An Alternative Method of Measuring SPT Energy

Despite problems associated with its repeatability and reliability, the standard Penetration Test (SPT) continues to be the most widely used in-situ test for liquefaction potential assessment. There are many factors known to influence the SPT results but the most significant factor affecting the N value is the amount of hammer energy delivered into the drill rods. The existing method of SPT energy measurement consists of attaching a load cell near the top of the drill rods and measuring the force time history during hammer impact. An alternative method of SPT energy determ1nat1on based on measurement of both force and acceleration time history is described. It is shown that the proposed method is more fundamental and avoids several shortcomings in the existing method. Field measurements are presented and SPT energies calculated by both methods are compared

General Report Session 3: Deformation and Liquefaction of Sands, Silt, Gravels and Clays

It has been almost 27 years since the damaging earthquakes of 1964 which occurred in Niigata, Japan and in Alaska, USA, focused the geotechnical engineers\u27 attention to liquefaction as a major problem in earthquake engineering. Considerable research and studies have been conducted on the subject of earthquake induced liquefaction since that time and these have included field observations, laboratory experiments and model tests, and theoretical studies. Progress in understanding the liquefaction phenomenon, in the assessment of liquefaction potential, and in the solutions to mitigate the liquefaction hazard has been made, yet the problem remains controversial in many respects, as reflected by the many stimulating papers presented in this session. The word liquefaction has been associated with many phenomena observed in the field during and after earthquakes such as sand boils, flow slides, lateral spreads, loss of bearing capacity and porewater pressure rise. In laboratory tests, liquefaction has been defined in several ways relating to pore pressure buildup under undrained cyclic straining or loading, or the development of a specified amount of shear strain in a fixed number of cycles of loading. Laboratory studies have also shown that the liquefaction phenomenon can be divided into three different behaviors, namely, true liquefaction, limited liquefaction and cyclic mobility. In theoretical studies, liquefaction occurs when the seismic-induced cyclic shear stress exceeds the cyclic shear resistance, or when the seismic porewater pressure increases to equal the effective stress. To compare the results from different papers, one must bear in mind the different definitions used by the various authors. Liquefaction-caused failure is really the result of excessive permanent deformation, e.g. tilting, settlement or heave of structures, excessive slumping or distortion, and sliding of slopes. Liquefaction-induced ground deformation is receiving more attention in the last decade. Soil failure due to liquefaction was the most dominant cause of damage in the recent M 7. 7 Luzon earthquake of July 16, 1990 in the Philippines. Remedial measures or ground improvement techniques to reduce the liquefaction hazards are becoming more common in recent years, not only for seismic rehabilitation of existing sites but also for newly developed sites. Refinements in equipment and techniques of existing methods are being developed. As well, new methods of ground improvements are being introduced. The M 7.1 Lorna Prieta earthquake of October 17, 1989 showed convincingly that liquefaction hazard can be avoided or effectively mitigated by soil densification prior to earthquake

Downhole Seismic Cone Analysis Using Digital Signal Processing

In-situ measurement of the dynamic characteristics of surficial soils is becoming more common in geotechnical practice for prediction of ground surface motions from earthquake excitation and to evaluate foundations for vibrating equipment. Techniques for these measurements have been under development at the University Of British Columbia (U.B.C.) since 1980. The paper discusses many practical considerations with respect to equipment (sources, receivers, trigger, etc.) and procedures that can affect the interpretation and analysis of seismic cone results. A brief review is given of the cross-over method as used at UBC to determine interval shear velocity travel times from downhole seismic cone testing. A more detailed description is provided for the cross-correlation technique used in the frequency domain that has recently been incorporated into the analysis procedure. Comparisons of these two methods are presented and discussed

Liquefaction Characteristics of Undisturbed Soils

Undrained cyclic triaxial tests were performed on undisturbed samples of natural soil deposits in order to investigate some of the factors affecting its liquefaction characteristics. It was shown that when the cyclic deviator stress is normalized with respect to major principal effective stress the number of cycles to liquefaction is not affected by sample size, consolidation stress, anisotropic consolidation, and grain size and density variations. However, liquefaction resistance was markedly increased by increasing over-consolidation ratio and aging. Also, sample disturbance of loose soils results in an increase, or unconservative measurement, of liquefaction resistance

lnsitu Measurement of Damping of Soils

The Seismic Cone Penetration Test (SCPT) has been shown to give reasonable results for insitu measurements of shear wave velocity, and this paper extends this work to include measurements of damping. The relevant equations of motion are described, factors affecting amplitude decay are discussed, and the nature of damping is summarized. Consideration is given to some of the practical aspects of pre-processing of signals. Three methods of damping calculation are presented. The first two, attenuation coefficient and modified SHAKE methods, require the application of amplitude corrections, which is not straight-forward, give variable results, and indicate negative damping in a clayey silt layer. The third, the spectral slope method eliminates the need for amplitude corrections and gives less variable and more acceptable results. The spectral slope method gave damping measurements of about 2% to 3% for sand and 0.3% to 0.5% for silt, at low strain levels of 10-4 to 10-3%

In-situ stress conditions at Nankai Trough, Site 808

Shipboard laboratory index property data, shore-based consolidation tests, and in-situ stress and pore-pressure measurements are used in this study to constrain the stress conditions at ODP Site 808, Nankai Trough. Results of these tests are presented along with additional intepretations of porosity rebound and permeability. The sediment at Site 808 is highly affected by excess fluid pressures throughout the sediment column. Excess fluid pressure is severe below the major fault boundary, the decollement. The in-situ measurement of lateral stresses, which are shallow in the sediment section, confirms that the principal stress direction is rotated from a "normal" basin-type condition where the principal stress direction is vertical

An energy efficiency analysis of single point incremental forming as an approach for sheet metal based component reuse

Producing materials causes about 25% of all anthropogenic CO2 emissions. Metals play a significant role, steel and aluminum account for 24% and 3% of worldwide material related emissions respectively. Fostering resources efficiency strategies in the field of sheet components could lead to a significant environmental impact reduction. Reshaping could be one of the most efficient strategy to foster material reuse and lower the environmental impact due to material production. Specifically, for aluminum recycling, the overall energy efficiency of conventional route is very low and, more importantly, permanent material losses occur during re-melting because of oxidation. The present paper aims at presenting the technical feasibility of Single Point Incremental Forming (SPIF)-based reshaping approach. Change in shape of aluminum stamped part is obtained through SPIF process implementation. Preliminary energy savings quantification through life cycle energy and material flows modelling are provided, energy efficiency of conventional recycling approach and SPIF-based reshaping routes are analyzed and compared

Mannheim Peritonitis Index (MPI) and elderly population: Prognostic evaluation in acute secondary peritonitis

Introduction. Acute Secondary Peritonitis due to abdominal visceral perforation is characterized by high mortality and morbidity risk. Risk stratification allows prognosis prediction to adopt the best surgical treatment and clinical care support therapy. In Western countries elderly people represent a significant percentage of population Aim. Evaluation of Mannheim Peritonitis Index (MPI) and consideration upon old people. Patients and methods. Retrospective study on 104 patients admitted and operated for \ue2\u80\u9cAcute Secondary Peritonitis due to visceral perforation\ue2\u80\u9d. MPI was scored. In our study we want to demonstrate efficacy of MPI and the possibility to consider older age an independent prognostic factor. Results. Mortality was 25.96%. Greatest sensitivity and specificity for the MPI score as a predictor of mortality was at the score of 20. MPI score of 22. Patients with MPI score 17-21 had 0.46 times lower risk of mortality compared to patients with MPI score >21. In the group of patients with MPI score of >20 the mortality rate was 48.5% for patients older than 80 years old and 12.1% for younger patients (p < 0.005); in the group with MPI score of < 20 mortality rate was respectively 8.4% and 1.4% (p < 0.005). Discussion and conclusions. Data confirm the accuracy of the test. MPI score and age over 80 years old resulted independent predictors of mortality at multivariate analysis

Sphingosine-1-Phosphate in the Tumor Microenvironment: A Signaling Hub Regulating Cancer Hallmarks

As a key hub of malignant properties, the cancer microenvironment plays a crucial role intimately connected to tumor properties. Accumulating evidence supports that the lysophospholipid sphingosine-1-phosphate acts as a key signal in the cancer extracellular milieu. In this review, we have a particular focus on glioblastoma, representative of a highly aggressive and deleterious neoplasm in humans. First, we highlight recent advances and emerging concepts for how tumor cells and different recruited normal cells contribute to the sphingosine-1-phosphate enrichment in the cancer microenvironment. Then, we describe and discuss how sphingosine-1-phosphate signaling contributes to favor cancer hallmarks including enhancement of proliferation, stemness, invasion, death resistance, angiogenesis, immune evasion and, possibly, aberrant metabolism. We also discuss the potential of how sphingosine-1-phosphate control mechanisms are coordinated across distinct cancer microenvironments. Further progress in understanding the role of S1P signaling in cancer will depend crucially on increasing knowledge of its participation in the tumor microenvironment

Thermo-mechanical behaviour of a compacted swelling clay

Compacted unsaturated swelling clay is often considered as a possible buffer material for deep nuclear waste disposal. An isotropic cell permitting simultaneous control of suction, temperature and pressure was used to study the thermo-mechanical behaviour of this clay. Tests were performed at total suctions ranging from 9 to 110 MPa, temperature from 25 to 80 degrees C, isotropic pressure from 0.1 to 60 MPa. It was observed that heating at constant suction and pressure induces either swelling or contraction. The results from compression tests at constant suction and temperature evidenced that at lower suction, the yield pressure was lower, the elastic compressibility parameter and the plastic compressibility parameter were higher. On the other hand, at a similar suction, the yield pressure was slightly influenced by the temperature; and the compressibility parameters were insensitive to temperature changes. The thermal hardening phenomenon was equally evidenced by following a thermo-mechanical path of loading-heating-cooling-reloading