Compositional and shear strength characteristics of a spoil heap at Littleton colliery, Staffordshire

Abstract

Since the Aberfan colliery spoil heap disaster the National Coal Board has sponsored a research programme on existing British spoil heaps. This thesis is part of that programme and considers an unburnt, unwashed, conical spoil heap at Littleton Colliery, Staffordshire. Tipping took place from about 1900 to about 1940 and records relating to discard constituents are very sparse. A slope failure in 1970 instigated this research project which is aimed at elucidating the compositional and shear strength characteristics affecting the stability of spoils in the Littleton area. Mineralogical, chemical and shear strength analyses were carried out on samples from the spoil heap and contributing underground measures. The absence of an underground measure from the original list of contributors was detected during the mineralogical and chemical analyses. This measure was identified, showing the value of such analyses in clarifying the history of such ancient tips. Mineralogy was found to correlate well with the chemical analyses of the samples, and the analyses of the spoil heap materials correlated well with those of the underground materials. No evidence of leaching or weathering was found in the tip. The shear strengths of the materials tested correlated well with the mineralogical and chemical analyses, the unusually low shear strengths of Littleton Spoil Heap No. 1 being reflected by high clay mineral contents. The slope stability problems occurring in the spoil heap are believed to be related to the Maclane Tippler method of spoil placement which has resulted in the spoil heap material approaching or achieving residual shear strength. A perched water-table within the spoil heap has initiated instability, giving rise to a deep-seated, circular slip.