Controlling strain in geosynthetic liner systems used in vertically expanded landfills

According to relevant new regulations in China,a composite liner system involving geosynthetic materials must be installed at the bottom of an expanded landfill.The deformation and integrity of the composite liner under a variety of factors are important issue to be considered in the design of a landfill expansion.In this paper,we investigate the strain distribution in geosynthetic materials within the composite liner system of expanded landfills,including strains in geosynthetic materials resulting from overall settlement and lateral movement of landfills,localized subsidence in landfills,and differential settlement around gas venting wells.The allowable strains of geosynthetic materials are discussed based on the results of tensile tests,and the corresponding design criteria for composite liner systems are proposed.Meanwhile,practical measures allowing strain control in geosynthetic materials used in landfill engineering are proposed.

Towards a sustainable geoliner construction in landflls by potential blending of fly ash with kaolin clay alternative:a review with an insight to Indian scenario

Electricity generated through coal-based Thermal Power Plants(TPPs)has played a pivotal role in shaping modern civiliza-tion,revolutionizing industries,and improving the quality of life for billions of people worldwide.These TPPs contribute to about 37%-40%of the global energy requirements.Energy production,in turn,has a direct impact on the economy of any country.Apart from this boon to humankind,these TPPs combusting coal as their primary fuel also have specific environmen-tal impacts,the major ones being water,air,and soil pollution due to unscientific disposal of high-quantity fly ash produced yearly.If we can put this ash to good use,it may assist us in mitigating the pollution caused by it.Although there are many conventional uses of fly ash,such as a pozzolanic material in the cement industry,more pathways need to be discovered to balance the high generation quantities with consumption.Therefore,a detailed description of its use in potential geoliner applications is presented in this article.A geoliner or a landfill liner acts as a virtually impenetrable layer to mitigate the leachate penetration into the underneath subsoil and groundwater,thus preventing contamination.There are presently some studies that support the use of only fly ash in such applications.Nevertheless,the properties of the geoliners using it are not so good to significantly mitigate environmental degradation owing to its high permeability and low densification tendency.The bentonite conventionally used has limited deposits and is mined intensively for its use as a natural sealant.Their depos-its must also be conserved,and an alternative material that may serve similar application benefits,like bentonite,must be selected.The desired aim can be fulfilled if we blend this combustion residue with other suitable materials(such as kaolinite clay)with low permeability.Thus,the article focuses on the possibilities of blending fly ash with different clays for geoliner construction to improve the individual properties of fly ash.This will contribute to developing a scope for future scientific research in deploying these blends in natural membrane materials for various industries.Different types of geoliners that are designed to contain the disposed-off waste are also explained in detail.Additionally,a glimpse of the global fly ash market is put forward to depict its importance for various industries in this technologically advancing world.This article profoundly observes an overall environmental management aspect regarding waste utilization.

HCWCI/Carbon Steel Bimetal Liner by Liquid-Liquid Compound Lost Foam Casting

Impact, friction and corrosion from the grinding balls and the grinding medium during the mineral processing result in liner breakage. Liner, made from Hadfield steel or alloyed steel, could not have served in wet grinding environment for more than ten months. Composite liner, made from HCWCI (high Cr white cast iron) and carbon steel, has been developed successfully with liquid-liquid composing process based on LFC (lost foam casting). The microstructure of composite was analyzed with optical microscope, SEM (scanning electron microscope)/EDX energy-dispersive X-ray and XRD (X-ray diffraction). According to micrograph, the combination region of two metals was staggered like dogtooth, no mixtures occurred between two liquid metals, and its interface presented excellent metallurgical bonding state. The results of mechanical property test show that, the hardness of HRC, the fracture toughness, and the bending strength are more than 61, 16.5 J/cm2 and 1 600 MPa, respectively. Comparison between liners made from bimetal composite and alloyed steel has also been investigated in industrial hematite ball mill. The results of eight months test in wet grinding environment prove that the service life of bimetal composite liner is three times as long as that of one made from alloyed steel.

Stability analysis and optimization of excavation method of double-arch tunnel with an extra-large span based on numerical investigation

The Xiamen Haicang double-arch tunnel has a maximum span of 45.73 m and a minimum burial depth of 5.8 m.A larger deformation or collapse of the tunnel is readily encountered during tunnel excavation.It is therefore necessary to select a construction approach that is suitable for double-arch tunnel projects with an extra-large span.In this study,three construction methods for double-arch tunnels with extra-large spans were numerically simulated.Subsequently,the deformation behavior and stress characteristics of the surrounding rock were obtained and compared.The results showed that the double-side-drift method with temporary vertical support achieves better adaptability in the construction of such tunnels,which can be observed from both the numerical results and in situ monitoring data.In addition,the improved temporary support plays a critical role in controlling the surrounding rock deformation.In addition,the disturbance resulting from the excavation of adjacent drifts was obvious,particularly the disturbance of the surrounding rock caused by the excavation of the middle drift.The present findings can serve as the initial guidelines for the construction of ultra-shallowly buried double-arch tunnels with extra-large spans.