Applied Mechanics and Materials Vols. 226-228

Abstract: In underground engineering construction of water conservancy and hydropower engineering, determining surrounding rock excavation and supporting construction measures and parameters according to the classification of surrounding rock's stability is an effective method. In hydropower engineering field, it made some achievements of surrounding rock classification through the engineering geological mechanics parameters. but there are some problems in the application. After the study, this paper established a fuzzy comprehensive evaluation model to determine the stability of surrounding rock. Practice has proved it to be more reasonable.

Abstract: In the construction of Yellow River-Crossing Project for the Middle Route of the South-to-North Water Transfer, the silt, silty sand and fine sand widely exist in the foundation, that it need to be processed in the region where the possibility of sand liquefaction because of the low bearing capacity. We had a detailed study and experiment for the sand compaction pile of the axis and the outside of the channel, and determined the compactness of pile body, pile length and the construction technology through the test. We also debugged the concrete construction parameters such as the amount of filling sand and stone, hoisting height and speed, extrusion times and so on. For these experiments, we attained the purpose of increasing the relative density, preventing sandy soil liquefaction, improving the shear strength of the foundation soil and the bearing capacity of the foundation, so as to reduce the foundation settlement.

Abstract: Concrete arch dams are critical structures, the failure of which would lead to catastrophic effects on a regional scale. Considering the uncertainty characteristics of earthquake and the self-adjustment of inner force of arch dams, it’s necessary to investigate the seismic performance index of arch dam for holistically evaluating the seismic safety of arch dam-foundation system subjected to high intensity seismic excitations. By considering the contraction joints movement and concrete material nonlinearity, a series of dynamic response-history analyses of arch dam were carried out under increasing levels of earthquakes. Based on these analyses, the performance index of crest deformation is recommended for the seismic safety assessment of arch dam. And several performance stages of seismic response including the opening of contraction joints and the distribution of concrete damage are also investigated.

Abstract: As a major hazard installation in mine the safe and effective running of a tailings dam is very important, therefore the stability analysis of tailings dam is necessary. In order to evaluate the effect of seepage on stability of mine tailings dam, in this paper, a numerical model of a tailings dam in Yunnan province was established by using ANSYS software. It was focused on the dam seepage field analysis and the seepage-stability analysis, and on using the strength reduction method to derive the safety coefficient of the tailings dam. The results were proved reasonable and could be used to provide helpful guidance of dam safety.

Abstract: The situation that the grouting borehole doesn’t intersect with natural fractures of rock masses is often met in practical grouting project. Hence, it’s very necessary to discuss whether the rock masses around borehole will split under the grouting pressure and the corresponding splitting orientation. After the splitting crack finishes propagation, we can estimate whether it will penetrate with original fractures, and it’s favorable for grouting theory analysis and numerical simulation and so on. According to this, the splitting criterion and splitting orientation are proposed with and without considering ground stress, respectively. In the meantime, under the situation of splitting, the singularity of crack-tip’s stress field is simulated by 6 nodes singular isoparametric element through secondary development of large-scale finite element analysis software-ANSYS. The stress intensity factor is introduced and the propagation of the splitting crack is simulated to obtain the final propagation length, which has significant guiding meaning to grouting theory and the practical grouting projects.

Abstract: The series of dam’s deformation data can be seen as a string of digital signal, which is composed of different frequencies. Because of the high frequency noise in the noise information, a new method of improved threshold’s lifting wavelet function is demonstrated. Using this new method to abstract components of dam monitoring data. This new method can eliminate the defect existing in traditional threshold function during the denoising process. The example shows that the lifting wavelet based on improved threshold function is more accurate and objective in the process of abstracting component compared with the traditional wavelet , which is feasible to analyze the dam performance precisely and practically. Therefore, it plays a pivotal role in the analysis of the dam performance.

Abstract: The eccentric discharge of stored solids in squat silos has caused many failures, especially that in metal silos. However, these failures are poorly interpreted by specialists. In particular, the lateral pressure distribution on vertical wall couldn’t be accurately recognized. In order to set out the method to calculate static lateral pressure, the appearance of stored solids in silos after eccentric discharge is researched. In this study, based on the overall balance method (OBM), the method for calculating lateral static pressure in squat silos after eccentric discharge is proposed. Four cases are listed according to different discharge stages. Calculative formulae are deducted for each case. This method is also focusing on unsymmetrical distribution characteristic of the lateral pressure. Two calculative examples are listed and the results of which illustrate the necessity of lateral pressure calculation in squat silos.

Abstract: The Method of Finite Element Method Strength Reduction is used to numerical calculate and analyse the subgrade with soil cave, by considering the influence of groundwater level fluctuation in its stability. Nondimensionalize the effect factors, and draw the stability curve to get the regression curve, then make the result regression coefficient directly to the project cases. The result shows that under the weight of the subgrade, the subgrade with soil cave is damaged by that the soil around the soil cave is sheared. The more the value of is, the larger the stability coefficient is, and the higher groundwater level is, the better the stability of the subgrade with soil cave is. With the value increases, the region of stability expands

Abstract: This paper presents a method converting the modal distance of the node into elemental strain based on the special characteristic of two-force element .The strain change before and after damage is applied to the damage identification. The change rule of the relative strain for the same location of the truss occur the various damage extent and the various location of the truss occur the same damage extent, respectively, is obtained according to the strain modal simulation using APDL language. The simulation results show that the strain modal change ratio is sensitive to the cantilever truss damage detection. The damage location and damage extent will be identified. It is an effective nodestructive test way to identify the cantilever truss structural damage.

Abstract: In this paper, dynamic measurement method is applied to test the damage of the bottom reinforced concrete column. The comparison between the calculated first order frequency of the bottom reinforced concrete column and the measured first order frequency shows that the result is consistent. This indicates that this approach is feasible. However, in recent years, dynamic measurement method is widely used in non-destructive testing of bridges and floors. The principle of the dynamic measurement method for the detection of reinforced concrete column utilizes the measured natural frequency, vibration model and damping ratio of reinforced concrete column and such inherent dynamic characteristics of indicators to reflect the damage of reinforced concrete column. And there is no secondary injury for the column. The simplified method of structure dynamics is applied to calculate the frequency of the bottom reinforced concrete column. And the simple calculation method is verified by experiment and practice.