Tolerable Settlement Research Articles

Shallow Foundations for Tall Structures in Florida

The use of shallow foundation systems with measurable but tolerable settlement of major building complexes constructed in the Miami, Florida area is demonstrated by three case histories, The Omni International, Turnberry Isle Complex, and the James L. Knight Convention Center. Subsurface exploration programs included conventional borings, static cone penetrometer tests, and large diameter coring of soft limerock zones. The compressibility of the subsurface materials can be confidently estimated through the proper interpretation of the field test results and the results of full scale instrumented preloads at geologically similar sites. High-rise structures can be constructed on shallow foundation systems with acceptable settlement behavior. The structures will have measurable but tolerable settlements. Settlements tend to become intolerable when the structures exceed 10 to 15 stories. However, effective precompression of the underlying soils by preloading can be achieved within a few weeks. This reduces total and differential settlements to tolerable limits and makes shallow foundation systems economically desirable for high-rise structures.

Tolerable Settlement of Buildings

Current practices and concepts for establishing the tolerable settlement of buildings are reviewed. The role of differential settlement is emphasized. Most current tolerance limits are shown to be based on the works of Skempton, MacDonald, Polshin, and Tokar. These criteria are compared with field observations of settlement and damage. A simple beam analogy, which was proposed by Burland and Wroth, is used to illustrate factors that influence tolerable settlement. The effects of the critical tensile strain of the structural materials, the L/H ratio of the building, the relative stiffness of the structure in shear and bending, the longitudinal stiffness of the foundation, and the shape of the settlement pattern are demonstrated. Different criteria are required for different types of structures. The allowable settlement is smallest for cases in which the settlement curve is concave downward.

Vertical Stress Chart for Rigid Circular Foundations

Vertical stresses in soil mechanics and foundation engineering are of interest in settlement analyses of soils, for checking overstressed zones in soil and in evaluating bearing capacity of rigid, circular pier foundations and piles based on a prescribed magnitude of tolerable settlement. This note presentes a method to facilitate a quick assessment of vertical normal spatial stresses in soil along the center line from a rigid circular foundation placed on the ground surface.