黑龙江绥芬河市北寒葱河河谷地下水水质保护及开发利用建议

为掌握绥芬河市北寒葱河河谷地下水的水质状况,向地方提供合理的水资源开发建议,本研究以地质、水文地质调查、水样采集等手段为基础,利用模糊综合评价法和层级阶梯法分别进行了研究区地下水水质和污染状况评价,应用物探测试、抽水试验等原位测试技术论证了区域地下水的富水性。以上工作基本查明了研究区地下水的水量和水质现状.认为研究区裂隙承压水一般为Ⅰ~Ⅲ类水质,污染等级为未污染水,水质状况较好,污染程度较低,宜于饮用;中生代构造破碎带涌水量可达350m³·d^-1以上,建议地方政府应重点围绕构造破碎带开展物探找水,并开展地下水源地分区保护规划.     

Changes in soil organic carbon and its active fractions in different desertification stages of alpine-cold grassland in the eastern Qinghai–Tibet Plateau

In recent years, the desertification of alpine-cold grasslands has become increasingly serious in the Qinghai–Tibet Plateau in China, but it has not received the same amount of attention as has desertification in (semi)arid areas. Little is thus known about the change in soil organic carbon (SOC) during alpine-cold grassland desertification. To quantify the impacts of desertification on vegetation, SOC and its active fractions in alpine-cold grasslands, areas of light desertified grassland, medium desertified grassland, heavy desertified grassland, serious desertified grassland, and nondesertified grassland were selected as experimental sites in the eastern Qinghai–Tibet Plateau in China. The species number, height and coverage of vegetation were surveyed, and the soil particle fractions, SOC and SOC active fractions (including dissolved organic carbon (DOC), microbial biomass carbon (MBC), and labile organic carbon (LOC) were measured to a depth of 0–100 cm. The results showed that alpine-cold grassland desertification resulted in a significant reduction in vegetation cover, plant biomass, fine soil particles, SOC, DOC, LOC and MBC. The decreases in DOC, LOC and MBC were more rapid and apparent than were those in SOC, and the decrease in MBC was the most obvious among them. The rates of reduction in SOC concentrations accelerated as desertification progressed; most of the SOC was lost in the middle and later desertification stages, with lower losses during early desertification. The results indicate that active SOC fractions, particularly MBC, are more sensitive to desertification and can be used as sensitive indicators of desertification. Efforts to limit desertification and reduce SOC loss in alpine-cold grasslands should focus on early desertification stages and adopt strategies to prevent overgrazing and control the erosion of soil by wind.     

Hazard degree identification and coupling analysis of the influencing factors on goafs

In China, there are a large number of mined-out area which bring a great hidden danger to the mine enterprise’s safety production and people’s life and property. Therefore, the stability evaluation and the mechanism analysis of goafs have become a hot issue in the study on sustainable development of mining industry. To solve the complexity, concealment, and uncertainty of goaf influencing factors, 14 factors, i.e., rock mass structure, goaf span, exposed area, and so on, were selected as the evaluation indexes according to an iron ore. Then, the hazard evaluation model of goaf was established by using the information entropy and the unascertained measurement (UM) theory to identify the hazard degree, and the hazard importance degree index was put forward by changing the influencing factors and its index value to quantitatively analyze the coupling degree of influencing factors. This paper takes the BFZ-8 goaf as an example to evaluate and analyze the goaf stability. The results show that the evaluation model about UM and the experimental schemes are feasible and practicability, and the UM evaluation grades are consistent with the fuzzy evaluation grades and the actual risk grades in the case of multi-factor coupling. And the experimental results quantitatively reflect the coupling degree of the influencing factors by comparing the relative change rate of the importance degree, and the coupling results are consistent with the actual situation. So, the method can guide the production safety of mine, protect life and property safety of miners, and provide technical support and a new method for hazard degree identification of the goaf.     

Full probabilistic design of slopes in spatially variable soils using simplified reliability analysis method

ABSTRACT

A simplified reliability analysis method is proposed for efficient full probabilistic design of soil slopes in spatially variable soils. The soil slope is viewed as a series system comprised of numerous potential slip surfaces and the spatial variability of soil properties is modelled by the spatial averaging technique along potential slip surfaces. The proposed approach not only provides sufficiently accurate reliability estimates of slope stability, but also significantly improves the computational efficiency of soil slope design in comparison with simulation-based full probabilistic design. It is found that the spatial variability has considerable effects on the optimal slope design.     

Research on the fault controlling mechanism of geothermal water in Zhangzhou Basin

Fault has an important influence on the storage and movement of geothermal water. The Zhangzhou Basin is wholly located in a granodiorite rock mass. Due to the low permeability of granodiorite, faulted structure has an evident control action on the hydrothermal activity of geothermal fields. Hot springs in Zhangzhou Basin crack along Pingtan-Dongshan Fault to the northeastern direction and emerge along Fu’an-Nanjing Fault. Through measurement of the temperature of several hot springs in the Basin, we found the temperature along the northwestern direction of Zhangzhou-Tianbao Fault is high and the temperature gap between the two sides of Yangxi-Yuanshan Fault is huge; the estimation of geothermal reservoir temperature of geothermal water through quartz geothermometer indicates that the geothermal reservoir temperature of the northern area of Nanjing-Xiamen Fault is obviously higher than that of southern area. Such result indicates that Fault obviously obstructs underground heat source. Under the condition that the average geothermal gradient of the Zhangzhou Basin is set, the circulation depth of the geothermal water of the Zhangzhou Basin measured by geothermal reservoir temperature is 3 550-5 200 m and the circulation depth of the geothermal water of the north of Nanjing-Xiamen Fault is deeper than that of the South.     

1979—2014年全球变暖背景下青藏高原气候变化特征

近几十年来全球变暖受到越来越广泛的关注,然而全球变暖从1998年开始趋缓,但青藏高原却呈现加速增暖的趋势。本文基于前人研究,系统回顾了青藏高原气温、积雪、降水和大气热源等四方面在全球变暖背景下的变化,指出高原的加速增温导致了积雪迅速融化,降水明显增多的同时,高原热源却呈现减弱趋势。     

2.5D direct‐current resistivity forward modelling and inversion by finite‐element–infinite‐element coupled method

To reduce the numerical errors arising from the improper enforcement of the artificial boundary conditions on the distant surface that encloses the underground part of the subsurface, we present a finite‐element–infinite‐element coupled method to significantly reduce the computation time and memory cost in the 2.5D direct‐current resistivity inversion. We first present the boundary value problem of the secondary potential. Then, a new type of infinite element is analysed and applied to replace the conventionally used mixed boundary condition on the distant boundary. In the internal domain, a standard finite‐element method is used to derive the final system of linear equations. With a novel shape function for infinite elements at the subsurface boundary, the final system matrix is sparse, symmetric, and independent of source electrodes. Through lower upper decomposition, the multi‐pole potentials can be swiftly obtained by simple back‐substitutions. We embed the newly developed forward solution to the inversion procedure. To compute the sensitivity matrix, we adopt the efficient adjoint equation approach to further reduce the computation cost. Finally, several synthetic examples are tested to show the efficiency of inversion.     

上地壳纵横波速度结构相关反演成像方法

基于纵横波初至走时数据的层析成像方法越来越广泛地被应用于揭示不同构造域壳幔速度结构特征.我们从同一地质体的纵横波速度属性相关这一基本思想出发,提出一种相关反演成像的方法:纵横波速度反演交替进行,在迭代反演过程中每通过一次反演获得相应的纵波速度(或横波速度)结构后,更新相应的纵横波速度比模型以及相应的横波(或纵波)速度反演的初始模型,然后继续开展后续横波(或纵波)速度反演工作.在反演过程中依据纵横波速度的相关性信息和射线路径长度将走时残差以不同权重分配到射线路径经过的单元,依据网格节点周围平均的慢度扰动更新速度模型.正反演过程分别基于有限差分走时计算方法和反投影成像方法.两种典型模型试验表明,该技术应用于上地壳速度结构反演成像过程,可有效提高反演结果的可靠性,在很大程度上避免了常规单独反演纵波和横波速度过程容易带来的畸变和失真.该方法应用于重建青藏高原西部札达—泉水沟深地震测深(DSS)剖面下方的上地壳速度结构,揭示出与青藏高原西缘板块碰撞相关的上地壳速度结构特征.     

长江中下游成矿带中段岩石圈电性结构研究

长江中下游成矿带位于大别造山带、长江中下游凹陷、江南隆起带等大地构造单元结合部位,通过在研究区内布设两条首尾相接共计150km长的大地电磁剖面,获得了50km以浅岩石圈尺度的电性分布.长江中下游地区中段地下电性结构显示出在地下10km和30km处分别存在明显的圈层结构,以此认为现今横向稳定的"电莫霍"反映了研究区经历燕山期陆内构造-岩浆活动后已基本上完成壳幔重新平衡;而分隔大地构造单元的郯庐断裂带、长江断裂带以及江南断裂带在电性上具有特征的梯度显现,在印支造山期后的引张背景下,断裂带成为强伸展活动带与控制了燕山期大范围的陆内岩浆活动;高导地幔的局域性存在以及从北向南地幔导电性的变化反映了在经受深部动力学过程中处于不同大地构造部位的地幔所遭受的不同类型的改造以及地幔深部的构造极性.     

浅部频率域电磁勘探方法综述

适用于近地表(2000m以内)勘探的频率域电磁法主要有音频大地电磁法(audio-frequency magnetotellurics,AMT),无线电大地电磁法(radio-magnetotellurics,RMT),可控源音频大地电磁法(controlled source audiofrequency magnetotellurics,CSAMT),广域电磁法(Wide Field Electromagnetic Method,WFEM).本文拟从最新的数据采集技术、数据处理技术、正反演算法、实例等四个方面,论述适用于浅部勘探的AMT,RMT,CSAMT和WFEM方法的国内外最新进展,总结目前AMT,RMT,CSAMT和WFEM方法遇到的困难,对潜在的发展方向提出建议.综述表明:(1)张量测量、多站阵列、多站叠加可提高AMT、RMT和CSAMT数据的质量.利用近区数据WFEM法可获得良好的效果.国产与国外仪器在质量方面的差距正在逐步缩小.(2)数学形态滤波技术、Hilbert-Huang变换等可有效分离出有用的数据,局部畸变仍然是亟待解决的难题,需要更为深入的研究.(3)矢量有限元与非结构网格的出现大幅度提高了有限元处理复杂电磁问题模拟的精度与应用范围,成为目前电磁正演的首选工具.完全非线性反演算法仍然局限于1D、2D问题,共轭梯度法和高斯牛顿算法等为解决3D问题的发展趋势.地质约束的引入和多数据联合反演可以减小反演的非唯一性.各向异性的反演为目前反演研究的热点之一.(4)野外数据解释的正确性严重依赖于对地下结构先期的维性判别,在2D特性不明显、3D特性明显时,需要采用3D进行反演解释.