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Numerical analysis of surface subsidence in asymmetric parallel highway tunnels

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第1期9卷 170-179页

作者： Ratan Das P.K.Singh Ashutosh Kainthola Suman Panthee T.N.Singh department of Earth Sciences Indian Institute of Technology Bombay department of Civil Engineering National Institute of Technology Central department of geology Tribhuvan University

Tunnelling related hazards are very common in the Himalayan terrain and a number of such instances have been reported. Several twin tunnels are being planned for transportation purposes which will require good understanding for prediction of tunnel deformation and surface settlement during the engineering life of the structure. The deformational behaviour, design of sequential excavation and support of any jointed rock mass are challenging during underground construction. We have raised several commonly assumed issues while performing stability analysis of underground opening at shallow depth. For this purpose, Kainchi-mod Nerchowck twin tunnels(Himachal Pradesh, India) are taken for in-depth analysis of the stability of two asymmetric tunnels to address the influence of topography, twin tunnel dimension and geometry. The host rock encountered during excavation is composed mainly of moderately to highly jointed grey sandstone, maroon sandstone and siltstones. In contrast to equidimensional tunnels where the maximum subsidence is observed vertically above the centreline of the tunnel, the result from the present study shows shifting of the maximum subsidence away from the tunnel centreline. The maximum subsidence of 0.99 mm is observed at 4.54 m left to the escape tunnel centreline whereas the maximum subsidence of 3.14 mm is observed at 8.89 m right to the main tunnel centreline. This shifting clearly indicates the influence of undulating topography and inequidimensional noncircular tunnel.

关键词： Twin tunnels Numerical analysis Stability Finite element method(FEM) Subsidence

Increase of forest carbon biomass due to community forestry management in Nepal

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Journal of Forestry Research 2018年第2期29卷 424-433页

作者： Anup K C Roshani Manandhar Rajeshor Paudel Sujan Ghimire department of Environmental Science Amrit CampusTribhuvan University Central department of Environmental Science Tribhuvan University department of Environmental Science Tri-Chandra CampusTribhuvan University

Community forest management helps in mitigating deforestation and forest degradation by addressing the negative aspects of rural livelihoods such as poverty and social *** is important in regulating global climate by encouraging sequestration of carbon in shoots,roots and *** studied the status of community forest management,forest resource harvest and carbon stocks in two community forests of the mid hill region of central and western *** study was based on primary and secondary data collected through carbon stock measurement from field visits and allometric equations,household surveys,focus group discussions,key informant interviews,and review of past *** variables such as gender,age group,livestock and landholding status were related to resource utilization,conservation,and management of community *** resources such as timber,firewood,fodder and leaf litter were harvested in sustainable *** were involved in forest thinning,co-management meetings,guarding and planting trees for forest conservation and *** and carbon stock of trees increased gradually in comparison to a previous *** recommend further research on other community forests for more accurate and better results.

关键词： Community forest management Resource use Carbon stock Nepal

Efficient contraflow algorithms for quickest evacuation planning

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Science China Mathematics 2018年第11期61卷 2079-2100页

作者： Urmila Pyakurel Hari Nandan Nath Tanka Nath Dhamala Central department of Mathematics Tribhuvan University department of Mathematics Bhaktapur Multiple Campus Tribhuvan University

The optimization models and algorithms with their implementations on flow over time problems have been an emerging field of research because of largely increasing human-created and natural disasters *** an optimal use of transportation network to shift affected people and normalize the disastrous situation as quickly and efficiently as possible,contraflow configuration is one of the highly applicable operations research(OR)*** increases the outbound road capacities by reversing the direction of arcs towards the safe destinations that not only minimize the congestion and increase the flow but also decrease the evacuation time *** this paper,we sketch the state of quickest flow solutions and solve the quickest contraflow problem with constant transit times on arcs proving that the problem can be solved in strongly polynomial time O(nm^2(long n)~2)where n and m are number of nodes and number of arcs,respectively in the *** contraflow solution has the same computational time bound as that of the best min-cost flow ***,we also introduce the contraflow approach with load dependent transit times on arcs and present an efficient algorithm to solve the quickest contraflow problem *** the claim,our computational experiments on Kathmandu road network and on randomly generated instances perform very well matching the theoretical *** a sufficiently large number of evacuees,about double flow can be shifted with the same evacuation time and about half time is sufficient to push the given flow value with contraflow reconfiguration.

关键词： evacuation planning contraflow flow over time quickest flow load dependent transit time

A Review of the Bentong-Raub Suture vis-à-vis New Insight of the Tectonic Evolution of Malay Peninsula,South East Asia

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Acta Geologica Sinica(English Edition) 2016年第5期90卷 1865-1886页

作者： Aftab Alam KHAN Mustaffa Kamal SHUIB department of geology University of Malaya department of geology University of Dhaka

Genesis of the so-called Bentong-Raub Suture of Malay Peninsula does not fit to the model of subduction-related *** has evolved from transpression tectonics resulting closure and exhumation of the inland basin which underwent extensive back-arc extension during *** having similar thickness（average-35 km） below entire Malay Peninsula nagate collision of two separate continental blocks rather supports single continental block that collided with South China continental block during *** subduction of intervening sea（Proto South China Sea） below Malay Peninsula resulted in widespread I- and S-Type granitization and volcanism in the back-arc basins during *** occurrence of Permo-Triassic Pahang volcanics of predominantly rhyolitic tuff suggest its derivation from back-arc ***-arc extension,basin development and sedimentation of the central belt of the peninsula continued until Cretaceous.A-Type granite of metaluminous to peraluminous character indicates their emplacement in an intraplate tectonic *** Peninsula suffered an anticlockwise rotation due to the rifting of Luconia-Dangerous Grounds from the east Asia in the Late Cretaceous-Early *** ductile and brittle deformation including crustal segmentation,pull-apart fracturing and faulting occurred during the closure and exhumation of the basins developed in the peninsula during Late Cretaceous-Early *** shortening in the central belt of the peninsula has been accomodated through strike-slip displacement,shearing and uplift.

关键词： Bentong-Raub fault intra-plate tectonics Triassic back-arc extension Cretaceoustranspression Malay Peninsula

Effect of disturbance on biomass,production and carbon dynamics in moist tropical forest of eastern Nepal

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Forest Ecosystems 2016年第3期3卷 221-230页

作者： Tilak Prasad Gautam Tej Narayan Mandal department of Botany Mahendra Morang Adarsha Multiple CampusTribhuvan University department of Botany Post Graduate Campus Tribhuvan University

Background： Forest biomass is helpful to assess its productivity and carbon （C） sequestration capacity. Several disturbance activities in tropical forests have reduced the biomass and net primary production （NPP） leading to climate change. Therefore, an accurateestimation of forest biomass and C cycling in context of disturbances is required for implementing REDD （Reducing Emissions from Deforestation and Forest Degradation） policy. Methods： Biomass and NPP of trees and shrubs were estimated by using allometric equations while herbaceous biomass was estimated by harvest method. Fine root biomass was determined from soil monolith. The C stock in vegetation was calculated by multiplying C concentration to dry weight. Results： Total stand biomass （***-1） in undisturbed forest stand （US） was 960.4 while in disturbed forest stand （DS） it was 449.1. The biomass （***-1） of trees, shrubs and herbs in US was 948.0, 4.4 and 1.4, respectively, while in DS they were 438.4, 6.1 and 1.2, respectively. Total NPP （***-1） was 26.58 （equivalent to 12.26 Mg ***-1） in US and 14.91 （6.88 Mg ***-1） in DS. Total C input into soil through litter plus root turnover was 6.78 and 3.35 ***-1 in US and DS, respectively. Conclusions： Several disturbance activities resulted in the significant loss in stand biomass （53 %）, NPP （44 %）, and C sequestration capacity of tropical forest vegetation is far greater than that returned to the soil n eastern Nepal. The net uptake of carbon by the by the turnover of fine root and litter. Therefore, both stands of present forest act as carbon accumulating systems. Moreover, disturbance reflects higher C emissions which can be reduced by better management.

关键词： Tropical forest Disturbance Biomass Production Carbon cycling Nepa

Geochemical Evaluation of the Permian Ecca Shale in Eastern Cape Province, South Africa:Implications for Shale Gas Potential

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Acta Geologica Sinica(English Edition) 2018年第3期92卷 1193-1217页

作者： Christopher BAIYEGUNHI Kuiwu LIU Nicola WAGNER Oswald GWAVAVA Temitope L.OLONINIYI department of geology University of Fort Hare department of geology University of Johannesburg

Shale gas has been the exploration focus for future energy supply in South Africa in recent time. Specifically, the Permian black shales of the Prince Albert, Whitehill, Collingham, Ripon and Fort Brown Formations are considered to be most prospective rocks for shale gas exploration. In this study,outcrop and core samples from the Ecca Group were analyzed to assess their total organic carbon(TOC), organic matter type, thermal maturity and hydrocarbon generation potential. These rocks have TOC ranging from 0.11 to 7.35 wt%. The genetic potential values vary from 0.09 to 0.53 mg HC/g,suggesting poor hydrocarbon generative potential. Most of the samples have Hydrogen Index(HI) values of less than 50 mg HC/g TOC, thus suggesting Type-Ⅳ kerogen. Tmax values range from 318℃ to601℃, perhaps indicating immature to over-maturity of the samples. The vitrinite reflectance values range from 2.22% to 3.93%, indicating over-maturity of samples. Binary plots of HI against Oxygen Index(OI), and HI versus Tmax show that the shales are of Type II and mixed Type Ⅱ-Ⅲ *** on the geochemical data, the potential source rocks are inferred as immature to over-matured and having present-day potential to produce gas.

关键词： geochemistry organic matter type thermal maturity hydrocarbons Ecca Group South Africa

Fire-induced carbon emissions from tropical mixed broad-leaved forests of the Terai–Siwalik region,central Nepal

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Journal of Forestry Research 2021年第6期32卷 2557-2565页

作者： Krishna Bahadur Bhujel Rejina Maskey Byanju Ambika PGautam Ramesh Prasad Sapkota Udhab Raj Khadka Central department of Environmental Science Tribhuvan UniversityKathmanduNepal Kathmandu Forestry College Tribhuvan UniversityKathmanduNepal

Forest fires are one of the major environmental issues *** Nepal,substantial amounts of forest biomass and carbon are lost due to ***’s high value lowland forests are particularly vulnerable to ***,there are limited studies on the estimation of biomass loss and carbon emissions due to ***,this research addresses the information gap in the tropical mixed broad-leaved forests of Nawalparasi *** forests were divided into three strata:Lower Tropical Sal Mixed Broad-leaved Forest,Hill Sal Forest and Riverine Forest,and from these four community-managed forests were selected for estimating above ground ***-two sample plots were set out for above ground biomass estimation in burnt and non-burnt *** fire incidences from 2001 to 2017 were acquired from the MODIS fire *** biomass and carbon emissions were estimated using standard allometric *** fuel fraction consumed during the fire was estimated through field surveys during the forest fire *** results show that every year,over 3158 ha of forests are burnt,resulting in some 1108 tons of carbon emissions,equivalent to approximately 4066 t CO_(2),2581 t CO and 1474 t *** the forests,the Hill Sal Forest was more vulnerable to *** management strategies,therefore,should include construction of fire lines and conservation ponds along with capacity building and raising awareness among local communities and stakeholders.

关键词： Atmosphere Biomass density Burnt area Carbon emission Greenhouse gases

Habitat Range of two Alpine Medicinal Plants in a Trans-Himalayan Dry Valley,Central Nepal

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Journal of Mountain Science 2009年第1期6卷 66-77页

作者： Bharat Babu SHRESTHA Pramod Kumar JHA Central department of Botany Tribhuvan UniversityKathmanduNepal

Understanding of the habitat range of threatened Himalayan medicinal plants which are declining in their abundance due to high anthropogenic disturbances is essential for developing conservation strategies and agrotechnologies for cultivation. In this communication, we have discussed the habitat range of two alpine medicinal plants, Aconitum naviculare （Bruehl） Stapf and Neopicrorhiza scrophulariiflora （Pennel） Hong in a trans-Himalayan dry valley of central Nepal, Manang district. They are the most prioritized medicinal plants of the study area in terms of ethnomedicinal uses. A. naviculare occurs on warm and dry south facing slopes between 4090-4650 m asl along with sclerophyllous and thorny alpine scrubs, while N. scrophulariiflora is exclusively found on cool and moist north facing slope between 4000 and 4400 m asl where adequate water is available from snow melt to create a suitable habitat for this wetland dependent species. The soil in rooting zone of the two plants differs significantly in organic carbon （OC）, organic matter （OM）, total nitrogen （N） and carbon to nitrogen （C/N） ratio. Due to cool and moist condition of N. scrophulariiflora habitat, accumulation of soil OC is higher, but soil N content is lower probably due to slow release from litter, higher leaching loss and greater retention in perennial live biomass of the plant. The C/N ratio of soil is more suitable in A. navuculare habitat than that of N scrophulariiflora for N supply. Warm and sunny site with N rich soil can be suitable for cultivation ofA. naviculare, while moist and cool site with organic soil for N. scrophulariiflora. The populations of both the plants are fragmented and small. Due to collection by human and trampling damage by livestock, the population of A. naviculare was found absent in open areas in five of the six sampling sites and it was confined only within the bushes of alpine scrubs. For N. serophulariiflora, high probability of complete receding of small glaeiers may be

关键词： Aconitum naviculare Neopicrorhizascrophulariiflora habitat degradation nitrogen organic carbon radiation Manang Nepal

Kinetic-theory-based investigation of electronegative plasma–wall transition with two populations of electrons

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Plasma Science and Technology 2021年第3期23卷 11-21页

作者： Suresh BASNET Atit DEUJA Raju KHANAL Central department of Physics Tribhuvan UniversityKirtipurKathmandu 44613Nepal

Kinetic theory has been employed to investigate the magnetized plasma-sheath structure and its characteristics in the presence of more than one species of negatively charged particles:hot electrons,cold electrons,and negative *** cold electrons and negative ions are considered to obey a Maxwellian distribution,whereas the hot electrons follow a truncated Maxwellian *** Bohm sheath condition has been extended for the case of more than one species of negatively charged particles,in which the concentration of hot electrons has a crucial role in achieving the Bohm *** thermal motion of hot electrons is much higher compared to cold electrons and negative ions,such that the variation of hot electron concentrations and the temperature ratio of hot to cold electrons play a key role in the determination of the plasma-sheath parameters:particle densities,electrostatic potential,the flow of positive ions towards the wall,and sheath *** have estimated the deviation of the resultant drift velocity of positive ions on the plane perpendicular to the wall from the parallel component at the presheath–sheath *** is found that the deviation between the two velocity components increases with an increase in the obliqueness of the magnetic ***,the results obtained from the kinetic trajectory simulation model are compared with the results obtained using a fluid model;the results are qualitatively similar,although the potential varies by less than 4%in terms of the magnitude at the wall.

关键词： Bohm velocity fluid theory plasma sheath electronegative plasmas