When shallow mine workings are present there is a risk to both future and existing developments from surface subsidence. We carry out remedial work to stabilise the mine working; the most cost effective way is for this to be done prior to development. We have however carried out innumerable contracts treating the mine workings beneath existing buildings.
The Groundshire treatment consists of forming a grout curtain in the workings and overlying rock strata around the areas requiring protection.
Within the grout curtain we drill primary and secondary infill grout holes to the base of the old workings on a suitable grid pattern. Grout is injected under the appropriate pressure to fill the workings and associated collapsed strata, thus stabilising the ground and preventing subsidence.
We at Groundshire have the expertise and experience to design appropriate treatment grids, which can often result in significant cost savings.
Construction may then be undertaken with confidence. All our work is in line with the recommendations of CIRIA Publication No. 32, “Construction Over Abandoned Mine Workings”, as well as Coal Authority, NHBC and Local Authority planning requirements.
Further applications of this technique are the consolidation of rubble filled cellars or back filled quarries, whilst empty basements, air raid shelters, disused petrol storage tanks, redundant bridges and tunnels may be grouted with little or no drilling involved.
We have extended the consolidation techniques to Permeation Grouting, which proved highly successful at several harbour redevelopments, most recently at Whitehaven and Seaham Harbours. Where used, this technique strengthens the existing harbour and quay walls, as well as significantly reducing their permeability, allowing water to be impounded and marinas formed.
Our range of drilling methods includes;
Rotary open hole using rock rollers, drag bits, PCD bits to 200mm diameter
Rotary percussive ‘top hammer’ Krupp drill units
Down the hole hammers
Overburden symmetrix casing systems 100mm and 150mm
Rotary coring 412 size air or water flush
Installation of permanent or temporary casing
Restricted access working spaces using 750mm wide mini rigs
Working in artesian water or gas conditions using well head control systems