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11.
Geotechnical and Geological Engineering - Ring foundations are commonly adopted to support tall and heavy cylindrical structures such as silos, chimneys, cooling towers, circular storage tanks, and... 相似文献
12.
In the hilly region due to scarcity of the plain area, buildings like set back-step back are more often used and also as a big surge in the telecommunication industries, rooftop tower adaptation is very common story nowadays. In the present study an analogy has been drawn to find out the influence of the rooftop telecommunication tower on the setback-step back building resting on ground at 20° and 30° slopes. A dynamic analysis has been performed and compared on the 4 legged angled section telecommunication tower which is located on the roof top of set back-step back building by varying positions of tower with the existing host structure built up on ground slope of 20° and 30° in both directions(X and Y). 相似文献
13.
Deepankar Choudhury Sanjay S. Nimbalkar 《Geotechnical and Geological Engineering》2006,24(5):1103-1113
Knowledge of seismic active earth pressure behind rigid retaining wall is very important in the design of retaining wall in
earthquake prone region. Commonly used Mononobe-Okabe method considers pseudo-static approach, which gives the linear distribution
of seismic earth pressure in an approximate way. In this paper, the pseudo-dynamic method is used to compute the distribution
of seismic active earth pressure on a rigid retaining wall supporting cohesionless backfill in more realistic manner by considering
time and phase difference within the backfill. Planar rupture surface is considered in the analysis. Effects of a wide range
of parameters like wall friction angle, soil friction angle, shear wave velocity, primary wave velocity and horizontal and
vertical seismic accelerations on seismic active earth pressure have been studied. Results are provided in tabular and graphical
non-dimensional form with a comparison to pseudo-static method to highlight the realistic non-linearity of seismic active
earth pressures distribution. 相似文献
14.
Economic importance of major ports is well known, and if ports are located in seismically active regions, then site-specific
seismic hazard studies are essential to mitigate the seismic risk of the ports. Seismic design of port sites and related structures
can be accomplished in three steps that include assessment of regional seismicity, geotechnical hazards, and soil structure
interaction analysis. In the present study, site-specific probabilistic seismic hazard analysis is performed to identify the
seismic hazard associated with four typical port sites of Gujarat state (bounded by 20°–25.5°N and 68°–75°E) of India viz.
Kandla, Mundra, Hazira, and Dahej ports. The primary aim of the study is to develop consistent seismic ground motion for the
structures within the four port sites for different three levels of ground shaking, i.e., operating level earthquake (72 years
return period), contingency level earthquake (CLE) (475 year return period), and maximum considered earthquake (2,475 year
return period). The geotechnical characterization for each port site is carried out using available geotechnical data. Shear
wave velocities of the soil profile are estimated from SPT blow counts using various empirical formulae. Seismicity of the
Gujarat region is modeled through delineating the 40 fault sources based on the seismotectonic setting. The Gujarat state
is divided into three regions, i.e., Kachchh, Saurashtra, and Mainland Gujarat, and regional recurrence relations are assigned
in the form of Gutenberg-Richter parameters in order to calculate seismic hazard associated with each port site. The horizontal
component of ground acceleration for three levels of ground shaking is estimated by using different ground motion attenuation
relations (GMAR) including one country-specific GMAR for Peninsular India. Uncertainty in seismic hazard computations is handled
by using logic tree approach to develop uniform hazard spectra for 5% damping which are consistent with the specified three
levels of ground shaking. Using recorded acceleration time history of Bhuj 2001 earthquake as the input time motion, synthetic
time histories are generated to match the developed designed response spectra to study site-specific responses of port sites
during different levels of ground shaking. It is observed that the Mundra and Kandla port sites are most vulnerable sites
for seismic hazard as estimated CLE ground motion is in order of 0.79 and 0.48 g for Mundra and Kandla port sites, respectively.
Hazira and Dahej port sites have comparatively less hazard with estimated CLE ground motion of 0.17 and 0.11 g, respectively.
The ground amplification factor is observed at all sites which ranges from 1.3 to 2.0 for the frequency range of 1.0–2.7 Hz.
The obtained spectral accelerations for the three levels of ground motions and obtained transfer functions for each port sites
are compared with provisions made in Indian seismic code IS:1893-Part 1 (2002). The outcome of present study is recommended for further performance-based design to evaluate the seismic response of the
port structures with respect to various performance levels. 相似文献
15.
Natural Hazards - This study examines the stability and failure mechanisms of two landslide-affected slopes in Kerala, India, after an extreme rainfall event. The landslide was triggered by an... 相似文献
16.
In earthquake prone areas, understanding of the seismic passive earth resistance is very important for the design of different geotechnical earth retaining structures. In this study, the limit equilibrium method is used for estimation of critical seismic passive earth resistance for an inclined wall supporting horizontal cohesionless backfill. A composite failure surface is considered in the present analysis. Seismic forces are computed assuming the backfill soil as a viscoelastic material overlying a rigid stratum and the rigid stratum is subjected to a harmonic shaking. The present method satisfies the boundary conditions. The amplification of acceleration depends on the properties of the backfill soil and on the characteristics of the input motion. The acceleration distribution along the depth of the backfill is found to be nonlinear in nature. The present study shows that the horizontal and vertical acceleration distribution in the backfill soil is not always in-phase for the critical value of the seismic passive earth pressure coefficient. The effect of different parameters on the seismic passive earth pressure is studied in detail. A comparison of the present method with other theories is also presented, which shows the merits of the present study. 相似文献
17.
V.?B.?DeshmukhEmail author D.?M.?Dewaikar Deepankar?Choudhary 《Geotechnical and Geological Engineering》2011,29(6):977-988
This paper presents the details of the theoretical analysis of net uplift capacity of horizontal strip anchor in cohesionless soil using Kötter’s equation. A plane failure surface inclined at a characteristic angle with the ground surface is assumed. Results obtained using the proposed method are compared with the available experimental results of 30 cases for dense to loose cohesionless soil, with the maximum embedment ratio of 8. It is observed that the proposed method leads to the predictions of net uplift capacity of horizontal strip anchor that are very close to the experimental results in 93% cases. The comparison of results with available theoretical solutions shows that, proposed method makes better predictions for anchor embedment ratio less than 8 in dense cohesionless soils. 相似文献
18.
V. S. Phanikanth Deepankar Choudhury G. Rami Reddy 《Geotechnical and Geological Engineering》2011,29(6):1109-1126
Any earthquake event is associated with a rupture mechanism at the source, propagation of seismic waves through underlying
rock and finally these waves travel through the soil layers to the particular site of interest. The bedrock motion is significantly
modified at the ground surface due to the presence of local soil layers above the bedrock beneath the site of interest. The
estimation of the amplifications in ground response due to the local soil sites is a complex problem to the designers and
the problem is more important for mega cities like Mumbai in India, where huge population may get affected due to devastations
of earthquake. In the present study, the effect of local soil sites in modifying ground response is studied by performing
one dimensional equivalent-linear ground response analysis for some of the typical Mumbai soil sites. Field borelog data of
some typical sites in Mumbai city viz. Mangalwadi site, Walkeswar site, BJ Marg near Pandhari Chawl site are considered in
this study. The ground responses are observed for range of input motions and the results are presented in terms of surface
acceleration time history, ratio of shear stress to vertical effective stress versus time, acceleration response spectrum,
Fourier amplitude ratio versus frequency etc. The typical amplifications of ground accelerations considering four strong ground
motions with wide variation of low to high MHA, frequency contents and durations are obtained. Results show that MHA, bracketed
duration, frequency content have significant effects on the amplification of seismic accelerations for typical 2001 Bhuj motion.
The peak ground acceleration amplification factors are found to be about 2.50 for Mangalwadi site, 2.60 for Walkeswar site
and 3.45 for BJ Marg site using 2001 Bhuj input motion. The response spectrum along various soil layers are obtained which
will be useful for designers for earthquake resistant design of geotechnical structures in Mumbai for similar sites in the
absence of site specific data. 相似文献
19.
Cyclic mobility is a mechanism of ground failure due to lateral spreading of soils during an earthquake that usually occurs in soft or medium stiff saturated soils. The simplified procedures developed by the researchers give a factor of safety for judging the cyclic mobility potential. However, the simplified procedures do not take into account the uncertainty in the parameters required to estimate the cyclic stresses in the soil. In this study, a reliability framework based on the simplified procedure, considering the parameter uncertainty, has been proposed for computing the probability of cyclic mobility of clay deposits for a metro city of India, i.e., Mumbai city (latitudes 18°53′N–19°19′N and longitudes 72°47′E–72°58′E). Extensive geotechnical borehole data from 1028 boreholes across 50 locations in the city area of 390 km2 and laboratory test data are collected and analyzed thoroughly. A correlation between undrained shear strength (Su) and other parameters such as natural water content (w), SPT N value, liquid limit (LL) and plasticity index (PI) has been established for Mumbai city and has been used in the proposed approach. The sensitivity analysis of the proposed approach predicts that Su has significant influence in the evaluation of the cyclic mobility. Cyclic mobility hazard maps are prepared using the geo-statistical analysis tool in GIS, and it shows that the clayey soils at few locations have a 60–90 % probability of cyclic mobility for a moment magnitude (M w) of an earthquake of 7.5. These hazard maps can be used by the geotechnical engineers for the cyclic mobility hazard assessment of Mumbai city. 相似文献
20.
Deepankar Choudhury Kanakapura. S. Subba Rao 《Geotechnical and Geological Engineering》2004,22(1):59-72
Uplift capacity of horizontal strip anchors in soil embedded under an inclined ground surface has been obtained under seismic
conditions. Limit equilibrium approach with logspiral failure surface together with pseudo-static seismic forces has been
adopted. The results have been presented in the form of seismic uplift capacity factors as functions of ground inclination,
embedment ratio, angle of internal friction of the soil and seismic acceleration coefficients. The uplift capacity factors
have been worked out separately for cohesion, surcharge and density components. Effect of the vertical seismic acceleration
coefficient has been found to always reduce the uplift capacity whereas the effect of horizontal seismic acceleration coefficient
has been found to reduce the uplift capacity in most of the cases. The obtained results of seismic uplift capacity factors
are found to be the minimum when compared with the results available in literature on the basis of planar failure surface.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献