Nepal Geological Society (NGS)

Nepalese National Group of IAEG Since 20 Years

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P.O.Box No. 231 Kathmandu, Nepal
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Category: ENGINEERING GEOLOGICAL MAPPING IN THE NEPAL HIMALAYA: IMPORTANCE AND CHALLENGES FOR UNDERGROUND STRUCTURES


ENGINEERING GEOLOGICAL MAPPING IN THE NEPAL HIMALAYA: IMPORTANCE AND CHALLENGES FOR UNDERGROUND STRUCTURES

September 27th, 2018 by
Geological mapping in the Nepal Himalaya: importance and challenges for underground structures

S. C. Sunuwar

Jour. Nepal Geol. Soc., Vol. 51, 2016, 89-95

 

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Abstract

Geological mapping is very important technique to predict geological condition for underground structures. It helps to construct geological model for site selection and designing of any underground structures. Geological uncertainty is directly proportional to the accuracy of geological mapping. More accurate geological mapping resulted fewer uncertainties. Precise delineation of faults, shear/weak zones and water bearing zones is important part of the geological mapping to predict uncertainties. Geological mapping to predict geological condition for underground structures is a challenge in the tectonically active Nepal Himalaya due to thrusting, faulting, folding and reverse metamorphism nature of rocks with difficult terrain and high overburden. Mapping for underground structures primarily focused on rock mass properties, faults, weak/shear zones, fractured zone, joints, folds, weathering depth and ground water bearing zones.

LITHOSTRATIGRAPHY AND STRUCTURE OF THE DHARAN–MULGHAT AREA, LESSER HIMALAYAN SEQUENCE, EASTERN NEPAL HIMALAYA

September 27th, 2018 by
Lithostratigraphy and structure of the Dharan–Mulghat area, Lesser Himalayan sequence, eastern Nepal Himalaya

L. K. Rai

Central Campus of Technology, Tribhuvan University, Dharan, Sunsari, Nepal

K. K. Acharya and M. R. Dhital

Central Department of Geology, Tribhuvan University, Kirtipur, Kathmandu, Nepal

Jour. Nepal Geol. Soc., Vol. 51, 2016, 77-88

 

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Abstract

The Dharan–Mulghat area of the eastern Nepal can be divided into three tectonic units: the Higher Himalayan Crystallines, the Lesser Himalayan Sequence and the Siwaliks from north to south separated by the Main Central Thrust (MCT) and Main Boundary Thrust (MBT), respectively. The Lesser Himalayan Sequence is divided into two groups separated by Chimra Thrust: the Bhedetar Group and the Dada Bajar Group. The Bhedetar Group includes the Raguwa Formation, the Phalametar Quartzite, the Churibas Formation, the Sangure Quartzite, and the Karkichhap Formation from the bottom to top, respectively; overthrusted by the Dada Bajar Group  consisting: the Ukhudanda Formation, the Mulghat Formation, the Okhre Formation, and the Patigau Formation, from lower to upper sections, respectively along the Chimra Thrust and the Bhorleni Formation as an individual formation overthrusted by Bhedetar Group along the Chhotimorang Thrust. The Main Central Thrust, the Main Boundary Thrust, the Chimra Thrust and the Chhotimorang Thrust are the major faults in Dharan–Mulghat area. The Leutiphedi Anticline and the Malbase Syncline are the major folds in the study area plunging towards east. The trend/plunge of anticline and syncline are 131º/24º and 096º/09ºrespectively. The microstructural study in the quartz grains reveals a sharp difference in the history across the MCT; dynamic in the rocks of the Lesser Himalayan Sequences and static in the rocks of the Higher Himalayan Crystallines.

PARAMETRIC EVALUATION OF SHEAR STRENGTH PARAMETERS ON THE STABILITY OF CUT SLOPE: A CASE STUDY FROM MAHABALESHWAR ROAD SECTION, INDIA

September 27th, 2018 by
Parametric evaluation of shear strength parameters on the stability of cut slope: a case study from Mahabaleshwar road section, India

Suman Panthee

Central Department of Geology, Tribhuvan University, Kirtipur, Kathmandu, Nepal

Jour. Nepal Geol. Soc., Vol. 51, 2016, 73-76

 

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Stability of rock cut slopes depends upon the type of material, discontinuity attributes and geometry present in any location. Although, gravity remains the constant important factor in dictating the slope failure but other parameters like shear strength and available shear stress along the slope also decides the stability of the slopes to great extent. The strength of the material comes from the internal bonding between the mineral grains, contact between the particles and the ability of the material to respond to the stress conditions. Variation of these material attributes fluctuate the cohesion and angle of internal friction that constitutes the most important properties in defining the strength of any material. Rock resists shear stress by these two internal mechanisms. Numerical simulation by Finite Element Method is attempted to assess the stability of the cut slope. An attempt has been made in this study to document the behavior of strength of the material in terms of stability of slopes by parametric study of cohesion and internal friction. This study was carried out to understand how the factor of safety changes with reference to change in cut slope height, cohesion and internal friction of the discontinuities that attributes the shear strength of discontinuities. The study is based on Finite Element Modeling (FEM). From the study it is found that factor of safety has strongly proportional relation with cohesion and internal friction but shown inversely proportional relation with height of cut slope.

EVOLUTION OF FLUVIAL SYSTEM AND RECONSTRUCTION OF PALEOHYDROLOGY OF LATE CENOZOIC SIWALIK GROUP, RELATED TO TECTONIC UPLIFT OF HIMALAYA AND CLIMATIC CHANGE, KANKAI RIVER SECTION, EAST NEPAL HIMALAYA

September 27th, 2018 by
Evolution of fluvial system and reconstruction of paleohydrology of late Cenozoic Siwalik Group, related to tectonic uplift of Himalaya and climatic change, Kankai River section, east Nepal Himalaya

Prakash Das Ulak

Department of Geology, Tri-Chandra Campus,Tribhuvan University, Kathmandu, Nepal

Jour. Nepal Geol. Soc., Vol. 51, 2016, 52-72

 

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This paper focuses on evolution of the fluvial system in the late Cenozoic Siwalik Group along the Kankai River section of east Nepal. The Siwalik Group lies on the southern flank of the Himalaya and composed of molasse sediments, which were derived from upheaval of the Himalaya. On the basis of lithology, assemblage of sedimentary structures and sediment body architectures, seven facies associations (FA1 to FA7) are recognized in the Kankai River section, east Nepal Himalaya. These recognized facies associations are closely related to each lithostratigraphic units of the area (Ulak 2009). The lower and upper members of the Lower Siwalik are the products of the fine-grained meandering and flood flow-dominated meandering systems, respectively. The lower, middle and upper members of the Middle Siwalik are interpreted as the deposits of the sandy meandering, deep sandy braided and shallow braided systems, respectively whereas the lower and upper members of the Upper Siwaliks are the products of the gravelly braided and debris flow-dominated braided systems, respectively. Paleohydrological characteristics and its evolutional changes of the group have been estimated by using grain diameter and thickness of fining upward fluvial successions. The paleohydrology suggests an increase in flow velocity, channel slope gradient, and discharge of the fluvial system. Paleovelocity varies from 0.19 m/s to 5.31 m/s. Similarly paleochannel gradient and paleodischarge changes from 6.67×10-5 to 2.97×10-4 m/m and 101 to 104 m3/s, respectively in stratigraphic upward. The progressively changes in the paleohydrology reflect the southward propagation of thrust activities, caused by the upheaval of the Himalaya.

GIS BASED STUDY ON LIQUEFACTION-INDUCED SOIL SUBSIDENCE, A CASE FROM URAYASU AREA, CHIBA, JAPAN

September 27th, 2018 by
GIS based study on liquefaction-induced soil subsidence, a case from Urayasu area, Chiba, Japan

Rama Mohan Pokhrel

Central Department of Geology, Tribhuvan University, Kirtipur, Kathmandu, Nepal

Takashi Kiyota

Institute of Industrial Science, University of Tokyo, Japan

Jour. Nepal Geol. Soc., Vol. 51, 2016, 52-72

 

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Urayasu City in Chiba prefecture, Japan, which is composed of young reclaimed land. Following the 2011 off the Pacific Coast of Tohoku Earthquake (M=9), severe liquefaction-induced ground subsidence was extensively observed in this young filled land. The major problems associated with liquefaction and ground subsidence like tilting of houses, buckling of roads and lifelines cut off were commonly observed. Therefore, a detailed study on possibility and amount of ground subsidence is essential to carry out in such area. In this paper, a variation of ground subsidence is studied after severe liquefaction takes place in an earthquake. Randomly distributed borehole locations were selected and calculated the liquefaction potential for each boreholes. Geostatistical method of interpolation a kriging method was applied to attain a spatial variation of liquefaction potential within the area by using selected borehole locations. The ground subsidence was estimated by using airborne LiDAR (Light Detection And Ranging) images before and after the earthquake which gives the spatial distribution of soil subsidence map. The liquefaction potential value was picked up from the liquefaction potential distribution map and the subsidence value of the corresponding points were picked up from the ground subsidence map. By comparing these two values the relationship between liquefaction potential and ground subsidence has been developed.

LAND USE/LAND COVER CHANGE DETECTION THROUGH TEMPORAL IMAGERIES AND ITS IMPLICATIONS IN WATER INDUCED DISASTER IN TRIYUGA WATERSHED, EAST NEPAL

September 27th, 2018 by
Land use/land cover change detection through temporal imageries and its implications in water induced disaster in Triyuga watershed, east Nepal

Rabindra Choudhary

Institute of Engineering, Tribhuvan University, Lalitpur, Nepal

Dinesh Pathak

Central Department of Geology, Geodisaster Research Center, Tribhuvan University, Kathmandu, Nepal

Jour. Nepal Geol. Soc., Vol. 51, 2016, 49-54
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Land use and land cover is an important component in understanding the interactions of the human activities with the environment. Land use planning is widely recognized as key non-structural risk mitigation measures. In the present study, decadal land use changes in the Triyuga watershed has been assessed for the period between 1980 and 2015. Satellite images of Landsat (ETM, TM and OLI) have been used to prepare land use maps for respective period. The relationship between disaster loss, land use and meteorological factor (rainfall) has been evaluated. Significant correlation between the parameters has been obtained.

TRACING THE MAHABHARAT THRUST (MT) ON THE BASIS OF LITHOLOGY AND MICROSTRUCTURES AROUND BHAINSE-MANAHARI AREA, CENTRAL NEPAL

September 27th, 2018 by
Tracing the Mahabharat Thrust (MT) on the basis of lithology and microstructures around Bhainse-Manahari area, central Nepal

Laxman Subedi

Department of Geology, Tri Chandra Campus, Tribhuvan University, Kathmandu, Nepal

Kamala Kant Acharya

Central Department of Geology, Tribhuvan University, Kathmandu, Nepal

Jour. Nepal Geol. Soc., Vol. 51, 2016, 39-48

 

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Lithological and microstructural study carried out in Bhainse –Manahari area, central Nepal revealed that the rock sequences of the Bhainse–Manahari area can be divided into two successions: the Nawakot Complex and the Kathmandu Complex. These two complexes are separated by a distinct thrust boundary, the Mahabharat Thrust (MT). The Nawakot Complex consists of low-grade metamorphic rocks such as slate, phyllite, quartzite and limestone while the Kathmandu Complex  comprises medium grade (up to garnet grade) metamorphic rocks like garnet-schist, marble and mica-schist. The Mahabharat Thrust (MT) and the Manahari Thrust (MnT) are the two major thrusts in the study area. The MT separates the rocks of the Nawakot Complex (foot wall) in the south from the rocks of the Kathmandu Complex (hanging wall) in the north. The Manahari Thrust in the western part of the study area separates the Dunga Quartzite and the older Benighat Slates lying above it. The microstructure analysis reveals that the rocks in the thrust zone show higher deformation than in the neighboring rocks, and this gradually decreases away from the MT zone. The strain analysis of quartz grains reveals that the rock sequences of the hanging wall of the MT showed pure, simple and complex shear senses and the rocks of the footwall also showed the same pattern indicating MT as a stretching fault.

INTEGRATED SURFACE GEOPHYSICAL APPROACH TO LOCATE A KARST CONDUIT: A CASE STUDY FROM ROYAL SPRING BASIN, KENTUCKY, USA

September 27th, 2018 by
Integrated surface geophysical approach to locate a karst conduit: a case study from Royal Spring Basin, Kentucky, USA

G. N. Tripathi

Department of Mines and Geology, Ministry of Industry, Government of Nepal

A. E. Fryar

Department of Earth and Environmental Sciences, University of Kentucky, Lexington, KY 40506-0053 USA

Jour. Nepal Geol. Soc., Vol. 51, 2016, 27-37

 

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Groundwater flow in karst terrains is difficult to map because it can be concentrated through conduits that do not necessarily coincide with the surface features. We applied electrical resistivity (ER) and self-potential (SP) techniques at three sites to locate an inferred trunk conduit feeding a major spring in the Inner Bluegrass region of Kentucky (USA). Royal Spring is the primary water supply for the city of Georgetown; the upper part of its basin coincides with the Cane Run watershed. ER profiles (972 m total length) were measured using a dipole–dipole electrode configuration with 2- to 3-m spacing. SP measurements were taken along those ER lines and an additional test profile (230 m) using one stationary reference electrode and another roving electrode at a fixed interval. The SP technique has been used by many researchers to detect the electrokinetic potential generated by groundwater flow. The low resistivity of water in the conduit, as compared to the high background resistivity of limestone bedrock, was the ER exploration target. A negative SP anomaly corresponded to a low ER anomaly for most of the profiles, but a few are not comparable. Although SP data collected over multiple days along the test profile differed significantly, they showed similar trends. Field drift in SP data was found to be highly sensitive to temperature changes during the time of measurement. Although the overall trends of the final SP profiles for different dates were similar, the SP magnitudes varied with the amount of precipitation and the average soil temperature. The low-resistivity anomalies in the 2D inverted sections and corresponding negative SP anomalies at two sites (Berea Road and Kentucky Horse Park) encountered water-filled conduits, although mudfilled voids encountered during drilling at University of Kentucky Agricultural Research Farm sites suggest that these may be tributary conduits rather than the trunk conduit.

SEDIMENTARY FACIES ANALYSIS OF THE FLUVIAL SYSTEMS IN THE SIWALIK GROUP, KARNALI RIVER SECTION, NEPAL HIMALAYA, AND THEIR SIGNIFICANCE FOR UNDERSTANDING THE PALEOCLIMATE AND HIMALAYAN TECTONICS

September 27th, 2018 by
Sedimentary facies analysis of the fluvial systems in the Siwalik Group, Karnali River section, Nepal Himalaya, and their significance for understanding the paleoclimate and Himalayan tectonics

Ashok Sigdel

Soil, Rock and Concrete Laboratory, Nepal Electricity Authority Swoyambhu, Kathmandu, Nepal

Tetsuya Sakai

Department of Geoscience, Shimane University, Matsue 690-8504, Japan

Jour. Nepal Geol. Soc., Vol. 51, 2016, 11-26

 

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Fluvial sediments of the Siwalik successions in the Himalayan Foreland Basin are one of the most important continental archives for the history of Himalayan tectonics and climate change during the Miocene Period. This study reanalyzes the fluvial facies of the Siwalik Group along the Karnali River, where the large paleo-Karnali River system is presumed to have flowed. The reinterpreted fluvial system comprises fine-grained meandering river (FA1), flood-flow dominated meandering river with intermittent appearance of braided rivers (FA2), deep and shallow sandy braided rivers (FA3, FA4) to gravelly braided river (FA5) and finally debris-flow dominated braided river (FA6) facies associations, in ascending order. Previous work identified sandy flood-flow dominated meandering and anastomosed systems, but this study reinterprets these systems as a flood-flow dominated meandering river system with intermittent appearance of braided rivers, and a shallow sandy braided system, respectively. The order of the appearance of fluvial depositional systems in the Karnali River section is similar to those of other Siwalik sections, but the timing of the fluvial facies changes differs. The earlier appearance (3-4 Ma) of the flood-flow dominated meandering river system in the Karnali River section at about 13.5 Ma may have been due to early uplift of the larger catchment size of the paleo-Karnali River which may have changed the precipitation pattern i.e. intensification of the Indian Summer Monsoon. The change from a meandering river system to a braided river system is also recorded 1 to 3 Ma earlier than in other Siwalik sections in Nepal. Differential and diachronous activities of the thrust systems could be linked to change in catchment area as well as diachronous uplift and climate, the combination of which are major probable causes of this diachronity.

GEOTHERMOBAROMETER BASED ON COEXISTING GARNET-ORTHOPYROXENE-PLAGIOCLASE-QUARTZ EQUILIBRIA

September 27th, 2018 by
Geothermobarometer based on coexisting garnet-orthopyroxene-plagioclase-quartz equilibria

Harel Thomas

Department of Applied Geology, Dr. H. S. G. University, Sagar (MP), India

Lalu P. Paudel

Central Department of Geology, Tribhuvan University, Kirtipur, Kathmandu, Nepal

Jour. Nepal Geol. Soc., Vol. 51, 2016, 1-10

 

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The garnet-orthopyroxene-plagiolcase-quartz pairs are commonly found in the assemblages of basic granulites/charnockite and hence are suitable for estimating equilibrium temperature and pressure of most metamorphic rocks. The temperature based on garnet-orthopyroxene Fe-Mg exchange reaction and pressure based on net transfer reaction of garnet-orthopyroxeneplagioclase-quartz equilibria, mainly based on reactions, using the equation given by different workers.

i. 1/2 Ferrosilite + 1/3 Pyrope = 1/2 Enstatite + 1/3 Almandine.

ii.  Ferrosilite + Anorthite = 2/3 Almandine + 1/3 Grossularite + Quartz

iii. Enstatite + Anorthite = 2/3 Pyrope + 1/3 Grossularite + Quartz.

The author developed software in visual basic with the executable code MPET3.EXE

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