Massachusetts Construction Supervisor License (CSL) Practice Test

Which foundation material has the greatest allowable bearing pressure?

1. Dense gravel

2. Foliated bedrock - slate

3. Stiff silty clay

4. Dense glacial till

The correct answer is: Dense gravel

The material with the greatest allowable bearing pressure among the options is dense gravel. This is primarily due to its physical properties, which include high density and excellent drainage capabilities. Dense gravel allows for the transfer of loads effectively, thereby supporting structures with minimal settlement or movement over time. The cohesiveness and angularity of the gravel particles contribute to its strength and stability, allowing it to resist lateral forces better than softer materials. This makes dense gravel particularly suited for various types of construction, forming a strong base for foundations. While the other materials listed—foliated bedrock (like slate), stiff silty clay, and dense glacial till—also have significant bearing capacities, they generally do not match the performance of dense gravel in terms of load distribution, drainage, and stability. For example, foliated bedrock can be stable but may have natural fissures or weaknesses that can compromise its load-bearing capacity. Stiff silty clay may offer good support but is susceptible to moisture changes that affect its strength. Dense glacial till can be variable in composition, which might impact its load-bearing properties. Therefore, dense gravel is typically favored for its superior bearing pressure.