3.Research and development on land subsidence 3.3.Monitoring and measuring techniques Three monitoring techniques have been developed and used for land subsidence.A discussion on each of the three techniques is given below
3. Research and development on land subsidence 3.3. Monitoring and measuring techniques Three monitoring techniques have been developed and used for land subsidence. A discussion on each of the three techniques is given below
3.Research and development on land subsidence 3.3.1.Wire-flex extensometers and automatic monitoring system The wire-flex extensometer is a popular measurement means for deformation and settlement in loose soils.In 1950s and 1960s,cement tubes were often adopted as the external tube to protect wire-flex extensometer in China.Since 1970, cast-iron tubes have been used for the protection.Steel pipes are used as the marking poles.Because of the possible flexible deformation in steel pipes,some improvements have been made to increase the rigidity of the steel pipes.The wire-flex extensometer network has been applied to the new land subsidence-controlling program in Shanghai
3. Research and development on land subsidence 3.3.1. Wire-flex extensometers and automatic monitoring system The wire-flex extensometer is a popular measurement means for deformation and settlement in loose soils. In 1950s and 1960s, cement tubes were often adopted as the external tube to protect wire-flex extensometer in China. Since 1970, cast-iron tubes have been used for the protection. Steel pipes are used as the marking poles. Because of the possible flexible deformation in steel pipes, some improvements have been made to increase the rigidity of the steel pipes. The wire-flex extensometer network has been applied to the new land subsidence-controlling program in Shanghai