Dipendra Gautam

Common structural and construction deficiencies of Nepalese buildings

This paper outlines the common observed failure patterns in the buildings of Nepal after MW 7.8 Gorkha (Nepal) earthquake. Several types of damage patterns were observed for reinforced concrete buildings, as well as for unreinforced masonry and adobe houses during the reconnaissance survey performed immediately after the earthquake of 25 April 2015. Several field visits in the affected districts were conducted and associated failure/damage patterns have been identified and analyzed. This paper also covers damage patterns in non-engineered buildings, middle and high-rise buildings, commercial complexes, administrative buildings, schools and other critical facilities from Kathmandu valley as well as other affected districts. The construction and structural deficiencies are identified as the major causes of failure, however local soil amplification, foundation problems, liquefaction associated damages and local settlement related damages are also significantly observed during this earthquake and reported in the present paper. In the end, the lessons learned from the field survey are resumed in order to give some guidelines for future construction practices.

Disaster resilient vernacular housing technology in Nepal

BackgroundDisasters like earthquakes and flood cause enormous loss of lives and property in Nepal frequently. However, during such events particular types of houses are found to be more resilient than common types of housing stocks. This paper outlines the disaster resilient vernacular housing technologies in two of the physiographic regions of Nepal. The vernacular houses are analyzed in terms of their performance and shortcomings during earthquake and flood disasters and found to be technologically resilient in many aspects of impending disasters in Nepal distributed within the physiographic regions. Using the comparative case study approach, field visits and non-structured interviews with local people, the resilient features in terms of construction technology of vernacular houses are identified in this study and the preliminary findings are highlighted as observed during the field visits without numerical modeling and analysis. The seismic performance of Rajbanshi, Gurung and Magar houses in Nepal during 1934, 1988 and 2015 earthquakes is presented in order to justify the performance of these particular housing stocks.ResultsThe vernacular construction technology in Terai is found to be technologically resilient in terms of floods and earthquakes, and earthquake resistant technologies are identified in the dwellings of the western mid-hill of Nepal. The traditional Rajbanshi houses in eastern Nepal are found to be resilient in terms of earthquake and flood disasters and the Gurung and Magar houses in western mid hills are found to be resilient in terms of earthquake disaster. The statistical distribution of housing stocks is presented and survival scenario is discussed with regard to specific building features. Apart from this, the field reconnaissance after Gorkha earthquake in western Nepal shows better performance of buildings with identified features in comparison to common housing stocks in neighborhoods.ConclusionsAs there is no instant possibility of enforcing building codes and guidelines for earthquake and floods resistant construction technologies and replacing the structures by modern reinforced concrete construction across the country and even people throughout Nepal are not able to afford the modern aspects of disaster resilient constructions; identified resilient features of houses are instrumental in assuring safety, serviceability, cultural comfort, patrimony and resilient livelihoods in rural and suburban setups of Nepal. The vernacular constructions also incorporate the cost effectiveness with proper use of local materials and cultural reflections in housing units. Global paradigms have shown significant performance during past disaster events, so replication of such technology with due incorporation of strengthening measures may be pivotal for country like Nepal.

Seismic Performance of World Heritage Sites in Kathmandu Valley during Gorkha Seismic Sequence of April–May 2015

AbstractThis paper outlines the damage observed in seven world heritage sites within the Kathmandu Valley because of the Gorkha seismic sequence of April–May 2015. Field reconnaissance was performe...

Drawdown and Dynamics of Groundwater Table in Kathmandu Valley, Nepal

Groundwater resources in Kathmandu valley provide water for human consumption, industry, hotels and agri- culture as well. Rapid urbanization, mushroomed increment in the built up area, overexploitation of surface and ground- water resource, removal of vegetation cover, change in land use pattern, and formation of impervious surface have led the ultimate lowering of groundwater table and minimization of groundwater recharge as well. This study quantifies the drawdown rate along with the groundwater dynamics across the Kathmandu valley, as the valley constitutes mostly of the urban population of Nepal including the capital city. In Kathmandu valley, for domestic purpose as well as the industrial purpose, water has been pumped continuously surpassing the natural recharge. The groundwater table drawdown has been estimated based on the recorded data of average static groundwater table depth and was found to be 0.7249 m in average and linear regression model of drawdown has been depicted along with the associated range of standard deviation. This drawdown has close proximity with the Mexico City alluvial deposit where ground subsidence is nowadays noticeably oc- curring. Similar land subsidence, water pollution and scarcity of water would be the near future consequence in Kath- mandu valley as nearly 50 % of valley population relies on groundwater resources. Similarly, the groundwater dynamics study has shown the shifting of drainage towards southwestern part of Kathmandu valley. Thus Kathmandu valley is in dire need of proper groundwater management execution in order to avoid the hydrological, hydro-geological and environmental impacts of rapid drawdown.

Seismic Hazard in the Himalayan Intermontane Basins: An Example from Kathmandu Valley, Nepal

Because of its location in the active plate boundary zone, in the last century, Himalaya witnessed eight lethal earthquakes that killed more than 46,845 causing hefty environmental costs in the form of loss of property and rehabilitation works. The first decade of twenty-first century became most unfortunate as the earthquake of magnitude 7.4 hit the Kashmir region of Pakistan killing at least 73,338 people leaving 51,28,309 affected. This single event caused economic loss of US

Revisiting Major Historical Earthquakes in Nepal: Overview of 1833, 1934, 1980, 1988, 2011, and 2015 Seismic Events

5.2 billion. These data have clearly pointed out the vulnerability level of the region and inadequacy of preparedness programme to mitigate earthquake disaster risk. Recurrence of such event in the area having soft sediment geology (e.g. fluvio-lacustrine deposits) would have even catastrophic devastation in the form of human causalities, structural damage and environmental degradation because soft sediments usually amplify the energy of the seismic waves. In this context, good amount of works has been carried out in the Himalayan region to understand the level of seismic hazard. However, there are limited works on seismic site response analysis of the soft sediments, which is a key to assess the intensity of ground deformation and structural damages. Therefore, in this contribution, first, a brief review on seismo-tectonics, paleoseismoloy, earthquake genesis, and active tectonics is presented; second, one-dimensional seismic site response analysis in the southern part of Kathmandu valley is presented to understand the seismic behaviour of the fluvio-lacustrine deposits in the intermontane basin. The results show variation of peak spectral acceleration from 1.27 to 1.28 g, which is usually a high value for the study area. On the other hand, amplification factor ranges from 1.908 to 7.788, which is similar to the Mexico earthquake (1985) that caused massive destruction in similar sediments of the Mexico City. The high amplification values are estimated mainly in densely populated urban areas of the valley. The obtained results show good correlation with the damage pattern of 1934 Bihar-Nepal earthquake indicating that the amplification of the ground motion would be the main culprit during the impending great earthquake in an already indentified “Central Seismic Gap”. An integrated approach comprising of paleoseismological studies, seismic microzonation, deployment of earthquake early warning system, development and enforcement of site specific building code, insurance policy along with preparedness directed awareness programs could be key measures in reducing earthquake risk in rapidly urbanizing intermontane basins.

Empirical correlation between uncorrected standard penetration resistance (N) and shear wave velocity (VS) for Kathmandu Valley, Nepal

Abstract Due to its location in the region of interaction between the Indian and Eurasian plates, several earthquakes hit Nepal each year. These shaking events, from weak to strong, characterize Himalayan earthquakes, and major events in the past caused enormous losses in terms of casualties, injuries, biodiversity, and the country’s economy. Due to lack of proper accounts related to the occurrence, damage, and losses of past earthquakes, few accounts of the 20th century earthquakes can be found in existing literature; and comparative analysis of these earthquakes has not been done. To fill this hiatus of detailed accounts and interpretation of notable earthquakes in Nepal, this chapter offers classified damage statistics, losses, and the impact on the socioeconomic setting of the affected areas. In addition, it presents the damage to gender, rural, and urban populations along with brief details of known earthquakes since 19th century.

Unearthed lessons of 25 April 2015 Gorkha earthquake (MW 7.8): geotechnical earthquake engineering perspectives

ABSTRACT The indirect method of estimation of VS is more important as geophysical tests associated with direct determination of VS are not feasible in developing countries like Nepal; on the contrary, standard penetration resistance (SPT-N) measurement is practised widely for building constructions even in residential buildings these days. Good SPT-N database is nowadays available so that eventual development of correlation between these two parameters may provide a strong basis of site characterization as the average shear wave velocity (VS, 30) of the upper 30-m soil layer is an important parameter for site characterization. Historically, Kathmandu Valley has experienced anomalous earthquake damage especially at locations with alluvial cover and site characterization is must for improving seismic design considerations. In order to depict a correlation between shear wave velocity and standard penetration resistance available 500 secondary data pairs are used and formulations are obtained considering the geological and geotechnical characteristics. Separate correlations for shear wave velocity as a function of uncorrected standard penetration resistance are developed for all soils, sands and clays separately. Correlation developed for Kathmandu Valley shows significant acquaintance with the existing correlations across the world developed for all soils, sands and clays.

Past and Future of Earthquake Risk Reduction Policies and Intervention in Nepal

ABSTRACT Gorkha earthquake (MW 7.8) of 25 April 2015 struck central, eastern and western Nepal and neighbouring areas. Enormous losses during Gorkha earthquake were attributed to collapse of 498,852 buildings, 446 public health facilities and partial damage of 256,697 buildings, 765 health facilities as well as severely affected 2900 cultural and historical sites. Anomalies were in particular observed in terms of localized damage and recurrent damages during 1833, 1934, 1988 and 2015 earthquakes. This paper reports geotechnical earthquake engineering observations noted during field reconnaissance conducted in affected areas. Damage reports from historical as well as recent Gorkha earthquakes are mapped in this paper. To depict lessons, forensic interpretations are presented considering 1833, 1934, 1988 and 2015 earthquakes.

Seismic Performance of Buildings in Nepal After the Gorkha Earthquake

Although Nepal formulated the Natural Calamity Relief Act earlier than its South Asian counterparts, earthquake risk reduction practices are relatively new for the country. This chapter presents the insights of existing earthquake risk reduction policies and interventions and postulates some important future insights based on the observations and experiences from the 2015 Gorkha seismic sequence.