Permeability of Hydraulic Fills and Barricade Bricks

Permeability is one of the most important parameters in the design of hydraulic backfilling of mine stopes. A simple and reproducible method was developed for preparing reconstituted hydraulic fill sample in the laboratory, that is representative of the hydraulic fill in the mine stope, replicating the slurry sedimentation process taking place in the mine. Constant head and falling head permeability tests were carried out on the samples, giving consistent results. A brick permeameter was developed to study the flow characteristics of the porous barricade bricks under one-dimensional flow, simulating the flow conditions in the mine. Three different methods were used to determine the permeability of the brick and the results showed very good agreement. This is the first rational attempt to measure the permeability of the porous barricade bricks that are used to close the horizontal access drives in the mines, thus retaining the hydraulic fill. The measurements show that the permeability of the barricade brick is about two to three orders of magnitude greater than that of the hydraulic fill.     

A Solution to the Problem of Predicting the Suitability of Silty–clayey Materials for Cement-stabilization

Major geotechnical problems in construction involving silty–clayey soils are due to their low strength, durability and high compressibility of soft soils, and the swell–shrink nature of the overconsolidated swelling soils. Confronted with these problems, a suitable ground improvement technique is needed, for deep excavations in soft clays, for stability, durability and deformation control. Cement-stabilization is one of the alternatives. An increase in strength and durability, reduction in deformability are the main aims of this method. Conventional cement-stabilization methods are used mainly for surface treatment. However, the use of cement has recently been extended to a greater depth in which cement columns were installed to act as a type of soil reinforcement (deep cement–soil mixing and cement jet grouting). In situ engineering properties of these silty–clayey soils are often variable and difficult to predict. For this reason cement-stabilization methods have a basic target to control the aforementioned engineering properties of these clays so that the properties of a silty–clayey soil become more like the properties of a soft rock such as clayey shale or lightly cemented sandstone. So cement-stabilization of these soils is essential to control their engineering properties and to predict their engineering behaviour for construction. In an effort to predict, classify and study the suitability of silty–clayey soils for cement-stabilization both slaking and unconfined compressive strength tests were carried out on clayey–sand mixtures consisted of two types of clays, kaolin and bentonite. Finally diagrams were prepared to study the variation of slaking and strength due to compaction, curing time and cement percentage and also to predict areas of efficient cement-stabilization.     

Dynamics and interaction of organic carbon, turbidity and bacteria in a karst aquifer system

The dynamics of organic carbon (OC), turbidity, faecal indicator bacteria and physicochemical parameters was studied in a karst system near Yverdon, Switzerland. Online measurements and sampling were done at a swallow hole draining an agricultural surface (the input), and two groups of springs (the outputs) that often show bacterial contamination. A fluorescent tracer that was injected into the swallow hole during low-flow conditions first arrived at the springs 10–12 days after injection; the total recovery rate was 29%. Previous tracer tests during high-flow conditions gave shorter travel times. After a major rainfall event, a primary turbidity peak was observed at the springs. It coincides with the rising limb of the hydrograph, indicating remobilisation of autochthonous particles from the aquifer. A secondary turbidity peak occurs several days later, suggesting the arrival of allochthonous particles from the swallow hole. Wider peaks of OC and bacteria were observed simultaneously. Applying methods from molecular microbiology (PCR-DGGE) allowed characterisation of the bacterial communities at the swallow hole and the springs. The results demonstrate that the swallow hole is an important source of groundwater contamination, while its contribution to aquifer recharge is insignificant. OC appears to be a better indicator for bacterial contamination than turbidity.     

交互的初至波反演及静校正

一种人机交互式的初至波反演方法是在反演过程中加入人为的干预,并利用人的经验控制反演的方向,使结果更加符合实际的地质情况。再将反演的结果与其它的短波长静校正方法相结合,就能够有效地提高静校正的精度。实例证明,这种方法是有效且可行的。     

迭代折射静校正技术在鄂北地震资料处理中的应用

在低速层速度(地表直达波)已知的条件下,利用生产炮初至信息,用加权最小平方法和共轭梯度法建立的折射静校正数学模型,迭代求取长波长、短波长静校正量,在解决鄂尔多斯盆地北部的虚假小幅度构造问题及改善剖面质量方面取得了明显的效果。     

条带开采煤柱稳定性的试验模拟与数值分析——以山东省济宁市太平煤矿为例

以山东省济宁市太平煤矿为例，采用煤柱模拟试验和数值分析手段，对薄基岩条带开采时所留设煤柱的应力应变状态、煤柱强度结构及煤柱长期稳定性进行了深入的分析与研究，揭示了煤柱稳定性及煤柱应力分布与条采尺寸、采出率、覆岩特征的相互关系，进行了条带煤柱的稳定性评价，为工程实践提供了理论依据。     

粉煤灰浸出特性试验研究

利用浸出试验方法,对火电厂粉煤灰进行浸出特性的测定,对其有害特性进行鉴别并分析其浸出规律,从而为地下水受粉煤灰排水影响后的水质预测、堆灰场选址、环境影响评价提供依据.     

地下导线随盾构推进逐段接测中的可靠性检验

盾构法施工的要点是需要在井下布设高精度的控制支导线，当我们根据盾构推进进度对导线接测时，由于观测条件、观测方法、观测仪器基本相同，但观测、的成果往往会存在一定的差异，有时我们无法直接判断成果的正确与否，此时，采用测量平差中的统计检验的方法来分析这些观测数据，可以取得比较满意的结果。     

DGSC—203型液动射流冲击器在地热井的试验

介绍了新研制的DGSC－203石油钻井液动射液冲击器的性能参数及结构设计上的创新点，测试所获得的排量与压降之间的关系曲线可指导冲击器的使用。生产性试验证明该冲击器工作稳定，可大幅度提高硬地层钻井效率，克服钻柱振动，延长钻柱的使用寿命，具有良好应用前景。     

A mathematical hysteretic model for elastomeric isolation bearings

An analytical model for high damping elastomeric isolation bearings is presented in this paper. The model is used to describe mathematically the damping force and restoring force of the rubber material and bearing. Ten parameters to be identified from cyclic loading tests are included in the model. The sensitivity of the ten parameters in affecting the model is examined. These ten parameters are functions of a number of influence factors on the elastomer such as the rubber compound, Mullins effect, scragging effect, frequency, temperature and axial load. In this study, however, only the Mullins effect, scragging effect, frequency and temperature are investigated. Both material tests and shaking table tests were performed to validate the proposed model. Based on the comparison between the experimental and the analytical results, it is found that the proposed analytical model is capable of predicting the shear force–displacement hysteresis very accurately for both rubber material and bearing under cyclic loading reversals. The seismic response time histories of the bearing can also be captured, using the proposed analytical model, with a practically acceptable precision. Copyright © 2002 John Wiley & Sons, Ltd.