花岗岩残积土动态冲击性能的SHPB试验研究

为研究花岗岩残积土的动态冲击性能,开展了高速冲击下的分离式霍普金森压杆（SHPB）试验,与常规应变率下的试验结果比较,分析了高应变率对花岗岩残积土的应力?应变特性和强度的影响。结果表明：低、高应变率下的花岗岩残积土的?-?a（轴向应力?轴向应变）曲线均呈现出软化型。随着应变率 增加,?-?a曲线向?a增大的方向移动,破坏应变?af增加。但高应变率下?af增加的程度更加明显。花岗岩残积土的峰值强度普遍具有应变率依赖性,二者可用直线关系拟合,但低、高应变率下的拟合关系并不一致。提出了率敏性因子m定量评价依赖性强弱。研究发现,随着应变率的提高,强度的应变率依赖性减弱,低应变率下的m为26.694,而高应变率下仅为0.013。相关试验结果指出,高速冲击荷载对土体总体有害。工程中应该采取合理措施控制冲击荷载的危害。该研究有助于深化花岗岩残积土动态冲击性能的理解,为相关工程的施工与设计提供技术参考。     

宝塔滑坡稳定性计算与评价

宝塔滑坡群是由多个滑体组成，本文着重阐述滑坡群中的主体─—宝塔滑坡的稳定性计算与评价。通过采用不平衡推力传递系数法，对宝塔滑坡各个可能滑动的滑动面进行多种方案的计算，以及长江库区水位对宝塔滑坡稳定性的影响。进而对宝塔滑坡作出了稳定性分析和评价，同时也阐明了宝塔滑坡所采用的计算模型的计算结果是切合实际的。     

土钉墙钉长确定和整体稳定性

土钉作为一种新型的挡土技术,已广泛地应用于边坡加固和基坑围护,但目前存在着土钉设计理论落后于实践的局面。本文就土钉的长度计算问题,结合目前土钉设计情况,谈谈如何就整体稳定性安全系数来确定土钉长度,使之既安全又合理。     

中国土壤有机质含量变异性与空间尺度的关系

以中国土种志资料为基础,分析了土壤有机质含量变异与空间尺度的关系及土类内和土类间的变异程度,探讨了不同空间尺度单元下,土壤有机质平均含量与土壤性质的相关性。结果表明,以土壤剖面为单元,随着土壤剖面数的增加,土壤有机质含量的变异系数增大;行政区域尺度单元内部土壤有机质变异程度大于单元间土壤有机质含量的变异程度。以土壤分类单元为空间单元,土类内的有机质含量变异程度小于土类间的变异程度。随着统计单元空间尺度的增大,土壤有机质含量与土壤性质之间的相关性减弱。因此,采用网格法或行政区划分空间区域,获得空间区域单元内土壤有机质含量或贮量的精确估算需要较多的剖面,但外推至数据不足的空间区域时,估算的不确定较小;采用土壤分类单元为空间区域单元,结果则相反。     

成层场地基本周期简化计算方法研究

从波动问题物理本质出发,提取阻抗比和周期比作为表征不同土层条件下场地周期变化规律的基本特征量。提出了子层周期贡献系数的概念,并指出其可由阻抗比和周期比唯一确定,建立了周期贡献系数与阻抗比和周期比一般关系。采用子层周期加权累加方式形成一套简单实用且具有明确物理意义的成层场地基本周期估算方法,以传递函数法结果为标准,就240种工况算例与现有简化方法进行对比,给出各方法偏差分析和适用性评价。主要结论为:阻抗比和周期比作为场地周期研究的基本特征量,结果具有完备性;传统法无法反映土层结构对场地周期的影响,对最普遍的渐硬型场地,偏差也有可能达到40%以上,对存在极端软夹层情况其偏差极易大于20%;Hadjian法精度明显优于传统法,但方法和参数本身缺乏明确的物理意义;新方法在一般和极端两种情况下最大偏差均不超过8%,偏差小于5%和2%工况数占比分别达到85%和60%以上,高于Hadjian简化法,可以在实际工程中推广应用。     

立井冻土掘进爆破技术的研究与应用

崩落爆破通常承担整个立井冻土掘进爆破40 %～60 %的破土量。宽孔距崩落爆破能够增加自由面的有效利用、增强自由面应力波的反射拉伸作用和消除或减小冻土中的应力降低区。在理论分析的基础上进行冻土爆破漏斗模型试验,综合考虑爆破漏斗体积和爆破后两炮眼间最大凸量,初步认为炮眼密集系数 =1.5左右时较为合理。结合立井崩落炮眼成圈弧形布置和冻土所受夹制作用相对较大的特点,建议应在此基础上适当降低立井冻土崩落爆破炮眼密集系数,这在进一步的工程实践中得到了验证。     

The value ofC efor the Arabian Sea during summer monsoon

We estimate, from the moisture budget the bulk aerodynamic coefficient for latent heat flux (C _e) during the monsoon season over the central Arabian Sea. The average value ofC _eunder active monsoon conditions was found to be 2.25 × 10⁻³ which is nearly 60% higher than those previously used.     

Migration and dispersion of trace elements in the rock–soil–plant system in areas underlain by black shales and slates of the Okchon Zone, Korea

The Okchon black shale in Korea provides a typical example of natural geological materials enriched with potentially toxic elements. The Chung-Joo, Duk-Pyung, Geum-Kwan, I-Won, Bo-Eun and Chu-Bu areas are underlain by these black shales and slates of the Guryongsan Formation or the Changri Formation, which are parts of the Okchon Group in the central part of the southern Korean Peninsula. In order to investigate the enrichment levels and dispersion patterns of potentially toxic elements in the rock–soil–plant system, environmental geochemical surveys were undertaken in the above six study areas in the Okchon Zone. After appropriate preparation, rock and soil samples were analyzed for potentially toxic elements by instrumental neutron activation analysis (INAA) and inductively coupled plasma atomic emission spectrometry (ICP-AES), and plant samples by atomic absorption spectrometry (AAS). In particular, Ba, Cd, Mo, V and U in Okchon black shales are highly enriched, and their mean concentrations are significantly higher than those in black slates. These elements are geochemically associated, and might be enriched simultaneously. The highest mean concentrations of 42.0 μg g⁻¹ As, 2100 μg g⁻¹ Ba, 10.9 μg g⁻¹ Cd, 213 μg g⁻¹ Mo, 83 μg g⁻¹ U, 938 μg g⁻¹ V and 394 μg g⁻¹ Zn are found in black shales from the Duk-Pyung area. Mean concentrations of As, Mo and U in soils overlying black shales occurring in the Duk-Pyung area (30 μg g⁻¹ As, 24 μg g⁻¹ Mo and 50 μg g⁻¹ U) and Chu-Bu area (39 μg g⁻¹ As, 15 μg g⁻¹ Mo and 27 μg g⁻¹ U) are higher than the permissible level. Enrichment index values of the six study areas decrease in the order of Duk-Pyung > Chu-Bu > Bo-Eun > Chung-Joo > Geum-Kwan = I-Won areas. Relationships between trace element concentrations in soils and plants are significantly correlated, and the biological absorption coefficients (BAC) in plants are in the order of Cd > Zn = Cu > Pb, which suggests that Cd is more bioavailable to plants than the other elements. Cadmium concentrations in plant species decrease in the order of chinese cabbage > red pepper > soybean = sesame > rice stalk > corn > rice grain. From the result of sequential extraction analysis of soils, relatively high proportions of Cu, Pb and Zn are present as residual fractions, and that of Cd as non-residual fractions. Cadmium occurs predominantly as exchangeable/water-acid soluble phase in soils, and this is in agreement with the findings of high Cd concentrations in plants.     

Measuring the k–S–p relations on DNAPLs migration

Migration characteristics of dense non-aqueous phase liquids (DNAPLs) in the subsurface can be expressed as a water–DNAPL two-phase system based on mainly the k–S–p relations, which describe the relations among relative permeability (k), degree of water saturation (S), and capillary pressure head (p). The aims of this research are to develop an experimental system with new type of probes, such as the electrical conductivity probe for measuring the degree of water saturation and the hydrophilic and hydrophobic tensiometer for measuring the pore water and DNAPL pressures, and also to estimate the results obtained from the developed experimental system. From these tests, the excellent k–S–p relations were obtained and the efficiency and validity of this developed experimental system have been confirmed in terms of the concept of the scaling coefficient calculated by interfacial tensions.     

土体颗粒破碎研究进展

在打入桩的桩端以及大型土石坝、海洋平台等的地基中常常会出现高应力区。在这些高应力区中,作为地基的粒状土的颗粒会发生不同程度的破碎。对高应力水平下粒状土体的破碎特性进行深入研究有助于解决这一类型的岩土工程问题。因此近年来土体颗粒破碎逐渐引起人们的重视。本文对土体颗粒破碎研究现状进行了详尽的阐述,并指出研究中存在的问题及今后研究发展方向。