江汉平原地下水化学特征及水流系统分析

江汉平原水质性缺水问题日益突出,识别江汉平原地下水流系统分布模式,对地下水资源的合理利用与保护具有重要意义.选取江汉平原典型区域,综合水文地质条件、水动力场及水化学同位素指标深入分析地下水补给过程、水岩作用及滞留时间.得出由于碳酸盐岩的溶解,研究区的地下水化学类型属于HCO3-Ca (Mg)型.地下水中典型离子随深度增加逐渐降低,同位素随深度增加逐渐偏负,表现出地下水流系统呈局部与区域水流系统的特点,系统深度界限在10~20m.独立而复杂的局部水流系统在平枯水期地下水向河渠地表水排泄.根据3H的含量,局部水流为现代水,水循环交替迅速.受地形控制,中深层地下水总体由西和西北向东和东南径流,汇入汉江和长江,为区域水流系统.由于补给源的高程效应,区域水流的18O值存在明显分区,指示不同的补给来源与水流路径.山前丘陵区基本为现代水,向平原腹地纵深至汉江和长江排泄区,地下水年龄在几百年至6000a不等,水循环交替缓慢.研究发现江汉平原低洼排泄区存在区域水流的顶托补给,可为原生劣质水的分布与聚集研究提供依据.     

Petrology,phase equilibria modelling and zircon U–Pb geochronology of Paleoproterozoic mafic granulites from the Fuping Complex,North China Craton

The Fuping Complex is one of the important basement terranes within the central segment of the Trans‐North China Orogen (TNCO) where mafic granulites are exposed as boudins within tonalite–trondhjemite–granodiorite (TTG) gneisses. Garnet in these granulites shows compositional zoning with homogeneous cores formed in the peak metamorphic stage, surrounded by thin rims with an increase in almandine and decrease in grossular contents suggesting retrograde decompression and cooling. Petrological and phase equilibria studies including pseudosection calculation using thermocalc define a clockwise P–T path. The peak mineral assemblages comprise garnet+clinopyroxene+amphibole+quartz+plagioclase+K‐feldspar+ilmenite±orthopyroxene±magnetite, with metamorphic P–T conditions estimated at 8.2–9.2 kbar, 870–882 °C (15FP‐02), 9.6–11.3 kbar, 855–870 °C (15FP‐03) and 9.7–10.5 kbar, 880–900 °C (15FP‐06) respectively. The pseudosections for the subsequent retrograde stages based on relatively higher H₂O contents from P/T–M(H₂O) diagrams define the retrograde P–T conditions of <6.1 kbar, <795 °C (15FP‐02), 5.6–5.8 kbar, <795 °C (15FP‐03), and <9 kbar, <865 °C (15FP‐06) respectively. Data from LA‐ICP‐MS zircon U–Pb dating show that the mafic dyke protoliths of the granulite were emplaced at c. 2327 Ma. The metamorphic zircon shows two groups of ages at 1.96–1.90 Ga (peak at 1.93–1.92 Ga) and 1.89–1.80 Ga (peak at 1.86–1.83 Ga), consistent with the two metamorphic events widely reported from different segments of the TNCO. The 1.93–1.92 Ga ages are considered to date the peak granulite facies metamorphism, whereas the 1.86–1.83 Ga ages are correlated with the retrograde event. Thus, the collisional assembly of the major crustal blocks in the North China Craton (NCC) might have occurred during 1.93–1.90 Ga, marking the final cratonization of the NCC.     

Characteristics of Collapse Accumulation Body in Roadway and Numerical Simulation of Rescue Channel Excavation

Geotechnical and Geological Engineering - After the coal mine disaster, the collapsed accumulation body blocked the roadway and interrupted the rescue route, which seriously affected the...     

1996~2017年枯水期地下水排泄对洞庭湖水量均衡的贡献及其时间变异性

地下水排泄在湖泊水量及营养盐均衡中发挥着重要作用,其中地下水向湖泊排泄的量化是关键,但目前对其时间变异性的研究却十分薄弱.针对这一科学问题,以长江中游重要调蓄湖泊-洞庭湖为例,通过收集1996~2017年洞庭湖流域的水文和气象数据,基于质量平衡模型,查明地下水排泄对洞庭湖水量均衡的贡献以及地下水向洞庭湖排泄强度随时间的变化.结果显示:（1）枯水期时地下水排泄量为（0.17~1.51）亿m3/d,地下水排泄强度为38.74~207.26 mm/d,地下水排泄对湖泊水量均衡的贡献为8.70%~30.37%;（2）地下水排泄量、地下水排泄强度、地下水排泄对湖泊水量均衡的贡献在1996~2017年间均呈现出明显的先降低再升高的变化趋势,三峡水库蓄水后至三峡工程全面竣工初期的地下水排泄相较于三峡水库蓄水前和三峡工程全面运行后显著降低;（3）三峡工程运行对长江水位及地下水位的改变可能是引起湖底地下水排泄时间变异性的重要原因.为洞庭湖区域的水量均衡提供了新的认识,也为今后洞庭湖区域水资源开发利用和区域生态安全管理提供了理论支撑.      

基于孔压监测的强夯置换和砂井-强夯处理饱和软土地基试验研究

在青岛某饱和软土场区采用强夯置换和砂井-强夯2种不同方案进行试夯试验。在试验区距夯点不同距离、不同深度的土层中埋设孔隙水压力计,通过观测,分析试夯过程中超孔隙水压力的变化规律,得出以下结论:2 000~2 500kN·m夯击能作用下,点夯试验最佳夯击数为强夯置换14击、砂井强夯16击,且2种方案强夯有效加固深度均可达6m;强夯置换区块距离夯点越近,超孔隙水压力累积幅值越大,而砂井-强夯区块这一趋势则不明显;砂井-强夯区块较强夯置换区快地基具有更好的均匀性,但其夯后超孔隙水压力消散速度比后者慢;孔压监测是确定强夯参数,了解加固深度,评价加固效果的有效手段。     

Statistical analysis of fracture properties based on particle swarm optimization and Pearson correlation coefficient method

Prediction of reservoir fracture is the key to explore fracture-type reservoir. When a shear-wave propagates in anisotropic media containing fracture,it splits into two polarized shear waves: fast shear wave and slow shear wave. The polarization and time delay of the fast and slow shear wave can be used to predict the azimuth and density of fracture. The current identification method of fracture azimuth and fracture density is cross-correlation method. It is assumed that fast and slow shear waves were symmetrical wavelets after completely separating,and use the most similar characteristics of wavelets to identify fracture azimuth and density,but in the experiment the identification is poor in accuracy. Pearson correlation coefficient method is one of the methods for separating the fast wave and slow wave. This method is faster in calculating speed and better in noise immunity and resolution compared with the traditional cross-correlation method. Pearson correlation coefficient method is a non-linear problem,particle swarm optimization( PSO) is a good nonlinear global optimization method which converges fast and is easy to implement. In this study,PSO is combined with the Pearson correlation coefficient method to achieve identifying fracture property and improve the computational efficiency.     

地面LiDAR点云数据先局部后整体配准方法

针对地面LiDAR获取的庞大点云数据,提出无人工标志的地面LiDAR点云先局部后整体的配准方法。分割出待配准的两测站重叠区域小块点云,采用基于KD-Tree遍历最近邻域点集的ICP算法计算三维坐标转换参数,实现地面LiDAR点云数据的快速配准。     

长三角区域对流层延迟简易模型的建立

在对流层经验模型Saastamoinen模型和EGNOS模型的基础上,通过对长三角地区近40年气象规律的研究,总结了温度、气压、相对湿度相对于年积日的函数关系,建立了适用于长三角区域的对流层天顶延迟的简易模型。通过实验验证了该模型的有效性,该模型输入参数是年积日,不仅方便快捷,还提高了经验模型的精度,为更精确的区域模型研究提供了参考。     

多因素灰色G(1,N)模型及其在基坑位移预测中的应用

G(1,1)模型只利用单点已测数据预测该点的位移,而不管别的因素影响。而事实上该点位移和围护桩上其他点的位移及锚索拉力是耦合的。针对传统的单因素灰色模型在基坑预测中的不足之处,本文提出采用多因素的G(1,N)灰色模型对基坑位移进行预测研究。计算实例表明,该模型预测精度高,所需数据少,简单实用,值得在基坑预测中推广。