Papers by Keyword: Back Analysis

Abstract: With the development of civil engineering, the box shaped beam has been widely applied in practical engineering. In general, it is composed of concrete and steel and compared with mechanical analysis, little research has been carried on the back analysis of elastic modulus of box shaped beam. With degraded solid element theory, the shell element is deduced and the displacement function is obtained. The necessary observation revision equation and Kalman regenerative matrix are derived. The stochastic filtering back analysis steps of elastic modulus of the box shaped beam are presented and the analytical procedure is compiled. Through analysis of a classic example, some important conclusions about stochastic filtering back analysis of elastic modulus of box shaped beam are obtained.

Abstract: Laboratory experiment and back analysis are common methods for selecting shear strength parameters. However, every way has its shortcomings. A way combining two methods is used to determine shear strength parameters for Hutoumao landslide. The result can meet the need of project according to comparison experience value.

Abstract: The paper deals with the back analysis method in geotechnical engineering, that goal is evaluation the more objective and reliable parameters of the rock mass on the basis of in-situ measurements. Stress, deformational, strength and rheological parameters of the rock mass are usually determined by some inaccuracies and errors arising from the complexity and variability of the rock mass. This higher or lower degree of imprecision is reflected in the reliability of the mathematical modelling results. The paper presents the utilization of direct optimization back analysis method, based on the theory of analytical functions of complex variable and Kolosov-Muschelischvili relations, to the evaluation of initial stress state inside the rock massif.

Abstract: With the popularization of falling weight deflectometer (FWD) to calculate the stiffness related parameters of the pavement structures, non-destructive evaluation of physical properties and performance of pavements has taken a new direction. FWD backcalculation is mathematically an inverse problem that could be solved either by deterministic or by probabilistic approach. A review of the currently used backcalculation procedures indicates that the calculation is generally based on a homogeneous, continuous, and linear elastic multi-layer system. Identifying effective data of dynamic deflection basins seems to be an important task for performing modulus backcalculation. Therefore, the main objective of this paper was to discuss the distribution features of dynamic deflection basins of asphalt pavements with crack distresses, and present the reasonable criteria to filter the testing data of FWD deflection basins. Finally, the study aims to validate the established criteria by conducting in-situ case study.

Abstract: Through the analysis of ‘gap parameter’ and ground movement pattern in shield tunnel, this paper researched and corrected the model of ‘equivalent circle zone’ proposed by predecessors. The ‘equivalent circle zone’, which is a comprehensive reflection of shield gap, grouting filling and stratum perturbation, is considered to be unequal thickness in this paper. With the measured data of practical shield tunneling, the unknown parameters of corrected ‘equivalent circle model’ can be obtained by back analysis through numbering analysis. The back analysis of Shen Zhen line-5 is carried out to validate the rationality of the method proposed in this paper. Research shows that: the corrected model can reflect the feature and values of ground settlement more factually than the previous model and can offer a reference to predict ground deformation during shield tunneling.

Abstract: The value of thermal parameter is very crucial in simulating analysis on temperature control for mass concrete. The inverse analysis on some practical project is done by genetic algorithm and finite element method on the basis of observational data of temperature on the site. The temperature control simulation calculation is performed based on parameters obtained from inverse analysis on this project, so that the temperature distribution is consistent basically with the practical one. With improvement of micro-genetic algorithm, the genetic algorithm becomes globally-optimal by changing the optimal reserving and re-starting strategies. The results show this method is very practical in high precision of calculation in mass concrete parametric inversion.

Abstract: Large scale underground caverns are under construction in high in-situ stress field at Houziyan hydropower station. To investigate deformation and damage of surrounding rock mass, a elastoplastic orthotropic damage model capable of describing induced orthotropic damage and post-peak behavior of hard rock is used, together with a effective approach accounting for the presence of weak planes. Then a displacement based back analysis was conducted by using the measured deformation data from extensometers. The computed displacements are in good agreement with the measured ones at most of measurement points, which confirm the validities of constitutive model and numerical simulation model. The result of simulation shows that damage of surrounding rock mass is mainly dominated by the high in-situ stress rather than the weak planes and heavy damage occur at the cavern shoulders and side walls.

Abstract: Foundation pit engineering is a critical part during the development process of underground space. With the increasing demands of underground space, foundation pit engineering is exposed to new challenges. This article firstly reviews the main features of shallow foundation pits in Beijing as well as the relevant design concepts of support, and then elaborates the features and challenges of urban large-scale deep foundation pits; a case study was introduced with the exploring practice of design and construction of the large-scale deep foundation pit of Wangjing SOHO project, the innovations of support design for this foundation pit are summarized; new prospects for development of support techniques of foundation pits are proposed.

Abstract: Accurate mechanics parameters are the precondition of reasonable calculation in the finite element method to calculate the deformation and stability of the rock mass engineering stability. Partition classification method can be used in the simulation of macro-mechanics parameters of rock mass, for the distribution of multiple sets of multi-level joint fissure in some engineering rock, the parameters of the rock mass can be simulated using the numerical method step by step or by group. Based on the partition classification method, the paper simulated the macro-mechanics parameters of natural slope upstream the left bank toe board of Maerdang hydropower station. The slope is divided into three areas according to the rock types and intensity, weathering degree, fracture, the trend and tendency of the fault, spacing and connected rate of the structure surface, the mechanics parameters of the structure surface, the groundwater conditions, and then use the partition classification method to calculate the region's macro-mechanical parameters, the results can be used to provide amount of reasonable parameters for the stability calculation of the slope in the subsequent deformation.

Abstract: The surrounding rock strain field monitoring have been done during a highway tunnel excavation. The rock rheological parameters was inversed by neural network based the field monitoring data. The predicted value and the field monitoring data have been compared, the result shows that the difference is 12%, the predicted value is credible.