![]() |
|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]()
|
![]() Once an area of ground has been treated and pore pressures have largely dissipated, repeated applications ("passes") of shaking caused by controlled blast sequences (video (9113 kb)) causes additional settlement depending on soil density and stiffness. The first pass destroys any bonds existing between cohesionless soil particles due to aging and other geologic processes, and causes the majority of settlement within the soil mass. Subsequent passes cause additional settlement by cyclic straining. As a result, surface settlement and increased soil resistance to cyclic loading will be caused by the blasting. Experience has indicated that the degree of ground improvement obtained by blasting depends on the initial density of the granular subsoils. The density of loose deposits can typically increase considerably to relative densities in the range of 70 to 80%, whereas soils with initial relative densities of 60 to 70% can only be densified by a small amount. Our experience also indicates that EC generally causes volume changes equal to or in excess of what would be anticipated under design levels of earthquake shaking, as described in the attached reference paper by Gohl et al (2000). |
Home | Contact Us |