strength. On account of these, well-graded specimens have higher static liquefaction resistance than the poorly graded specimens. Within the range of normal stresses employed in the tests, results reveal that not only are poorly graded sands more likely to suffer higher postfailure strength reduction, but that their steady-state strengths are easily reduced to zero, the magnitude of the confining stress notwithstanding. This reduction of shear resistance to zero has been described as complete liquefaction in this paper. While almost all of the narrowly graded specimens suffered complete liquefaction, widely graded ones did not; an observation that seem to highlight the influence of grading on the mechanical behavior of the sands.

The influence of grading on the shear strength of loose sands in stress-controlled ring shear tests

The Iva Valley area has one of the highest densities of landslides in Nigeria, and impacts the residents, local economy, and the environment. Slopes in the area sit on unconsolidated, cross-bedded, friable sandstone units with interbeds of claystone. Past research efforts had proposed theories explaining the mechanism of failure based on the limited-liquefaction behavior of the slope materials. But as landslide prevention works on the slopes began to fail, it became apparent that those theories were inadequate solutions to the devastating effect of mass wasting processes. This paper presents the results of landslide susceptibility assessment based on the new evidence of complete-liquefaction behavior observed in the samples when back-pressure is employed to accomplish full saturation. Loose, saturated specimens failed after attaining maximum strength at shear displacements less than 1 mm. The failure was marked by rapid reduction in shear strength and accompanied by a steady increase in pore water pressure until the ratio of pore pressure and normal stress approached unity indicating complete liquefaction. This behavior simulated the response of the slope soils to varying stress and drainage conditions in the field, and seems an adequate mechanism for the incessant failure of slopes and prevention works. Because the geology of a vast area of the South-East Nigeria is similar, the results obtained at the study area are also applicable in other areas within the region for sustainable preventive and mitigating measures.

Ogbonnaya Igwe

Papers

The analysis of rainfall-induced slope failures at Iva Valley area of Enugu State, Nigeria

Loess caves, a special kind of geo-hazard on loess plateau, northwestern China

The geotechnical characteristics of landslides on the sedimentary and metamorphic terrains of South-East Nigeria, West Africa

The influence of grading on the shear strength of loose sands in stress-controlled ring shear tests

The effect of water-saturation on the stability of problematic slopes at the Iva Valley area, Southeast Nigeria