nmwdoc 2014 conference flood control dams on basalt foundations – two case studies dan aguirre, pe...
TRANSCRIPT
NMWDOC2014 Conference
Flood Control Dams on Basalt Foundations – Two
Case Studies
Dan Aguirre, PE - Wilson & CompanyCraig Hoover, PE - Bohannan Huston Inc.
May 7, 2014
Contents/Agenda
▲Las Ventanas Dam – Craig Hoover▲Boca Negra Dam – Dan Aguirre
Las Ventanas Dam
Las Ventanas Dam
Las Ventanas Dam
Las Ventanas Dam
Las Ventanas Dam
▲Site Geology– West mesa formed by up faulted blocks– Followed by sedimentation– Followed by volcanic eruptions– Olivine basalt flows characterize the site– Basalt is exposed at the surface in many places– Covered with up to 12’ of sand in other areas
Las Ventanas Dam
▲Site Geology/Field Investigation– GeoTest Inc.– Core drilling indicated the depth of basalt was
typically 30 feet thick– At least one core found the basalt to be more
than 50 feet thick– Material beneath the basalt – calcareously
cemented sand and gravel of the Santa Fe Formation
Las Ventanas Dam
▲Site Geology– Basalt – gray to black to black-red– Vesicular to varying degrees– Areas where highly vesicular the vesicles
(cavities) were large and appear interconnected– Singular joints and fractured zones were
observed in the basalt cores
Las Ventanas Dam
▲Site Geology– Joints either bare or coated with carbonate
deposits– Fracture zones 1 to 2 feet thick– During coring water was lost in most corings-
attributed to interconnected vesicles– Air found blowing from one boring after
completion of drilling and varied with the atmospheric wind indicating fractures connected to the surface
Las Ventanas Dam
▲Foundation for a Dam? – Highly variable surface and depth to rock– Highly vesicular areas– Apparent high permeability– Water lost during coring indicating
interconnectedness of vesicles– Fractures connected to the surface
Las Ventanas Dam
▲Foundation Treatment and Cutoff
Las Ventanas Dam
▲Foundation Treatment and Cutoff
Las Ventanas Dam
▲Foundation Treatment and Cutoff
Las Ventanas Dam
▲Foundation Treatment and Cutoff
Las Ventanas Dam
▲Cutoff Trench and Cement Treated Slurry
Las Ventanas Dam
▲Cutoff Trench and Cement Treated Slurry– Flowable mixture of Portland cement,
aggregates, admixtures (water reducing and air entrainment) and water
– 28 day compressive strength 500 psi to 1,000 psi
– Placed to full depth of trench
Las Ventanas Dam
▲Foundation Treatment Cement Treated Soil
Las Ventanas Dam
▲Foundation Treatment Cement Treated Soil– Scarify soil to full depth– Dampen soil– Add cement per mix design– Mix and add water to optimum moisture content
minus 1% to plus 2%– Compact to 96% maximum density
Las Ventanas Dam
▲Foundation Treatment Cement Treated Soil
QUESTIONS?