Field monitoring of wicking geotextile to reduce soil moisture under a concrete pavement subjected to precipitations and temperature variations

Wicking geotextile can reduce water contents in pavement layers under unsaturated conditions due to capillary action through grooves of wicking fibers. Reduction of soil water content under the pavement can minimize pavement distresses. So far, there have been limited use and verification of the wicking geotextile in reducing water content of soil under concrete pavements in the field. In this field study, moisture sensors were installed in three test sections under a newly-built concrete pavement during its re-construction. The base course in one test section had a higher percentage of small particles than those in other two sections. The wicking geotextile was used between the base course and the subgrade in two test sections while a nonwoven geotextile was used in one test section. All test sections were subjected to precipitations and temperature variations. Field monitoring data showed that the wicking geotextile reduced the volumetric water content (VWC) of an aggregate base more than the nonwoven geotextile and its wicking ability decreased as the content of small particles increased. In addition, the wicking ability of the wicking geotextile decreased as the temperature decreased due to the reduction in the evaporation rate and the increase in the water retention capacity of the soil at low temperatures.     

A laboratory investigation on the impact resistance of a woven geotextile

This paper focuses on the impact resistance of geotextiles when subjected to impact loadings induced by dropping of stones. Such scenarios occur when geotextiles are used as a protective measure for fine granular material where is prone to be washed away. Usually, these geotextiles are restrained by placement of stones on top of them. A laboratory testing program is performed to expose a woven geotextile under dropping of a concrete block with various dropping energies and geometries. The induced damage on the geotextiles is inspected after the drop. Results indicate that as the drop energy increases, not only the possibility of puncturing of geotextiles increases but, in case of puncturing, the punctured area of geotextile expands as well. In addition, it is found that the geometry of the concrete block, where it collides on the geotextile, plays an important role on the survivability of geotextiles. In addition, PIV analysis has been performed to better understand the deformation pattern of the geotextile under impact loading. Based on the PIV results a simple scheme is suggested to estimate the drop energy threshold that the geotextile can survive under certain block geometry.     

武山尾矿坝无纺土工织物滤层化学淤堵问题初探

土工织物作为滤层在尾矿坝排渗设施中已得到广泛应用,但有些尾矿坝遇到了土工织物淤堵问题。本文针对武山铜矿尾矿坝排渗系统中发生的土工织物淤堵问题,通过一系列试验研究对无纺土工织物化学淤堵问题进行了初步探讨。研究结果表明氢氧化铁凝胶在织物纤维上的附着是化学淤堵的主要机理,尾矿中含有充分多的细粒黄铁矿且滤层处于非饱和渗流带或饱和- 非饱和交替变化渗流带是土工织物发生严重化学淤堵的必要条件     

Application of a new binary harmony search algorithm in highway rehabilitation decision-making problems: a case study in Iran

Due to the importance of optimisation in highway rehabilitation projects and the shortcomings of mathematical programming in performing such a task at a quite reasonable runtime span, a new binary harmony search (BHS) is devised to accomplish the decision-making process of highway rehabilitation problems. A new formulation and a BHS are developed and applied to a case study problem consisting of 96 highway segments needing rehabilitation, a number of which should be selected to be rehabilitated at a fixed budget in order to maximise the total quality of the highway network with the minimum possible cost. The BHS provides the value 1 for the segments which must be reconstructed and 0 for the remaining. Pavement Condition Index is employed to assess the quality of the highway. Several sensitivity analyses were performed to examine the influence of different parameters on the output.     

Field behaviors of a geogrid reinforced MSW slope in a high-food-waste-content MSW landfill: A case study

A one-year field monitoring of a geogrid reinforced municipal solid waste (MSW) slope was conducted in the Xingfeng Landfill. Settlement tubes, strain gauges and earth pressure cells were used to measure the vertical settlement, the reinforcement strains and the vertical earth pressures in the reinforced MSW slope, respectively. During the monitoring period, the waste sliding occurred and the fresh MSW was dumped at the top of the reinforced slope. The vertical settlement along the reinforcement was nonlinear and the peak settlement occurred at the central part of the reinforcement. The reinforcement strains and the vertical earth pressures at various positions were affected by the sliding and the waste dumping to differing extents. Along the lengths of the geogrid reinforcements, the reinforcement strains showed single-peak distributions. The peak strains were attained in the central part of the reinforcements and the minimum strains were attained at the tail ends. The vertical earth pressures mainly depend on the overlying loads; however, the distributions of them along the reinforcement were nonlinear. Based on the monitoring results, the slope stability evaluation was conducted. It shows that the internal stability of the reinforced MSW slope might be sufficient, while the external stability was insufficient, meaning that this reinforced project was unsuccessful. Finally, various lessons and design suggestions learned from this unsuccessful project were discussed, which could provide valuable references for the future practice of geosynthetic reinforced MSW.     

Design optimization and observed performance of a super-large foundation pit excavation subjected to unsymmetrical loading in water-rich floodplain: A case study

In this work, a whole-process solution was presented to reduce the risks of a super-large foundation pit excavation in water-rich floodplain and subjected to unsymmetrical loading. Firstly, numerical simulations were conducted to study the “size effect”, and the optimal control measures were proposed, i.e., 2 circles of diaphragm wall were used to divide the original super-large foundation pit into the inner and the outer pits, and the central-island style zoned excavation was adopted. Similarly, the “unsymmetrical loading effect” was studied, and the optimal control measure was proposed, i.e., an additional level of horizontal struts was added at the side with unsymmetrical loading. Then, considering the above suggestions, the design optimizations of supporting system, water proof system, and construction sequence were conducted. Next, a numerical model considering the adopted design optimizations was established to predict the excavation-induced retaining wall deflection, ground settlement, etc. Finally, an automatic and manual monitoring combined system was established, and the deformation and force behaviors of the foundation pit excavation were captured to verify the rationality of the adopted design optimizations. According to the observed performance, the risk assessment, warning, and disposal were conducted. The research can provide useful experience for similar projects.     

Ecological networks as a new approach for nature conservation in Turkey: A case study of İzmir Province

This paper aims to identify and evaluate a potential ecological network including core areas and large-scale corridors in the İzmir Province and its surrounding areas, Turkey. It is one of the first studies on the connectivity for mammal species and the detection of potential ecological corridors for Turkey. Four wide-ranging species (Hyaena hyaena, Lynx lynx, Caracal caracal, and Felis chaus) have been chosen as target species. Existing Key Biodiversity Areas (KBAs) and surrounding lands have been evaluated based on a three criteria: (1) vegetation/habitat types, (2) carrying capacity and (3) road density using simple GIS-based models.The results are evaluated using the Minimum Viable Metapopulation (MVMP) standards. No KBA in the study region has a Key Population (KP) or Minimum Viable Population (MVP) with the exception of Boz Dağlar. Least cost-path analysis has been applied to identify linkages between KBAs relevant for the four target species. The conclusion is that it is possible to maintain MVPs in the region when the KBAs are linked by ecological corridors.     

15分钟生活圈公共服务设施绩效评估方法构建——基于供需平衡视角的长沙市实证研究

结合长沙市“一圈两场三道”两年行动计划的实践经验,从供需平衡的视角切入15分钟生活圈的公服设施绩效评估,围绕日常生活、长者照料、教育培养、文体娱乐、医疗护理、社区就业、公共空间、慢行环境等8个维度建立了28分项的指标评价体系,并通过手机信令数据测度居民小区的设施需求度、通过开源数据与调研数据测度设施供给情况,采用先评估居民小区、再均值降维至生活圈单元的方法展开分析,结果发现：（1）强政府导向型、弱市场导向型、景观导向型设施在空间分布存在不同偏好特征,并浅析了差异产生的原因;（2）不同年龄群体对公服设施的需求偏好不同,引入设施需求紧迫度的概念,可辅助判断设施缺项生活圈单元的建设时序,为其他城市的生活圈规划研究与实践提供一定参考。     

A numerical study of THM effects on the near-field safety of a hypothetical nuclear waste repository—BMT1 of the DECOVALEX III project. Part 3: Effects of THM coupling in sparsely fractured rocks

As a part of the international DECOVALEX III project, and the European BENCHPAR project, the impact of thermal–hydrological–mechanical (THM) couplings on the performance of a bentonite-back-filled nuclear waste repository in near-field crystalline rocks is evaluated in a Bench-Mark Test problem (BMT1) and the results are presented in a series of three companion papers in this issue. This is the third paper with focuses on the effects of THM processes at a repository located in a sparsely fractured rock. Several independent coupled THM analyses presented in this paper show that THM couplings have the most significant impact on the mechanical stress evolution, which is important for repository design, construction and post-closure monitoring considerations. The results show that the stress evolution in the bentonite-back-filled excavations and the surrounding rock depends on the post-closure evolution of both fields of temperature and fluid pressure. It is further shown that the time required to full resaturation may play an important role for the mechanical integrity of the repository drifts. In this sense, the presence of hydraulically conducting fractures in the near-field rock might actually improve the mechanical performance of the repository. Hydraulically conducting fractures in the near-field rocks enhances the water supply to the buffers/back-fills, which promotes a more timely process of resaturation and development of swelling pressures in the back-fill, thus provides timely confining stress and support to the rock walls. In one particular case simulated in this study, it was shown that failure in the drift walls could be prevented if the compressive stresses in back-fill were fully developed within 50 yr, which is when thermally induced rock strain begins to create high differential (failure-prone) stresses in the near-field rocks.