The future of the dolomitic springs after mine closure on the Far West Rand,Gauteng, RSA

Approximately 1.2 km of dolomitic limestone overlies the Far West Rand gold reefs southwest of Johannesburg, South Africa. This karst aquifer is partitioned into several groundwater compartments by predominantly north–south trending syenite dykes. Prior to mining, the primary water flow was westwards, decanting over dyke boundaries as a succession of springs along the Lower Wonderfontein Spruit. Dewatering of the overlying dolomitic aquifer for safety and economic reasons by deep gold mining operations, caused the water levels of four compartments to drop and their respective springs to dry up. By perforating dykes, formerly separated aquifers were hydraulically interconnected by mining. Using historical and recent data of water flow—surface and groundwater—and pumping rates, a geohydrological model is presented. The results suggest that the water tables will rise to their pre-mining levels within 30 years after mining ceases and that the dry springs will flow again, despite the compartments being connected by the extensive mining operations.

A technique for estimating permeability of a randomly fractured rock mass

Extensive field and laboratory testing programs were performed to develop a relationship between the permeability of a fractured limestone and the core recovery values. The studied limestone does not encompass any jointing system but is consistently and randomly fractured. Nineteen in situ falling head permeability tests were carried out to measure permeability of the fractured rock mass at a representative study area. Analysis of test results has led to the formulation of an empirical equation that estimates the permeability of the rock mass in terms of its solid core recovery value and the permeability of the fractures filling material. Unlike the existing equations for estimating the permeability of rock masses, the proposed equation is simple and utilizes parameters that can be easily determined in regular geotechnical field and laboratory investigations. A technique is also presented to estimate the permeability of a rock layer, the quality of which significantly changes with depth, using the proposed equation that utilizes a single value of core recovery. Analysis of well-documented pumping test results supported the validity of the proposed equation and technique.     

基坑降水值得重视的问题

本文介绍基坑降水工程值得重视的问题:正确测定基坑降水设计的水文地质参数；强化基坑工程施工的管理与监测，并推荐适用于工程勘察的小口径井抽水试验。     

Characterization of bottom sediments from Osaka Bay,Japan

The physical, chemical, and dewatering characteristics of 19 bottom sediments from Osaka Bay, Japan, have been analyzed to aid in the development of sediments in the coastal bay area. The sediments in the east near Osaka Port were highly polluted from the influence of human activities and were difficult to dewater. These sediments were composed of fine particles, low in pH, zetapotential, and initial settling rate, and were high in ignition loss, metal concentrations, compression volume, specific resistance, cake water content, and drying index. However, the sediments near Akashi Channel showed the reverse where they are affected by strong tidal current. A correlation analysis has been made of all the parameters. There are significant relationships between all the dewatering parameters. Therefore, sediments difficult to dewater by gravity settling are also difficult to dewater by vacuum filtration and solar evaporation. Sediments containing fine particles and pollutants are difficult to dewater. Several forms of pollutants can occur in the sediments.     

南京G大厦环境工程地质问题原因探析

就G大厦环境工程地质问题产生的原因进行了分析 ,提出了在城市兴建大型建筑物进行的深基坑开挖前 ,一定要重视环境工程地质的调查 ,预测将产生的环境工程地质问题 ,并进行合理的处理及必要的检测 ,以保证施工及其使用的安全。     

复合含水层地区深基坑降水三维渗流场数值模拟--以上海环球金融中心基坑降水为例

长江三角洲分布有巨厚、松散的第四纪沉积层,地下含水系统为一复合含水层系统,深基坑降水一般采用非完整井,且由于深基坑周围连续挡水墙难以深入含水层底板,所以其地下水渗流场变化极其复杂,具有明显的三维流特征。本文以上海环球金融中心深基坑降水为例,采用数值模拟方法,模拟了在多层含水层复合存在、含水层最深底板埋深达149m、基坑周围挡水连续墙埋深达34m、基坑内地下水位降深达26m的情况下的地下水三维渗流场特征,并以此为据确定出了该基坑降水的最优化方案。     

Calculation of head difference at two sides of a cut-off barrier during excavation dewatering

This paper proposed a series of simple equations to calculate the head difference at the two sides of waterproof curtain. The barrier effect of waterproof curtain is considered from two situations with respect to without barrier case: (i) groundwater head difference below the barrier and (ii) groundwater head difference by convergence into the opening. The solution for the first situation can be derived from hydraulic analyses and the second situation can be obtained using a numerical analysis. The final groundwater head difference is the sum of these two situation according to the superposition principal. In the proposed equations, the head difference is expressed as a function of the inserted depth of the barrier into confined aquifer, the ratio of the hydraulic conductivity of the aquifer, the thickness of the aquifer, and hydraulic gradient under normal conditions. Finally, the proposed equation was applied to a field case to verify the validity of the proposed approach. Compared with the field data, the results show that the proposed method is reasonable.     

城市给水厂排泥水处理工艺设计

介绍了北方城市某水厂A排泥水处理工程的工艺流程以及构筑物设计.该设计采用调节池、重力浓缩和带式压滤机脱水的处理工艺,节约了水资源.工程自动化程度高,运行管理方便,有效保证了水质安全.     

Parameter estimation and simulation of dependence of constant pressure batch dewatering on initial solids concentration

The problem of predicting dependence of constant pressure batch dewatering of particulate suspensions on feed solids concentration is considered. Scaling transformations which demonstrate that evolution in the cake consolidation stage of dewatering is governed by an underlying self-similar behavior are proposed. The self-similar master curve, which can be obtained using only one set of experimental dewatering data obtained with a feed suspension having solids concentration above the gel point, is employed for estimating dependence of key dewatering process parameters on feed solids concentration. Using the parameter estimates in a Darcy's law based dewatering model, it is shown that the complete evolution of dewatering for a desired feed solids concentration can be predicted with reasonable accuracy. The approach is simpler to implement in comparison to available pressure filtration models, which require several suspension characterization experiments.     

降水强夯结构填石处理大面积软弱粉土地基试验研究

浙江省粉土、砂土分布广泛,但使用强夯法处理软弱粉土地基鲜见报道。通过某工程降水强夯结构镇石处理软弱粉土地基的试验研究,笔者认为用该方法处理大面积浅层粉土地基可取得良好的效果,具有很好的社会和经济效益。