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Build Simple Open House May 11, 2019 in Albuquerque, NM
Intern Christian Ernstsen is visiting after building earthbag in Asia and Africa. Come meet him and view our improved testing frame and current research. Try out building both modular and solid wall contained earth, and see how solid CE can be used to reinforce adobe and other materials.
Drop by 2909 Rio Vista Court SW, 87105 between noon and 4 pm on Saturday, May 11. Tours will include the historic Leon Watson home and discussion of evaluating bracing for all types of earthen walls.
First Engineering Lab Shear Tests of Cured Earthbag
Four large contained earth (CE) walls were tested at Santa Clara University last year. Two student teams directed by professor Tonya Nilsson found that inserted rebar
anchored and spliced with a small plug of concrete was buildable and performed well (34 Strong, Huebner Jensen).
The SCU test results are understated due to the lack of plaster, and due to the separation of their bond beams when special rebar clamps failed from uplift. Horizontal forces on narrow wall lengths between corners and openings cause well-bonded panels to rotate, breaking into separate segments. Although earthbag has continuous wire to resist segmentation, some type of continuous tensile reinforcement from footing to bond beam will be critical for every earthbag building in seismic risk regions to maintain contact between the dried earthen matrix and the barbed wire ‘velcro’ between layers.
Structural analysis by the team testing inserted rebar without any anchoring showed that since the walls were highly flexible, small buildings with strong soil would be strong enough to resist earthquake forces (31 Rodriguez, Stein, Darby). While other earthen wall types, including cob tested by other SCU teams, are brittle, after earthbag walls pass yield point they resist much higher forces without cracking or losing material. The teams deduced a seismic resiliency factor of 6 or more for their walls, in contrast to factors of 1- 2 for most earthen walls.
Plastered and Unplastered Shear Testing comparing 60% scale to 80% scale Underway by BSI
BSI is currently performing shear tests to compare the weak SCU unplastered wall results to the strength of typical plastered construction.
Test Results Prove Earthbag can be Stronger than Sandbags
Funded by the builders of more than a thousand needed homes in Nepal, BSI proved that strongsoils increase earthbag wall strength. Rebar embedded in soil is stronger than rebar on wall edges. Rebar anchored at the base makes walls stiffer to reduce damage by strong earthquakes.
Read the report Estimated-Shear Strengths-CE (1.7 MB pdf).
Earthbag is Spreading
Since 50 earthbag buildings survived in the areas devastated by Nepal’s 2015 quakes, Good Earth Global trained and other builders gave work experience to thousands of builders. The Nepali government included earthbag in their residential code for rebuilding.
The government of Nepal wants more test results before allowing needed schools and clinics to be built out of earthbag. BSI continues research into strengths of contained earth for high seismic risk.