西安地区黄土台塬和黄土洼地土层特征分析及桩基工程应用建议

Analysis of soil layer characteristics and application suggestions for pilefoundation engineering in loess plateau and loess depressions in Xi’an area

西安地区地貌单元多,本文主要基于工程勘察资料对西安地区黄土台塬和底张洼地两种地貌单元的土层工程性质进行了对比,分析地下水对黄土工程性质的影响。从工程分析可知,湿陷性黄土受地下水长期浸泡后,土的物理力学性质发生明显的变化,含水率变大,孔隙比变小,液性指数变大,湿陷性消失,可压缩性增大,压缩模量锐减,土的强度明显降低。基于底张洼地场地静力触探试验、静载试验成果及桩基工程经验,对该区域或类似地层情况场地建设小高层或高层建筑物提出了适用的桩型、桩长方案及各土层桩的极限侧摩阻力及端阻力标准值的建议值,可为类似场地工程建设提供借鉴。

Within the Xi’an region,a diversity of geomorphic units exists.The primary focus of this work is to compare the soil engineering properties of two specific geomorphic units in the Xi’an area:the loess plateau and Dizhang depression,utilizing engineering survey data as the basis.The analysis delves into the influence of groundwater on the engineering properties of loess.An engineering analysis reveals that prolonged exposure to groundwater induces substantial alterations in the physical and mechanical properties of collapsible loess.This includes an increase in water content,a reduction in void ratio,an increase in liquidity index,the disappearance of collapsibility,increased compressibility,a sharp reduction in compression modulus,and a significant decrease in soil strength.Based on the findings of cone penetration tests,static loading tests conducted in Dizhang depression,and insights gained from pile foundation engineering experience,this work presents recommendations for the construction of low-rise and high-rise buildings in the study area and similar geological conditions.These recommendations encompass suitable pile types,optimal pile length configurations,and suggested values for the ultimate skin friction and tip resistance standards of piles in various soil layers,providing valuable guidance for engineering construction in analogous settings.