Often, an apparently compatible relationship between mat and soil deteriorates due to the plague of construction details and the design-construction relationship. This paper reviews subgrade reaction in case studies of four landmark buildings in Houston. Concepts related to mat foundation analysis using the finite element method are discussed to acquaint the practitioner with the related soil-structure interaction concepts. Also included is an examination of structural considerations in connection with mat foundation design.

SP152 Design and Performance of Mat Foundations is the first state-of-the-art review. Within its 267 pages, you will find informative papers dealing with mat foundations and its interaction with the superstructure, design considerations for soil-structure interaction problems, subgrade reaction, subgrade modeling, foundations for tall buildings, mass concrete pour techniques for the mat foundation geotechnical-structural interactions for innovative mat design, and large mat on deep compressible soil. Obtain your copy of SP-152 and see how the science has progressed to the use of present day technological advances. All captured in the 10 technical papers from distinguished international engineers.

Describes three innovative mat foundation designs and the close interaction required between the structural engineer and the geotechnical engineer. The significance of load deformation prediction reliability in the three different soil profiles is illustrated. The cases reviewed include a three-story office building with single basement build on a mat over peat; a 26-story apartment building with basement built on a modified mat in a thin dense sand stratum over soft clay; and a 19-story hotel with two basements built on a mat in a sand layer over medium clay. The mat of the 19-story hotel was supplemented with selective high capacity piles at the column locations designed to ultimate soil capacity at working loads and utilized to reduce both mat settlement and design mat thickness. The instrumentation used to confirm design assumptions in the three cases is briefly described.

Over the years, methods of analysis, design, and construction for structures have gone through major modifications; however, the use of mat foundations to support building loads is ancient and very well documented. The mat foundation is a result of merging individual spread footings which support column loads and rest on soil strata, piles, or piers. The size of the mat foundation partially or fully covers the footprint of the tower structure and usually extends well beyond its footprint. The bearing strata of a mat foundation is determined by the allowable soil bearing capacity, the mat performance in terms of its settlement, and its impact on the structural behavior of the superstructure. This paper discusses the analysis of a soil-supported mat foundation with emphasis on the variation of both structural members and soil properties as they impact design. The different parameters considered in this study are structural property of concrete mat; variation of modulus of subgrade reaction, both in spatial and time domain; and variation in the loading pattern imposed on the mat. An interaction between a realistic superstructure having a perimeter tubular structural frame and a corresponding mat foundation is investigated for different parametric values, such as the stiffness of structural frame and soil properties.

The St. Luke's Medical Tower is the Texas Medical Center's tallest building and Houston's tallest building to open the 1990s. The combination of the following unique foundation features reduced development costs by over $1,000,000: (1) tallest soil-supported building on shallow foundations in the Southwest; (2) temporary dewatering system designed to function as the permanent system; (3) excavation-bracing system designed to form the permanent basement wall and only individual braces were temporary; (4) basement walls esigned to accept loads from future contiguous towers; (5) drilled pier soldier piles installed with polymer drilling fluid (the first use on a major Texas project); and (6) drill pier soldier piles installed in accordance with the new American Concrete Institute Standard Specification for the Construction of Drilled Piers (ACI 336.1-89), the first known use of the specification. The factored load condition was considered fictional in foundation, and basement wall design in that factored load-concrete-subgrade compatibility was not achieved. Significant cost savings was achieved by allowing the geotechnical engineer to be part of the design team beginning with project concept studies and extending throughout underground construction. The geotechnical engineer and the team developed feasible foundation schemes that could be integrated into construction needs, instead of relying only on specialty design builders.