Study On Deformation Characteristics Of Compacted Gravelly Soil Under Static And Dynamic Loads

Gravelly soil is often used as filling material in engineering such as water conservancy project,subgrade engineering and high fill engineering,for its good compaction,high shear strength and good permeability.With a complex material structure,the mechanical property of gravelly soil is influenced by numerous factors,the operational performance of the material is closely related with the mechanical property of gravelly soil.The paper proceeded with the indoor tests,and conducted a series of static and dynamic triaxial tests,studied the mechanical properties of compacted gravelly soils in three different working conditions.By triaxial test on five groups of gravelly soils with different grading under 3 kinds of different conditions,the deformation and strength characteristic of gravelly soils were obtained,and the effects of gravel content,clay content and the moisture content of sample preparation on the mechanical properties of compacted gravelly soil is analyzed.The results indicates:The compaction gravel soil manifests a strong shear expansion under low confining pressure.Under unconsolidated undrained(UU)test,the strength of the compacted gravel soil with little fine particles depends on the interlock force of the large particle size,and is in proportion to the gravel content;the initial moisture content of the mixture has a great influence on the strength of the compacted gravel soil,and the clay grain in the particle group can be easily sliding with a moisture content higher than the optimum moisture content,in which the stress-strain behavior is influenced and the shear strength of the compacted gravel soil is significantly reduced.And there is no direct relation between the strength of the gravel soil and the gravel content under saturated consolidation.High gravel content does not represent the absolute high strength,and rational particle grade is an important factor in determining the strength of specimens under CU and CD test.The increase of clay content of the compacted gravel soil will lead to the decrease of its strength.In order to study the effect of dynamic stress that induced by the moving load of the aircraft in sub-grades excavated in two different ways on the dynamic deformation of the sub-grade soil,unidirectional and bidirectional dynamic loads texts are carried out on the compacted gravelly soil by using the GDS dynamic triaxial apparatus,and the results are analyzed.It indicates that,(1)For these two kinds of sub-grades,the cumulative deformation of the compacted gravelly soil under unidirectional dynamic loading is bigger than the bidirectional dynamic loading under the identical experimental conditions.This is due to the radial dynamic stress ratio(RCSR)in the bidirectional dynamic loads is bigger than that in the unidirectional dynamic loads,the larger the RCSR,the restrained on the cumulative deformation is more obvious.(2)The waveform of the dynamic stress has a great influence on the cumulative deformation of gravelly soil.In the condition that only considering the unidirectional loading(RCSR=0),the cumulative deformation obtained by using the waveform extracted from the excavation and fill sub-grade as the waveform of dynamic loading is larger than that extracted from the uniform excavation sub-grade.While considering the bidirectional loading(RCSR=0.3),the cumulative deformation obtained by using the waveform extracted from the excavation and fill sub-grade as the waveform of dynamic loading is smaller than that extracted from the uniform excavation sub-grade.(3)With small dynamic stress ratio(CSR),the influence of the initial moisture content on the development of cumulative deformation of gravelly soil is less,while as the CSR increases,the influence of the initial moisture content on the development of cumulative deformation of gravelly soil is obvious,and the higher the moisture content,the lager the cumulative deformation.