某软土深基坑工程时间效应有限元分析

软土地区的深基坑因土体的固结作用和流变性而具有了时间效应。本文以Biot固结有限元法为基础,用三元件模型中的第一个线性弹簧模拟固结作用,弹性模量考虑了开挖应力路径和应力历史的影响;另外一部分(KELVIN模型)来模拟土体的流变性,以实际变形的反演来得到两个参数的大致取值,再对基坑的变形情况以及进一步开挖进行分析。假定为正常固结饱和粘土,平面应变问题。通过对某饱和软粘土地基深基坑开挖工程实例的分析,得到的挡墙水平位移曲线与实测曲线很吻合,表明程序较好地反映出基坑的时间效应。     

Coseismic surface rupture characteristics and earthquake damage analysis of the eastern end of the 2021 MS 7.4 Madoi (Qinghai) earthquake

At 02:04 on May 22, 2021, an M_S 7.4 earthquake occurred in Madoi County in Qinghai Province, China. This earthquake is the largest seismic event in China since the 2008 M_S 8.0 Wenchuan earthquake. Thus, it is critical to investigate surface deformation and damage in time to accurately understand the seismogenic structure of the Madoi earthquake and the seismogenic capacity of the blocks in this region. This study focuses on the Xuema Village, located at the eastern end of the coseismic surface ruptures produced by the event, and assesses the deformation and seismic damage in this area based on field surveys, UAV photogrammetry, and ground penetrating radar (GPR). The results indicate that the rupture scale is substantially smaller at the eastern end of the rupture zone compared to other segments. En echelon type shear tensile fractures are concentrated in a width range of 50–100 m, and the width of single fractures ranges from 20 to 30 cm. In contrast, the degree of seismic damage significantly increases at this site. All of the brick and timber houses are damaged or collapsed, while the steel frame structures and the color steel houses are slightly damaged. More than 80% of the bridge decks on the Changma River Bridge collapse, similar to the terraces along the Youerqu and Changma Rivers and the cut slopes of Provincial Highway S205. We infer that the seismogenic fault of the Madoi earthquake exerts a tail effect in this segment. The tension zone has led to a reduction at the eastern end of the rupture zone, causing shaking damage. Local topography and buildings without earthquake-resistant construction along the strike of the rupture zone have undergone different levels of seismic damage.     

内蒙古二连盆地阿特巴音敖包地区eU、eTh、K等天然放射性水平调查评价

为了对内蒙古二连盆地阿特巴音敖包调查区铀成矿潜力做出评价,通过对其天然放射性水平测量数据的统计分析、参数构建等手段,多维度探索了铀(eU)、钍(eTh)、钾(K)元素含量及γ照射量率在空间上的分布规律及其变化趋势。结合区域地质资料对古铀含量、活化铀量、铀迁移富集指数、地化活动性指数等新构建参数特征进行了综合解释,成功预测了调查区铀成矿有利地段,经钻探查证,发现了良好的铀矿化信息。     

Research on shaft resistance of rock-socketed piles based on the cavity expansion theory

The shaft resistance of rock-socketed piles depends not only on the properties of its surrounding rock, but also on the radial force induced by the load imposed on the top of the pile. This paper deduced a plastic zone of rock around a single pile and obtained the shaft resistance of a rock-socketed pile based on the theories of cavity expansion and shear strength. The research results showed that the magnitude of the radial force in the socketed portion of a rock-socketed pile was related to the pile diameter, Poisson’s ratio, and properties of the surrounding rock. The influence area of rock decreased with increasing pile diameter. The radial force and lateral friction decreased with the increasing relative stiffnesses of the pile and rock. The radial stress on the elastic–plastic interface can be analytically determined based on the rock properties and depth. A field test was used to validate the proposed method, and a good agreement was obtained between the field data and predicted results of the proposed method. The research results in this paper are beneficial to guide actual practice.