According to the standard code, the minimum acceptable soil compaction for fill under a structure is _________ percent of maximum density.

The minimum acceptable soil compaction for fill under a structure is 90 percent of the maximum density. This standard is crucial because proper compaction is essential for ensuring the stability and longevity of the structural foundation. Achieving 90 percent density minimizes the likelihood of settlement and movement that can lead to structural issues in the future.

Compaction helps to eliminate air pockets and higher moisture content, providing a solid base that can support loads effectively. This level of compaction allows for enough stability without reaching excessive compaction levels, which could lead to diminishing returns or increased risk of soil rupture. Thus, ensuring the fill material is compacted to at least 90 percent of the maximum density is a key practice in excavation and grading operations.