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Cases and solutions in' -_ ~ ANKARA Van Lake ~ .~%;i:: : - ~:~;z:~:~::i~.. ~ ` ~ Tuz Lake A . NI~iDE ~ w ' :::::~ :: ... :L:::; :::;`~:::::( i:.. ~:~i:::;:::.:;:::: :::.,~ -(`?:"--"~' ~"" 100 :. .. ~:. ~:. ~.::.. ~ MEDITERRANEAN SEA -km ~~~~~~~~ <`:~~:~:~ ~. :~>:~:~'~': ': .. y ~V` ,. Dam V .. '.::: : : :: ' : ' .. .. .. Y V V V V ~. :: ': :': :'::: :.... ,.:i;:~;:::: :: ~:: DipsizLake. :: : ;=:-: : :.: 2 <~~~....... V ~ :~... Alluvium Explanations Quaternary Travertine Tertiary-Quaternary I ~ Tuff ~ Lahe Tertiary ~ Conglomerate ,/ Fault Neogene ®twtudstone, ~_ 8uried limestone * fault Paleozoic ~ Marble, amphybolite, quartzite, gneiss General background on subsidence There are different types of karstic features in karstic ar- eas due to stratigraphy where three main mechanisms are responsible for collapse dolines (Fig. 3a-c) (Ford and Williams 1939): 1. solution from above that weakens the span of a cave roof, 2. collapse from below that widens and progressively weakens the span of a cave roof; 3. removal of buoyant support by water table lowering, that increases the effective weight on the span so that its strength is exceeded. Collapse dolines occur at the cave space between ground surface by a CO: runoff infiltrating into the completely 336 I Environmental Geology 36 13-a1 December 1998 ~ ~~~ Springer-Verlag Dam ~\ Creek _ , . Road Fig. 1 .. Geology and location maps of study area . ~ Pumping (modified after hITA (1961) and Pasquare well and others (1983)J karst terrain (Fig. 3a). IE impervious units occur on thee? upper zones of karstic limestones, doline section gets =,, narrower from bottom to upper parts. If cave space de~j velops toward the ground surface then collapse doline ~;i' will occur (Fig. 3b). Sinkholes in karstic limestones oe?'~- curred in Mio-Pliocene (Ktziiren-Karapmar/Konya-Ttu=. key), in addition to those formations developed from.the,_ roof of caves to the surface (Canik and Criirek4ioglu '::~% 19S5). If karstic limestones are covered by unconsolidated soils the space [videos and followed by a subsidence (Fi&~ The actual subsidence mechanism becomes involved iti;~'it the compaction of individual grains of the earth mateiial as the grain-to-grain load increases because of a lowering of fluid pressure (Keller 1992). [" The lowering of groundwater level is the cause of redo[-;_. [ion in buoyant forces or an increase in effective stress.