Experimental study of the overconsolidation and saturation effects on the mechanical characteristics and residual strength of Chlef river sandy soil
This paper presents a laboratory study of the influence of the saturation evaluated in terms of Skempton´s pore pressure coefficient (B) and overconsolidation ratio (OCR) on the behavior of Chlef sand. The study is based on drained and undrained triaxial compression tests which were carried out for Skempton´s pore pressure coefficient varying between 13 and 90% and OCR varying between 1 and 8. Tests were conducted on medium dense sand samples having an initial relative density Index Id = 0.5 at an effective stress of 100 kPa. The paper is composed of two parts. The first one presents the characteristics of the sand used in this study, the second provides an analysis of the experimental results and discusses the influence of Skempton´s pore pressure coefficient (B) and OCR on the mechanical characteristics of the sand. The tests show that the increase in the Skempton´s pore pressure coefficient (B) reduces the soil dilatancy and amplifies the phase of contractancy and reduces the frictional and characteristic
angle of the sand. The increase of OCR improves the stiffness of sand and accelerates the appearance of dilatancy; and increases frictional and characteristic angle of the sand. Moreover, the present study focuses on the effect of saturation and overconsolidation on the residual shear strength of sand.
Test Procedures for Measuring Soil Liquefaction Characteristics
The merits and limitations of laboratory simple shear and triaxial compression tests, conducted under cyclic loading conditions, are analyzed. In addition the theoretical relationships between the stress conditions causing liquefaction in simple shear and triaxial compression tests, based on several different failure criteria, are investigated. Finally data are presented for 35 sites where liquefaction is known to have occurred or not occurred during earthquakes, providing a means for evaluating the stress conditions causing liquefaction of sands in the field. It is shown that both analytical and experimental evidence, as well as field data, suggest that most laboratory triaxial compression test data, expressed in terms of σ dc /(2σ a ) should be reduced by a factor of 0.55 to 0.7, depending on the density of the soil and the duration of the earthquake, in order to determine values of τ Dhv /σ' o causing liquefaction during earthquakes under field conditions. Considerable judgment is involved in evaluating such relationships, and data from field studies may provide the basis for evaluating the liquefaction characteristics of sands.
Seismic and Sequence Analysis of Middle to Late Miocene Deposits of Northeast Java Basin
DOI: 10.17014/ijog.2.2.101- 110 This study is focused on Middle to Late Miocene sediments. As depicted in the regional geology of Indonesia, the area of study is part of Northeast Java Basin. There are three phases of tectonism in the basin: extensional tectonics at Eocene-Oligocene time, compressional tectonics at Middle Miocene, and compressional tectonics at Miocene-Pliocene time. The result of the study shows three sequences were developing during Middle to Late Miocene, those are: (1) Middle Miocene sequence-1 (MM-1 sequence) consisting of a Lowstand Tract System deposition in Middle Miocene-1 (LST MM-1), Transgressive System Tract deposition in Middle Miocene-1 (TST MM-1), and Highstand System Tract deposition in Middle Miocene-1 (HST MT-2); (2) Middle Miocene sequence-2 (MT-2 sequence), comprising Transgressive System Tract Middle Miocene-1 (TST MM-2), and Highstand System Tract deposition in Middle Miocene-1 (HST MM-2); (3) Late Miocene sequence-1 (LM-1 sequence), composed of a Lowstand Tract System deposition in Late Miocene -1 (LST LM-1) and a Transgressive System Tract deposition in Late Miocene-1 (TST LM-1).