APPLICATION OF THE JOINING PILE FOR FOUNDATIONS ON EXPANSIV CLAYS AND ROCKS

Abstract

The expansive clays occupy about 20 per cent of a building area in the United States. Similarly the problem is also significant in Africa, India, Asia, Australia and partly in Europe. Expansive clays are present on many areas of the hot temperate zones, also in many enclaves of soils and rock eluvia containing minerals belonging to the groups of montmorillonite, illite etc. Identification of expansive clays ability and methods of its investigations were described in early papers Jaremski J.:(1994),Jaremski J.:(1995),O’Neill, M.W., N. Poormoayed 1980. Losses caused by soil swelling in building industry are comparable to losses caused by environment. Usability of the joining pile on the expansive soils gives an important advantage. So-called joining piles represent a new idea of piling where the basic part of the pile (the base of the high-diameter pile) is located at the depth of the foundation occurrence. Depending on the ground conditions, in many pile structures the basic part of loading is carried by the pile base. The joining pile is an example of such piles. It is a combined foundation including the base made in the soil, and the post elements (a bundle of piles or micropiles) joining the base with the girt. In the case of swelling soils, capacity of the system of piles or micropiles bundle is making a base joining them to make up the role of the anchoring pile. The joining pile has a relatively small lateral surface
There are many reasons for which the received results should be compared with the results of research conducted in other countries as it makes possible to know the geological properties of several kinds of soils. Author compared the properties of many swelling soils and soft rocks. Considering mainly on their origin and mineralogy. The worked-out associations permitted to compare the phenomenon of swelling occurring in different soil media and to also analyze the researches made in various countries and at the same time, to including the exploitation problems of building founded on expansive soils and including the placement
moisture -water content and to determine the value of maximum swelling. The process of swelling occurring in soil and rock media brings about the changes in volume which are the reasons for settlement (shrinkage) or displacement of the foundation upwards (swelling). The recognition of the ability of swelling of some cohesive soils is of great importance for the selection of foundation for building objects and for determining the exploitation conditions of objects and for site planning. The range of swelling should be taken into consideration in order to determine the reasons of cracking and failures of existing buildings. In the rock media and particularly in their weatherings e.g. in marl eluwium, swelling brings about continuous changes in fissures or in spaces between larger rock fragments, exerting an influence on the strength of a medium , and also leads to the continuous variations of the medium which is debris under extreme humidity conditions and which in proper, changes in moisture content, preceded by the periods of drought, becomes similar to cohesive soil. The phenomena of swelling and shrinkage may them bring to the extremal states. First of all it should be stressed, that the phenomenon of swelling occurs only in the aeration zone identified with zone of fluctuation of the level of underground water and foundation layer. It has been explained that there is maximum swelling or soil shrinkage if near the outer surface of the ground soils (or rock weathering) have minerals of distinctly high negative charges montmorillonite, illite, baidelite et. and when the environmental conditions of soil allow moisture to change the essential variations in maximum swelling occurred in the plan area of impended buildings. According to the present world knowledge much has been already done for better understanding of the processes occurring within expansive clays. This problem is, however, considered as an extremely complex one and it seems impossible to forecast and evaluate the subsoil movements (for needs of practical engineering).