Project:

Geotechnical Investigation of open pit sidewall failure at the Skorpion Zinc Mine in Namibia

Date:

May 2018

Location:

Rosh Pinah, southern Namibia

Client:

Vedanta Zinc International

Business Sectors:

Mineral Resources

Services:

• Geotechnical Engineering
• Structural Geology
• Monitoring & Instrumentation
• Hydrology
• Risk Assessment and Management

Project Objectives:

A large planar slope failure occurred on the pushback of the open pit. The failure involved approximately 400,000t of rock and covered an area approximately 150m wide and 70m high.

Although monitored by Movement and Surveying Radar (MSR) no alarms were triggered.

An excavator working at the toe of the failure was partially covered by fall material but there were no personal injuries.

This project was delivered in collaboration with LTMS and GI Panel Expert Joe Burke (Avoca Geotech Ltd).

Our Role:

A Geotechnical review of the failure was conducted to understand the possible causes of the failure and propose options and measures to re-establish safe mining for the pit 112 project going forward (extend from 200 to 300m BS)

• This involved assessing the failure mechanism and current stability of the loose rock mass.
• Developing options for rehabilitating the sidewall.
• Evaluating the monitoring systems particularly the failure to warn of the risk.
• Establish a more robust program of monitoring the pit.
• Carry out a Gap Analysis of the pit management.
• Develop a program of proactively managing the pit using design, blasting, sequencing of extraction, hydrology, monitoring, operator engagement and modelling.

Picture: Sidewall failure at Skorpion Zinc Mine – planar failure on parallel structures in weak Arkos rock.

Geoscience Ireland Contact:

Brendan Morris – b.morris@ltms.ie