Modelling the time-varying extent of groundwater seepage on tidal beaches

The outcrop of groundwater on tidal beaches distinguishes an upper unsaturated region from a lower saturated region of the intertidal profile. Since the 1940s, it has been recognized that the extent of groundwater seepage at the beach face is one factor determining the tendency for erosive or accretionary conditions to prevail. As a primary step towards incorporating bed saturation characteristics within cross-shore sediment transport models, this paper (and accompanying program disk) details a simple model to simulate the time-varying extent of seepage face development across tidal beaches. From a comparison with field results obtained on the macrotidal Central Queensland (Australia) coast, the model appears to provide an encouraging degree of predictive capability. The model also assists in highlighting the sensitivity of seepage face development to varying beach face, tide and wave characteristics.     

花岗岩残积土基础施工降水技术研究

本文通过某科技大楼深基坑排降水的设计及施工效果,并对花岗岩残积土若干岩土工程问题进行分析和探讨,指出降水是直接影响岩土工程设计与施工的成败关健。     

江苏省里下河沼泽地地下水位对Ⅰ-69杨生长的影响

长江中下游地区丰富的江河滩地和水网沼泽地是重要的土地资源,也是血吸虫(Schistosoma japonicum)病的主要发生区域。营造人工林有利于控制血吸虫的中间寄主钉螺(Oncomelania hupensis)的孳生,也有利于提高土地的生态效益和经济效益。耐湿树种的选择是滩地和沼泽地造林的重要环节。通过对江苏省里下河沼泽地主要造林树种I-69杨(Populus deltoides)的生长状况进行调查可知,在高水位(年平均地下水位-29cm,每年淹水1～2个月)、中水位(年平均地下水位-59cm,每年淹水0～10d)、低水位(年平均地下水位-87cm,常年不淹水)立地上,10a生的I-69杨平均树高分别为16.4m、19.8m、22.9m;平均胸径分别为12.8cm、18.2cm、21.2cm;平均蓄积量分别为67.9m3/hm2、193.1m3/hm2、313.6m3/hm2;地上部分生物量分别为51.8t/hm2、130.0t/hm2、201.4t/hm2;总生物量分别为67.1t/hm2、161.7t/hm2、241.2t/hm2。因此,I-69杨虽然具有较强的耐水能力,在地下水位较高的情况下,其生长也会受到明显抑制,这一结果将为今后湿地造林中的立地选择和树种选择提供参考。