任意角度水平向荷载下现浇X形桩力学特性研究（I）：惯性矩

现浇X形桩是为了提高单位混凝土承载力性能而开发的一种新型桩,异形横截面在确保桩周周长的前提下,能有效地减少混凝土用量;但目前针对异形横截面对水平向承载力特性影响方面的研究相对较少。基于X形横截面的3个控制参数：外包圆直径、开弧间距和开弧弧度,建立任意方向轴惯性矩控制方程,并分析X形横截面3个控制参数对截面轴惯性矩的影响规律。最后,提出控制截面面积或周长情况下X形截面惯性矩的最优化设计方案。研究结果表明,X形截面惯性矩随着开弧角度、开弧间距的减小而增大,随着外包圆直径的增大而增大。因此,在等混凝土材料用量或者控制桩周长情况下,适当增大外包圆直径、减小开弧角度和开弧间距有利于提高X形截面轴惯性矩,从而提高X形桩整体水平向承载力。     

Application of multimedia methodology for investigation of karst water in highland regions of Ha Giang Province, Vietnam

Ha Giang is one of the largest, northern border provinces of Vietnam, consisting of four districts: Yen Minh, Quan Ba, Dong Van and Meo Vac. This province features varied karst landscape of Carboniferous–Permian limestone. The region has been recognized by UNESCO as one of the 77 geological parks in the world and the second in Southeast Asia on 3 October 2012. In the dry season, little or no rain is recorded; therefore, surface water is very scarce. For this reason, proper delineation and exploitation of the groundwater resource is critical for sustainable water supply. This has been identified as an important challenge under the scientific project KC-08-10 in the national program KC-08. Remote sensing and GIS were used to decipher the signature of karst water in the highland of Ha Giang. Information layers generated were subjected to multi-criteria evaluation using analytic hierarchy process for decision making to identify ideal locations for groundwater prospecting. The study resulted in delineation of ten zones for all regions and 18 ideal drilling sites in Tam Son Town of Quan Ba District. Drilling and resistivity soundings were performed to assess the success of the interpretation. Deep resistivity survey confirmed low resistivity (200–300 Ωm) near the identified potential sites in Tam Son Town of Quan Ba District. Further, successful drilling at site LKTS1 with a discharge of 7–9 l/s is observed, proving the potential of this methodology for rapid exploration of groundwater in water-scare karst terrains of Vietnam.     

Establishing an early warning system for flash floods in Hoang Su Phi District,Ha Giang Province,Vietnam

Hoang Su Phi is a mountainous district in Ha Giang province, Vietnam. When the rainy season arrives in these parts, flash floods (besides landslides), frequently occur in many areas, seriously affecting the socio‐economic condition of the district. Therefore, in this paper, we have developed an early warning system for flash floods, established based on a geomorphological and hydrological approach. The basic principle underlying this system is the fact that flash floods will often occur where there is high potential risk with sufficient rainfall. In the model, eight parameters of the basin were used to build a potential flash flood map. Using the spatial processing module in an open source software, early predictions from automatic weather stations were interpolated and processed online to produce a potential risk map. Depending on the threshold of precipitation values, the results determined locations where flash flood may occur at various flash flood risk indices (FFRI). The system may be applied to support provision of early flash flood warning up to 1?6 days in advance in the district, allowing the local government ample time to make appropriate decisions on the prevention and/or mitigation of damages caused by flash flood hazards.