Date of Graduation

5-2024

Document Type

Thesis

Degree Name

Master of Science in Civil Engineering (MSCE)

Degree Level

Graduate

Department

Civil Engineering

Advisor/Mentor

Coffman, Richard A.

Committee Member

Barry, Michelle L.

Second Committee Member

Wood, Clinton M.

Keywords

compaction; Harvard Miniature Compaction Apparatus; modified energy; Proctor compaction; reduced energy; standard energy

Abstract

Compaction with the Harvard Miniature Compaction Apparatus (HMCA) was investigated to develop a method that can be used in place of typical Proctor compaction. Advantages for compaction with the HMCA include the need for less soil for testing and less preparation time. To investigate the potential for HMCA as a replacement, soil specimens were compacted with both the Proctor and HMCA methodologies at equivalent energies. For this testing, the testing included modified energy (56,250 ft-lbf/ft3 [2693 kN-m/m3]), standard energy (12,375 ft-lbf/ft3 [593 kN-m/m3]), and reduced energy (6188 ft-lbf/ft3 [296 kN-m/m3]). Because there is a difference in compaction methods (impact for Proctor compaction and kneading for HMCA), the energy applied to the specimens was computed differently. The established equation for the energy for Proctor compaction included the weight and drop height of the drop hammer. An equation was developed for the HMCA using the potential energy of the spring that was encompassed within the HMCA tamper rod. The spring constant for each tested spring was determined and then the required displacement to achieve modified, standard, and reduced energy was calculated. After the spring was tensioned properly, a minimum of five specimens were prepared at each energy level for each compaction method for two fine-grained soils. Based on the similarity of the results (less than one percent difference), there is potential for the HMCA to be used as a replacement for Proctor compaction at low energy levels (standard or reduced energy). However, there was difficulty in replicating the results at modified energy when using the HMCA (percent difference between the two compaction methods as large as 40 percent). Therefore, the Proctor compaction method should continue to be used for testing that requires modified compaction.

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