Four Varandh ghat slopes found critically unstable despite relatively good rock quality: Study

PUNE: Four road-cut slopes along the Varandh ghat section of national highway 965DD have been identified as critically unstable, while six others have been identified as unstable; according to a study by researchers from Savitribai Phule Pune University (SPPU) and Banaras Hindu University (BHU)

PUNE: Four road-cut slopes along the Varandh ghat section of national highway 965DD have been identified as critically unstable, while six others have been identified as unstable; according to a study by researchers from Savitribai Phule Pune University (SPPU) and Banaras Hindu University (BHU).

Published on September 1, 2026 in Transportation Infrastructure Geotechnology, the study assessed 16 slopes along the Varandh ghat corridor using field investigations and established methods to understand how and why individual slopes can fail. Of the 16 slopes studied, only one was found to be stable; whereas five were found moderately stable; six (VS2, VS9, VS11, VS12, VS14 and VS16) unstable; and four (VS4, VS5, VS10 and VS13) critically unstable. The critically unstable locations were largely concentrated in the central and upper sections of the corridor. The researchers said five slopes were close to the boundary between stable and unstable conditions. These slopes could become more vulnerable with continued weathering, heavy rainfall, water entering the rock mass, or further excavation.

One of the key findings was that the condition of the rock itself wasn’t the only factor determining the danger. Most of the locations had moderate to good-quality rock. However, fractures and cracks within the rock were oriented in ways that could allow blocks to slide, fall or topple from the slope face. The study found that wedge-shaped rock failure was a possible risk at 11 out of the 16 locations; while planar sliding was possible at 10 locations; and toppling at eight. At several locations, more than one type of failure was possible, making the slopes particularly complex. The study’s hazard assessment showed that more than half of the 16 slopes fell in the ‘poor’ or ‘very poor’ hazard categories. Importantly, some slopes with reasonably good rock quality still recorded high hazard levels because of rainfall, water seepage, weathering and drainage conditions.

Lead researcher Amit Shirke of the SPPU said, “The objective of the study was not to oppose infrastructure development but to ensure that construction in the western ghats is backed by detailed geological and geotechnical assessment. There is need for continuous monitoring because conditions can vary significantly from one road-cut slope to another.”

Bhavana N Umrikar, head of the department of geology at the SPPU, said that the geological and environmental complexity of the western ghats makes it important to consider geological, landform, engineering and water-related factors while planning infrastructure.

Co-researcher D P Mohanty of the SPPU said that rock-slope failures are generally linked to a combination of cracks and fractures, the shape of the slope, and water entering the rock. Understanding the specific cause of instability at each location is therefore important.

Maria Asim of the BHU, another co-researcher, said that slope-risk management should focus on identifying vulnerable locations before failures occur. She highlighted regular monitoring, early-warning systems, and awareness among local communities and other stakeholders as important measures.

Among the recommendations, the researchers have suggested that the slopes identified as vulnerable should not be treated uniformly. Depending on the condition of each location, measures could include improving drainage, removing loose rocks, and installing rock bolts or anchors where necessary. Surface protection may also be required at highly weathered and fractured sections. The researchers have further recommended regular inspection, particularly after the monsoon, to check for new cracks, changes in water seepage, weathering and movement of loose rock blocks. The researchers have called for further testing, rainfall-threshold studies, and computer-based modelling to improve the prediction of slope failures and help authorities plan long-term safety measures along vulnerable mountain roads.