Numerical Analysis on Dynamic Response of Saturated Elasto viscoplastic Soft Clay

In the framework of porous media model developed from mixtures theories, Solid skeleton of soft clay was viewed as elasto viscoplastic material,and an elasto viscoplastic model of saturated soft clay was established. According on the model of saturated so     

Effect of Disturbance on the Cylindrical Cavity Expansion in Saturated Soft Clay

According to the fact that the undrained shear strength decreases in the field vane test,applying the cylindrical expansion theory and assuming that the saturated soft clay satisfies Tresca yield criterion,the disturbance degree function D is given on the basis of the sensibility of saturated soft clay.Considering that the undrained shear strength is the linear function of the disturbance degree D in plastic region,the elastic-plastic solution of the cylindrical expansion has been gained.     

On Elasto-Plastic Consolidation Settlement of Saturated Soft Clay

The specific properties of soft clay are characterized by higher void ratio, lower permeability and higher compressibility, the consolidation settlement of soft clay is affected by the imposed stress history, the stress paths, the consolidation pressure and the soil properties. In this paper, the porous media theory based on the mixture theory was applied in the study on the consolidation settlement of soft clay, which was more rigorous than the conventional consolidation settlement theory and the coupling between soil and water can be taken into account in the analysis.     

Dynamic Evolution Pattern of Compression Modulus of Soft Clay

Under the external loads, the volume of soft clay decreases with the time and several subsidence phases could be classified with the during development characteristics. And the compression indicators should develop gradually. With the soft clay samples taken from representative soft base before and after geotechnical process in some express highway area of the Pearl River delta, indoor consolidation tests were carried out under different pressure levels. With the data analysis, quantitative relation formulas were obtained for the compression modulus of silt soil with pressure and time. Consequently, dynamic evolution pattern of compression modulus was obtained.     

Cyclic Creep Constitutive Model of Magnesium Alloy at High Temperature

With high strength-to-weight ratio and excellent technological properties, Magnesium Alloy plays a more and more important role in automotive industry. But the inferior high temperature creep resistance limited its application to power components such as engine and transmission cases. In order to investigate the cyclic creep behavior of Magnesium Alloy at high temperature, creep tests of plate specimens AM50 were conducted. Through the analysis about the microstructure and defects of AM50, an isotropic and scalar damage parameter was introduced into an existing creep constitutive model. Furthermore, a Fortran code based on numerical algorithm was developed to simulate plasticity, cyclic creep, and recovery phenomenon observed. Comparisons between calculated results and experimental data show good agreement.     

Dynamic Properties of Saturated Clay and Undisturbed Silty Clay

The apparatus for static and dynamic universal triaxial and torsional shear soil testing was employed to perform stress-controlled cyclic torsional shear testing under isotropic consolidated conditions. We conducted a dynamic torsion test of a single hollow sample to obtain its dynamic property data at different effective confining pressures with saturated clay and disturbed silty clay. The results show that the maximum dynamic shear modulus Gmax and ξ obtained from single sample of the cyclic shear test approached those of the traditional method of dynamic torsional testing. We indicate that G/Gmax～ γ andξ/ξmax ～γ of the two soils are independent of confining pressure and testing methods. Each G and ξ can be obtained from the equations we provide. Furthermore, the single sample test method can diminish the differences between the samples during experimentation and effectively provide convenience with authentic experimental results.     

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.     

Uniaxial Experimental Analysis on Creep Properties of Deep Limestone

The uniaxial creep tests were carried out for deep limestone from Chongqing adoptal by the MTS815 servo controlled rock mechanical test system. Meanwhile, the DISP 2 based AE system was used to test acoustic emission (AE) signal. It is found that AE can better reflect rock microstructure such as diffusion of lattice defects, opening and close of the pore and fracture, compatible deformation among particles, the generation and connection of micro ruptures. Through different creep model parameter inversion, 〖JP2〗it is concluded that either the logarithmic function creep model or the exponential function can better reflect deep rock creep deformation behavior and the logarithmic function creep model is much better. 〖JP〗     

Upper Bound Solution of the Limit Support Pressure during Shield Tunneling in Soft Clay

Considering the nonhomogeneity and anisotropy of the undrained shear strength of soft clay, the face stability of shield tunnel was studied by upper bound limit analysis, and the formula for calculating the limit support pressure was obtained. The influences of nonhomogeneity and anisotropy on the limit support pressure amplify with each other.The relationship between limit support pressure and tunnel depth also depends on the nonhomogeneity and anisotropy; the limit support pressure reaches maximum value at a certain tunnel depth when nonhomogeneity and anisotropy are strong enough. These results show the nonhomogeneity and anisotropy of clays cannot be neglected when analyzing the stability of tunnel face.     

Experimental Study on Influence of Stress Path on the Constitutive Relations for Reshaped Clay

In order to study the influence of stress path on the constitutive relations for reshaped clay,the triaxial compression tests under stress paths with drainage in cases of increased,constant and decreased mean normal stress and undrained conventional triaxial compression test have been carried out,the stress-strain relations under the four stress paths are obtained.Through visualization the three-dimensional surfaces of shear and volume strain in the whole stress field under the four stress paths are given respectively by numerical modeling.In addition,the four families of shear and volume yield loci are plotted respectively.It is found through comparing the deformation results under the four stress paths that there are obvious differences in the stress ranges,the strain peaks,the shapes of strain surfaces and the trends of variation of volume yield loci,however,for the four families the shear yield loci are similar.These results demonstrate that the influence of stress path on the constitutive relations of clay is considerably large and could not be neglected,and it relates to the effective mean normal stress closely.     

Experimental Investigation on the Aseismic Behavior of Seismic Damage Masonry Wall Retrofitted with Grouting and Steel Hoops

In order to accurately evaluate the aseismic behavior of the seismic damaged masonry pagodas destroyed by Wenchuan earthquake and strengthened after the earthquake, a test was conducted to acquire related parameters on seismic performance from the specimens made by masonry and retrofitted with grouting and steel hoops. Taking a seismic damaged ancient masonry pagoda in Sichuan as a case study, four kinds of primitive specimens are fabricated by simulating the conformation of the masonry pagoda. Then the primitive specimens are destroyed under cycle loads and the damaged specimens are repaired by grouting and steel hoops. Cycle controlling tests are conducted with the specimens and relevant data are acquired. Experimental results showed that grouting combined with steel hoops could improve the ductility and energy dissipation capacity of a seismic damage of brick masonry structure, but it do a little to improve the stiffness of a seismic damage structure. And the cracking load of the repaired masonry is much lower than the original undamaged structure.     

波浪循环荷载作用下滨海软土水平向动力特性试验研究

为研究海上风电桩基在波浪荷载作用下,产生水平向循环荷载对桩基周围土体动力特性的影响,以唐山地区滨海软土为研究对象,通过室内动三轴试验,研究不同围压、动应力幅值和振动次数条件下对软土水平向动力特性的影响。结果表明：软土水平向动强度随围压增加而增加,随振动次数增加而减小;动应力幅值增大,破坏振次减小;水平向动应变εd随振动次数增加变大,且动应力幅值越大,增速越明显,变化规律遵循Monismith模型;动应力幅值改变时,软土水平向动模量变化明显,当围压减小,动弹性模量减小;曹妃甸软土水平向间具有明显的结构性,不同围压条件下,随动应力幅值增加动阻尼比均表现增大趋势。     

种棉改良对粘质盐土物理性状及水盐动态的影响

为了研究棉花种植对滨海粘质盐土物理性状及水盐动态的影响,笔者在黄河三角洲滨海粘质盐化潮土区进行田间试验,设置了连续种棉改良3年和盐碱荒地2种不同处理,探讨种棉改良对土壤容重、饱和导水率和不同条件下土壤水盐动态的影响。结果表明:与盐碱荒地相比,种棉改良后0~20 cm土层的土壤容重降低了15%(P0.01),土壤饱和导水率增加了89.23%(P0.05)。在春季蒸发条件下,0~20、20~40、40~60、60~80、80~100 cm 5个土层中,种棉改良的土壤含盐量比盐碱荒地分别降低了52.07%、55.17%、55.23%、53.78%和47.43%。种棉改良还增加了少量降雨对土壤盐分的淋溶,有效抑制表层土壤盐分积累,使棉花生育期内的土壤耕作层含盐量低于3 g/kg,保证了棉花不同时期的正常生长,是盐碱荒地改良和高效利用的有效途径之一。     

Deformation of Soft Ground with Consideration of the Concomitant Damage

On the basis of continuum damage mechanics theory, the effective stress theory of damaged porous media was presented and its modified self contained seepage differential equation was deduced. The traditional Drucker Prager yield criterion subsequently was modified, and a coupled seepage and damage finite element computer program compiled that was combined with the modified Biot consolidation equation. A simple roadbed foundation model then was analyzed and calculated using the computer program we compiled, and the typical node settlement, pore pressure, and damage variables were discussed and compared with those from the analytic solution. The results show that the damage finite element program we compiled is reasonable and effective.     

Distribution Characteristics and Prediction of Equilibrium Moisture of Non saturated Clay Subgrade

The space distribution characteristics of equilibrium moisture of non saturated clay subgrade were surveyed along the road cross section by the in situ and laboratory tests. Based on the basic theory of unsaturated soil mechanics, matric suctions of soil samples with different kinds of moisture condition were determined and the soil water characteristic curve model was calibrated to reflect a single valued function relationship between water content and matric suction of clay soils. Combining the above results, an estimation method of the equilibrium moisture of the unsaturated clay subgrade outside the affected zone of atmospheric precipitation/evaporation was established. The results show that the atmospheric precipitation/evaporation has significant effect on moisture condition of the subgrade soil located in the upper part of the subgrade near the central reserve and hard shoulders. However, equilibrium moisture of subgrade soil outside the affected zone of atmospheric precipitation/evaporation is mainly controlled by the impact of the groundwater table. Fredlund & Xing model can be used to characterize the relationship between the unsaturated clay soil moisture and matric suction, and the fitting results of model parameters have high reliability. A consistency between the predictive results and the experimental data shows the presented model is accurate and credible.     

Experimental Analysis of the Electro-Osmosis Consolidationof Soft Clay Under Anode Follow-up

Under the equipotential premise gradient, anode follow-up technical was proposed in the electro-osmosis reinforcement of soft clay. Eight electro-osmosis contrast tests were conducted through the experimental test. Currently, shear strength, displacement, moisture content, pH, conductivity of the soil and other indicators were monitored in the electro-osmosis test. Different electro-osmotic reinforcement effects were analyzed. The results show that: when the anode follow-up is used, the first anode follow-up can get a most significant effect. When the current density is high, arranging the anode follow-up will lead some extent reduce of the effect of the electro-osmosis, while the effect will be promoted when the current density is low. By carrying out the anode follow-up on the cathode region soil, a significant reinforcement effect can be obtained. Anode follow-up can reduce the resistance of the circuit in the anode region and effectively promote the electro-osmosis reinforcement effect.     

Experimental Study on the Compressive Property of Luojiashan Clay

This paper carried out an experimental study on the compressive property of Luojiashan Clay at Wuhan University. In order to investigate the influence of compaction degree, compaction water content and saturation state of compacted soil on the compressive property of clayey fill, compression tests were done on the samples compacted to different water content around optimum moisture content by different degrees of compaction. The theory of compacted soil structure was used to explain mechanism of the influence, and it was the change of soil structure that caused the variation of compresSive property. The results of the tests show that it was at agiven range of stress that degree of compaction and compaction water content have influence on the compressive prop- erty of clayey fill. Around optimum moisture content with degree of compaction decreasing or compaction water content increasing, the compressive deformation of clayey fill increased. When compacted fill was saturated by water soaking, the compressive deformation increased much, and the clayey fill compacted at greater water con- tent than optimum moisture content showed smaller compressive deformation caused by saturation at other conditions the same.     

Study on Tensile Creep Characteristics of High Performance Concrete

The understanding of tensile creep behavior is extremely important in accurate stress analysis and crack prediction. A set of concrete tensile creep testing apparatus was constructed. The characteristics of tensile creep under different loading ages(1,3 and 7 days),different water-binder ratio(0.29,0.33 and 0.37) and different fly ash proportion (0%, 20% and 40%) were discussed. The results show that tensile creep of HPC decreases as the loading age and water-binder ratio increases. The creep-resistance of HPC enhances with the increase of fly ash proportion. Tensile creep counteracts free shrinkage by 42%～62%,decreases the possibility of cracking of HPC at early ages.     

针叶樱桃软糖的研制

以针叶樱桃粉为主要原料,通过正交试验确定软糖的最佳配方。结果表明,针叶樱桃软糖的最佳配方为针叶樱桃粉用量5 g,白砂糖用量35 g,麦芽糖浆用量50 g,柠檬酸用量0.6 g,明胶用量9 g,果胶用量0.5 g。在最佳工艺配方条件下,得到的产品糖体饱满、表面光滑细腻、软硬适中,具有针叶樱桃特有的风味。