固结度对复合土工排水网-废弃黏土界面拉拔特性的影响

The effect of consolidation degree on the pull-out behavior of geocomposite drainage layer-abandoned clayed soil interface

中国沿海沿江软土地区产生的废弃渣土主要为渗透性差、抗剪强度低的黏性土,采用排水筋材进行加筋回填时,深入认识固结度对复合土工排水网(Geocomposite drainage layer,GDL)-黏性土界面强度的影响规律是工程渣土堆填场稳定性分析的重要基础。以武汉某基坑开挖渣土和商品化GDL为试验材料,开展了12组固结-拉拔试验,分析了固结度对GDL-黏土界面拉拔特性的影响规律。结果表明:界面拉拔曲线为应变软化型,固结度越大,达到峰值和残余拉拔力的位移也越大;随着固结度提高,界面峰值和残余摩擦角均呈增大趋势,而界面峰值和残余黏聚力变化不显著;随着拉拔位移的增大,GDL拉应力逐渐由坡形分布转向均匀分布。当固结度从0增大至90%时,界面峰值和残余强度分别提高了20.8%~111.1%和21.8%~101.7%,排水网芯的拉力承担比例则从80.4%~81.8%降低至62.5%~63.4%。该研究有助于深入认识GDL-黏土界面的相互作用机理,为废弃黏土堆填工程的稳定性分析提供依据。

The abandoned soils generated in coastal and riverine areas of China are dominated by cohesive soils with poor permeability and low shear strength.When reinforcing backfill with drainage reinforcement materials,a thorough knowledge of the effect of the consolidation degree on geocomposite drainage layer(GDL)-clayed soil interface strength is an important foundation for the stability analysis of excavated soil landfills.With representative excavated soil samples obtained from a foundation engineering site in Wuhan and commercialized GDL as the test materials,12 sets of combined tests of consolidation and pull-out were conducted to investigate the effect of the consolidation degree on GDL-clayed soil interface pull-out characteristics.The results show that the pull-out curve is strain-softening,and the higher the consolidation degree,the further the displacement to reach peak and residual pullout force.Both interfacial peak and residual friction angle tend to increase with the enhancement of the consolidation degree,while the interfacial peak and residual cohesive force change insignificantly.With the increase of pullout displacement,the GDL tensile stress gradually switches from a slope-shaped distribution to a uniform distribution.As the consolidation degree increases from 0 to 90%,the interfacial peak and residual strength increase by 20.8%-111.1%and 21.8%-101.7%,respectively,while the proportion of drainage core tension decreases from 80.4%-81.8%to 62.5%-63.4%.This study contributes to an in-depth understanding of the interaction mechanism at the GDL-clay interface and provides a basis for the stability analysis of abandoned clayed soil landfills.