Effect of Soil Parameters on Dynamic Cone Penetration Indices of Laterite Sub-grade Soils from India

The focus of this study was on correlating the effect of grain-size, maximum dry-density (MDD), field moisture content, and the void ratios on penetration measured using the dynamic cone penetrometer (DCP) for laterite soils blended with fines. Tests were performed on soil samples compacted to MDD for moulding water contents set to the optimum moisture content (OMC), dry of OMC, and wet of OMC un-soaked condition. The results indicated that an increase in the fines-content caused a decrease in the MDD, and an increase in the OMC and the DCP penetration. Regressions were developed correlating various parameters.     

Dynamic responses under the excitation of pulse sequences

This paper studies the dynamic responses of SDOF system under pulse-dominant excitations. The purpose of the study is to prepare for scrutiny of some near-field pulse-dominant ground motions and their potential to cause structural damage. Extending the single pulse dynamics, we consider the effect of pulse sequences. This kind of excitation was particularly obvious in some of previous earthquakes such as Northridge (1994) and Chi-Chi (1995). Based on the duration,peak and rise and decay era of the main pulse as well as its relationship with the predecessor and successor pulses, we propose a classification for the pulse sequences. Consequent studies have been carried out for acceleration, velocity and displacement response spectra of the main pulse with either a predecessor or a successor pulse. The analysis also includes general response behaviors in different fundamental period segments and special aspects of response at certain points (e.g., the corresponding peak points).     

Liquefaction mitigation in silty soils using composite stone columns and dynamic compaction

The objective of this study is to develop an analytical methodology to evaluate the effectiveness ofvibro stone column (S. C.) and dynamic compaction (D.C.) techniques supplemented with wick drains to densify and mitigate liquethctionin saturated sands and non-plastic silty soils. It includes the following: (i) develop numerical models to simulate and analyze soil densification during S.C. installation and D.C. process, and (ii) identify parameters controlling post-improvement soil density in both cases, and (iii) develop design guidelines for densification of silty soils using the above techniques. An analytical procedure was developed and used to simulate soil response during S.C. and D.C. installations, and the results were compared with available case history data. Important construction design parameters and soil properties that affect the effectiveness of these techniques, and construction design choices suitable for sands and non-plastic silty soils were identified. The methodology is expected to advance the use of S.C. and DC. in silty soils reducing the reliance on expensive field trials as a design tool. The ultimate outcome of this research will be design charts and design guidelines for using composite stone columns and composite dynamic compaction techniques in liquefaction mitigation of saturated silty soils.     

Planetary core size: A seismological approach

A key parameter for understanding the geodynamics of a terrestrial planet is the size of its core. Numerical evaluation of 28 different interior structure models of Mercury, Venus, Earth, the Moon, and Mars suggests that there is an almost linear relationship between the core radius and the extent of the seismic P-wave core shadow. A scaling law is derived from a simple mantle density and velocity model that permits the interpretation of respective seismic measurements on terrestrial planetary bodies.     

The dayside magnetospheric boundary layer at Mercury

Magnetic field and plasma data from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft on the outbound portions of the first (M1) and second (M2) flybys of Mercury reveal a region of depressed magnetic field magnitude and enhanced proton fluxes adjacent to but within the magnetopause, which we denote as a dayside boundary layer. The layer was present during both encounters despite the contrasting dayside magnetic reconnection, which was minimal during M1 and strong during M2. The overall width of the layer is estimated to be between 1000 and 1400 km, spanning most of the distance from the dayside planetary surface to the magnetopause in the mid-morning. During both flybys the magnetic pressure decrease was ∼1.6 nPa, and the width of the inner edge was comparable to proton gyro-kinetic scales. The maximum variance in the magnetic field across the inner edge was aligned with the magnetic field vector, and the magnetic field direction did not change markedly, indicating that the change in field intensity was consistent with an outward plasma-pressure gradient perpendicular to the magnetic field. Proton pressures in the layer inferred from reduced distribution observations were 0.4 nPa during M1 and 1.0 nPa during M2, indicating either that the proton pressure estimates are low or that heavy ions contribute substantially to the boundary-layer plasma pressure. If the layer is formed by protons drifting westward from the cusp, there should be a strong morning–afternoon asymmetry that is independent of the interplanetary magnetic field (IMF) direction. Conversely, if heavy ions play a major role, the layer should be strong in the morning (afternoon) for northward (southward) IMF. Future MESSENGER observations from orbit about Mercury should distinguish between these two possibilities.     

Strong shock-phenomena at petawatt-picosecond laser side-on ignition fusion of uncompressed hydrogen-boron11

An extreme anomaly of laser-plasma interaction with petawatt-picosecond (PW-ps) pulses of very high contrast ratio for suppression of relativistic self-focusing permitted a come-back of the Bobin-Chu side-on ignition of uncompressed deuterium-tritium (DT) fusion fuel. The plasma blocks for the side-on ignition have to be produced by the well confirmed nonlinear force acceleration which is about 100,000 times higher than thermo-kinetic fluid-dynamic acceleration for comparison with astrophysical cases. It is essential that the dielectric plasma properties within the nonlinear force are used. Using the measured ion beam densities above 10¹¹ A s/cm² the ignition mechanism needed numerical and theoretical studies of extremely strong shock phenomena. When extending these results to the side-on ignition of uncompressed hydrogen-boron11 (HB11), surprisingly, the ignition by this shock mechanism was only about 10 times more difficult than for DT in contrast to ignition by spherical laser driven compression using thermo-kinetic conditions in which case HB11 ignition is 100,000 times more difficult than DT.     

Barnacle larval transport in the Mandovi–Zuari estuarine system, central west coast of India

A two-dimensional hydrodynamic and particle tracking model was used to estimate the dispersion and retention of barnacle larvae from their possible spawning sites in a tropical monsoon-influenced estuarine system (central west coast of India). Validation of the hydrodynamic simulations yielded a good match with field measurements. The pattern of larval dispersal in the region varied with the winds and currents. The seasonal changes in abundance could be attributed to physical forcing and weather conditions. The extent of barnacle larval dispersal from spawning sites varied from 10 to 78 km for different sites and seasons. During a 24-h cycle, the larval abundance showed one to two peaks in the estuarine area. The increased larval abundance is favored by the flood currents, pushing the larvae into the estuary. Physical forcing in the region helps in transport of the larvae from their spawning sites hugging to the coast and contributing to the population within the estuary. Field observations and numerical experiments suggest the occurrence of higher larval abundance in the estuary during post-monsoon. The dispersal pattern indicated that the barnacle population present in the estuary is well mixed, and with a seasonally changing pattern.     

Collocation resolution of the oceanic geoid based on satellite altimetry

The approach presented is directed toward a specific adaptation of the least‐squares collocation with noise, yielding smooth predictions of geophysical quantities. The smoothing corresponds here to a truncated gravity field equivalent to an (n’, n') spherical‐harmonic expansion. This is reflected in the truncation, at the degree n‘, of the pertinent covariance and cross‐covariance functions in most (but not all) instances. The smooth predictions of geophysical quantities, made in an equilateral grid corresponding to the truncation degree n‘, serve in constructing contour maps after having been densified for the needs of a contour routine. Such a densification is carried out efficiently via errorless collocation with the degree truncation n‘ throughout. Consistent with this procedure, “residuals” at observation points (i.e., discrepancies between the contour map and the data) are computed using the same algorithm. The complete collocation approach is utilized for a 2° resolution of the earth's gravity field with emphasis on the oceanic geoid, based on the residuals from a global spherical‐harmonic adjustment of SEASAT altimetry. The presented results include contour maps of geoid undulations and gravity anomalies. They are compared to the results of a point‐mass adjustment, another technique based on the spherical‐harmonic adjustment. The agreement between these two techniques is found to be excellent.     

Guest editorial

The Jason-1 satellite was launched on 7 December 2001 with the primary objective of continuing the high accuracy time series of altimeter measurements that began with the TOPEX/Poseidon mission in 1992. To achieve this goal, it is necessary to validate the performance of the Jason-1 measurement system, and to verify that its error budget is at least at the same level as that of the TOPEX/Poseidon mission. The article reviews the main components of the Jason-1 altimetric error budget from instrument characterization to the geophysical use of the data. Using the Interim Geophysical Data Records (16DR) that were distributed to the Jason-1 Science Working Team during the verification phase of the mission, it is shown that the Jason-1 mission is performing well enough to continue studies of the large-scale features of the ocean, and especially to continue time series of mean sea-level variations with an accuracy comparable to TOPEX/Poseidon.