土工织物散体桩桩体大三轴试验研究

对密实状态的土工织物散体桩桩体进行大三轴试验,研究其在不同围压和不同聚丙烯土工编织布筋材强度下的应力–应变特性,并据此提出桩体强度及模量理论计算公式。研究结果表明:土工织物散体桩桩体在三轴压缩下呈剪胀破坏,其剪切带上主要是筋材的横向筋丝产生断裂,且桩体剪切角与碎石的莫尔–库仑理论破裂角比较接近;在加载初期,土工织物散体桩应力–应变曲线下凹,而后近似线性增长至峰值应力,随后应力随应变减小并趋于稳定,表现为应变软化特性;同一筋材强度、不同围压的土工织物散体桩桩体强度所对应的轴向应变值比较接近;土工织物散体桩桩体的似黏聚力随筋材强度呈较好的线性增长关系,其较碎石的似黏聚力大很多,而筋材对桩体碎石的内摩擦角影响不大;建立了土工织物散体桩桩体强度及模量的理论计算公式,并采用试验值对理论公式进行修正,经修正后的结果与试验值吻合很好。

Large triaxial compression tests on geosynthetic-encased granular columns

Large triaxial compression tests are performed on geosynthetic-encased granular columns (GEGC) with gravels in dense state. The stress-strain characteristics of GEGC with different strengths of polypropylene woven geotextiles and different confining pressures are investigated. The theoretical formulas to compute the strength and modulus of GEGC are then proposed. The results show that the GEGC exhibits dilative shear failure under triaxial compression, and mainly the horizontal textile slices at the shear band break. The shear angle is close to the rupture angle of the Mohr-Coulomb strength theory. The stress-strain curve of GEGC at the preliminary loading stage is concave down, then its stress approximately increases linearly up to a peak stress, and subsequently decreases to a stable value, showing strain softening characteristics. The axial strains corresponding to the strengths of GEGC with the same reinforcement strength under different confining pressures are even close. The quasi-cohesion of the GEGC has a good linear relationship with the strength of reinforcements, and it is much larger than that of the gravels, but the strength of reinforcements has little effect on the internal friction angle of the gravels of GEGC. Theoretical formulas are established to compute the strength and modulus of the GEGC. The formulas are verified through the test data, and the correction factors for the formulas are obtained. The results of the modified formulas agree well with the test ones.