土石混合料强度特性的试验研究

Experimental study on intensity character of rock-soil aggregate mixture

开挖山体得到的土石混合料因强度高、施工方便而被广泛用作路基或基础的填料,但由于受地质条件、含石量、粒度分布范围及颗粒粒径等因素的影响,土石混合料的力学性质表现出明显的非线性,强度指标无法通过常规的试验设备检测,导致应用土石混合料填筑的路基或基础经常出现较大的差异沉降或滑塌,严重影响上部结构的使用。为了研究土石混合料的强度特性及其随各影响因素的变化规律,对室内大型直剪试验进行了改进,研制了新型的大型直剪试验系统,对不同类别土石混合料在不同影响因素下进行了击实试验和大型直剪试验。研究发现,在高应力条件下,土石混合料的剪切破坏不再完全符合库仑定律,抗剪强度应进行一定的折减;试验结果揭示了土石混合料的强度指标随各主要影响因素的变化趋势,初步建立了土石混合料指标随各影响因素的变化规律。结果还表明,母岩性质及含石量对混合料的强度指标影响较大,硬岩类混合料的内摩擦角普遍比软岩类高,混合料的强度随含石量变化规律为,当含石量小于30%时,含石量的变化对强度影响较小,随含石量的增加,混合料的强度也呈抛物线形增长,一般至含石量为70%左右达到峰值。

Rock-soil aggregate mixture come from excavation is broadly used as filling in roadbed and foundation for its high density and convenience construction; affected by geology, rock-soil ratio, grain size distribution and other factors, the mechanical behavior of rock-soil aggregate mixture puts up obviously nonlinearity; additionally its intensity index can＇t detect by routine tests, so that roadbeds or foundations filled with rock-soil aggregate mixture always occur a rather large differential settlement or slump, severely affecting the function of superstructure. To disclose its intensity character and variety rules with influencing factors, this study improved large scale direct-shear test, developed a large scale direct-shear test system, using this improved large scale direct-shear test system, carded out shear test on different kinds of rock-soil aggregate mixtures. The results show that the shear destroying rule of the mixture did not obey Coulomb law on high stress condition; its intensity should be discounted. Test results show the variety tendency of intensity index with influencing factors; the elementary rules of the friction angle varied with apiece influence factor are established. Test results also show that the character of native rock and rock-soil ratio of mixture have relatively bigger influence to the intensity index; the friction angle of hard rock mixture general is greater than that of soft rock mixture; rock-soil ratio has little influence on the intensity while the rock-soil ratio less than 30 %; the intensity of mixture increases with the increment of rock-soil ratio as parabolic curve, generally reach peak value at the ratio about 70 %.