Location

New York, New York

Session Start Date

4-13-2004

Session End Date

4-17-2004

Abstract

Hollóháza is a little mountain village in North-East Hungary. Following a long wet period in 1999 the largest mass-wasting event of the 20th century occurred. The total volume of mobilized earth material was over 1.5 million m3. One major concern of problem management was that the value of the damaged infrastructure was less than the total costs of restoration and stabilization, while the natural potential of the settlement is outstanding. After investigating the causes of the landslide the cheapest effective solution had to be found. Hollóháza is surrounded with the residuals of a 4-6 km diameter volcanic caldera. The settlement was established in the natural depression of the caldera where the bottom andesite is covered with varying depth of rhiolite-tuff and clayey marine deposits with the tilt of 10-25 degree toward the valley. The rhiolite-tuff that is originally fallen into seawater has a high bentonite content, montmorillonite content is close to 60%. The covering clay layers has almost 40% illite-montmorillonite content. Water from precipitation moves toward the village from every direction both on and bellow surface of the steep slopes. Slope stability analysis was conducted using the GEOSLOPE software. The goal of our investigation was to identify those areas where only by lowering the groundwater levels the stability can be achieved with a reasonable factor of safety. Our analysis proved that out of the three exposed location 2 can be stabilized by managing the groundwater level, while in the third case other engineering solutions are also needed. Due to limited financial resources the stabilization of the former two one is accomplished by lowering the groundwater levels using drains and horizontal wells. The measurements prove that the movement have ceased due to these installations. Besides the slope stability assessment the landslide risk mapping of the area was also accomplished. The risk mapping incorporates the landslide hazard mapping of the site and the damage potential of the settlement. In risk terms high values are the results of significant probability of mass movement and the cost of the potential damages caused. The risk reduction of the stabilizing intervention is the result of the decrease of the former factor while the value of the infrastructure may be considered constant.

Department(s)

Civil, Architectural and Environmental Engineering

Appears In

International Conference on Case Histories in Geotechnical Engineering

Meeting Name

Fifth Conference

Publisher

University of Missouri--Rolla

Publication Date

4-13-2004

Document Version

Final Version

Rights

© 2004 University of Missouri--Rolla, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

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Apr 13th, 12:00 AM Apr 17th, 12:00 AM

Geotechnical Investigation of the Hollóháza Landslide Case

New York, New York

Hollóháza is a little mountain village in North-East Hungary. Following a long wet period in 1999 the largest mass-wasting event of the 20th century occurred. The total volume of mobilized earth material was over 1.5 million m3. One major concern of problem management was that the value of the damaged infrastructure was less than the total costs of restoration and stabilization, while the natural potential of the settlement is outstanding. After investigating the causes of the landslide the cheapest effective solution had to be found. Hollóháza is surrounded with the residuals of a 4-6 km diameter volcanic caldera. The settlement was established in the natural depression of the caldera where the bottom andesite is covered with varying depth of rhiolite-tuff and clayey marine deposits with the tilt of 10-25 degree toward the valley. The rhiolite-tuff that is originally fallen into seawater has a high bentonite content, montmorillonite content is close to 60%. The covering clay layers has almost 40% illite-montmorillonite content. Water from precipitation moves toward the village from every direction both on and bellow surface of the steep slopes. Slope stability analysis was conducted using the GEOSLOPE software. The goal of our investigation was to identify those areas where only by lowering the groundwater levels the stability can be achieved with a reasonable factor of safety. Our analysis proved that out of the three exposed location 2 can be stabilized by managing the groundwater level, while in the third case other engineering solutions are also needed. Due to limited financial resources the stabilization of the former two one is accomplished by lowering the groundwater levels using drains and horizontal wells. The measurements prove that the movement have ceased due to these installations. Besides the slope stability assessment the landslide risk mapping of the area was also accomplished. The risk mapping incorporates the landslide hazard mapping of the site and the damage potential of the settlement. In risk terms high values are the results of significant probability of mass movement and the cost of the potential damages caused. The risk reduction of the stabilizing intervention is the result of the decrease of the former factor while the value of the infrastructure may be considered constant.