Some aspects on applied geomorphology in periglacial regions
221
with continuous use require costly special construction techniques. Preferably they should
follow well-drained areas with a gentle topography to avoid cuttings. Generally, the key
problems are the adequate selection of the trace and the necessity of having available
grounded gravels for the fill. The volume of rock or gravel needed for the fill is usually
very large since this is commonly 0.6 to 1.5 m thick (Linell and Johnston, 1973). The fill is
installed to support the load and vibrations induced by the transport and is penetrated by
the permafrost. The thickness required for the fill may be reduced with the use of
insulating materials like polystyrene layers (Figure 9.10).
In permafrost areas the large rivers are commonly crossed with ferries. However, in
some cases the construction of bridges is necessary. The lateral migration of the fiver may
modify the talik developed beneath the channel causing subsidence of the bridge piers
(Figure 9.11). In case the channel shifts significantly, the permafrost may undergo local
aggradation involving an uplift (French, 1996). For these reasons, one of the main
protection measures is stabilization of the fiver channel.
Before
Active Layer
I I
: -..,
-.,' --' 7.,: ..,.,..,"-7., ~,~.~.~
~,~,.~
~~.
,.-.~, ~ ~.,'.':"-:",'.';"",;'-"
```~:`~```-``'`.``~:;~`:.~`~;~`~.`~`.;~`~'~i~`~;`~`~`~`~'`~:;`~.~'~.``~`~ ;;,d'-" ,','",'; "..-:;'~;,: i:";; :' ,';']'.;,.'-'.~"i:.,'."-:'?:.".'.",':;:::'.,
~"";',":',i','".',:'; .. ~'.'.',,.,:7,?.,;,,: :, ?.':'.,": .: .; .,"-",;-';,'A-; .,V.-,,
;, . :- "; :;:, '.:.'".: ~ ".= :",";,., :.'.,., % ,",;, f',:, L'," ::, ".-.,:, :, :'--,',]-;~ ,. ;",:, ,"- ",'~ .",,':.,;.:;. ;:; ;-":, ',','-,',-,.
Pad Construction
(, :: ':; ,, i ;.,: .~...,..~' :,: :.I:- .:'.:':~ :,: ,% :. :.'. ::, ~.' :,':.'. :." :".":
~ Permafrost
Gravel
Insulation
~.~Active L~...~,~
Insulated Pad Construction
,.-'r--~
..,. ...... ~_~{,
"
Active Layer
"i':':,';i ),',;..,"...._~.:'~.,::',;.'.'!.:,;;i'.',!';:".):,!.V,;',. ' ;' .~;i(i' ;:::' :' ,i' ~,.~, -.. ', ':.V:':"-: :!i~
ii!ii!!i:!!iiiii !ili!!iii iij!i;i!::iiii!iiii:ii!iiiiiii:i!ii i
o
Figure 9.10. Effects on the top of the permafrost beneath a road caused by gravel fills with or without an
insulator. The thickness of gravels required for fill is reduced with the use of an insulator (following
Harris, 1986).
221
with continuous use require costly special construction techniques. Preferably they should
follow well-drained areas with a gentle topography to avoid cuttings. Generally, the key
problems are the adequate selection of the trace and the necessity of having available
grounded gravels for the fill. The volume of rock or gravel needed for the fill is usually
very large since this is commonly 0.6 to 1.5 m thick (Linell and Johnston, 1973). The fill is
installed to support the load and vibrations induced by the transport and is penetrated by
the permafrost. The thickness required for the fill may be reduced with the use of
insulating materials like polystyrene layers (Figure 9.10).
In permafrost areas the large rivers are commonly crossed with ferries. However, in
some cases the construction of bridges is necessary. The lateral migration of the fiver may
modify the talik developed beneath the channel causing subsidence of the bridge piers
(Figure 9.11). In case the channel shifts significantly, the permafrost may undergo local
aggradation involving an uplift (French, 1996). For these reasons, one of the main
protection measures is stabilization of the fiver channel.
Before
Active Layer
I I
: -..,
-.,' --' 7.,: ..,.,..,"-7., ~,~.~.~
~,~,.~
~~.
,.-.~, ~ ~.,'.':"-:",'.';"",;'-"
```~:`~```-``'`.``~:;~`:.~`~;~`~.`~`.;~`~'~i~`~;`~`~`~`~'`~:;`~.~'~.``~`~ ;;,d'-" ,','",'; "..-:;'~;,: i:";; :' ,';']'.;,.'-'.~"i:.,'."-:'?:.".'.",':;:::'.,
~"";',":',i','".',:'; .. ~'.'.',,.,:7,?.,;,,: :, ?.':'.,": .: .; .,"-",;-';,'A-; .,V.-,,
;, . :- "; :;:, '.:.'".: ~ ".= :",";,., :.'.,., % ,",;, f',:, L'," ::, ".-.,:, :, :'--,',]-;~ ,. ;",:, ,"- ",'~ .",,':.,;.:;. ;:; ;-":, ',','-,',-,.
Pad Construction
(, :: ':; ,, i ;.,: .~...,..~' :,: :.I:- .:'.:':~ :,: ,% :. :.'. ::, ~.' :,':.'. :." :".":
~ Permafrost
Gravel
Insulation
~.~Active L~...~,~
Insulated Pad Construction
,.-'r--~
..,. ...... ~_~{,
"
Active Layer
"i':':,';i ),',;..,"...._~.:'~.,::',;.'.'!.:,;;i'.',!';:".):,!.V,;',. ' ;' .~;i(i' ;:::' :' ,i' ~,.~, -.. ', ':.V:':"-: :!i~
ii!ii!!i:!!iiiii !ili!!iii iij!i;i!::iiii!iiii:ii!iiiiiii:i!ii i
o
Figure 9.10. Effects on the top of the permafrost beneath a road caused by gravel fills with or without an
insulator. The thickness of gravels required for fill is reduced with the use of an insulator (following
Harris, 1986).