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Performance of Embedded, Base-anchored 'Cut-bag' Reinforcement in Contained Earth Earthbag Walls

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Earthbag walls with conventional inserted rebar reinforcement are too highly deformable for many projects in high seismic risk areas. Two 0.9 m (3') x 1 m (3.3') wide 60% scale sample walls were built to test a novel embedded but base-anchored 'cut-bag' rebar technique. Under static horizontal force these plastered samples showed that better connection at the wall base of embedded rebar increased both strength and stiffness 22% more than inserted overlapped rebar and decreased deformation by 66% despite using weaker fill soil.
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Performance of Embedded, Base-anchored ‘Cut-bag’ Reinforcement
in Contained Earth Earthbag Walls
Patricia N. Stouter, June 2021


Abstract        
               
 !
        "        
#$%&'()*+
 '((,*  -%.  !         
  ,)    /  0    1    
!!2
 #33.!!
         --. !      "  
 !! # !
04
Keywords:   !"!"#$"%$
&%$"
INTRODUCTION
'"&("&)* 
""#   & 
+"#, +-   .//0,!"$" $
"" 1)2$
&+3./45,+33""
6".//0,&&&
-"+-!,"$ &"
&   "   ) 7   )   - 
)""")
8 ") & "   $    "" 
1
)
&"9):;
"            "  (* 
<2+=./4>,
3&"<  &?"""! 
".//>""))
"2)"& ")  !
&+@./4/,
)" )
    "  1  " &  
  +  ././ A,       "  "    +3, :  
77"8
-&)2 "
")2+B .//>,""($ *
+=./4>, ")2
""+ ././4/,""""-!
&")2)& 
"$")22"& '"&
")    & "  -:) +-:, "
 $ $&$< -!  8 ) " ") " 
3&    "       
)&8& &4/4#+..>>,
  &  "<   +  6    =$""  ./4>  5/,  
""""5/C
+ 55D 3<    ./4> 5/, ) )  
""#")+3<5E,
3 &#.E/+4/F,
&" -:  4 +55*,     "$
2"#" " +,"
#    "&:& $
"     &   2 "  +  ./.4 5A,   
 "& ")&
"             "        $"
)     ("*      "    &       $
"     & "     
  "  ($*    "  "               
&&            
#+./.4A,
')" &$"&
2
:)*)"":) &
G/C  &$'"/H. +HA &,  .5/ +HF, "#
+I4,")""""+././,
'"  "2""&$  
"  " "    & ""*

EXPERIMENTAL WORK
Materials
"  2   2  "  2   "
 +B  '" .//>,  " " 2   &  "
 9# 2 "2 "$
 +B ,    "  "    ) :2
)"&&#4/5 +4E/
, "  &  "    &        4>   +.G/ ,
")+././4A,""""45+4>>,
" &  "  #      )$  "      &    J
+J4HH>,
B )  "  K  "   "    !"
&)&.4+5//,+3%./4E,
B  &)&55/+45F,+L,&
""G//+.0F,
>G0$H0/+50$5AF,""4/.+0/F, .GA
+4/EF,&E/4//+.0,"
E/.//+.>,4+5HF,+I4,
"&$ &&  ) M4/+5N> ",  &
""""7"""
+I4,O&"""
.0$
Procedures
;&7""#I
" &(*"")
"   "  '" ) 8 2
"7"-"
3
4E$./&&)"
"""+I.,
7" " &"
""&""")"8
 )&)"9"""
" &:;""& "
"""&" +I.,
I4+8",P,&,&,
@"")
 .E/  +4/F, "& 2   ) & "  &"
2+I.,""'"2
" "'"
)"7""
")&#&"&"
#&;"&+I.,
=&&&+I5,4//4E/+0G,#"
&"3" "<&"&
7""   " &    ) "$ +I 5, "$
00#+4////$&," Q#$""4.GR
+4HG,        "  & '"   &
 &""""+I5,440
 +0EF,      GH#B +4/// ,   &  &
)04B+G///,&""*)"
4
"""##"
I.+8",P,,&7 :;
&22),;

'" Q#    & ) & "  " " "  " 
)&!"&&""
I5'&+8",P,I7","$
"<,B" &#2
B    )      ) )   " &  "    
" 
5
'    "    2        "  "     ""  "
'"#2"
""
RESULTS
B#E#+44.0$&,"#2A#+4EA0$&,
"2"8""&+I
0,""""
"8I"""N
"
& >A # +4HEG$&,  " #2  +' 4,&
"'"#&  .E  +4F,  4./
+0EF,&"""
"+I0,
I0P&+8",P,9#2,
'"2)"""&)" 
8"$&"I))
)A#+4EA0$&,
O"#2""E4+.F,'"
2#""""&2"
&"#2
6
Table 1: In-plane test results
Weak fill sample Defective medium fill sample
kN mm Comments kN mm Comments
 0 0 0 0
5.23 23 1.74 5
0 8 5.23 10 First plaster crack
5.23 33 Lifting, cracking 5.23 15 No rotation
5.67 63 0 2 Adjusted jack
6.53 50 6.98 16 Plaster cracking on top course
0 85 6.10 26 Lifting
8.72 120 5.23 26
0 89 5.23 36 Top course compressing
6.98 150 6.10 50 Pressure plate tilted
6.98 65 Piston broke through plate
0 33
""" 2  &  +'.,
&)L7&" &$& ) +I E, "
"&#
'.PB$""&$
9#2 2 )
S$#+%$I, E.+44AG, A/+4EG>, G4+45A.,
S&$+, .5+/H4, 4/+/0, 4A+/GA,
$#+%$I, >A+4HG4, A/+4EG>, AH+4AGE,
&$+, 4./+0E, GE+.E, H5+5A,
7
IEPI$&"&"<&
 &)&8  ""2
+IG,&2"#&""
'"& 2&4/+/0F,  &GE
+.EF,"" " 2
"
EVALUATION
"&"$")2"
& +; ./4/ 0/,  " # 2
&"&
#T4/+40E,2&-!"
&#) 2"""
&"#
9""2&
L  "   "      
""   "2I"
'"&"""&#"2
  "  "" "  & & "    ")
 "  ) " # )   +U  
.//>,-!" " "     &
"
8
'"# 2 L  " 
Q
'"2*2" " #""
"" )& &""" '"&2"
&"" &"N""+I G,
'"2"
"+IG,$Q"
IGP2+8",P,-2&,) 
#" "",38
- &  " &   $  " "" 
"    )  &) " )  )
""    1 & +' 5,-
4>+.G/,2$& "
..C )    >.C )    "  50C  "
&       -  "  "      "  )  &  "
"""&)2""1
)2-$*""" )
 )  ") 
") 5/C#+././,""&
&$"
9
'5P=<$&&/H."4P4
  S
"
#N+&,
S&$

+V,

"
#N+&,
&$

+V,
5!!
..B+5./,24AH+E04, 04+4G, 4..+>5G, 45A+E0,
..B+5./,245 0>+5.H, .4+/>, H4+G.0, H4+5G,
4>B+.G/,24G/+044, 0G+4>, GH+0A5, >4+5.,
4>B+.G/,240/+.A0, >+/5, >/+E0>, E4+./,
4>B+.G/,2$.0 A5+E//, 4G+/G, A5+E//, GE+.G,
4/B+4E/,2$.E>+5HA, 4H+/A, HG+GE>, 44H+0A,
4+././,.-5&)#"&
"0&)& "
"""# &"
7 ) & & "
+'0,
'0P=<$&&/H."4P4
  S"
#N+&,
S&$
+V,
"
#N+&,
&$
+V,
6!
-$)40B2.G0+05H, 4>+/A, HG+GE>, 4/H+05,
)./24A/+0>/, 00+4A, HG+GE>, 4/H+05,
!)./2400+5/4, 4E+/G, >G+E>H, A4+.>,
..2+W,4G0+05H, 54+4., 4/A+A55, 440+0E,
4>B2+W,4E/+505, .A+44, A0+E/A, GG+.G,
4+././,.-
10
-  &  )  )  &        "  )  &  
 " $ ) & 2  '" ) & )
""" "   &.>C # 2 
".>C 0EC&.>C#"2"4>+.G/
,2$& "")&"
"     E #N +505 &,    E5 #N +5G5 &, 
'"")&0EC 4.C
$"&05C2)
CONCLUSIONS
I"&"&")&""$
$"&"1 "
4>+.G/,"55C&""
3 "  " (" ""  ")* +B , 
&      &  "      &      
    ""    #   B)  "  "  "  7
&2&
 "& 7  $ & + ././,
-  $    "  )    )    L    

'"") ")"
$")2&(""""&
"*+-8./44,-!""")2")2$
  " ) "   '"  # 2 * 
&#&2 &""&"2
&&&"&&
        &  "        ")  4    +40E  ,    ""
2  )  "  %      &       
&& #  " &"  2    " 
"")"&&-!
"&
RECOMMENDATIONS
  & "    2  " " 
 "  &           
            :;$    
11
&""
 I) "#&") ""&"
 "   "  N   7"     "
&
I""
"1&&
&
 $ "      "  1  "" 
"  "    &    "  )  &"  "  '"
   "   "  I  " 
""""
& &        )        "  &  -!  "  "
&  "2
" 7   &  &             
#
REFERENCES
--)<)I<Q@"
-" * "I"?66B%
.//0V-"!"#!B&F/
5!./+),P4/0HX4/EGP4/44H5N44>/H
-8-"./44V3&!"=Q=<%F
&!":) ./44
"7PNN"NN$3$&$!"$=$
Q$C5$-8NG0/5/HA.&&404/0AA>A&>E/H4A
@O./4/(3&!"2*78
"7PNN""N N&$"$2
=? ./4>99!5!5!:
@"-P B"
3%./4E3%+;87<79'40-"AB0
"7PNN4G0G044/450NN40N40//A///0"3
%I
B 3".//HVB% &!"F&!
":) .//H"7PNNNQN)N)$>H$+"$$
./44,N$45N$$ $&$"$N
12
B )'".//>V!' IF"7
?"7PNN###NNI.>E.&
3?Q3""?6".//0V-3&
&!"#3 F45"9-&!"#
!4HG>;)--
"7PNN#NNNN45Y4HG>&
3<)61'  ./4>V- '&3&
!"9F"&-)!-:) ./4>
"7PNN"NYNG>N
3"9B3 7./45V9%'&
!"9F<5+,PE5.XE00P4/55H/N5/5/E5.
J4HH>8=5>3&?7@!<
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13
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Experiment Findings
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Earthbag is an intrinsically contained wall material with fine grained tensile reinforcement of layered barbed wire. One story buildings in Nepal survived earthquake forces near 0.7g acceleration. Tests of well-dried cohesive soil 1:1 aspect ratio wall samples with reinforced earthen plaster under static monotonic horizontal force compare conventional inserted reinforcement with external base-anchored reinforcement. Component samples also compared external placement of rebar in stucco to shallow and full embedment. Bimodal response curves show initial stiffness is increased by base-anchored vertical rebar, but strength increased by fully embedded rebar.
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Earthbag construction is a sustainable, low-cost, housing option for developing countries. Earthbag structures are built of individual soil-filled fabric bags (i.e., sand bags) stacked in a running bond pattern. Once stacked, earthbags are compacted and the soil inside the bags is dried in-place to form earthen bricks. Barbed wires are placed between each course to affect shear transfer within the wall. Results of an out-of-plane load test on a full-scale earthbag wall are presented in this paper. The wall was subjected to out-of-plane pressure up to 3.16 kPa, which resulted in plastic deformations up to 50 mm. The wall did not collapse during loading. Wall behavior and force transfer mechanisms are discussed.
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This paper describes the method of earth reinforcement using soilbags and illustrates its application for case studies involving a pond and the expansive soil slope protection for a highway. The strength properties of soilbags were investigated using unconfined compression tests and bearing capacity tests on real soilbags containing either medium grained sands or gravels. The test results show that soilbags have high strength when subjected to an external load. This is primarily attributed to the mobilization of tensile forces in the bags. It is concluded that earth reinforcement using soilbags could substantially improve the bearing capacity of soft ground as well as minimizing deformation under working loads.
A Challenge to Earthquake Engineering Professionals
  • Craig Comartin
  • Svetlana Brzev
  • Farzad Naiem
  • Marjorie Greene
  • Marcial Blondet
  • Sheldon Cherry
  • Mohammed Farsi
  • K Sudhir
  • Jelena Jain
  • Laura Pantelic
  • Mauro Samant
  • Sassu
Comartin, Craig, Svetlana Brzev, Farzad Naiem, Marjorie Greene, Marcial Blondet, Sheldon Cherry, Dina D'ayala, Mohammed Farsi, Sudhir K. Jain, Jelena Pantelic, Laura Samant, and Mauro Sassu. 2004. "A Challenge to Earthquake Engineering Professionals," Earthquake Spectra, 20 (November): 1049-1056. doi: 10.1193/1.1809.
Structural Resistance of Earthbag Housing Subject to Horizontal Loading
  • Chris Croft
Croft, Chris. 2011. "Structural Resistance of Earthbag Housing Subject to Horizontal Loading." Masters of Engineering, Bath University, 2011. https://www.semanticscholar.org/paper/Structural-Resistance-of-Earthbag-Housing-Subject-%3A-Croft/64dc03097a2fef1e41047ad787faecce85c0917c.
Reinforced Earthbag Specifications
  • Owen Geiger
Geiger, Owen. 2010. 'Reinforced Earthbag Specifications,' Mother Earth News online. https://www.motherearthnews.com/diy/reinforced-earthbag-specifications
Essential Earthbag Construction: the Complete Step-by-Step Guide
  • Kelly Hart
Hart, Kelly. 2018. Essential Earthbag Construction: the Complete Step-by-Step Guide. Gabriola Island, British Columbia: New Society Publishers.
New Mexico Regulation and Licensing Department
  • Nmrld
NMRLD. 2015. 2015 New Mexico Earthen Building Materials Code. Title 14 Chapter 7 Part 4, http://164.64.110.134/parts/title14/14.007.0004.html. New Mexico Regulation and Licensing Department, Santa Fe, New Mexico.
Plastic Limit Analysis of Earthbag Structures
  • Ralph Pelly
Pelly, Ralph. 2009. "Plastic Limit Analysis of Earthbag Structures." Masters of Engineering, Bath University, 2009. https://www.istructe.org/journal/volumes/volume-89-(published-in-
Estimating Soil Texture by Feel
  • Deann Presley
  • Steve Thien
Presley, DeAnn, and Steve Thien. 2008. "Estimating Soil Texture by Feel." Manhattan, Kansas. https://www.bookstore.ksre.ksu.edu/pubs/MF2852.pdf.