Raju Sarkar

Probabilistic Approach Towards Darjeeling Himalayas Landslides- A Case Study

Abstract The Himalayan region with its complex geological features, steep slopes, rugged topography, and intense monsoonal rainfall create ideal conditions for landslides. The damage caused due to landslides is immense causing significant loss of life and property initiating a dire need to formulate strategies in minimizing its impact in areas affected by landslides. Several attempts have been presented by various researchers in order to establish rainfall intensity thresholds using various parameters of rainfall conditions. These methods provide deterministic thresholds, i.e., landslide or no landslide; such thresholds are not always suited for landslides. In this paper, rainfall thresholds have been evaluated using a statistical method which results in the probability of landslide occurrence for single or multiple rainfall parameters leading to slide initiation. The results are expressed in terms of probabilities by analyzing two different variants of Bayes theorem, i.e., 1D and 2D. Probabilistic thresholds were calculated for Kalimpong region of Darjeeling Himalayas using available rainfall and landslide data during the year 2010–2016. The probabilities calculated for landslide occurrence were found to be 0.37 for rainfall intensity greater than 10 mm/day. However, the probability for a combination of rainfall intensity of 30 mm/day with duration of 3 days was calculated to be 0.67. The results also depicted that landslides are related to rainfall event parameters especially with rainfall intensity.

Major Issues of Post-earthquake Housing Construction during Resettlement

Natural disasters provide an acute image of how man-made technologies are a cause of conflict when it comes to nature. It is man versus wild in its true means. The nature lets us grow and increase our settlements. We encroach on other animals’ territories and it is only when the environment’s patience runs out that it retaliates in forms of natural disasters. These disasters affect numerous lives and kill a lot of humans. This is the main reason why we require more stable structures and preventive measures to battle the wrath of the nature. Rescue and search operations are conducted by many different government and private agencies including NGOs. These operations aim at providing the required relief and supplies after the disaster. Injured people need to be treated. People in dangerous zones need to be evacuated. Help is needed in many forms. Out of the many natural disasters, this paper will focus on the occurrence of earthquakes. Severe earthquakes destroy buildings and structures like roads, bridges etc. and wreak havoc in the community. Earthquakes largely damage all human constructions, including houses. This is the reason why a reconstruction program for dwellings and housings is of utmost importance. A home is only secondary to basic needs such as food and water. A well-planned strategy is important when it comes to launching a post-earthquake reconstruction program. The strategy should be reasonable and should consider the best interests of everyone affected; self-help and imported fabrication should play no part in the decision-making procedures. Creating awareness, physically demonstrating options and delivering are the three steps for the success of reconstruction programs. The extent of affected area and the magnitude of earthquakes are variable in nature and it is on these two aspects that the reconstruction strategy is devised. Technical aspects are focused towards the development of the affected areas and conceptual design of surrounding neighborhoods. It also aims at identifying seminars and programs based on easy financing for a new home. Along with these, review processes are conducted for the analysis of new residential needs based on optimizing the use of available land for planning and development. The paper discusses the construction of housing and resettlements as prioritized activities that must be undertaken post an earthquake. Earthquakes physically only destroy structures and buildings but for the people affected, they destroy lives, jobs, companies, sources of food and the sense of safety and traumatize the ones who come out alive.

Economic assessment of use of pond ash in pavements

Abstract The paper introduces a new type of industrial waste-based subbase material which can replace conventional subbase material (CSM) in pavement construction. Utilisation of this industrial waste, namely pond coal ash produced from a thermal power plant in road construction will help to reduce the disposal problem of this waste and also will help to reduce the problem of scarcity of CSM. Lime and fibre were also added to the pond ash at various percentages to improve the suitability of this type of mix as subbase material. The optimum service life of pavement is studied with the help of numerical modelling and the cost benefit is also presented in the current study. The study reveals that stabilisation of the coal ash with 2% lime may produce an optimal material and, even though a greater thickness may be required to deliver the same pavement performance, direct cost savings of around 10% may be achieved in addition to less easily quantifiable environmental benefits. Design charts are provided to exploit the findings.

Effective Design of Flexible Pavement on Treated Expansive Soil

Expansive soil poses plenteous problems to the structures placed over it, such as, road pavements, buildings and canals, etc., mainly because of high swell index induced by its high-water retention capacity. Flexible pavements with expansive soil as a subgrade material are characterized with meager performance mainly due to cracking and differential settlement. The current study engages with the cost effectiveness of treated expansive soil as subgrade material. Lime and stone dust have been blended with soil at varied percentages to enhance the suitability of this mix as subgrade material. To catch on the extent of influence of stabilizing mixture, Modified Proctor and California Bearing Ratio tests have been performed on treated soil. The thickness of various layers of pavement has then been evaluated in conformity with IRC: 37 [1] and then cost analysis has been made for pavements with both untreated and treated subgrade course. It has been discerned that when expansive soil is stabilized with lime-stone dust mix (5–12% by weight of mix), the drop in the cost of flexible pavement is found to be maximum, i.e., 6.55% of cost reduction can be achieved if the pavement subgrade section is made up of treated soil instead of untreated one.

Use of paper mill waste for brick making

Abstract The intent of the present research work is to explore the prospect of replacing natural soil used in brick making by some extent with industrial waste, that is, lime mud, as obtained from paper mill waste. Extensive adoption of this mill waste as a brick making material will deter the environmental effects of this waste disposal. Moreover, its adoption will not only solve the problem of stocked waste piles but also scale down the usage of natural soil as a brick making material. In consideration of the central intend of this study to utilize industrial waste as an alternate raw material, yet another industrial waste—fly ash, has also been blended to the mix to manufacture unburnt bricks, such that, it may produce cementitious compounds with lime mud. So, the materials used for brick making in this study are: lime mud, collected from the dumping site of M/s Hindustan Paper Corporation Limited, Jagiroad, Assam, India; soil, collected from a brick manufacturing unit also near Jagiroad; and fly ash, collected from National Thermal Power Station, Badarpur, Delhi, India. The materials have been characterized with respect to their chemical and geotechnical properties. Then, experiments have been conducted on hand-moulded bricks of aforementioned mix in distinct proportions. In this study, all the bricks have been dried in the natural condition and then tested for compressive strength conforming to International standards. It has been duly noted that none of the treated unburnt bricks satisfies the requirements of standard codes. Nonetheless, in case of burnt bricks, the compressive strength satisfies the requirements of International standard codes wherein lime mud has been added up to a certain percentage (=20%) in soil-lime mud mix.

COST EFFECTIVENESS OF FLEXIBLE PAVEMENT ON STABILISED EXPANSIVE SOILS

Black cotton soil also known as expansive soil poses a lot of problems to structures resting over it. Flexible pavements with expansive soil subgrade have shown very poor performance due to differential settlement and cracking. The present study deals with the cost effectiveness of flexible pavement on stabilized expansive soil. The subgrade course was stabilized with lime and California Bearing Ratio (CBR) test was performed for different proportions of lime content. The thickness of various layers of pavement was then calculated in accordance with IRC: 37 [1]. Cost analysis was then made for pavements with both unstabilized and stabilized subgrade course based on Public Works Department (PWD) of Delhi. It was observed that when expansive soil was stabilized with 5% lime content, the drop in cost of flexible pavement was maximum.

EFFECT OF LIME AND STONE DUST IN THE GEOTECHNICAL PROPERTIES OF BLACK COTTON SOIL

In the present study Black Cotton Soil was stabilized with a mixture of lime and Stone Dust. First an optimum value of lime was determined on the basis of some geotechnical properties of mixture of lime and Black Cotton Soil. Then Stone Dust was mixed upto 25% by weight with an increment of 5% in the optimized mixture of lime-Black Cotton Soil. California bearing ratio, unconfined compression strength and maximum dry density values were determined of these modified mixes. Morphology of the soil and admixture has been studied by Scanning electron microscope (SEM), while mineralogical composition has been determined by X-Ray diffraction technique (XRD).