Evaluating the overconsolidation ratios and peak friction angles of granular soil deposits using noninvasive seismic surveying

Acta Geotechnica - The main objective of this study was to propose an approach to estimate the peak friction angles of over-consolidated granular soil deposits by using the P-wave velocity and the...     

A COMPARISON OF LABORATORY AND FIELD MEASUREMENTS OF P-WAVE ANISOTROPY1

P-wave velocity anisotropy determined from a cross-hole survey at the Imperial College borehole test site compares favourably with that measured in the laboratory on core from the holes. The holes penetrate a layered sequence of sandstones, shales and carbonates of the Namurian Upper Limestone Group. The Laboratory measurements of the vertical and horizontal velocities of core samples indicate that the shales exhibit P-wave anisotropies of over 20% but that the sandstones and limestones are only slightly anisotropic. These discrete measurements have been used in combination with wireline data to produce a log of P-wave anisotropy. Including the anisotropic information vastly improves the match between observed and synthetic traveltimes from the cross-hole data set. This implies that there is little frequency dependence of intrinsic P-wave anisotropy. Inversion of the cross-hole traveltimes highlights the need for good angular coverage in order to resolve the anisotropy parameters. The observed P-wave anisotropy of the field data is due to the combined effect of sedimentary layering and the intrinsic anisotropy of the rocks. The intrinsic anisotropy is found to be the dominant factor.     

Biostratigraphy and Paleoecology of Maastrichtian Sediments in the Zagros Basin, Iran

To enable the lithostratigraphic and biostratigraphic study of the Gurpi Formation,within the ‘Dezak’ or Globigerina Marl,a stratigraphic section at Booraki,located to the NNW of Shiraz,SW Iran,through the late Cretaceous was examined.The formation consists of shale and greenish-gray marls interbedded with cream limestone,brown sandstones and siltstones with an exposed thickness of 160 m in the studied section.Samples were taken at regular intervals in all yielding 14 genera and 16 different species of benthic and planktic foraminifera that allowed determination of the age of the beds as Maastrichtian.To examine the paleoecology of the formation,some important ecological factors including water level,salinity,and oxygen regime change during the depositional courses of the formation were analyzed.The density of foraminiferans decreases from the base to top of the Gurpi Formation whereas the ratio of planktic to benthic Foraminifera(i.e.,P/B) and proportion of shallow-water fauna increase.These foraminiferal changes indicate an increase and decrease in depth,temperature,salinity and oxygen,respectively,at the base and top of the Formation.