The rapid growth in the rate of construction of multi-storey blocks has been an important feature of the building industry over the past fifteen years. Much of this construction has occurred in areas underlain by the cyclothemic rocks of the Coal Measures. The aniso-tropic properties of this sequence lead to rapid horizontal and vertical variations in foundation conditions, which must be assessed in selecting the type and depth of foundation and the allowable bearing pressure. Special problems occur in areas which have been undermined by shallow mineral workings. Such sites require special investigations, careful evaluation of the site conditions and the design of appropriate foundations. The desirable approach in many instances is to plan developments on a large scale so that the greatest economic advantage may be taken of the best site conditions.
During the past fifteen years there has been a rapid increase in the rate of construction and size of multi-storey blocks for dwellings and commercial development. Information on the total numbers of such blocks constructed in the United Kingdom per year is not conveniently published but is probably of the order of four to six hundred. Of this number, possibly one-third are constructed annually in areas underlain by Coal Measure rocks. This represents a national investment of about £70 million per year; the importance of the Coal Measures as a foundation is, therefore, underlined. This trend in building development reflects the increasing scarcity and cost of urban building land, coupled with the desire to confine