Part 4Part 4Part 4Part 4

MITIGATION OF MITIGATION OF FOUNDATION FOUNDATION

PROBLEMS ON PROBLEMS ON EXPANSIVEEXPANSIVE

SOILS SOILS

Schemes employed to Schemes employed to combat expansive soilscombat expansive soils

Solutions for Expansive Soil ProblemsSolutions for Expansive Soil Problems

An alternative method for handling highly An alternative method for handling highly expansive soils using mass grading is to expansive soils using mass grading is to cover them with 15 feet of select non-cover them with 15 feet of select non-expansive fill, as sketched here.expansive fill, as sketched here.

Theory of Theory of Drilled PiersDrilled Piers

Drilled piers and Drilled piers and grade beam grade beam foundation systemsfoundation systems must extend below must extend below the zone of the zone of seasonal seasonal moisture variationmoisture variation, , which can be difficult which can be difficult to predict with any to predict with any meaningful certainty, meaningful certainty, because it often because it often depends on depends on landscape wateringlandscape watering by the homeownerby the homeowner

Drilled piersDrilled piers are intended to extend are intended to extend below the below the zone of seasonal moisture fluctuationzone of seasonal moisture fluctuation, , holding the structure downholding the structure down, when lightly , when lightly loaded elements are subjected to moisture loaded elements are subjected to moisture absorption and heaveabsorption and heave. .

Many factors can contribute to Many factors can contribute to poor foundation poor foundation performanceperformance in areas underlain by in areas underlain by expansive soilsexpansive soils

Most of these are beyond the control of the Most of these are beyond the control of the geotechnical engineer who was associated with the geotechnical engineer who was associated with the foundation recommendations foundation recommendations

Geotechnical engineers must design redundant Geotechnical engineers must design redundant support systems; sufficiently robust so as to resist support systems; sufficiently robust so as to resist long-range human and environmental factors beyond long-range human and environmental factors beyond their control, such as water leaks and abnormally wet their control, such as water leaks and abnormally wet weather. weather.