深圳地区第四系主要地层特征探讨

Shenzhen Quaternary Stratigraphy of the Main Layer

深圳地区三面临海,地势东南高西北低,可分为三个地貌带,各带地貌类型复杂。河流短小众多,降雨量丰沛,河流属雨源型,其径流量、流量和洪峰与降雨量密切相关,洪峰暴涨暴落。第四系沉积厚度及种类各地相差悬殊,与下伏基岩密切相关。位于燕山晚期侵入的中粗粒花岗岩区的河流上游风化壳厚度大,水土流失严重,下游淤浅严重,第四系沉积层厚度大,种类多;位于碎屑岩、变质岩、火山岩及燕山早期细粒花岗岩区的河流,因岩石风化壳厚度小,植被覆盖好,水土流失轻微,下游第四系沉积层厚度小,种类少。深圳地区第四系地层按C14年龄划分为全新统、上更新统和未分统的残积层三类。按沉积成因分为海积、海陆交互沉积、沼泽沉积、冲积+洪积、坡积和残积六类。在深圳经济特区30年大规模城市建设中进行了大量的岩土工程勘察和岩土物理力学性质试验,经统计、分析、应用,总结出"深圳地区第四系地层特征综合表和物理力学性质指标经验值",供同行参考。

Shenzhen facing ocean to east, west and south, the high terrain southeast, northwest low, containing three different complex topography types of geomorphologic zones. Numerous short rivers, abundant rainfall, rivers source form of rains, so the river runoff, flow and flood peak are closely related to rainfall, storm surge peak off. The thickness and types of quaternary sediment are significant differences between locations, which closely related to the underlying bedrock. Due to the large thickness of crust of weathering and serious soil erosion in upstream of the late Yan medium coarse grained area, the quaternary sediment is thick and various. On the other hand, owning to the thin crust of weathering, well vegetation cover and slightly soil erosion in the river area which combining clastic rock, metamorphic rock, volcanes, and the early Yan granitello, downstream of quaternary sediment is thin and less species. According to the C14 aging system, Shenzhen quaternary stratigraphic castigates to Holocene series, Upper Pleistocene and non-intagration of the residual layer of sub-categories. There are six categories classified by sedi- mentary composition： marine deposition, land and sea interactions deposition, marsh sedimentation, alluvial ＋ flu- vial, slope and residual plot. During the 30 years of Shenzhen special economic zone large-scale urban construction periods, through statistics, analysis, applications a large number of geotechnical engineering investigation and geotechnical physical and mechanical properties of test, concludes into ＂Shenzhen area quaternary clay layer feature grouping sheets＂ and ＂The physical and mechanical indexes of experience＂ .