土工合成材料改善砂土性能的进展研究

Review of Engineering Property Improvement and Modification of Sand By Geosynthetics

综述了土工合成材料的性能及其在提高砂土强度性能方面的实际工程应用效果,着重分析了筋土界面抗剪特性试验方法及其作用机理。(1)不同方法求得的筋土界面抗剪强度,斜板试验 >直剪试验 >拉拔试验、三轴试验。(2)粗、细砂由于粒径一致,能产生更好的钳固和咬合能力,而粗细混合砂由于细砂在其中的"滚轮"效果,却有着更小的抗剪能力。(3)填料为土类时,砂土含水率的增加会填充黄土颗粒间的孔隙和溶解颗粒间部分胶结物质,起到润滑作用。而填料为砂类时,加筋砂体含水率的增加却能有效提高筋土界面间抗剪强度。(4)在密实度或者竖向应力增大的情况下,砂土界面抗剪强度都会得到提高。最后指出,由于土工格室拥有着立体结构,会具有更好的抗弯能力,通过分散上部竖向应力,相对其他土工合成材料对于地基承载力的提高有着更好的效果。同时,暴露出土工合成材料相关的多数试验难以标准化,对试验仪器、试验方法以及机理的了解还不够完善,并且与实际工程运用的接轨还不够透彻等一系列问题,这将很大制约其相关的研究以及探索,因此,室内试验与实际工程运用的契合变得异常重要。

In this paper,the properties of geosynthetics and their practical engineering applications are reviewed.The test methods and results of the mechanical behavior at the soil reinforcement interface are also presented.The following conclusions can be drawn:(1)Various test are applied to obtain the soil-reinforcement interface shear strength and the results are different.From the highest shear to the lowest,they are:plate test,direct shear test,pull out test and triaxial shear test.(2)The poorly graded coarse or fine sand have a better interface shear strength due to the higher adhesion in the uniform graded particles.Whereas,the well graded sand samples have a lower interface shear strength due to the"lubrication effect"from particles of different sizes.(3)When the backfill soils are predominantly silty,clayey sands or dandy silt,sandy clays,the moisture increase will fill in the voids among particles and even dissolve some cementations and therefore results in a decrease of the interface shear strength.When the backfill soil consisting predominately sandy soils,the increase of moisture content can increase the interface shear strength.(4)When the increase of unit weight or normal stress will increase the interface shear strength of sandy soils.Compared with other geosynthetics,geogrids have the three-dimensional structure,and therefore,have a better interface shear strength potential for they have a moment resisting and can divert the upper stress to a larger area below the geogrid structure.This property of geogrid can effective improve the bearing capacity of sandy soils.The literature review also indicates that the standardization of laboratory test of geosynthetics still has a long way to go due to the lack of standardizing of test equipment,test procedure as well as the understanding of testing mechanism.It is very important that the laboratory testing should be able to simulate the practical engineering applications.