含石量与含泥量对压实砾石土力学特性影响的试验

对于夹泥砾石土，在应力、颗粒组成、含水率等因素影响下，其变形特性非常复杂。针对重庆机场道路工程填筑中所用的压实砾石土，通过中型样三轴试验开展了一系列力学特性试验研究，重点分析了含石量与含泥量的变化对于压实砾石土力学性能的影响，及不固结不排水（UU）、固结不排水（CU）、固结排水（CD）3种条件下的抗剪强度与变形特性；同时研究了UU条件下，不同制样含水率对压实砾石土的抗剪强度的影响。试验结果表明：压实砾石土在低围压条件下表现出强烈的剪胀性；UU三轴压缩试验条件下，小含泥量的压实砾石土的强度取决于大粒径颗粒间的咬合力，与含石量成正比；初始拌和含水率对压实砾石土UU强度的影响很大，颗粒粒组中的泥粒在高于最优含水率下易产生滑动，影响其应力-应变性状并导致其抗剪强度大幅降低；饱和固结后，压实砾石土的强度与含石量并没有直接的联系，高含石量并不代表高强度，合理的颗粒级配是决定试样CU，CD强度的重要因素；压实砾石土中含泥量增加会导致其抗剪强度的降低。另外，含石量和含泥量对压实砾石土的临界状态影响不大，同种矿物成分、不同颗粒组成的压密砾石土在CU，CD试验下的临界应力比为1.73。

Experiment of Influence of Stone Content and Clay Content on Mechanical Properties of Compacted Gravelly Soil

Under the effect of some factors such as the stress, particle composition, and moisture content, the deformation characteristics of gravelly soil mingled with clay materials are very complex. This type of soil is widely used in subgrade filling engineering. In the field construction, the composition of the filler fluctuates significantly, and so, the research on the effect of the mechanical properties of gravelly soil mixed with clay is of tremendous significance in engineering design. For the purpose of compaction, gravelly soil is used in the construction of an airport runway, and the influence of the gravel content and fine content on the mechanical properties of compacted gravelly soil is analyzed by a series of medium triaxial compression tests. In addition, its shear strength and deformation characteristics under the three different conditions of unconsolidated undrained, consolidated undrained, and consolidated drained are studied. Concurrently, the effect of different sampling water contents on the shear strength of compacted gravelly soil is studied. The test results show that the compaction of gravelly soil exhibits a strong shear expansion under a low confining pressure. Under the unconsolidated undrained (UU) triaxial compression test, the strength of compacted gravelly soil with small fine particles depends on the interlock force of the large particle size. It is in proportion to the gravel content; the initial moisture content of the mixture has a significant effect on the strength of the compacted gravelly soil, and the clay grain in the particle group could be easily slid with a moisture content higher than the optimum moisture content, influencing the stress-strain behaviour and significantly reducing the shear strength of the compacted gravelly soil. Moreover, there is no direct relation between the strength of the gravelly soil and gravel content under saturated consolidation. High gravel content does not represent the absolute high strength, and the rational particle grade is an important factor in determining the strength of the specimens under consolidated undrained(CU) and consolidated drained (CD) triaxial compression test. The increase in the clay content of the compacted gravelly soil will lead to a decrease in its strength. Moreover, the gravel content and clay content have little effect on the critical state of compacted gravelly soil. The critical stress ratio of compacted gravelly soil with the same mineral composition and different particle composition is 1.73 under the CU and CD tests.