Changzhou City, underlain by a multi layered aquifer system in Quaternary sediments in the Great Yangtze River Delta region, experienced a maximum land subsidence rate of 147 mm/year in the early 1980s due to excessive groundwater extraction. A large scale monitoring station of 11 borehole extensometers was established in the city in 1983 to investigate land subsidence. Nine strata were predetermined in the Quaternary depth interval and monitored by borehole extensometers. Presented in this paper are the long term observations of land subsidence, strata compression and groundwater level in four aquifers from 1984 to 2002, and discussion on strata compression based on the measured data with reference to the stratigraphy, soil properties, groundwater withdrawn and literature of similar situations. The compression of strata varies significantly and is strongly influenced by groundwater drawdown in the second confined aquifer, or CA2. The groundwater level in CA2 declined from −55 m in 1981 to −76 m in 1994 and the land subsidence rate remained high. After the city government enforced restrictions on groundwater extraction in 1995, the extraction rate sharply reduced, the groundwater level in CA2 steadily recovered to −56 m until 2003, and the land subsidence rate declined to 10 mm/year in 2002. From 1984 to 2002, the land subsidence was mainly attributed to the consolidation of the thick aquitard overlying CA2. In the future, to prevent the subsidence rate from rising, it is vital to stop groundwater drawdown in aquifers.

Earth fissures are a geohazard in Jiangsu Province, China. They can be caused by earthquakes and active faults, underground mining, groundwater extraction and landslides. In order to establish a provincial rehabilitation plan in Jiangsu, a range of monitoring programs, surveys, geological investigations and modeling have been implemented or planned. One of the focuses of the project is the land subsidence and earth fissures caused by excessive groundwater withdrawal in Suzhou, Wuxi and Changzhou (Su-Xi-Chang) area, southern Jiangsu Province. Hetang earth fissure within the Su-Xi-Chang area was first reported in 1995 and a series of investigation has been conducted since then. The site investigations and geophysical survey in 1997 have recognized the causative factor as the excessive groundwater drawdown coupled by the underlying bedrock ridge. An open trench excavation in 2007 and a plane strain analysis suggest that Hetang earth fissures may have cracked from the bedrock ridge to ground surface. Geological drilling in 2007 has further confirmed the existence and configuration of the ridge and extracted soil samples for laboratory tests to obtain soil parameters for numerical analyses and modeling of land subsidence and earth fissures in the Su-Xi-Chang area, Jiangsu, China. The laboratory tests are currently in progress and the result of numerical analyses and modeling is expected to be presented in the near future.

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This paper describes the application of a cable disc elevator to continuous lift ore vertically from underground mines. Application of this system requires the tensions developed within the cable must remain within the carrying capacity of the cable including applicable safety margins. A critical element occurs at starting the system when it is fully loaded which requires the force developed by the system to exceed the static friction forces.This paper describes the laboratory rig developed to investigate the static friction forces. Details of the results of tests on three different ores for both dry and wet conditions are given. These results are discussed.

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