eChapters

Abstract

The softer rock types belonging to Tertiary period, intense deformation and the related more frequent tectonic weak planes, high degree of weathering and extensive road cutting are the inherent systems in provoking Landslides in Noney-Nungba segment of NH-53 in the state of Manipur. So Landslide Hazard Zonation mapping was carried out in this segment using BIS method and also geotechnical investigations were carried out in Awang Khull part-II slide and Raungdai slide and on the basis of type of failure and the morphotectonic conditions mitigation strategies were suggested.

Abstract

The state of Nagaland located in the northeastern part of the Indian subcontinent is also prone to landslides similar to the other north eastern states due to the softer lithologies, intense deformation and extensive anthropogenic activities. So in order to understand the landslide vulnerability and to evolve remedial measures, a 12 km stretch of the NH-2 from Kohima town in the south to Zhadima junction in the north was studied. The study comprises the preparation of landslide hazard zonation map using BIS method and detailed studies in six major landslides involving RMR, SMR and Kinematic analysis and also the suitable remedial measures for such landslide phenomenon.

Abstract

Due to fragile lithology belonging to Disang and Barail groups of the Cretaceous-Tertiary period, intensive structural deformation related to collision tectonics, extensive weathering and the anthropogenic activities in the form of slope cutting for the development and widening of roads lead to frequent landslides in the state of Manipur, India. In this connection, the road section between Tengnoupal and Sita has been studied to understand the landslides vulnerability and to evolve mitigation strategies. The study involved the Petrochemical analysis to elucidate the weathering potential of the rocks, kinematic analysis to understand the network of joints and the strain, slope stability analysis to prepare Land Hazard Zonation mapping and estimation of factors of safety in selected locations. On the basis of these studies, long & short term remedial measures were suggested to mitigate the landslide hazards.

Abstract

Geological conditions in the Tertiary mountainous areas of the western and eastern hill ranges of Manipur often cause landslide movements. These repeatedly occur mostly in old landslide regions during rainy seasons on a large scale, causing considerable economic loss and injuries and deaths of humans. In order to improve such landslide hazard assessment of the region for effective mitigation, Electrical resistivity surveys were conducted using Schlumberger array technique on the very unstable and problematic frontal part of the Kotland landslide, NH-37, Manipur along three profiles. Electrical resistivities aided the characterization and quantification of the subsurface rock units, structure and tectonic conditions of the Landslided area which can contribute for the better planning of mitigation strategies. The results lead to the elucidation of depth of the different litho-units and the geometry of failure surface. The probable failure surface was observed between 10 and 22m depth, characterised by low resistivity (< 150 Ωm) and geometry of the sliding surface was rotational. In addition, a fault was also inferred in the resistivity pseudosection model and hence the area may be highly vulnerable to landslides.

Abstract

The present study deals with the slope instability analysis of a vulnerable stretch of 16 km between Pratapgarh road intersection and Mahabaleshwar town, which is a part of the state highway-72, Satara district, Maharashtra, India. The highway remains closed during the monsoon seasons, due to the recurrent instances of cut slope failures. So the present research work was conducted with an aim to study the reasons, extent and mechanism of the cut slope failures along the road sections as well as optimization of tools for the assessment of road cut stability of the area. The 16 km stretch was divided into seven vulnerable sections (M1; near Mahabaleshwar - M7; near Poladpur) based on the geological, geometrical and structural attributes. The slope forming mass primarily consists of laterite, weathered basalt and fresh jointed basalt, which are interbedded with red bole at some sections. Limit equilibrium, finite difference and finite element simulation were performed for seven cut slope sections, using similar geometries and material strength attributes for all the analyzing techniques. The assessment was carried out for both dry and saturated conditions to emulate the monsoons. The factor of safety yielded through the limit equilibrium method was the most conservative of all the tools; while the finite element method gave the least conservative figures in terms of factors of safety, being close to the field observations, the safety factor results of finite difference methods were between the limit equilibrium and finite element methods. The cut slope sections composed of weathered basalts and laterites (M1, M2, M3, M6) were found most vulnerable to failure during rains, while the sections composed of fresh jointed basalts (M4 & M5), though overall stable, are susceptible to planar and wedge failures.

Abstract

The Himalayas of Himachal Pradesh is prone to landslides due to inherent geodynamic conditions, rainfall and anthropogeny. Besides multi-variate studies on the landslides of Himachal Pradesh, instrument based early warning system was attempted by taking Jhakri landslides as the test site. Various instruments viz; piezometer, vertical inclinometer, Rain gauge, etc. were installed and the paper discusses about the methodology adopted in the installation of the instruments and the observations made from the instruments. While Piezometer did not reveal much information, the Tiltmeter showed minor movements.

Abstract

The landslide is a disaster which causes rampant loss to life, property and ecosystems. With increased awareness and technological development, the number of monitoring stations near hazardous regions have increased. To give warning prior to the occurrence of a landslide, the soil/rock mechanics of the underlying bed needs to be studied and understood. This paper examines the current literature and elucidates some features of state-of- the-art landslide monitoring systems.

Keywords: Field based sensors, Wireless sensor network, Landslide monitoring

INTRODUCTION

Advancements in technology have helped us to understand nature better than before, yet the geotechnical parameters causing landslides could not be quantified accurately. The efforts taken in predicting landslides are clearly moving towards this objective and this can be seen by the number of monitoring stations that have been setup in landslide prone areas around the world. The data that is obtained at each location is important in understanding landslides. Each location is unique in terms of soil properties, groundwater, inclination of the slope and weather conditions and consequently, each deployment is unique.

The paper narrates the instrumentation based forewarning systems functioning around the world. The paper discusses these aspects hierarchically viz; Landslide prone areas in India, geotechnical instrumentations and their merits, influence of rainfall on landslides, correlation between rainfall and pore pressure, the relevance of different systems for different scenarios etc.

Abstract

Since the landslides have started spreading over to the most of the mountain provinces of all over the world, having developed expertise in Landslide vulnerability mapping, Factor of safety, Rock mechanic studies etc. the scientists and the technocrats have started focusing towards developing landslide early warning systems using instruments. As the instrumentation in such vast areas is not feasible satellite based monitoring of landslide movements is fast emerging. In this connection the paper discusses InSAR interferometry based landslide movements carried out in Nainital and Mansadevi areas, Uttrakhand Himalayas, India.

Keywords: SAR interferometry, Monitoring movements, Nainital & Mansadevi Landslides.

INTRODUCTION

Landslides pose greater threats to the population of India also, especially those living in mountainous regions, the top being the Himalayas. Many villages and vital transport routes are endangered by landslides and losses of lives and important infrastructure now become a routine phenomenon. Therefore, studies on surface displacements and landslide movements have become very important. However, due to the large aerial extent of the landslide prone provinces, this task may not be effectively carried out by ground based methods. In the recent years, the availability of interferometric Synthetic Aperture Radar (InSAR) data from a variety of satellite and airborne remote sensing sensors has emerged, as a potential tool that can yield accurate data on surface displacements. Although, monitoring of such low velocity deformations, as we observe in landslides, is only possible if considerably long time series images are available. InSAR derived displacement measurements are not only feasible but also moderate in their costs compared to many ground-based methods. This paper discusses Small Baseline Subset (SBAS) algorithm used to monitor landslide movements.

Abstract

Kaliasaur landslide located 18km from Srinagar on the NH-58 in Uttrakhand Himalayas has been repeatedly sliding for the last over 5 – 6 decades totally paralyzing the transport operations in the region and causing beeline of issues not only for the people living in the hilly state but also the tourists and the pilgrims. The study of Geosystems & geodynamics, large scale micro zonation and geotechnical studies using RMR and SMR techniques show that the slide is located in high hazard zone and follow the pattern of wedge and planar failures with vulnerable zone of factor of safety. The toe erosion by the acutely turning Alaknanda river and the mitigation measures in the form of slope disturbance in the upslope part rather protecting slide, has been responsible for the recurring slides. The study further revealed that excessive rainfall is also a triggering parameter and the crown part is widening. On the basis of the studies, mitigation measures have also been brought out.

Keywords: Kaliasaur landslides, Micro LSV zonation, Factors of landslides, Mitigation.

Abstract

The Nilgiri Mountains of South India is one of the Landslide prone hill ranges in India. The landslides, in general, are due to the independent, interdependent and the combined effects of natural earth system processes, triggering phenomenon and anthropogenic activities. So the scientists, technocrats and the academicians from all over the world have started studying the landslides using various techniques and advanced tools in mapping the morphology, preparing the vulnerability maps and carve out mitigation strategies. But the discrimination of active slides is a difficult task and also needs continuous monitoring and further a time consuming process too. So, in this context, an attempt has been made to study the signatures of active sliding in one of old slides namely the “LINGASLIDE” in which frequent minor sliding events are often reported. In the study, Total station based large scale topographic survey was carried out in LINGASLIDE and from the same 50 cm topographic contours were generated. From such large scale contours, Digital elevation Model (DEM) was generated and from the DEM, shaded relief map was generated.Uutilizing both the contours and shaded relief maps, small slides were mapped in the LINGASLIDE from the well exhibited subsidiary crowns, toes and the traverse cracks. Resistivity tomography surveys were also carried out along two longitudinal profiles and one traverse profile to identify the subsurface geology, the slip surface and the zones of moisture accumulations, if any. The subsidiary crowns, toes, the conjugate fracture systems and the resistivity tomography showed that the LINGASLIDE is active and the sliding is going on towards easterly because of the easterly compression,resulted from the higher slopes caused by the settlements raised over Lingaslide and the obstruction provided by the retaining walls at the toes in the east. Such compressive forces are clear from the NW-SE and NE-SW fractures seen in Lingaslide and the sliding is clear from the cracks seen and monitored in the buildings constructed over Lingaslide.

Abstract

The Rawana landslide, located in Sirmuar district of the Shimla Himalayas, Himachal Pradesh is repeatedly active in the recent years. It is a NE-SW oriented slide with the crown in the southwest and the wider toe in the northeast resting in Giri River. During some of the sliding events emanations of heat and gases were also inferred. In order to understand the landslide phenomenon and the causative factors, and there from to evolve mitigation measures, detailed studies of the slides were under taken. The Landslide hazard zonation mapping carried out in Rawana landslide using LHEF rating based BIS method indicates that it is located in high hazard zone. The detailed studies show the complex geological, structural, morphotectonic and hydrological setting. From the studies it is surmised that the toe erosion by Giri river and the rainfall infiltration in the mid slope region are responsible for the slide. Remedial measures have been accordingly evolved.

Abstract

The landslide vulnerability of the state of Mizoram is already high due to lithology, structure, geomorphology and seismotectonics and also the rainfall, like the other states of the northeastern region of India. The extensive mining activities along the highways for the building and road materials appear to cause additional problems of landslides. So two prominent landslides occurring in Keifang and Tlungvel quarries,Mizoram were studied. Besides taking stock of the geosystems, boreholes were drilled in both slides and from the total depth drilled and the modified core recovery, the RQD were worked out for the rocks which indicates that geotechnically the rocks of Keifang quarry are weak when compared to Tlungvel quarry. The geophysical surveys too lead to similar inferences. On the basis of the studies a set of mitigation strategies have been suggested.

Abstract

The landslides that swallowed the whole of Malin village, Maharashtra on the early morning hours of 30 July, 2014 is one of the major disasters, next only to Kedarnath episode in the recent years. Consequently, the Department of Science and Technology, New Delhi, constituted an expert committee comprising the authors of the article which made a visit and took the on the spot assessment of the disaster. Their observations show that the area is covered by the Deccan basalts, which are layered with compact and vesicular basalts; fractured and jointed basalts due to tectonics and the cooling of the basalts; and have also undergone extensive geomorphic evolution. Due to such geologic/geomorphic setting, the flow layered basaltic hillock in which Malin is located is naturally benched, which is further being leveled for the agriculture purposes. The deforestation, leveling of the hills, excessive usage of water for irrigation and the lack of drainages outlet in such benched and leveled slopes have assigned high degree of landslide vulnerability to the area. Over this, when torrential rainfall occurred in the last week of July, the landslide was triggered. On the basis such inferences, some mitigation measures have been evolved after the visit.

ABSTRACT

The multi-sensor airborne geophysical survey was carried out over Nalgonda district, Andhra Pradesh, during the field season 2002-03, with an objective to locate potential areas for mineral exploration. The area comprises older metamorphic rocks of Peninsular Gneissic Complex of Archaeanage represented by gneisses, granite, amphibolite and banded magnetite quartzite. Leucocratic intrusive granite, extending over a length of about 40 km around Suryapet in NNW-SSE direction exhibits intense fracturing. Two sets of vertical to sub-vertical fractures have been noted in granite. Yellow stains observed in granite near fracture planes reveal the presence of secondary radioactive mineral encrustation. The ground magnetic and spectrometric observations indicated that the uranium mineralization is confined to these fractures in granite. Petrographic, ore-microscopic and scanning electron microscopic studies revealed evidences of metamict alteration surrounding monazite/apatite inclusions within biotite, and magnetite grains in granite. These studies also indicated evidences of discrete grains of uraninite / coffenite / pitchblende (containing Thand Ce). Chemical analysis of the rock samples (by NAA) collected from anomalous zone reveal high uranium concentration of the order of 1200 ppm, marked by high values of total Rare Earth Element concentration (800 ppm).

The leucogranites are characterized by high LREE and a negative Eu anomaly suggesting plagioclase fractionation. An ultramafic enclave near village Kutubsahipur shows highest concentration of both uranium (1240 ppm) and REE (890 ppm) analyzed by BARC and NAA Lab, GSI.

ABSTRACT

The carbonatites are genetically and geochemically distinct and contain several rare earth minerals that are unknown or are very rare in other types of rocks. A useful review of the REE’s in carbonatites is given by Cullers and Graf (1984), who point out that carbonatite contains the highest concentration of REE’s and highest LREE: HREE (La:Lu) ratio of any igneous rock. High REE abundances are considered as the diagnostic character of carbonatites to discriminate them against recrystallized limestone. Rare earth mineralization in carbonatities can be classified into three categories. The first is primary magmatic crystallization (bastnaesite). The second is hydrothermal mineralization and the third is supergene mineralization produced by weathering of carbonatitie bodies. The only economic Nb mineral in carbonatite is pyrochlore. Apatite deposits constitute the largest bulk mining in carbonatites and have higher phosphate content than marine phosphorites. Pyrochlore, cubic fergusonite, eschynite, Fe-Nb rutile, monazite apatite, bastnaesite and allanite are the rare earth minerals that are enriched in Tamil Nadu carbonatites. Such enrichment of above rare earths is typical of undersaturated alkaline complexes. The lanthanides are seen associated with these minerals, mainly the light lanthanides are predominant than heavier ones. Thus the carbonatite complexes provide the locus for several metal deposits that are presently of strategic importance, containing elements, which are otherwise largely dispersed in earth crust.

ABSTRACT

Worldwide reinterpretation of evolutionary history of sedimentary basins had commenced with the introduction of sequence stratigraphic concepts by geoscientists of Exxon. The eustatic sea level controlled deposition in sedimentary basins together with synchronous excursions of many trace elemental and stable isotopic compositions of sedimentary strata have led to a proposition that geographically widely separated sedimentary strata could be classified and correlated with ease by application of sequence stratigraphy and chemostratigraphy, relatively younger branches. This paper reviews the key definitions of these stratigraphic methods, presents an overview on their applicability in petroleum exploration, reservoir characterization and stratigraphic correlation. Considering the man-hours required for interpretation of sequences and chemozones from large quantum of core samples being generated from exploration activities and the possibility of human-error and biased nature of interpretations, an automation scheme involving statistical discrimination is suggested. The statistical discrimination method has been tested to have 76-100 % distinction of depositional units of Recent – Cretaceous in age in terms of sequences, chemozones, lithostratigraphic units, petrographic types and sedimentary microenvironments with 100% reproducibility of predictions. Hence, creation of a large database with well constrained subpopulations and putting it to use for recognition of depositional units and correlation of strata and reservoir characterization is suggested which may reduce operational inconsistencies and improve exploration strategies.

ABSTRACT

India is blessed with large reserves of strategic and economically important heavy minerals such as ilmenite, rutile, leucoxene, zircon, monazite, garnet and sillimanite. These deposits are mostly located in the coastal stretches of Peninsular India especially between the high tide line and 200-250m inland, with the exception of few inland deposits. Ilmenite is the largest constituent of the Indian beach sand deposits, followed by sillimanite and garnet. These minerals are one of the largest and higher grades in the World. The Indian Ilmenite resource base totals 348 million tones (Mt), along with 18 Mt of rutile, 21 Mt of zircon, 8 Mt of Monazite, 107 Mt of garnet and 107 Mt of sillimanite. Although Indian heavy mineral resources are one of the largest in the world, it is observed that the Production to Reserve Ratio (PRR) is a meager 0.0013; that is insignificant compared to other countries with similar resources.

ABSTRACT

Mineral exploration is not only highly imaginative and creative but a very costly activity as well. The fast emerging Geomatics technology is a real boon in mineral exploration as it encompasses a whole spectrum of solutions and services which are of great help for exploration geologists. Geological maps which generally form the basic requirement for any kind of natural resources inventory operations currently witness tremendous changes and the same is mainly attributed to the integration of Geomatics technology. Usage of Geomatics has revolutionized the art of mineral exploration as geological maps can be easily integrated with other important details like geomorphology, structure and tectonic pattern, geophysical data etc. This kind of data integration facilitates for the better identification of mineralized zones. In addition, GIS with its powerful analyzing capability provides tools at several stages in the process of mapping for building up a database containing various types of data for quantifying and extracting features related to mineralization. The present paper narrates an overview of mineral exploration using Geomatics technology.

ABSTRACT

We report here the occurrence of chrysoberyl bearing gem pegmatitesof Southern India. The Pan-African Chrysoberyl mineralization is associated with intrusive event of grey pegmatites within granulite facies parametamorphic aluminous khondalites. Lithological and structural controls of chrysoberyl mineralization are discussed. The chrysoberyl occurrences in southern India, southern Madagascar and Sri Lanka provide strong evidence for India-Sri Lanka-Madagascar juxtaposition in the East Gondwana assembly with the Achankovil Shear Zone of Southern India one side extending into Ranotsara Shear Zone in Southern Madagascar and other side into southern tip of Sri Lanka.

ABSTRACT

Sedimentological studies such as textural, heavy mineral and clay mineralogy have been carried out for Warkalli Formations at Varkala, situated in the southern part of Kerala, India. The X-ray diffraction study reveals that kaolinite is the only clay mineral present in all the samples with trace amounts of gibbsite and goethite. The higher amount of kaolinite and gibbsite indicates warm and humid paleoclimatic conditions. The textural analysis shows that the sediments are moderate to poorly sorted, nearly symmetrical to fine skewed and lepto to mesokurtic in nature. A plot of skewness against sorting shows fluvial trend. The major heavy minerals present in the samples are magnetite, ilmenite, rutile, sillimanite, anatase and zircon. It can be inferred from these studies that these sediments would have been deposited in a lagoon by fluvial action. During that time, the source region has experienced tropical humid climate with mean annual precipitation (MAP) above 200 cm and intensive chemical weathering. Heavy mineral assemblage indicates medium to high grade metamorphic source rocks.