流土和管涌破坏机理研究

首先针对渗流破坏的机理进行研究,区别在堤防工程中常用的流土和管涌的概念,从现有的大量土的渗流破坏的实验资料,结合理论分析,从微观的角度去阐述渗流破坏的形成机理,提出了在级配连续性土和级配不连续性土中进行管涌型土和流土型土判别的标准.然后从定量的角度去推导出各种渗流破坏类型的判别公式以及临界抗渗坡降计算公式.     

利用因子分析和分形分析识别内蒙古黑鹰山地区矿致地球化学异常

结合因子分析和分形分析对内蒙古黑鹰山地区1∶5万地球化学数据进行研究,提取了矿致地球化学异常。针对10个元素的因子分析共提取出3个因子:F1-Zn、Cd、(Cu);F2-Ag、Mo、Cu、Bi;F3-Sn、As、Pb、Sb。进而利用C-A分形分析模型对矿化因子F2进行了分形建模。从"面积-F2因子得分"双对数图中提取出4段分形拟合线,分别代表了"无找矿潜力低背景区"、"背景区"、"高背景区"、"高找矿潜力区"。后续地表检查工作中在"高找矿潜力区"发现了不同程度的矿化蚀变现象。结果表明, F2因子反映了热液成矿过程,可作为研究区主要成矿元素空间聚集的综合指标; C-A分形模型可以准确圈定F2因子"高成矿潜力区"的边界;高成矿潜力区准确指示了进一步的找矿工作。     

反射波成像与纵波径向速度成像在华北油田裂缝型碳酸盐岩储层勘探开发中的联合应用

碳酸盐岩地层因成藏复杂,缝洞储层非均质性强、常规测井响应特征不明显,给勘探和有效开发带来较大难度。缝洞型储层有效性评价是深层油气勘探开发中面临的主要难题。对于储层中尺度较小的裂缝,由于地震的分辨率较低,常规测井方法探测深度较浅,难以对数十米地质构造进行准确评价。近年来发展起来的单井偶极横波反射成像技术能够有效利用低频横波的传播特点,对井旁20～30 m范围内的声反射体进行成像。纵波径向速度成像技术利用多接收阵列反演井壁1 m以内的纵波速度变化,能较好地指示储层的可改造性。偶极横波反射成像较好地发现井壁裂缝延伸以及井旁裂缝,纵波径向速度成像可反映井壁附近储层纵波速度变化,综合认为裂缝较发育,延伸较远或存在井旁隐蔽裂缝储层且井壁纵波径向速度变化较大的层段,具有较好的储层改造潜力。应用该方法对华北油田河西务潜山几口井进行处理分析,分析结果与储层改造后产液有较好的对应性,值得进一步推广应用。     

敏感频率地震属性在薄层砂体预测中的应用——以松辽盆地肇源地区为例

以松辽盆地北部肇源地区Y5井区扶余油层河道砂体为研究对象,针对砂体厚度薄、横向变化快以及相同厚度砂体地震响应特征不一致的现象,在正演模拟分析目标砂体的地震响应特征基础上,采用时频分析技术,通过广义S变换在频率域优选不同厚度及组合砂体对应的敏感频率,依托敏感频率重构数据,消除砂体理论响应地震波形与地震剖面特征不一致情形,进而优选地震属性预测砂体展布。研究结果表明:利用敏感频率重构数据体提取的地震属性,可以有效提高薄层河道砂体的预测精度,大大降低油田勘探开发风险。     

中主应力系数影响下的冻结砂土损伤本构模型

人工冻结法是饱水砂层开挖过程中常用的止水和临时支护方法,通过冻土损伤特性研究为冻土力学特性和冻结体稳定性分析奠定基础。为研究冻结砂土的损伤力学特性,在-5℃下进行了不同中主应力系数的冻结砂土三维室内试验。从冻土微元破坏服从Weibull随机分布的特点出发,将Drucker-Prager强度准则作为冻土微元统计分布变量,利用应变等价性假说,建立了三维应力状态下冻结砂土损伤本构模型;在此基础上,讨论模型参数F₀与m和中主应力系数的关系,对模型参数进行合理修正,建立中主应力系数影响下的冻结砂土损伤本构模型,并与试验结果进行对比。分析结果表明：参数F₀和m随着中主应力系数的增大呈现先减小后增大的趋势;参数F₀反映了冻结砂土的强度特性,参数m代表了冻结砂土的延性及脆性特征,考虑中主应力系数影响的冻结砂土损伤本构模型能很好地模拟冻结砂土应力-应变全过程曲线。研究成果为人工冻结法工程设计提供一定的理论依据。移动阅读     

赣南江贝变质岩风化壳离子吸附型稀土矿床特征及成因

通过对赣南江贝稀土矿床进行岩相学、矿床学和地球化学研究,表明该矿床成矿母岩主要为寻乌岩组变质岩,岩性有变粒岩、片岩和片麻岩,其中云母片岩稀土元素含量最高,是最有利的成矿母岩,属轻稀土富集型母岩,是近些年新发现的1处中深变质岩风化壳离子吸附型稀土矿.矿区呈低缓丘陵地貌,风化壳平均厚度12.33 m,矿体主要赋存于全风化层中,矿体平均厚度4.68 m, SRF2 O3品位0. 035%~0. 122%,属离子吸附型稀土矿.稀土主要来源于易风化的水磷酸盐类矿物和稀土氟碳酸盐类矿物,风化壳化学蚀变指数CIA>90 %,表明了强烈的风化作用为矿床的形成创造了有利条件.会昌—安远—寻乌地区中深变质岩广泛分布,具有大型稀土矿成矿潜力.     

基于国产高分遥感数据的矿山环境监测系统研究

以国产高分辨率卫星影像数据为主要信息源,通过对影像进行数据处理,根据影像特征建立了矿山环境遥感解译标志,并对标志图斑进行了野外验证,结合多时相影像的对比,查明矿山基建、开采过程中造成的地貌景观破坏、土地压占、矿产资源开采情况等,分析矿山开发利用状态和地质环境问题.以遥感技术为基础,并利用GIS平台,结合土地利用现状、土...     

New graphical methods for estimating aquifer hydraulic parameters using pumping tests with exponentially decreasing rates

Actual pumping tests may involve continuously decreasing rates over a certain period of time, and the hydraulic conductivity (K) and specific storage (S_s) of the tested confined aquifer cannot be interpreted from the classical constant‐rate test model. In this study, we revisit the aquifer drawdown characteristics of a pumping test with an exponentially decreasing rate using the dimensionless analytical solution for such a variable‐rate model. The drawdown may decrease with time for a short period of time at intermediate pumping times for such pumping tests. A larger ratio of initial to final pumping rate and a smaller radial distance of the observation well will enhance the decreasing feature. A larger decay constant results in an earlier decrease, but it weakens the extent of such a decrease. Based on the proposed dimensionless transformation, we have proposed two graphical methods for estimating K and S_s of the tested aquifer. The first is a new type curve method that does not employ the well function as commonly done in standard type curve analysis. Another is a new analytic method that takes advantage of the decreasing features of aquifer drawdown during the intermediate pumping stage. We have demonstrated the applicability and robustness of the two new graphical methods for aquifer characterization through a synthetic pumping test.     

Hydrological cycle and water balance estimates for the megadune–lake region of the Badain Jaran Desert,China

The hydrology and water balance of megadunes and lakes have been investigated in the Badain Jaran Desert of China. Field observations and analyses of sand layer water content, field capacity, secondary salt content, and grain size reveal 3 types of important natural phenomenon: (a) vegetation bands on the leeward slope of the megadunes reflect the hydrological regime within the sandy vadose zone; (b) seepage, wet sand deposits, and secondary salt deposits indicate the pattern of water movement within the sandy vadose zone; (c) zones of groundwater seeps and descending springs around the lakes reflect the influence of the local topography on the hydrological regime of the megadunes. The seepage exposed on the sloping surface of the megadunes and gravity water contained within the sand layer confirm the occurrence of preferential flow within the vadose zone of the megadunes. Alternating layers of coarse and fine sand create the conditions for the formation of preferential flows. The preferential flows promote movement of water within the sand layer water that leads to deep penetration of water within the megadunes and ultimately to the recharging of groundwater and lake water. Our results indicate that a positive water balance promotes recharge of the megadunes, which depends on the high permeability of the megadune material, the shallow depth of the surface sand layer affected by evaporation, the occurrence of rainfall events exceeding 15 mm, and the sparse vegetation cover. Water balance estimates indicate that the annual water storage of the megadunes is about 7.5 mm, accounting for only 8% of annual precipitation; however, the shallow groundwater per unit area under the megadunes receives only 3.6% of annual precipitation, but it is still able to maintain a dynamic balance of the lake water. From a water budget perspective, the annual water storage in the megadunes is sufficient to serve as a recharge source for lake water, thereby enabling the long‐term persistence of the lakes. Overall, our findings demonstrate that precipitation is a significant component of the hydrological cycle in arid deserts.