土工织物拉伸对孔径特征及反滤性能影响的研究

As filtration materials, geotextiles are widely used in water conservancy, civil engineering, transportation and many other fields. Pore size characteristics are important parameters in filtration applications. The filtration applications of geotextiles are usually subjected to tensile loads, whereas the characteristic pore sizes are commonly tested and determined in the unstrained condition, which results in clogging or leaking of soil despite the satisfaction of design criteria. Nowadays, the conclusions are based on accumulated experience, the relationships among plane tensile strain, pore size characteristics and filtration characteristics have not been established. Characteristic pore sizes are related with the geometry of pores, which are not suitable to be studied on stress. Hence, it is quite important to explore the influence of tensile strains on pore size characteristics. The biaxial tensile strain can be accurately maintained by biaxial orientation stretching machine. The strained pore size of woven geotextiles can be determined by imagine analysis. The strained pore size of nonwoven geotextiles can be tested by dry sieving. The strained filtration characteristics can be studied by the gradient ratio test. The relationships among plane tensile strain, pore size characteristics and filtration characteristics will be established to serve for design, production and construction.

土工织物作为透水和反滤材料广泛用于水利、土木、交通等领域，其特征孔径是渗透性能和反滤性能的重要指标。反滤材料主要工作状态和破坏状态均为受拉，而产品标准和设计参数均为未受力状态，导致反滤失效，工程失败。现有研究主要限于拉伸对特征孔径和反滤性能的分别影响，尚未建立起拉应变、特征孔径和反滤性能三者的有机联系。受拉后孔径改变包括几何尺寸和形状，亟需在严格应变控制下开展研究。本项目采用独立控制双向拉应变试验，通过图像法和干筛法分别测量有纺、无纺织物孔径，利用梯度比渗透仪测试不同应变状态下土工织物反滤指标；建立基于几何尺寸和形状变化的有纺织物特征孔径预测模型，基于特征孔径或空间概率理论的无纺织物孔径预测模型。利用应变控制下的实验数据对预测模型加以修正，最终确立拉应变、特征孔径和反滤性能三者的量化关系，指导生产、设计和施工。

土工织物作为反滤材料广泛应用于防洪减灾、近海工程和环境保护等领域。织物的反滤设计依据保土、透水、防淤堵三个准则。特征孔径和孔径分布是重要的反滤设计参数。土体变形使织物处于受拉状态。目前的产品标准和设计参数均为未受拉状态。现有研究主要限于拉伸对单个特征孔径O95或O98及渗透性能的影响，尚未建立织物的拉应变、孔径分布和渗透性能三者的关系表达式。.本项目测试了土工织物在严控拉应变下的孔径变化，揭示了特征孔径和孔径曲线随拉应变的变化规律，建立了土工织物的拉应变、孔径特征、反滤性能三者之间关系。针对有纺织物建立了拉应变下的孔径追踪机制，测试了拉伸作用下有纺织物特征孔径和孔径分布曲线的变化规律；针对无纺织物，采用干筛法测试拉伸作用下特征孔径和孔径分布的变化规律；研究了土工织物作为滤膜时“土工织物-桩”排水体系的固结解析解。基于以上理论，研究了遗址保护中“土工织物-土-糯米-桐油”保土体系的微观尺寸形态和隧道开挖中“土工织物-土”体系的保土性能。建立拉应变-孔径-渗透性能三者关系。取得以下研究成果：.（1）针对土工织物的特征孔径和孔径分布开展研究，通过数字图像法和干筛法，测试拉应变下的孔径变化规律。建立能反映拉伸作用、孔径与反滤性能三者关系的表达式。孔径分布曲线对不同孔径受拉时的反滤设计需求更具有参考性。基于孔径变化探究了土工织物作为滤膜时“土工织物-桩”排水体系的固结解析解。.（2）研制了土工织物侧限拉伸仪器，实现了对土工织物侧向限制的同时进行拉伸，开展了侧限拉应变下土工织物的孔径变化研究，建立了侧限拉应变和土工织物孔径的关系表达式。更好地模拟了工程中侧向限制工况下土工织物的孔径变化。.（3）针对土工织物受拉状态下孔径尺寸、孔径形状等参数的变化规律进行研究。基于孔径特征的变化规律，分别研究了遗址保护中“土工织物-土-糯米-桐油”的微观尺寸形态、隧道开挖中“土工织物-土”保土体系的土体稳定性。