高密度电法在复杂岩溶地区路基勘测中的应用

用高密度电法来查明复杂岩溶地区路基的物性特征是一种很好的手段。通过高密度电阻率法对广西境内某铁路路基进行岩溶勘测,查明了该段路基的地层结构和岩溶发育情况,解释结果与真实情况非常吻合,为以后的工程设计和工程施工提供了依据。在复杂岩溶地区路基勘测工作中,高密度电法具有成本低、效率高、效果好、显示直观等特点,不失为一种值得大力推广的好方法。     

Les relations karst-rivière dans les calcaires barrémo-bédouliens du Diois (Drôme – France) Exemple de la Gervanne

The karst in the Gervanne river is a well-developed system found in a limestone formation from the Barremian-Bedoulian that is about 400?m thick. Although its limits are not known to any great precision, they are very similar to those of the geographical area of the Gervanne watershed. Explorations have brought to light a dense system of cavities and one main outlet: Les Fontaigneux spring, a permanent spring. The relationships between the river and the karst are complex. They can be analysed by studying the hydrological data and tracer information. During low waters, seepage from the river often reduces river flow to nothing. Tracer tests were carried out to check the conditions in which water circulates in the karst. The rate between the first arrivals of the tracer and the peak velocity shows that the flow takes place in a channel pattern with very low longitudinal dispersal during low waters. Dispersion was only seen to occur during high waters, when the karst feeds water back into the river in a flow that takes into account the fissuring and joints between the rock. The seepage discharge in the Gervanne therefore depends on the amount of water in the karst. In fact, it does not seem possible to conduct artificial maintenance of the water level in order to avoid losses from the river into the karst. If artificial measures were to be taken to maintain a minimum water level in the river, for instance, by building a dam, watertightness could not be guaranteed because the basin is much too permeable.     

A new approach to evaluate spatiotemporal dynamics of controlling parameters in distributed environmental models

Distributed environmental models are usually high-dimensional and non-linear. To comprehensively evaluate the spatiotemporal dynamics of model controls, we propose a novel multi-step approach based on Sobol's method to evaluate parameter sensitivity as well as interactions with respect to different model outlet points, using different objective functions to assess different hydrodynamic conditions; all varying through time. This complete sensitivity analysis can be performed for prior and posterior parameter ranges. The difference between them can be used to assess the influence of parameter constraints on the results of sensitivity analyses. We applied this holistic approach to an existing distributed karst watershed model. The results demonstrated that 1) a limited number of spatially-distributed parameters control the varying flow pattern, 2) the model is nonlinear and the influential parameters are highly correlated in the model domain and 3) the spatial patterns of identified parameter sensitivity and interactions are strongly influenced by the specified parameter bounds.     

新建贵广铁路岩溶地区钻孔桩施工技术研究

结合新建贵广铁路桩基础工程施工实践,介绍了岩溶地区桥梁钻孔桩施工控制及注意事项,以期为类似岩溶地区桩基础施工提供借鉴。     

Risk assessment of water inrush in karst tunnels based on attribute synthetic evaluation system

A veracious and feasible method is presented to systematically evaluate the risk of water inrush in karst tunnels. The methodology consists of two attribute recognition models: one is used in design stage, and the other one is applied in construction stage. Based on the principles of scientificity, rationality, operability and representative, several influence factors are selected as evaluation indices. In order to meet the requirement of the data format of attribute mathematical theory, a couple of evaluation indices are modified and quantitatively graded according to four risk grades through expert evaluation method. The weights of evaluation indices are rationally distributed by comprehensive assignment method, and the attribute measure functions are constructed to compute single index attribute measure and synthetic attribute measure. A confidence criterion is adopted to discern the risk grade of water inrush. Comparisons of the results derived from the present method and a case study are made. The results of the comparisons indicate that the evaluation results obtained from the proposed method are generally in a good agreement with the field-observed results. This risk assessment methodology provides a powerful tool for systematically assessing the risk of water inrush in karst tunnels.     

索风营水电站库区左岸河间地块喀斯特渗漏勘察技术

喀斯特渗漏勘察是喀斯特地区水利水电工程建设项目勘测设计的重要内容,成果评价将对工程产生重大影响甚至制约到工程成立与否.文中以索风营水电站水库左岸河间地块的喀斯特水文地质勘察为实例,对有关勘察工作的技术路线、勘察技术、喀斯特水库渗漏评价方法及处理思路作相应的探讨.     

地下水升降分析的灰岩地区生态环境问题

土洞、天坑等岩溶塌陷的发生越来越频繁，严重威胁人民群众的生命财产安全。文中从灰岩地区发生岩溶塌陷的主要诱因地下水水位升降的角度入手，分析导致岩溶塌陷进而破坏生态环境的原理，并针对基于这种诱因的岩溶塌陷的发生原理提出相应建议。     

280排水平峒岩溶施工技术研究

结合工程实际,介绍了在岩溶巷道施工中遇到的岩溶问题,在采取超前支护、护帮固底等技术措施后,确保了施工安全和施工质量,取得了良好的施工效果。     

四川盆地中二叠统储层特征与勘探方向

近年来,四川盆地中二叠统天然气勘探取得了可喜的进展,多口井在中二叠统茅口组、栖霞组白云岩孔隙型储层段钻获高产工业气流,中二叠统成为该盆地现阶段最现实的接替层系之一。为明确下一步的勘探方向,分析了四川盆地中二叠统的沉积背景和有利储层类型。结果表明：沉积环境主要为开阔台地浅水碳酸盐岩沉积环境;沉积时,古地貌西高东低,中西部生屑滩相储层较东部更为发育;地壳拉张使得中二叠统具备热水沉积、热液改造的良好条件;对勘探有利的3种储层类型为栖霞组滩相白云岩孔隙型储层、茅口组热水白云岩孔隙型储层和茅口组岩溶储层,其中白云岩孔隙型储层是中二叠统最有前景的勘探目标。结论认为：①川西北部—川中地区中二叠统灰质烃源岩生烃强度大,具有形成大中型气田的物质基础;②川西地区栖霞组白云岩储层较厚,是中二叠统天然气勘探的最有利地区;③上述3种储层类型均发育的地区主要分布在川中地区,其3套储层纵向上叠置,勘探潜力大;④剑阁—南充—丰都地区位于热次盆区带,其茅口组热水白云岩储层发育且叠加茅口组岩溶储层,天然气勘探前景好。