Seismic hazard and probability assessment of Kashmir valley,northwest Himalaya,India

Seismic hazard analysis of the northwest Himalayan belt was carried out by using extreme value theory (EVT). The rate of seismicity (a value) and recurrence intervals with the given earthquake magnitude (b value) was calculated from the observed data using Gutenberg–Richter Law. The statistical evaluation of 12,125 events from 1902 to 2017 shows the increasing trend in their inter-arrival times. The frequency–magnitude relation exhibits a linear downslope trend with negative slope of 0.8277 and positive intercept of 4.6977. The empirical results showed that the annual risk probability of high magnitude earthquake M?≥?7.7 in 50 years is 88% with recurrence period of 47 years, probability of M?≤?7.5 in 50 years is 97% with recurrence period of 27 years, and probability of M?≤?6.5 in 50 years is 100% with recurrence period of 4 years. Kashmir valley, located in the NW Himalaya, encompasses a peculiar tectonic and structural setup. The patterns of the present and historical seismicity records of the valley suggest a long-term strain accumulation along NNW and SSE extensions with the decline in the seismic gap, posing a potential threat of earthquakes in the future. The Kashmir valley is characterized by the typical lithological, tectono-geomorphic, geotechnical, hydrogeological and socioeconomic settings that augment the earthquake vulnerability associated with the seismicity of the region. The cumulative impact of the various influencing parameters therefore exacerbates the seismic hazard risk of the valley to future earthquake events.     

The structure of urban space, movement and co-presence: The case of Atlanta

Urban areas in Atlanta are analyzed using a computer based technique known as ‘space syntax’ to reveal an underlying systematic and consistent relationship between pedestrian or vehicular movement and spatial configuration. This provides a framework for discussing how far different urban morphologies are characterized by similar regular patterns; how design choices can affect the social use of space; and how methodological and theoretical issues, such as the study of the effects of scale, can be formulated with greater clarity.     

Long-term variability in mesopause region temperatures over Fort Collins, Colorado (41°N, 105°W) based on lidar observations from 1990 through 2007

During 1990–2007, there were 894 lidar observations of nocturnal mesopause region temperatures over Fort Collins, Colorado. In an earlier analysis with data to April 1997, an unexpected episodic warming, peaking in 1993 with a maximum value over 10 K, was reported and attributed to the Mount Pinatubo eruption in June 1991. With all data, long-term temperature trends from a 7-parameter linear regression analysis including solar cycle effect and long-term trends leads to a cooling of as much as 6.8 K/decade at 100 km, consistent with some reported observations but larger than model predictions. Including the observed episodic warming response in an 11-parameter nonlinear regression analysis reduces the maximum long-term cooling trends to 1.5 K/decade at 91 km, with magnitude and altitude dependences consistent with the prediction of two models, Spectral Mesosphere/Lower Thermosphere Model (SMLTM) and Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA). In addition, the mid-latitude middle-atmospheric response to solar flux variability in Thermosphere–Ionosphere-Energetics and Dynamics (TIMED)/Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperatures is presented.     

Development of a New Empirical Relation to Assess P-wave Velocity Anisotropy of Rocks

Geotechnical and Geological Engineering - Several physical parameters and anisotropy related to rock textural arrangements, schistosity and weakness planes such as cracks and joints affect the...     

Bearing capacity of soft soil model treated with end-bearing bottom ash columns

Granular column technique is a soil improvement method used to increase the bearing capacity of a soft soil area by replacing the soil with a group of granular column materials. The by-product utilisation is a worldwide interest for sustainable infrastructure development. Bottom ash, which is a combustion deposit derived from coal burning, is a potential by-product that could be used alternatively to sand or aggregate as a green granular column material. This research is to study the potential use of the bottom ash column-improved soft clay by conducting a series of small-scale physical modelling test. The bearing capacity behaviour and failure mode of soft clay improved with end-bearing group of bottom ash columns with and without geotextile encasement are investigated. The bearing capacity of soft clay is significantly enhanced by the inclusion of bottom ash columns; that is, 239% of bearing capacity improvement is observed with only 13% of improvement area. The bulging of the bottom ash column is transferred to buckling failure with higher bearing capacity when the bottom ash column is encased by geotextile. The outcome of this research leads to the usage of bottom ash by-product as a granular column material in sustainable soil improvement technique.     

The Deep Mixing Method: Bearing Capacity Studies

Nowadays, several techniques are employed to improve the problem of carrying out construction in soft soils by increasing the strength of the soil foundation and reducing the settlement of the soil. Among these stabilizing techniques, the deep mixing method is regarded as the most popular. The deep mixing method is a soil modification method where the soil is mixed in situ with stabilizing agents, commonly soil–cement columns. It increases the strength of the soil, providing bearing resistance and improved settlement performance. Deep mixing is carried out in situ using a machine equipped with mixing blades mounted at the end of a tube that has a nozzle at the lower end. The stabilizer agent is injected into the soil via the nozzle using a pumping system so that it mixes with the soil as the blades are rotated. Throughout this paper, previous works by numerous researchers on deep mixing including laboratory work, full-scale field tests, analytical and numerical analyses related to bearing capacity are reviewed. The techniques and results used are discussed with the help of figures depicting charts, failure modes, and the model configuration setup. It was found that the deep mixing method is suitable for use with any type of soil and provides a better alternative to the existing method of improving soft clay ground, especially with regard to the soil bearing capacity. In addition, future research is needed to improve the use of the method for soil improvement in the construction industry.     

Sustainable Improvement of Tropical Residual Soil Using an Environmentally Friendly Additive

Many tropical residual laterites have relatively poor engineering properties due to the significant percentage of fine-grained soil particles that they contain, which are formed by the soil weathering process. The widespread presence of laterite soils in tropical regions often requires that some form of soil improvement be performed to allow for their use in various civil engineering applications, such as for road base or subbase construction. One of the most commonly utilized stabilization techniques for laterite soils is the application of additives that chemically react with the minerals that are present in soil to enhance its overall strength; effective soil stabilization can allow for the use of site-specific soils, and can consequently result in significant cost savings for a given project. With an increasing focus on the use of more environmentally friendly and sustainable materials in the built and natural environments, there is an emerging interest in eco-friendly additives that are an alternative to traditional chemical stabilizers. The current study examines the viability of xanthan gum as an environmentally friendly stabilizer that can improve the engineering properties of tropical residual laterite soil. Unconfined compressive strength (UCS) tests, standard direct shear tests, Brunauer, Emmett, and Teller (N₂-BET) surface area analysis tests and field emission scanning electron microscopy (FESEM) tests were used to investigate the effectiveness of xanthan gum for stabilization of a tropical laterite soil. The UCS test results showed that addition of 1.5% xanthan gum by weight yielded optimum stabilization, increasing the unconfined compressive strength of the laterite soil noticeably. Similarly, direct shear testing of 1.5% xanthan gum stabilized laterite specimens showed increasing Mohr–Coulomb shear strength parameters with increases in curing time. From the FESEM results, it was observed that the stabilization process modified the pore-network morphology of the laterite soil, while also forming new white layers on the surface of the clay particles. Analysis of the test results indicated that xanthan gum stabilization was effective for use on a tropical residual laterite soil, providing an eco-friendly and sustainable alternative to traditional soil stabilization additives such as cement or lime.     

Bearing capacity of sandy soil treated by Kenaf fibre geotextile

Bio-based materials are widely used recently in order to introduce a more sustainable construction material. Kenaf is a type of bio-based material that can be easily obtained in a tropical country, which could be a potential material to be utilised as a geotextile material because it has good tensile strength. The geotextile could be used to improve the bearing capacity of a loose soil. This paper presents a series of small-scale physical modelling tests to investigate the bearing capacity performance of Kenaf fibre geotextile laid on and inside the sand layer. A rigid footing was used to replicate a strip footing during the loading test, and sand was prepared based on 50% of relative density in a rigid testing chamber for ground model preparation. In order to treat the soil, Kenaf fibre geotextile was laid at four difference locations which are on the soil surface and underneath the ground model surface at 50, 75 and 100 mm deep. It was found that the usage of the Kenaf fibre geotextile has improved the bearing capacity of the sandy soil up to 414.9% as compared to untreated soil. It was also found that the depth of the Kenaf fibre geotextile treated into the soil also affects the soil performance.