谈路下采煤对高速公路的损害影响

高速公路的选线主要从总体经济社会效益考虑,特别是在山区选线难度大,工程造价高,往往不能顾及局部地段的特殊情况。重庆綦万高速公路(綦江-万盛)就从南桐矿业公司南桐煤矿北翼煤田上通过,压占该矿大量煤炭资源。因此,开展高速公路下采煤,运用采煤后上覆岩层移动变形规律的科研成果,对高速公路的下沉、倾斜、曲率、水平移动和水平变形等采动损害做出定性和定量的研究与分析,对其安全性做出评估和判断,并提出安全对策,就成"三下"(建筑物下、水体下、铁路下)采煤研究者的新课题。针对山区高速公路的特点,以綦万高速公路为例,系统研究了地下采煤对高速公路的影响,并进行了采动损害评估,对运营中的綦万高速公路下采煤做了初步探讨,提出了应采取的安全技术措施。

采空区沉陷对运营隧道结构的影响

为了评价采空区沉陷对运营隧道结构的影响,通过对运营隧道变形现场调查及原因分析,结合采动评估模型,对运营隧道结构变形进行研究。结果表明:隧道病害的主要原因是地表沉陷和水平位移,开采过程中会出现衬砌拉伸开裂、变形缝挤死、混凝土崩落、拱顶脱皮等危害性变形,应做好监测工作,设置变形缝;对部分二次初衬应做配筋;对隧底部分冒落带和导水裂缝带围岩进行注浆加固,可有效减少对隧道结构的影响。

Assessment of potential impacts to surface and subsurface water bodies due to longwall mining

Ground movements due to longwall mining operations have the potential to damage the hydrological balance within as well as outside the mine permit area in the form of increased surface ponding and changes to hydrogeological properties. Recently, the Office of Surface Mining, Reclamation and Enforcement(OSMRE) in the USA, has completed a public comment period on a newly proposed rule for the protection of streams and groundwater from adverse impacts of surface and underground mining operations(80 FR 44435). With increased community and regulatory focus on mining operations and their potential to adversely affect streams and groundwater, now there is a greater need for better prediction of the possible effects mining has on both surface and subsurface bodies of water. With mining induced stress and strain within the overburden correlated to changes in the hydrogeological properties of rock and soil, this paper investigates the evaluation of the hydrogeological system within the vicinity of an underground mining operation based on strain values calculated through a surface deformation prediction model. Through accurate modeling of the pre- and post-mining hydrogeological system, industry personnel can better depict mining induced effects on surface and subsurface bodies of water aiding in the optimization of underground extraction sequences while maintaining the integrity of water resources.

Assessment of noise and ground vibration induced during blasting operations in an open pit mine——A case study on Ewekoro limestone quarry,Nigeria

Our study was carried out to assess the level of noise generated and ground vibrations induced during blasting operations at the Ewekoro limestone quarry in Nigeria.To achieve this objective,vibro monitor equipment was used to take readings related to noise generated and ground vibrations during all blasting operations that took place in the quarry for a period of one month.As well,a digital camera was used to take photographs of residential structures within villages near the quarry.The results obtained indicate that the ground vibration readings fall between 0.5 mm/s and 2.1 mm/s and the noise generated during the blasting operations between 82 dB and 89 dB.These readings when compared with the limits set by FEPA(Federal Environmental Protection Agency) of 5.0 mm/s and 150 dB) all fall within the permissible limits.However the photographs of most structures near the quarry reveal cracks and dilapidated building walls.Recommendations are made on how to sustain and improve current blasting techniques.

Condition evaluation of a unique mining site

The primary objective of this study was to evaluate the existing conditions and the stability of a mining site in which the unique features of seismicity, mining activity, hydrological conditions, geological conditions, environmental conditions, and future development plans were considered. In particular, the potential subsidence locations near the proposed construction site, the effects of mining boundary profile,and the influence scope of the mining activity on the neighboring areas were investigated using the finite element method. The study results indicate:(1) the overlying sandstone layer to the coal layer is the key to the stability of the mining roof;(2) the broken boundary has the most effect, followed by the arc boundary and linear boundary;(3) the safe distance from the mining boundary should be at least400 m if the proposed structure is to be built near an active mining site. Other relevant engineering recommendations are also proposed. The concluded results from this study may serve as a guide to other similar sites in the world.

Dynamic evaluation of traffic flows on city roads

This paper presents an analysis of the random fluctuations, deferred conduction effect and periodicity of road traffic based on the basic features of road networks. It also discusses the limitations of road network evaluation theories based on road "V/C". In addition, it proposes a set of theoretical and technical methods for the real-time evaluation of traffic flows for entire road networks, and for solving key technical issues, such as real-time data collection and processing in areas with no blind zones, the spatial-temporal dynamic analysis of road network traffic, and the calibration of key performance index thresholds. It also provides new technical tools for the strategic transportation planning and real-time diagnosis of road traffic. The new tools and methodology presented in this paper are validated using a case study in Beijing.

k-step adaptive cluster sampling with Horvitz-Thompson estimator

Adaptive cluster sampling （ACS） has been widely used for data collection of environment and natural resources. However, the randomness of its final sample size often impedes the use of this method. To control the final sample sizes, in this study, a k-step ACS based on Horvitz-Thompson （HT） estimator was developed and an unbiased estimator was derived. The k-step ACS-HT was assessed first using a simulated example and then using a real survey for numbers of plants for three species that were characterized by clustered and patchily spatial distributions. The effectiveness of this sampling design method was assessed in comparison with ACS Hansen-Hurwitz （ACS-HH） and ACS- HT estimators, and k-step ACS-HT estimator. The effectiveness of using different k- step sizes was also compared. The results showed that k-step ACS^HT estimator was most effective and ACS-HH was the least. Moreover, stable sample mean and variance estimates could be obtained after a certain number of steps, but depending on plant species, k-step ACS without replacement was slightly more effective than that with replacement. In k-step ACS, the variance estimate of one-step ACS is much larger than other k-step ACS （k 〉 1）, but it is smaller than ACS. This implies that k-step ACS is more effective than traditional ACS, besides, the final sample size can be controlled easily in population with big clusters.