Chapter 7 Mat Foundation
Chapter 7 Mat Foundation
7.1 Introduction What's mat foundation-A mat foundation is a large concrete slab used to interface one column,or more than one column in several lines,with the base soil. Application of mat foundations-Mats are used to support on-grade storage tanks,several pieces of industrial equipment,silo clusters,chimneys,and various tower structures
7.1 Introduction ❖ What’s mat foundation-A mat foundation is a large concrete slab used to interface one column, or more than one column in several lines, with the base soil. ❖ Application of mat foundations-Mats are used to support on-grade storage tanks, several pieces of industrial equipment, silo clusters, chimneys, and various tower structures
7.1 Introduction Suitable conditions of mat foundation -Where the base soil has a low beating capacity and/or the column loads are so large that more than 50 percent of the area is covered by conventional spread footings. -For deep basements. -where the settlements may be a problem. Advantages of mat foundation -there is a stress compensation from excavated soil so that the net increase in pressure is controlled. -provide a water barrier when basements at or below the GWT
7.1 Introduction ❖ Suitable conditions of mat foundation ❖ -Where the base soil has a low beating capacity and/or the column loads are so large that more than 50 percent of the area is covered by conventional spread footings. ❖ -For deep basements. ❖ -where the settlements may be a problem. ❖ Advantages of mat foundation ❖ - there is a stress compensation from excavated soil so that the net increase in pressure is controlled. ❖ -provide a water barrier when basements at or below the GWT
7.2 Types of Mat Foundations -flat plate -plate thickened under columns -waffleslab (beam and slab) -plate with pedestals -basement walls as part of mat
7.2 Types of Mat Foundations ❖ -flat plate ❖ -plate thickened under columns ❖ -waffleslab (beam and slab) ❖ -plate with pedestals ❖ -basement walls as part of mat
7.3 Bearing Capacity of Mat Foundations Requirement of design -to limit settlements to a tolerable amount. -stable against a deep shear failure,which may result in either a rotational failure,or a vertical(or punching)failure. Determination of bearing capacity -the beating-capacity equations. -penetration tests(e.g.,SPT,CPT). -laboratory unconfined(or confined triaxial)compression tests. -pressuremeter -borehole shear
7.3 Bearing Capacity of Mat Foundations ❖ Requirement of design ❖ -to limit settlements to a tolerable amount. ❖ -stable against a deep shear failure, which may result in either a rotational failure, or a vertical (or punching) failure. ❖ Determination of bearing capacity ❖ -the beating-capacity equations. ❖ -penetration tests (e. g. , SPT, CPT ). ❖ -laboratory unconfined (or confined triaxial) compression tests. ❖ -pressuremeter ❖ -borehole shear