The Suzhou-Wuxi-Changzhou (known as "Su-Xi-Chang") area, located in the
southern part of Jiangsu Province, China, experienced serious land
subsidence caused by overly exploitation of groundwater. The largest
cumulative land subsidence has reached 3 m. With the rapid progress of land
subsidence since the late 1980s, more than 20 earth fissures developed in
Su-Xi-Chang area, although no pre-existing faults have been detected in the
surroundings. The mechanisms of earth fissure generation associated with
excessive groundwater pumping are: (i) differential land subsidence, (ii)
differences in the thickness of the aquifer system, and (iii) bedrock ridges
and cliffs at relatively shallow depths. In this study, the Guangming
Village Earth Fissures in Wuxi area are selected as a case study to discuss
in details the mechanisms of fissure generation. Aquifer exploitation
resulted in a drop of groundwater head at a rate of 5–6 m yr−1 in the 1990s,
with a cumulative drawdown of 40 m. The first earth fissure at Guangming
Village was observed in 1998. The earth fissures, which developed in a zone
characterized by a cumulative land subsidence of approximately 800 mm, are
located at the flank of a main subsidence bowl with differential subsidence
ranging from 0 to 1600 mm in 2001. The maximum differential subsidence rate
amounts to 5 mm yr−1 between the two sides of the fissures. The fissure
openings range from 30 to 80 mm, with a cumulative length of 1000 m. Depth
of bed rock changes from 60 to 140 m across the earth fissure. The causes
of earth fissure generation at Guangming Village includes a decrease in
groundwater levels, differences in the thickness of aquifer system, shallow
depths of bedrock ridges and cliffs, and subsequent differential land
subsidence
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