| The basic features of high speed railway system include high safety, high reliability, highly controlling ability and minimized maintenance, so the rail structure needs to ensure not only smooth but also a high stable nature, to achieve that criterion, the road-bed needs to ensure the seriously control of settlement deformation. Road bed settlement deformation controlling includes controlling settlement deformation of road foundation and of embankment, for a long time, the analysis on controlling road bed deformation only focuses on analyzing the deformation of road foundation, and there is a lack of the analysis on the deformation of embankment, especially the analysis on the embankment part under the robust layer. Seriously controlling the deformation of embankment can satisfy the basic stable requirement of road composition, and implement the realization of the long term stable and the high smoothness for high speed railway. The embankment under the robust layer bears the load of the robust layer and of itself, being directly influenced by the changing conditions of weather and hydrography. With the load and those other conditions, the plastic deformation of embankment can occur and influence largely to exploitation. Focus on the plastic deformation of embankment, then figure out the method of designing embankment to satisfy the necessary required usage, this method is not only a complete one where the argument is developed with new design, but also a meaningful method for the existing road to evaluate whether it can ensure the ability of long term serving according to the deformation requirement or not, which is also a very important meaning.By analyzing and summarizing with the basic of the analyzed results, analyzing and commenting deeply the deformation trend of soil, then figuring out the judgment method, the approach of classifying in detail and comprehensive the deformation of soil, setting up the device model to explain the deformation states of soil and proposing the equation of soil deformation in time; using the self-reform creep direct shear apparatus to implement the experiment of creep shear for soil, since that verifying the development of the deformation of states, then figuring out and quantifying the state judgment standard and states deformation parameter. Combine with the design requirement for high railway road bed to implement discussion about the rules of control and design conditions, base on the state deformation. The main work and results are as follow:1. Analyze the creep deformation characteristic of soil under the impact of long term loadThrough the analyzed results, in can be seen that at every different shearing stress (τ), specifically at a relatively small value of stress(τ<τk, τk-initial limit of creep, or it can be considered as the yield strength of soil structure), shearing transposition basically has no time specific, the transposition can promptly reach the stable value, so soil in this case can be considered as in "quick stable" state; when the shearing stress increase over a certain value (τk≤τ<τT, τT-the contiguous bound between absolute extinguishment creep and sabotage creep, or it can be considered as the long term strength of soil) shearing transposition although develops in time but finally is still absolute extinguished and reach stable value, soil now can be considered as in "slowly stable" state; if shearing stress still keep increasing (τT≤τ <τf) then timely increasing shearing transposition also gradually increases until soil is sabotaged in final, the sabotage time is long or short depends on shearing stress, thus this state can be considered as a "slowly sabotage" state; when the shearing stress exceeds a relatively large value (τ≥τf, τf with shearing resistant strength according to consolidated quick shear condition is almost indifferent, so these two values can be considered as one) shearing transposition speed develops very fast, shearing transposition reaches a large value and makes soil sabotaged quickly, this can be considered as a "quick sabotage" state. Consequently, it is shown that under the effect of long term load, soil deformation state depends on increasing shearing stress that is shown as four states of quick stable, slowly stable, slowly sabotage and quick sabotage; correspondingly build a device model that shows the relation of force sustainment creep deformation, this model can reflect completely and visually the development of deformation states of soil under the effect of different loading capacities, provide a meaningful reference to describe and understand precisely every deformation state; meanwhile petition to use exponential function to implement simulation of creep deformation in time.2. Research on the improvement of the creep direct shear apparatusFor the limitations at small stress due to friction of steel frame type stress controlled direct shear apparatus, design and improve it to make a flexible pull-type stress controlled direct shear apparatus. Deploy the verification of the effect of friction and changing temperature to these two equipments, focus on discussion about the accuracy degree and stable nature of these two equipments under the effect of small stress, the researching result shows that the relative error of the equipment does not exceed 5% at a relative large stress, thus it can satisfy the basic requirement about accuracy degree of the experiment; but in case of small stress, relative error is in range of 8-22%, which means that the accuracy degree of this equipment is significantly reduced at small stress, therefore this equipment arises relative error in special demand cases. Therefore it can be designed and improved to become a flexible pull-type stress controlled direct shear apparatus to be applied to direct shear experiment, moreover, this equipment can also ensure a good performance at large shearing stress with a relative error which is smaller than 5%, simultaneously reduce the effect of friction at a relative large shearing stress, for this equipment the relative error is only in range of 6-13%, the effect of friction is diminished of about 40% comparing to the existing equipment, the accuracy degree is significantly enhanced. The researching result also proves that changing of environment temperature also interferes with equipment state, in which, for the improved equipment, the changing temperature leads to the changing of shearing force value and average error standard are all smaller than the existing equipment which proves that the improved equipment possesses a good temperature stable characteristic.3. Consider soil deformation in time through direct shear experiment and research on state classificationIn case of being under the impact of long term static load, soil state deformation can be defined in 4 types according to shearing stress level, propose to base on deformation speed as a center standard, using exponential function, through the exponential value p to reflect the classification rule of the shearing transformation state of experimential sample. Through improved creep shear equipment, for different tight degrees of impressive ramming soil in the saturated state, implement the experiment to determine timely shear transformation in form of load adding sample type (defines one load adding level for one sample) and load adding by level type (defines different load adding levels for one sample). Using parameter γ (shearing stress ratio) which is defined as the ratio of load adding shear stress τ and shearing resistant intensity limit of soil τf. The experiment proves:according to "exponential value based classification method", when p≥2, soil is in the quick stable state, correlates to γ≤10%; when 1<p<2, soil is in the state of slowly stable,10%< γ<80%; when 0<p≤1, soil is in the state of slow sabotage,80%≤γ< 100%; when p≤0 that correlates to γ≥100%, soil is in the state of quick sabotage. Base on "exponential value p-stress level γ relationship line" to show the specific that is in the shape of an inverse S line, propose a stress level correlatively to 2 points whose angle factors have a maximal change and a stress level that correlates to this relationship line that intersects the horizontal axis as 3 loading thresholds to divide into 4 types of soil state deformation, it is called "state line based classification method", γ=30% that correlates to soil structure repairing intensity, γ=70% that correlates to long term intensity of soil, γ=100% is the limit intensity of soil.Through the comparison process, it can be seen that "exponential value based classification method" obtains the load threshold of quick stable state more strictly than "state line based classification method". Besides, although soil is in different tight degrees, when simulates by the trend evolution of soil sample shearing transformation, it still achieves the same exponential value p in correlation with stress ratio value γ, it means that P value changes only depends on γThrough Coulomb intensity argument, base on stress threshold of state deformation types and relatively relationship of soil shearing resistant intensity limit, the relative equation of state deformation intensity parameter and state limit intensity can be derived.4. Consider long term plastic deformation state development to bring out the embankment design technique for high speed railwayFor high speed railway, it can be seen that the service life is hundreds of years, difficult to repair, the railway composition requires a very high degree of smooth and stable, moreover, under the effect of load of embankment itself, embankment deformation control must end within one year, which proves that embankment deformation must be controlled in quick stable state. The advantage of this method is that it bases on physical parameter and a very clearly distinguishing method, hence, when building high speed railway, by means of adjusting embankment height (level load), choosing banking material and tight degree standard to conduct state deformation control, using this method ensures a reliability to control the deformation of high speed railway road-bed along with service life, and in the mean time, optimize execution mastering, reduce project construction cost. When conduct high speed railway road-bed banking, there is a need to control level load (the foundation height) to constrain state deformation in the range of loading threshold of quick stable state. Through soil at side pressure limitation states (positive state, total constrain condition of side pressure limitation state OCR=1 and OCR>1), argue the equation for computing the highest height of embankment base on its load and banking material strength. For the difficult-to-repair characteristic of high speed railway using panel composition, propose technical condition and designing rule base on load control, choose material and compaction standard to ensure that the road-bed is in quick stable state; argue the equation of controlling largest height of embankment through considering embankment load and banking material nature. The analysis shows that silty clay is of low pressure nature with the load is the height of embankment of 6 meters, embankment is in quick stable state.The computational results show that high speed railway embankment with normal height (≤6m) has a relative small plastic deformation, and in this case the very small deformation can be considered as "quick stable" state. Norm (practical) of high speed railway design (norm explanation) shows that settlement deformation of high speed railway embankment is approximately 0.1%～0.5% of embankment height (the specific value depends on various natures of soil), in normal condition, this settlement deformation part will stop deforming one year after execution of road bed, so that the road bed settlement deformation can be chosen as 0.1% of embankment height to be the value that divides embankment deformation into deformation with time and without time particularities. Through this concept, tight degrees of 95% and 100% can be achieved, embankment in "quick stable" state, the height limit of embankment are 4.2 and 5.5 meters, respectively. The results of this method are in the range between those results achieved using positive states and static state methods. So it leads to the conclusion that it is unable to use small tight degree for high speed railway embankment, besides,0.1% of embankment height can be used as the deformation limit of high speed railway embankment. |
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