PERMFILE102368 - Laserfiche WebLink

Home Browse Search

Cases and solutions . ........................ y....... --~--~ .............................................. Overflow water DIPSIZ LAKE Lowered water ~i~: z Fig. 8 m ~ Schematic cross section of tF. z .~:~d:~:~i~~ Lake Dipsiz (1: unconsolida;, tl soils, 2: travertine, }cave space, 4: subside p. unconsolidated soils into tae to zo ao m space, 5: arc, 6: landslides) activities have a close relationship with water table fluc- tuation: the fluctuation of the water table in the underly- ing karstified strata plays an important role in the pro- cess of collapse in the overlying soil (Daoxlan 19SS). Bowl-shaped graded land subsidence of Lake Dipsiz oc- curred due to excessive pumping, and recharge and dis- charge of aquifer (White and others 1956), and at the same time unconsolidated soil grains were removed down the lake. It is believed that voids in karstic formations might have occurred under the landslide areas and this gave rise to landslide possibilities. Dipsiz Lake's length is 215 nt and the width is 110 m. There exist five landslides at SW and several small-scale landslides at NE and ENE. Landslide slotes have a depth of 10-90 cm and a width of 15-SO cm; the relative slide measures are between 0 and 60 cm (Fig. 3). There were at least ten solution-subsidence areas with a distance of about 350 m from Lake Dipsiz. Pumping from the lake results in dra+vdotvn in the groundwater level, and therefore the main causes of solution-subsidence in such soils are the readjustment of soil particles to better packing conditions, and increase in effective stress. Fur- thermore, underlying karstic voids are rising to the top through the unconsolidated soils as an arc (Ivlilanovic 1931; Beck 198S). A fete cavities in unconsolidated dept its hace risen to the ground surface. The decompositio of natural equilibrium condition of soils leads to solu- tion-subsidence in the around surface benceen karstic strata (Fig. 3c). Solution-subsidence in the area may be dry or contain some groundwater depending on the sea sonal variations. Several solution-subsidences are preset. ly developing (Fig. 9). Generall}', slopes of solution-subs deuces hace a vertical position (SO°-90°) with no horizo. tai motion in the study area (Figs. 9-] l). Therefore, the unconsolidated soils have cohesion and carbonated stra: under the ground surface/at ground surface. In addition to Lake Dipsiz solution-subsidence, there were other solution-subsidence occurrences. One of the: is close to the pumping well (well no. 1995) south of Lake Dipsiz. This subsidence area is 9.60 m away from the pumping well. It has an ellipsoidal shape and a lent' of 14.50 m, and a width of 12.40 m. Its maximum collap depth is 0.70 m (Figs. 1?, 13). These structures are thought of the results of pumping drawdown and poor well construction. Some portion of drilling mud tvas lost in formations suc as conglomerate, sandstone, and lacustrine limestone within the wells drilled in the study area and its vicinity s - u.dV'i.'t: ~: -' ~: Fig. 10 Solution-subsidence of annular diameter (wish no 340 I Environmental Geology 36 13-4) December 1998 ' ~ Spanner-Wd.~n Fig. 9 Solution-subsidence of restriction formation