ENGINEERING GEOLOGICAL ZONATION AND RELATED EVALUATION OF THE PEARL RIVER MOUTH BASIN

Engineering geological zonation and related evaluation of the Pearl River mouth basin are an important result of the UNDP Project CPR/85/044.Integrated studies of multi-disciplines indicate the surveyed area which covers the segments of continental shelf(Ⅰ) and slope(Ⅱ)can be divided into five subzones.The unfavourable engineering geological factors in Subzone Ⅰ1 are low soil strength,strong hydrodynamics and many geohazards such as buried channels,shallow gas.The potential geohazards and geological coastraints in SubzonesⅠ2 include shelf valleys,ancient shoals,sand domes and pockmarks on the seafloor,and differential sedimentary faults within the subbottom.The major geological constraints in Subzone Ⅰ3 are characterized by development of paleao-delta sedimentary system,complexity in lithology and stratigraphic structure,frequent earthquakes with stong intensity.In subzone Ⅱ1,seafloor instabilities include landslides,slumps, turbility currents and dense growing faults.The constraints for seafloor engineering in Subzone Ⅱ2 are principally steep topography and occurence of mud diapir. In this paper,all engineering geoloical problems mentioned above are discussed in detail and assessed through the aspect of geomorphy,siol property,slope stability and neotectonics.