排水条件对土工合成材料加筋黏性土特性的影响

Effect of drainage conditions on performance of clayey soil reinforced with geosythetics

通过固结排水和不固结不排水条件下的三轴剪切试验,研究了加筋对黏性土体强度和应力应变关系的影响以及不同排水条件下的加筋效果。结果表明,在排水条件下,筋材与土体的相互作用相对充分,明显提高了土体的峰值强度和残余强度,且峰值后强度的降低幅度较小,改善了土体的应力应变特性;随加筋层数和筋材拉伸模量增大,加筋效果明显提高。而在不排水条件下,由于孔隙水压力的影响,筋材与土体的作用相对复杂,加筋土体的强度和变形特性以及加筋效果与排水条件下的大不相同;在剪切初期,筋材的作用几乎被超静孔隙水压力抵消,加筋甚至对强度起相反作用,使加筋试件的强度低于素土试件;仅当应变较大时,加筋对抗剪强度才有轻微的增强作用,同时,在不排水条件下,筋材拉伸模量和加筋层数提高对加筋土体强度的影响不明显,因此,在加筋土工程中,排水条件是首先要考虑的因素。

The triaxial tests for consolidated-drained and unconsolidated-undrained clayey soils reinforced with geosynthetics are carried out to study the effect of drainage conditions on the performance of reinforced soils. The results show that under the condition of consolidated-drained both the peak strength and residual strength of reinforced soils are enhanced greatly and the reduction of post-peak strength is limited. As a result the stress-strain behaviors are improved. The effect of reinforcement increases with the increase of the amount of geothetics layer and elevation of tensile modulus of soils. Under the condition of unconsolidated-undrained, the interaction between reinforcement and soil become complicated due to the influence of the excess pore-water pressure. In the initial stage, the reinforcement effect is counteracted by the excess pore-water pressure and the reinforcement exhibits negative impact on the strength of soil resulting in the strength lower than that of without reinforcement. The strength of reinforced soil will not increase until the axial strain becomes large. It is concluded that the drainage conditions is the decisive factor in ensuring the effect of reinforcement.