Basal stability analysis of braced excavations in anisotropic and non-homogeneous undrained clay using streamline velocity fields

Acta Geotechnica - A basal heave stability analysis in anisotropic and non-homogeneous undrained clay by using the kinematic approach of limit analysis is presented. The proposed failure mechanism...     

Field study on the behavior of pre-bored grouted planted pile with enlarged grout base

This paper presents the results of field tests performed to investigate the compressive bearing capacity of pre-bored grouted planted (PGP) pile with enlarged grout base focusing on its base bearing capacity. The bi-directional O-cell load test was conducted to evaluate the behavior of full scale PGP piles. The test results show that the pile head displacements needed to fully mobilize the shaft resistance were 5.9% and 6.4% D (D is pile diameter), respectively, of two test piles, owing to the large elastic shortening of pile shaft. Furthermore, the results demonstrated that the PHC nodular pile base and grout body at the enlarged base could act as a unit in the loading process, and the enlarged grout base could effectively promote the base bearing capacity of PGP pile through increasing the base area. The normalized base resistances (unit base resistance/average cone base resistance) of two test piles were 0.17 and 0.19, respectively, when the base displacement reached 5% D_b (D_b is pile base diameter). The permeation of grout into the silty sand layer under pile base increased the elastic modulus of silty sand, which could help to decrease pile head displacement under working load.

     

全尾砂-废石混合回填膏体流动特性变化规律

质量浓度、废石掺量是影响尾砂-废石混合回填体流动特性的主要因素,研究这些因素对膏体流动性的影响规律,对于控制膏体流动性具有重要意义。采用改进的小型直剪装置进行混合回填体直剪试验,以黏聚力、内摩擦角、抗剪强度为依据,综合得出了混合回填膏体流动性变化规律。试验结果表明,膏体在受力变形前期呈较为明显的似弹性性质,随废石掺量增加,位移-剪应力曲线中阶梯状变化趋势增加;回填体黏聚力取决于质量浓度,内摩擦角受质量浓度和废石掺量影响程度基本相同,两者协同作用;质量浓度在80%～88%范围时,黏聚力随质量浓度增大呈非线性增大,内摩擦角与质量浓度呈S型变化趋势;抗剪强度随质量浓度的增大而增加,在82%～84%区间抗剪强度变化显著,流动性出现突变。     

An Urban Heat Island in the Atmospheric Boundary Layer and the Concentration of Pollutants Over the City of Ufa in 2021

Doklady Earth Sciences - The urban heat island and the level of atmospheric air pollution in the city of Ufa are investigated by analyzing the diurnal data from nine stationary stations of the...     

The influence of variations of the elemental composition on the thermal properties of gas behind shock fronts

The homogenization of inhomogeneities in the elemental composition of the interstellar medium due to stellar evolution and weak mixing are inevitably related to the action of shocks. This paper considers the influence of variations in the elemental composition on the thermal and ionizational evolution of a collisional gas with the solar metallicity that is cooled behind a shock front with a velocity of 50–120 km/s. The intensities of lines of heavy elements in plasma cooling behind a shock front depend not only on variations in the elemental composition, but also on the shock velocity, due to the different values of the critical density for the transition to the equilibrium level populations in atoms and ions of heavy elements. This circumstance can be used to determine the elemental composition of cool and warm gas of the interstellar medium, as well as the thermal history of the gas.     

青藏高原西部降水中δ18O变化特征

根据青藏高原西部阿里地区狮泉河气象站和改则气象站取得的降水水样和降水气象资料, 分析了该区域降水中δ18O的变化特征.结果表明: 在长时间尺度上, 狮泉河和改则两站点历次降水中δ18O和气温之间都有较好的正相关, 尤其是降水中月平均δ18O与月平均降水温度之间相关性更加显著, 降水中δ18O主要受"温度效应"的影响.而在其中的某一年, 这种相关性不是很明显, 而且在降水中δ18O和降水时温度之间的相关性很好的年份, 在7月底或8月份初短期内降水中δ18O几乎都有一个突然降低的事件, 这可能与印度季风水汽输送有关.与狮泉河站相比, 在改则降水中δ18O和气温二者之间这种相关性相对较弱, 这与改则当地内陆水循环特别是强烈蒸发引起的降水有关.     

Destressing Mechanics Effect of Surrounding Rock Induced by Blasting Precondition at Deep Drift Development

Geotechnical and Geological Engineering - Using a detailed modeling simulation technology, a mechanics simulation model was constructed, including multiple development rounds, stress relief holes...     

Index Minerals of the Hydrothermal Arsenide Process of the Formation of Cobalt Deposits of the Bou Offro–El Graara Ore Belt in the Anti-Atlas Province,Morocco

Geology of Ore Deposits - The distribution of index minerals of the hydrothermal arsenide process of the formation of Ni‒Co–As (±U–Ag), Co–S–As...     

红原泥炭6000a以来元素异常及其可能反映甘青地区人类活动信息的初步研究

通过对红原泥炭沉积剖面Pb,Zn,Fe,Mn,Cu,Co,Ni,Ti,V,Al等10种元素和灰分的测试,发现多数元素在该剖面的变化与灰分变化较为一致,但Cu,Pb和Zn元素的变化在剖面300cm以上出现较大异常:这3种元素的变化与其他元素变化呈相反的规律,而且Pb和Zn两种元素的含量较之剖面下部出现数量级的增大。通过对比,发现元素含量的异常与位于剖面上风区的甘青地区新石器时代晚期-青铜时代文化在发生时间上较为吻合,认为这可能是人类活动环境效应的记录。用600~300cm段的元素变化作为背景值,用与Pb,Zn元素相关较好的4种元素分别计算出二者变化的自然背景值,从而分离出了人类活动强度信息与自然环境背景值,分离结果与著名的青海柳湾墓地出土人口规模对比较好。