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Cases and solutions <br />• <br />'y area <br />~oquare <br />,200 ,200 <br />1199 1199 <br />1198 <br />1200 <br />1199 <br />1198 12071200 <br />1197 j.; <br />51200 <br />7197 <br />51000 <br />a <br />O~~Om <br />57800 58000 <br />Fig. 2 <br />Topographic map of around Lake Dipsiz <br />~~ Doline <br />'`'1 s r. <br />r f, <br />-Imp meable <br /> <br />:Original water:::. ; <br />:~:~;;:~ table .. . <br />~^~ <br />d. <br />~=~~~'S <br /> <br />Lowered <br />Fig. 3a-c <br />Mechanisms gluing rise to the development of collapse dolines <br />(Ford and Nilliams 1989) <br />This is explained by the fundamental soil mechanics <br />equation by Terzaghi(1943): <br />P.=P+Ph <br />uble rocks such as travertine are detectable through [he <br />clear lake water at the bottom of Lake Dipsiz which has a <br />hydraulic connection with groundwater. In this respect, <br />the Lake Dipsiz has a unique feature. The other collapse <br />features are quite shallow and do not penetrate into the <br />underlying soluble rocks. The nomenclature for the sub- <br />ject topic is somewhat different throughout the literature, <br />as shown it1 Table 1. <br />To be consistent throughout this study as to what term <br />should be used, the term solution-subsidence has been <br />preferred. <br />i the <br />as <br />de- <br />fine <br />oc- <br />fur- <br />nn the <br />~lidated <br />e (Fig. <br />d in <br />aterial <br />veering <br />edue- <br />ress. <br />t~.tere P,=total pressure, kN/mZ, P=effective pressure, <br />kN/m', Ph=hydrostatic pressure, kN/mZ. <br />The porosit}• of the deposits undergoes a reduction in <br />volume, the surface manifestation of which is the subsi- <br />dence. Subsidence occurs over a longer period of time <br />than that taken for abstraction. However, in aquifers <br />composed of sand and/or gravel the consolidation which <br />takes place due [o the increase in effective pressure is <br />more or Tess immediate (Bell 1993). <br />The development of subsidence sinkholes, such as cover <br />collapse or cover subsidence, is a function of the pres- <br />e;tce of suitable cavities in the limestone, the physical <br />characteristics of the overburden sediment, and the in- <br />tensity of recharge through the mantling sediment to the <br />limestone aquifer (bVilson and Beck 1992). <br />The collapse features originated from limestone dissolu- <br />tions in the study area are encountered mostly in uncon- <br />solidated deposits overlying the soluble rocks. The sol- <br />Hydrogeology of the study area <br />Paleozoic marble presents karstic features and is frac- <br />tured in nature. Amphybolite, quartzite, gneiss, and mica <br />Environmental Geology 36 (3-.1 December 1999 ~ CJ 9pnngerVerlag 337 <br />