Coupled Vibration of Saturated Fractional Derivative Type Viscoelastic Soil of a Circular Tunnel with Partially Sealed Shell Lining

Considering the compression of medium and fluid, coupled vibration of saturated fractional derivative type viscoelastic soil and a circular tunnel with partially sealed shell lining in the frequency domain is investigated according to theories of Biot and elastic shell. The stress and displacement constitutive behavior of the soil skeleton is described by fractional derivative model which reflects the rheological properties of the medium while regarding soil as a liquid-solid saturated porous medium. The expressions of displacement, stress and pore water pressure are obtained while the inner boundary of circular tunnel is subjected to axially symmetric radial traction and axially symmetric fluid pressure respectively by introducing a partially permeable boundary condition. With the parameter analysis, it is revealed that the order of fractional derivative model on the responses for the system subjected to the symmetric radial traction is much greater than that of the system under the axially symmetric fluid pressure. And resonance phenomenon occurs obviously. Nevertheless the system responses do not have remarkable resonance phenomenon under axially symmetric fluid pressure.     

Axial Response of Viscoelastic Pile-soil Coupling Interaction in Three-dimensional Inhomogeneous Soil

Considering the three-dimensional inhomogeneity of soil surrounding the pile, the response of non-uniform viscoelastic pile under axial dynamic loading is studied. Firstly, combining the boundary condition, the complex stiffness of axial different soil layers are obtained by the complex stiffness transfer model of radial multi-zone plane strain. Then, the analytical solution of dynamic response at pile top in frequency domain is proposed by solving the dynamic equation of non-uniform viscoelastic pile section one by one from the bottom up to the top, and the relevant semi-analytical solution response in time domain is adopted by the convolution theorem and the Inverse Fourier Transform. At last, the effect of parameters of pile and soil are investigated to get the nature of the dynamic response of pile top in frequency domain and time domain.     

秸秆改良材料对沙质土壤饱和含水量的影响

为提高沙质土壤饱和含水量,以作物秸秆为主材,以膨润土和聚丙烯酰胺(PAM)为添加剂配制沙质土壤改良材料,采用模拟试验研究秸秆改良材料不同配比、施用量与时间等因素对沙质土壤饱和含水量的影响。结果表明：施加秸秆改良材料可以增加沙质土壤饱和含水量,不同秸秆改良材料改良效果不同,且随着改良材料施用量、配方中PAM含量（<2%）的增加、土培时间（< 60天）的延长,沙质土壤饱和含水量呈现增加趋势;添加剂量为10 g/kg,配方中PAM含量为2%的麦秆改良材料的土样,在土培60天后,饱和含水量为52.6%,是对照的2.32倍,对沙质土壤团粒结构改良效果最为明显。可见,添加秸秆改良材料可以增加沙质土壤饱和含水量。     

An Equivalent Shear Displacement Method of Single Capped Pile in Layered Soil

Based on the interaction of single pile, cap and soil, the load transfer matrixes of single pile and soil were proposed to establish an equivalent shear displacement method of single capped pile in layered soil. With the compatibility of displacement at the interface between the pile and the soil, equilibrium equations of pile and soil could be derived. With the increase of the total load on the pile cap, the lateral friction at the interface of the pile and the soil becomes so large that the occurrence of the sliding takes place. While there is little sliding at the interface between the soil under cap and the soil outside of the cap because of the less lateral friction, which gives rives to less settlement of the soil outside of the cap. Eventually, the results of the finite element method, existing theoretical method and the model tests were compared with those from the analytical method and were found to be in good agreement. The increase of the ratio of length to diameter does not infinitely enlarge the overall stiffness of the single capped pile, because the pile cap would afford part of the loading all the time.     

Research On Laws of Actually Consolidation time Calculate in Saturated Soft Clay Soil by Using Vacuum-Preloading Method

Vacuum-surcharge combined preloading method have been become the most commonly used method on the dredger fill and saturated soft clay soil consolidation beside the coast.The long time of consolidation is one of this method’s most characteristics,as we always think that 3 months is the academic time.In fact,we always can’t accomplish the consolidation of siaturated soft clay soil by using vacuum-surcharge combined preloading method in 3 months because of the complex nature of the soil horizon and the effects of the construction technology.The mian mission of the article is to supply a substantial time and a reliable basis that are needed by the vacuum-surcharge combined preloading method and the construction period.The mian data sources are come from the ground treatment project of a cogeneration power plant in Zhuhai Guangzhou.We adopt the exponential curve fitting method and the method of Asaoka to count the degree of consolidation of the saturated soft clay soil.     

Shear Deformation Properties of Sliding Zone Soil and Its Effect on Sliding Mechanism of a Landslide in the Three Gorges Reservoir Area

The mechanical properties of slip soil play a key role in landslide stability. In order to study this control mechanism, multigroup experiments on the slip soil of a landslide were conducted in the Three Gorges reservoir in Zigui county involving consolidated quick direct shear test and consolidated drained direct shear test, through which the strain hardening property of this slip soil has been studiedas well as mechanism of landslide deformation resulting from the strain hardening slip soil. The results show that from plastic deformation to shear failure, the shear stress applied to this slip soil increases all the way. After repeated shearing, its shear strength increases, and the greater the normal stress, the more the shear strength increases, in which process the angle of internal friction contributes the most to its shear strength variation. Through the field investigation and numerical modeling, how the strain hardening slip soil affects the landslide stability was studied. In the process of sliding, the frictional strength of the strain hardening slip soil increases after being shearing, leading to the consumption of the landslide’s kinetic energy, following the phenomenon that a temporary steady state occurs after a short distance sliding.