Land instability can harm human health, property, infrastructure and the environment. PBA has considerable experience in conducting investigations to identify the causes of movement, assessing and mitigating risk and making unstable land safe to bring it back into productive use.
PBA holds the industry recognised national databases of non-coal mining and natural cavities that can be searched to provide initial information to determine the geohazard setting of sites.
Land instability can include:
Natural cavities: sinkholes and caves are formed by the dissolution of soluble rock, such as chalk and limestone. Gulls and fissures are formed by cambering. Ground instability results from movement of the loose materials contained within the cavities often triggered by water. Understanding the cavity model is key to the investigation strategy.
Mining cavities: degraded mines may result in hazardous subsidence (crown holes). Climatic conditions and water escape can trigger subsidence over mine entrances and workings. To investigate the cause often requires caution, risk assessment and a specific investigation strategy sometimes involving specialist downhole equipment (e.g. laser survey).
Failing slopes and cliffs: slopes can become over-steepened or undercut by natural processes, such as sea erosion, or by man such as by quarry extraction or engineering works. Poor drainage control, vegetation control and erosion, for example, can lead to slope failure. Our understanding of all land instability types and drivers enables us to generate practical, sustainable solutions.