人工挖孔桩施工精准降水控制方法及应用

人工挖孔桩施工降水常导致周边建筑物基础和地表沉降破坏现象,为此提出了精准降水方法,将其负面影响降为最低。首先依据水力影响半径、降水深度和附近建筑物基础埋深确定地下水位预期标高,利用降水影响线计算理论降水深度,通过调整滤管埋深,优化降水影响线;利用深井降水控制仪,自动控制降水深度。遵循群桩孔至集水井等距原则布井,能使集水井的降水效率得到最大发挥。实践证明,上述措施可准确地控制地下水位标高,最大限度地控制了降水的负面影响;集水井数量可减少20%~30%,节约抽水台班费15%~25%,实现降本增效,值得推广应用。

Establishment and Data Processing of High-Precision City Subsidence Monitoring Network by GPS Surveying Instead of Leveling

The feasibility of moni-toring the change of city settlementusing GPS surveying instead of level-ing is studied. A fiducial network anda monitoring network are establishedin Ningbo city. Two periods of GPSobservation are completed. Somemeasures are taken during the obser-vation in order to ensure to obtain thehigh-precise height component. TheSaastamoinen model is adopted in thedata processing of the dry componentpart of the tropospheric delay. Thewet component change of the tropo-spheric delay is estimated by stochasticprocesses model. When Bernese soft-ware is used to process the data, themillimeter level precision of heightmeasuring is achieved.