Experimental Study on the Interaction Mechanism of Cap—Pile Group—Soil

Static load tests on pile group with prototype size were carried out in order to study the behavior and the working properties of the cap—pile group—soil interaction in the pile group foundation. The soil resistance under the cap, the pile shaft resistance and the tip resistance were measured by installing various measuring gauges. Based on these test results, the cap—pile group—soil interaction characteristics were analyzed. The regulations of the soil reaction on the cap, the shaft resistance and the tip resistance of pile, the mechanism of load transfer have been discussed with comparison to the result of the single pile tests. The bearing capacity of pile group is greater than the sum of the bearing capacity of the single pile obtained from testing in the same site in pile group foundation in the case presented here.     

豫西嵩县盆地周边地区地震空区地质环境初探

通过时豫西嵩县中～新生代断陷盆地构造类型、断裂发育及其活动程度的初步分析，认为该盆地及其邻区具有断裂发育规模小、新构造活动程度低、盆内无次级断裂及其所围限的地堑和地垒断块构造发育等特征，从而形成了被深断裂割开的地震空区     

大型地下洞室群地震模拟振动台试验研究(Ⅱ):试验方案设计

为了解大型地下洞室群在地震过程中的动态响应特征,以大渡河流域的大岗山水电站大型地下洞室群为原型,开展地震模拟振动台物理模型试验研究。作为国内外首次进行此类振动台试验研究,系统介绍整个试验的方案设计。首先,根据本次试验的目的和特性,给出试验基本简化原则,并对模型体系进行相似设计,按照完全相似模型推导出各物理量的动力相似常数、确定模拟范围、模型尺寸和相似材料配比。然后,对试验边界条件进行设计,确定了作为柔性边界的聚苯乙烯泡沫板的材料和几何参数,制作了用于测量围岩内部应力的应变砖传感器,并介绍模型制作、洞室成型与开挖等工艺步骤;最后,确定试验输入波形,并按相似理论要求进行调整,给出模型试验的加载工况。经后期试验数据的分析,证明试验条件简化合理,模型设计与制作成功。一整套模型设计方法与制作工艺,可供今后类似试验作为参考。     

层状土中群桩非线性沉降的摄动分析

采用包含一个内变量的连续化St Venant模型,即连续的Masing-Iwan模型,模拟桩-土界面扰动区土体的非线性行为。基于两种分析单桩的荷载传递模型,假设桩-土-桩相互作用为弹性且服从叠加原理,推导出了适用于群桩中基桩的两种荷载传递新模型。采用荷载传递法建立了单桩和群桩的非线性控制方程,提出了近似求解该控制方程的摄动分析法,得出了单桩和群桩的荷载沉降和轴力分布方程。所得结果表明,在低荷载水平下严格趋近于弹性解;而在高荷载水平下,能够反映直到破坏阶段的桩的荷载-沉降特性。通过一个现场试验的理论预测结果与实测数据的对比分析,验证了方法的有效性和适用性。     

中国铂族金属矿床找矿方向初探

根据 2 0世纪 90年代铂族金属矿床勘查的新发现 ,提出铂族金属矿床成因分类 ,探讨中国铂族金属找矿方向 ,提出“以绿找铂”、“以黄找铂”和“以黑找铂”的找矿原则 ,即在蛇绿混杂岩或基性—超基性岩分布区寻找基性—超基性岩浆岩型、岩浆热液型铂族金属矿以及与之有关的砂铂矿床 ,在金矿田中寻找伴生铂族金属矿床 ,在黑色页岩分布区寻找黑色页岩型铂族金属矿床。     

不同演替阶段白刺灌丛沙堆土壤因子与叶功能性状关系研究

植物功能性状与环境之间的关系是功能性状研究的重点,环境因子驱使植物功能性状发生变化,进而推动群落发生演替.本研究以民勤不同演替阶段(发育阶段、稳定阶段、衰退阶段、严重衰退阶段)白刺(Nitraria tangutorum)灌丛沙堆为研究对象,分析不同演替阶段白刺叶功能性状差异及其与土壤因子的关系,旨在揭示白刺对干旱荒漠...     

基于离散元模拟的巨厚煤层分层开采覆岩裂隙演化分形特征

为了探究左权五里堠煤业有限公司上组煤5号煤层老空水是否对下组煤15号煤层首采面综放开采造成突水水害威胁,以下组煤首采面为背景,系统分析了研究区地质及水文地质条件,建立了两煤层开采后顶底板变形破坏空间分布特征模型,提出了老空水是否威胁下组煤综放开采的3个可能条件。在此基础上,采用具有针对性的经验公式和数值模拟相结合的方法,综合获得了下组煤15号煤层首采面最大导水裂隙带高度和上组煤5号煤层底板最大破坏深度量化参数,并与下组煤首采面附近施工的地面钻孔揭露这两层煤间距进行对比。认为下组煤15号煤层开采后,通过导水裂隙带将会波及到上组煤采动底板破坏带内部,在正常条件下可能与上组煤5号煤层老空水导通,建议开采前要进行提前探查和疏放。研究结果对下组煤首采工作面顶板老空水害防治具有很好的参考价值。     

Fractal characteristics of sand grain group changes under freeze-thaw cycles and its correlation with long-term strength北大核心CSCD

Seasonally frozen soils are widely distributed in China in terms of area,and the freeze-thaw cycle effect generated by the alternation of cold and warmth is one of the causes of engineering damage in cold areas during construction,and it is particularly important to restore the nature and state of the soil when it is subjected to freeze-thaw action. Therefore,sandy soil specimens with different numbers of freeze-thaw cycles were prepared,and the long-term strength of frozen sandy soil was tested using a spherical template indenter. Using fractal theory and the microstructure image processing software ImageJ,the change law of grain group and long-term strength of two frozen sandy soils under different numbers of freeze-thaw cycles were studied. The results show that：for fine sand（FS）,the fractal dimension DB has a highly significant positive correlation with the long-term strength variation,among which ≥0. 15~0. 20 mm and ≥0. 25~0. 40 mm have the best fit with the long-term strength,and are the dominant grain classes of FS. For medium sand（MS）,the fractal dimension DB is slightly positively correlated with the long-term strength,and the variation shows a“vertical N”trend,in which the grain size content of ≥0. 30~0. 40 mm and ≥0. 40 mm fits better with the long-term strength,and is the dominant grain class for MS. The content of other grain groups did not correlate significantly with the long-term strength change. The freeze-thaw action changed the content ratios of coarse and fine grain agglomerates in the soil. With the increase of the overall particle size interval,the dominant particle size also increases,which shows that the long-term strength of frozen sandy soil tends to decrease and then increase with the increase of the content of some particle sizes. The results of the study can provide theoretical reference for the determination of long-term strength in areas subject to freeze-thaw action. © 2022 Science Press (China).     

Driving factors and spatiotemporal effects of environmental stress in urban agglomeration: Evidence from the Beijing–Tianjin–Hebei region of China

Environmental stress is used as an indicator of the overall pressure on regional environmental systems caused by the output of various pollutants as a result of human activities. Based on the pollutant emissions and socioeconomic databases of the counties in Beijing–Tianjin–Hebei region, this paper comprehensively calculates the environmental stress index(ESI) for the urban agglomeration using the entropy weight method(EWM) at the county scale and analyzes the spatiotemporal patterns and the differences among the four types of major functional zones(MFZ) for the period 2012–2016. In addition, the socioeconomic driving forces of environmental stress are quantitatively estimated using the geographically weighted regression(GWR) method based on the STIRPAT model framework. The results show that:(1) The level of environmental stress in the Beijing–Tianjin–Hebei region was significantly alleviated during that time period, with a decrease in ESI of 54.68% by 2016. This decrease was most significant in Beijing, Tangshan, Tianjin, Shijiazhuang, and other central urban areas, as well as the Binhai New Area. The level of environmental stress in counties decreased gradually from the central urban areas to the suburban areas, and the high-level stress counties were eliminated by 2016.(2) The spatial spillover effect of environmental stress increased further at the county scale from 2012 to 2016, and spatial locking and path dependence emerged in the cities of Tangshan and Tianjin.(3) Urbanized zones(development-optimized and development-prioritized zones) were the major areas bearing environmental pollution in the Beijing–Tianjin–Hebei region in that time period. The ESI accounted for 65.98% of the whole region, where there was a need to focus on the prevention and control of environmental pollution.(4) The driving factors of environmental stress at the county scale included population size and the level of economic development. In addition, the technical capacity of environmental waste disposal, the intensity of agricultural production input, the intensity of territorial development, and the level of urbanization also had a certain degree of influence.(5) There was spatial heterogeneity in the effects of the various driving factors on the level of environmental stress. Thus, it was necessary to adopt differentiated environmental governance and reduction countermeasures in respect of emission sources, according to the intensity and spatiotemporal differences in the driving forces in order to improve the accuracy and adaptability of environmental collaborative control in the Beijing–Tianjin–Hebei region.