Applied Mechanics and Materials Vols. 105-107

Abstract: The reliability index is not only nonlinear but also continuous, so we design the real coded genetic algorithm to improve the performance of the algorithm. The experimental results indicate that our method is 10 times faster than the binary-coded genetic algorithm, more accurate and stable than other methods.

Abstract: Fractured rock mass is one of the most important engineering materials for civil engineering in rock mass and rock layer, and has special failure model and constitutive relationship different from other man-made materials. A new numerical model is introduced and applied in studying the deformation, strength, and the failure mode of fractured rock mass, with the consideration of the damaged plasticity theory for intact rock, and joints distribution in fractured rock mass. A series of numerical experiments on jointed rock mass samples are performed to verify the validity of the new numerical model for fractured rock sample. Some feature datum from lab experiment is used to compare the results from numerical tests by the new model. According to these results, the initiation and propagation of induced fracture, and the failure mode of the fractured rock mass samples, are agreed with their associated feature datum by lab experiments.

Abstract: Based on dynamic triaxial test results of saturated soft clay, influence factors and variations on accumulated deformation were analyzed. The Parr’s equation on accumulated deformation was modified to create an attenuation-type curve model on accumulated deformation of saturated normal consolidation clay. In this model, dynamic strength was introduced and a new parameter called equivalent dynamic stress level was added. Besides, based on comparative analysis on variations between failure-type and attenuation-type curves, a failure-type curve model was created on accumulated deformation of saturated normal consolidation clay. The two models can take cycle number, coupling of static and dynamic deviator stress, consolidation way into consideration. The models were verified by test results. The correlation coefficients are more than 0.96 for optimization of test results based on the two models, and there is good agreement between optimized and test curves, which show that the two models are suitable to predict variations of accumulated deformation under different loading cases and consolidation ways. In order to improve prediction accuracy, it is suggested that loading cases and consolidation ways should be consistent with in-situ conditions when dynamic triaxial tests being used to determine the constants in the models.

Abstract: Similitude design of a model test concerns the size and materials of the model. For the similitude design, the most important factors include not only that the test should simulate well the interaction of soil-pile of the prototype, but also that the model test should reflect well the failure mechanism of the corresponding prototype. In this paper, firstly, the similitude relation between the model pile and the prototype pile in the soil-pile interaction centrifugal modeling is derived by means of analytical equation method. Then, in order to investigate the failure mechanism of stabilizing pile, the physical properties of model materials and the difficulty of making of model pile are taken into consideration. The results show that the failure mechanism of stabilizing pile in the centrifugal model tests can be reflected reasonably.

Abstract: As the special soil, turfy soil and peat soil in China contained some similar properties with high void ratio, high water content, high organic content, etc. But turfy soil also had properties which difference from peat soil. In this paper, based on the formation of the cause and geological environment and geomorphologic characteristics of geological in the quaternary, took the typical and widespread turfy soil and peat soil regions for example, systematically discussed the material composition and macroscopic and microcosmic structural features, put further research on the physical chemistry mechanical characteristics. Then the come to the conclusion that the essential reason for difference between turfy soil and peat soil were decomposition degree and organic content. The result that worse engineering properties such as higher the moisture content, porosity, compressibility, internal cohesion and the lower specific weight, consolidation coefficient and permeability were due to the lower decomposition degree and higher organic content of turfy soil than peat soil. It can provide reference to the practical projects of turfy soil to distinguish peat soil according to this characteristic.

Abstract: This paper analyzes the tunnel rock ultimate displacement,proposes using acceleration to determine the tunnel surrounding rock stability.Acceleration compared to determine the stability of surrounding rock ultimate displacement method obtained consistent results.Acceleration improved the ultimate displacement method to determine the shortcomings are difficult to quantify.Acceleration of rock deformation by the positive and negative judgments, rock deformation can clearly reflect the trends and status, you can clearly see which one works in a specific state of rock a dangerous warning signal.With a typical project examples validate the method used to determine the displacement acceleration stability of surrounding rock is accurate, feasible.Research and analysis to help build a tunnel surrounding rock stability analysis of the forecasting system.

Abstract: The shortages and drawbacks of traditional geotechnical engineering monitoring and controlling system(GEMCS) is reviewed and the necessity and inevitability to establish a modern GEMCS are argued and discussed sufficiently. Modern GEMCS are fundamentally divided into two subsystems, remote management subsystem and site management subsystem respectively. Each of the subsystems is introduced and described subsequently by their components, main functions and capability in solving issues. Then, the predominant characteristics and advantages of the modern GEMCS are specified with two facets: components features and unlimited time-spatial domain monitoring. Applications in deep pit constructions are illustrated to visualize the functions of the modern GEMCS, followed by three research strategies of scholars from home and abroad are analyzed and summed up. Last, based on two levels, which are completions and evolutions of monitoring and controlling system itself as well as its generalizations in applications and promotions in geomechanics, developments supposed to achieve in modern intelligent GEMCS in 21st century are prospected and forecasted.

Abstract: The calculation and analysis of single pile settlement was one of the important geotechnical engineering issues, and many geotechnical engineers and scholars investigated and formed a systematic analysis method. Among the existing methods of analysis methods, the elasticity theory method was relatively mature. However, the traditional elasticity theory method could not consider the slip properties between pile and soil, and did not match the actual working properties of pile foundation. In this paper, based on Mindlin's solution, the pile is assumed to be elastic and the relationship between shear stress and relative displacement at the pile-soil interface is assumed to follow hyperbolic function, then series equations were derived and solved by Finite Difference Method. Two cases were demonstrated and the computed results agreed very well with testing data. The advantage of the analysis method proposed was that the interaction of pile and pile, and pile and soil can be considered.

Abstract: The collapse settlement of loess foundation is one of issues in engineering which need to be solved. Firstly, a finite element program was developed and the computational function of collapse deformation was implemented based on chord modulus method. Then, the comparison of the measured collapse settlement in a loading plate test and the computational collapse settlement based on the finite element were analyzed. The computational results show that the nonlinear finite element method based on the chord modulus should be recommended to evaluate the collapse deformation, owing to its potential application that it may consider the collapse deformation field of the whole collapsible loess foundation.

Abstract: In order to study the rule of highway subgrade settlement, both on-site experiments and theoretical analysis methods were used to analysis high fill embankment settlement. Gray model theory can be effectively forecasted the embankment of the different stages and the final settlement. According to the measured data of deposition tests, the comparative analysis of predicted results was carried out and some conclusions were drawn: 1) It is feasible that gray model theory is used to predict the settlement of the subgrade; 2) gray theory predictions adapt to these situations that similar information is less known, uncertainties and some rock deformation issues; 3)gray prediction accuracy is higher. The prediction model of GM established (1, 1) is reliable.