M. K. Ansari

Instability investigations of basaltic soil slopes along SH-72, Maharashtra, India

Mahabaleshwar is one of the most attractive and important destinations for tourists in Maharashtra, India, which experiences frequent slope failure due to high-intensity rain and complex geological conditions. The litho unit of the area is the Deccan Trap Basalt, the most famous consecutive basaltic flows during the late Cretaceous to Tertiary periods. The area is very susceptible to weathering, different degrees of alteration, formation of soils and occurrences of bole beds in between two consecutive basaltic flows. Soil formation process in this area is one of the most influencing factors for slope failure; in addition to this, joints, sub-vertical-to-vertical slopes, heavy rainfalls, etc. also play a pivotal role in instability. These transformed soils create instability on the slopes and ultimately converge to slope failures. Five types of soils have been identified during field investigations, petrographic study and X-ray diffraction that indicate change in composition and colour variations. Geomechanical properties viz. bulk density, grain size analysis, Atterberg limit, uniaxial compressive strength, cohesion and angle of internal friction were calculated for five types of soil samples. Effects of these soils on slope stability have been depicted with the help of numerical program Slide 6.0 based on limit equilibrium method.

Rockfall risk assessment for pilgrims along the circumambulatory pathway, Saptashrungi Gad Temple, Vani, Nashik Maharashtra, India

This paper mainly describes the assessment of rockfall risk for the large number of pilgrims along the parikrama path (circumbultory or pathway around the shrine) at the Saptashrungi Gad Temple, Vani, Nashik, Maharashtra, India. The temple is constructed on moderately weathered and fractured basaltic terrain along the steep high hill slope. The loose rockmass from the top of the hill occasionally fall, bounce, roll and slide down along the slope of the temple with some rockmass blocks landing on or passing the parikrama path. This leads to risk while taking parikrama along the hill. A quantitative risk assessment (QRA) was undertaken to determine the risk for the pilgrims performing parikrama along the parikrama paths struck by rockfalls and the risk reduction capabilities of various remedial work. The obtained QRA results indicate that, the societal risk cannot be acceptable.

Assessment of Durability and Weathering State of Some Igneous and Metamorphic Rocks Using Micropetrographic Index and Rock Durability Indicators: A Case Study

Weathering and durability are the key factors of the rock in the suitability and usefulness of different construction materials, building materials and engineering structures. A single test never predicts the entire factor for suitability of rock stone and aggregate in different uses. Thus, variety of physical, mechanical and chemical tests and indices of rocks are widely used to estimate and evaluate the rocks for the suitability of the required purpose. In all the cases, knowledge of durability and weathering properties are the most important along with the strength of the rock. Micropetrographic index and rock durability indicators (dynamic and static) are the one of the best methods to evaluate the rock for weathering and durability. To estimate these indices, variety of tests are performed such as petrographic examination test, point load index, sulfate soundness test, water absorption test, modified aggregate impact value test and test for specific gravity. Slake durability index and impact strength index tests were also performed for correlation with static and dynamic rock durability indicators due to its application and usefulness in the durability and strength of the rock materials. Micropetrographic index was obtained by petrographic examination test and correlated with all the physical and mechanical properties used for find out the durability indicators. The present study is to express the usefulness of these three indices in the classification of weathering and durability classes and estimation of durability indices by slake durability index, impact strength index and micropetrographic index.

Assessment of Potential Alkali Aggregate Reactivity for Siliceous and Carbonate Aggregates: A Case Study

Alkali-aggregate reactivity (AAR) involves a reaction between the pore solution of concrete and certain minerals found in some aggregates. To assess the potential AAR various physical and chemical tests are available and extensively used. The petrographic examination is the initial assessment that decides the further investigation for potential reactivity of an aggregate. A chemical approach is another option to assess the aggregate for potential AAR. The accelerated mortar bar method and concrete prism tests are other very important tests for determination of potential AAR of aggregates samples. However, a combination of the results of all the techniques provides most reliable results for potential AAR in aggregates. Moreover, each test represents the stepwise investigation and provides the decision for the test of next approach. Petrographic examination and chemical test methods are the quick decision-making methods for the estimation of potential AAR. In some cases, by these two methods, the aggregate can be selected and rejected confidently. However, for critical values or doubtful aggregates, further tests are necessary to develop a higher confidence level of the results. The present study comprises of the assessment of the alkali-reactivity of siliceous and carbonate aggregates using petrographic and chemical approaches. X-ray diffraction analysis was used as a complementary method to the petrographic evaluation. Moreover, under chemical approach, two separate test methods were used for siliceous and carbonate aggregates. The study also included a comparison between the petrographic examination and chemical analysis for the same aggregate samples and found significant results.