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k <br />cC <br /> <br />„s. <br />n <br />a- <br />nt <br />~si- <br />on- <br />2 <br />at <br />i <br /> <br />1' 'a <br />_ <br />_ ~~- <br />w ~ ` X`L't~~~ ~ l ~' <br />~ <br /> <br /> <br /> <br /> <br /> <br /> <br />z~ .- <br />Fig. 1} roundwater) <br />eta, ~n-subsidence of annular diamecer ls.'ith g <br />'se <br />,gth <br />pse <br />uch <br />ty <br />(piQ. ;). These units were encountered at depths between <br />q0 and 130 m. There might be some water fluxes at <br />dzptbs depending on hydrodynamic conditions. There- <br />fore, large solution-subsidences are expected to form in <br />the area. )e orchard in the Sazhca <br />A solution-subsidence in an aPP the doline was filled <br />province developed as a hole. Then, <br />by neighboring communities with the earth material. Ex- <br />cess;~~e pumping and irrigation might have helped the <br />sub Jence Formation. Lake Human is aesent sLak aHu e <br />area that occurred long time ago. At p <br />man has lost its water: its depth is about 0.5 m and it <br />contains no water. No tear suvcture was found on the <br />lake margin. <br />Precipdation <br />Fig. 12 in well <br />tr{1 ~ Schematic cross section ar°und pump g <br />Cases and solutions <br />Conclusions and discussion <br />Landslides like collapses toward the Lake Dipsiz, bowl- <br />shaped subsidence areas around the lake, collapse doline <br />and similar karstic strucnues acre observed in the study <br />area. <br />Landslides in the Lake Dipsiz are due to excessive pum - <br />ing repeated in the lake and the removatlOe tlo,°a~ lake <br />dated grains at the base Thenaoraebasement carving in <br />water tow'ard> Pump g~ <br />unconsolidated soils is thought to be the agent causing <br />and accelerating the formatio e a~~tngs[he unconsolidated <br />The lowering o[ porosity by P roundwater level <br />grains as a result of tluduatio Coon toegrain compaction <br />and therefore an increase in g <br />_, and lowering of porewater pressure below the surface <br />giving rise to an increase in effective stress played an im- <br />- portant role in the Formation of subsidenceearens onathe <br />velop in a bowl shape. The subsidence aporosiry occurs a <br />surface due to the lowering of sedtment p <br />long time after the drawdown of groundwater level. How- <br />': crate and/oraandstonehs a9ected f ~m suddzrtEmaeases <br />in effective stress (Bell 1993). Subsidence Eormatwn Is as- <br />sociated with the depth of the aquifer from the surface. <br />-- As the depth of the aquifer increases, subsidence forming <br />_ _ at the surface will be retarded. <br />Based upon the effective stress computed using the phy- <br />sical features of the soil samples collected around Lake <br />Dipsiz, each 1-m drop of groundwater level will ca.tse a 8 <br />-..-, (7.947) kN(m' increase in the effxiive stress. This is only <br />- valid for the vicinity of Lake Dies <br />_--- According to Xiujun and Xiaodong (1996the elastic depo- <br />- rising of the groundwarer level, not onl}' <br />sition of aquifer but also the pressure of cold water can <br />be gradually improved, and therefore the subsidence wdl <br />Progress downward. <br />cwhonmental Geology 36 13-a1 Oerer.h?r 1995 ~ ~ Spnn9a'"ferlag 1341 <br />Fig. 13 ',n well <br />Solution-subsidence oaurring close to pump S <br />