Kolmogorov entropy analysis of surrounding rock system in the processing of unloading for deep buried tunnels

Rock is a kind of physical nonlinear complicated medium, under deep buried condition the surrounding rock system deformation shows geometrical nonlinear characteristic, and the interaction between the two nonlinear mechanism makes the unloading of surrounding rock system evolving complexly. Based on the Lagrangian method and large deformation caculation method, both the double nonlinearity and nonlinear dynamics character of deep buried tunnel surrounding rock system under unloading are studied. The numerical model results show that the Kolmogorov entropy has been extracted from the evolution data in the unloading process of surrounding rock system. The analysis indicates that the typical chaos character has been demonstrated in the process of unloading for deep buried tunnel surrounding system and the rock mass energy dissipation is analyzed at the stage of unloading.     

Deformation and Failure Model Test of Steep Dip Excavation Bedding Slope under the Action of Seismic Load

In the Wenchuan earthquake, steep dip bedding slope is a kind of slope that seismic mountain disaster very development and the slope earthquake disaster is often exacerbated by the excavation. In order to reproduce the process and analysis regularity of slope deformation and failure under the action of seismic load. The author chooses San Shuping landslide located Pingwu County as the typical examples of steep dip excavation damage bedding slope, and the indoor physical model test of slope deformation and failure under the action of seismic load are carried out. The results show that slope deformation and failure is intensified by the excavation. Collapse and sliding is the main form of failure and the results consistent with the field investigation. From the whole process of deformation and failure of view, it can be divided into the four stages. First, the initial phase of the earthquake. A wedge rock by excavation small slides along the rock layers and the slope toe stress increase sharply under the action of seismic load in this stage. Second, rock layers by excavation break-bend at slope toe. Third, the rock layers by excavation overall decline stage. Last, the rock slide blocked and dumping.     

Study on Anchorage and Failure Mechanism of Mortar Bolt

Anchorage system can transfer or enhance intensity and steady ability of the geotechnical project. Based on the simplification of a project, the process of anchorage and failure of bolt is simulated in laboratory. The analytical expressions of stressed bolt in elastic rock under axial symmetry condition are deduced. The pilot study of the relativity of anchorage stress and acoustic parameter is discussed by ultrasonic transmission way in this paper.     

Space time evolution rules study of acoustic emission locations in rock under cyclic loading

An acoustic emission (AE) location experiment was performed on sandstone using an advanced AE test system. The space time evolution rule regarding damage was analyzed under cyclic loading as well as AE. The results show that: AE on static loading process is consistent with the damage evolution rule of compression and the elastic plastic deformation phase;At the beginning of cyclic loading with low duration time and energy, AE events came from a small crack. The location result showed that most events occurred in the core zone forming at the static loading process and the location points changed slowly. AE energy changed little during the metaphase of the cyclic process. There was a modest increase of location points in every cycle. The tendency of steady development could be predicted from the AE location events. At the end of each cyclic loading, the quantity of AE events and energy increased rapidly, reaching a maximum at the last cycle. AE events had high energy and duration time. Location events changed quite rapidly, and assembled and linked continuously in the core zone. At the same time, they expanded to the top of specimen. A macroscopic crack finally formed. In the post failure process, some AE events still existed due to fracturing of gliding friction. Owing to the inner stress balance of rock even after loading stopped, minor AE events still occurred.      

Correlation dimension analysis of AE sequence under failure process of gas-filled coal

The correlation dimension evolution characteristics of acoustic emission(AE) time-series during the instability and failure of coal with and without gas are analyzed base on fractal theory. The results show the coal rock’s AE time-series of deformation stages have obviously fractal characteristics under uniaxial loading. The processes of AE of deformation have different self-similarity, and the correlation dimension can describe the mechanical state of coal. During the triaxial loading process, the stress-varying trend of AE time-series of coal with and without gas is similar to the trend of AE correlation dimension. The sharp decrease of AE time-series’ correlation dimension can be considered as a “precursor” for failure. This feature doesn’t change with the change of confining pressure and gas pressure.     

Numerical simulation of dynamic response and radiation noise of gearbox

Considering the internal dynamic excitation produced by stiffness excitation, error excitation and mesh impact excitation, a dynamic finite element model of transmission system and structure system of gearbox is established. The normal mode and the dynamic responses of gearbox under the internal dynamic excitation are calculated by using the numerical simulation software ANSYS. Based on the result of dynamic responses, the boundary excitation condition is determined, and then the acoustic boundary element model is built. With the software of SYSNOISE, the surface acoustic pressure of gearbox and the radiation noise of field points are solved by the direct boundary element method. The test of airborne noise is carried out. The computational results obtained are in a good agreement with the data of experimental test.     

DC electrical resistivity CT survey of deformation and damage law of coal floor

Abstract: Based on the general laws of the floor damage caused by coal mining, the response relation between the floor rock damage and its electrical resistivity are mainly discussed. Then, the principle and method of the direct current electrical resistivity CT surveying technology are introduced. The survey plan is made according to movement characteristics of mining rock strata in floor, and the dynamic direct-current resistivity CT survey is then applied to predict the damage depth of coal floor. In the return airway of face 1028 in Huaibei Mine, two boreholes were drilled in the coal floor, with a certain number of electrodes buried in the holes, the survey profile was formed between them. With characteristics of electric fields in rock strata in different time measured according to advance of working face, and its electrical resistivity values simulated inversely, the responses of rock strata to electrical resistance during the evolution of fractures were obtained and the damage depth of coal floor in face 1028 was determined to be 17m, which provides visual and effective technical parameters for the coal mining safety. Test results show that direct current electrical resistivity CT technique can detect coal floor mining damage evolution process effectively, and illustrate the floor deformation and damage in the process of mining, which is conducive to the water-inrush forecast, prevention and control.     

Lateral unloading true triaxial test and analysis of mechanical properties for red clay

The actual excavation process of the deep foundation pit is simulated by single sided lateral unloading true triaxial test by using rigid-flexible compound true triaxial apparatus.The stress-strain relation,breakage process and change characteristics of the soil strength parameters are analyzed under lateral unloading and vertical loading conditions during the excavation of the pit.Then the reduction factor is determined according to the change characteristics of the red clay strength parameters during the excavation and experience in engineering practice.The soil strength parameters are reduced with double strength reduction methods step by step.The mechanical process for the excavation of the red clay pit is simulated by using FLAC 3D procedures and Mohr-Coulomb model.The results show that the mechanical mechanism of the deformation and breakage process for red clay under lateral unloading condition is completely different from that of vertical loading.Soil strength parameters decrease while the depth of the excavation increases and the changes in range,magnitude and speed are changed incrementally.In the same vertical load condition,the soil under excavation condition is more deformable and easy to breakage compared to that under pressure conditions,which leads to the instability.     

Analysis of Failure Behaviors in Glass under Shock Loading

The failure wave phenomena in glass media under shock loading are analyzed. The propagating mechanism and dynamic characteristics of failure wave and the property of failure layer are revealed. On the basis of experimental analysis, a damage accumulating model determinated by partial stress impulse is proposed, which describes the phenomenon of failure delay in materials being done with the Heaviside function. The propagating procedure, the evolution characters of transverse stress and longitudinal compression strain in failure layer are simulated. Furthermore a phenomenon is revealed that the failure wave velocity decreases after reflection of rarefaction wave at the boundary of failure layer.     

Experimental Study on Damange and Breakage of Bedded Composite Rock

Damage evolution processes of bedded composite rock have been studied by use of acoustic emission method. The process and characters of damage acoustic emission between different kinds of rocks are compared, and useful results are obtained.     

Numerical analysis on the evolutionary features of deformation and failure modes of slopes

The failure of slope is a gradual accumulation process. Under the effect of many interior and exterior factors, some parts in the slope reach yield with the increase of stress, and sliding surface forms gradually till complete transfixion. With continuous increase of the plastic strain, overall failure happens on the slope. Traditional analysis method cannot display the mechanic conditions and the whole process of deformation, transfixion of sliding surfaces and failure. Meanwhile, FEM strength reduction can quantitatively show the deformation features and the process of occurrence and development of sliding surface. Based on the previous researches, the paper classifies slopes according to the features of rock and soil and the slope structure. Through analyzing the graphs of deformation and the nephograms of plastic strain under different reduction factors or safety factors, the researchers can directly find the deformation tendency of slopes and the whole process of the extension, transfixion and failure of sliding surface with the reduction of safety factor. So, the failure mechanism of slope can be found intuitively, which can provide effective basis for the prevention and governance of slopes.     

Study on Acoustic Emission of Limestone in Uniaxial Compression Test

In order to study the acoustic emission of rock under compression by means of the rock acoustic parameter dynamic testing system (RAPDTS), some uniaxial compression tests on a kind of limestone from Guangxi Province were carried out. It was concluded that the formations of new micro clefts generated in the rock and the enmargements of existing clefts are the principal factors that cause the acoustic emission.     

Effect of outburst coal’s gas seepage properties under stage cyclic loading

Experiments of outburst coal’s gas seepage and deformation under cyclic loading of the stationary gas pressure and different confining pressures are made by “fluid-solid-heat coupling with axis servo seepage system of coal”. The results show that loading route has a significant effect on mechanical properties of coal sample. Although the complete stress-strain curves and one cyclic loading curve present similarity in the overall trend, the stress peak value of coal sample under cyclic loading is lower. Under cyclic loading, the stress-strain curves during loading and unloading don’t overlap. They connect to form a hysteretic loop. The permeability is in close relation with the damage deformation process of coal sample. Under cyclic loading, permeability is increasing during the unloading and decreasing during the loading. The permeability-strain curves during loading and unloading form a hysteretic loop, which is corresponding with the hysteretic loop of stress-strain curves of coal sample.     

Rough Sets Theory and Its Application to Data Mining

Rough sets is widely applied to dealing with the information under uncertainty. The data mining technology based on the rough sets is being increasingly attached importance by mathematicians and computer scientists. This paper introduces the development process and basic characteristics of rough sets, the application of rough sets theory to the data mining, and the typical system of the data mining based on the rough sets, as well as the directions and fields for future researches. Finally, this paper discusses the necessities through combining rough sets theory and intelligent methods to process information.     

Experimental study on acoustic emission characteristics of coal rock at different confining pressure

This paper conducts experimental investigation on acoustic emission(AE) characteristics of coal rock at uniaxial and triaxial compression by MTS815 rock mechanics test system. The results show that the variation of AE has tendency effect at uniaxial compression and confining pressure experiments. We indicate that AE signal decreases significantly in the elastic stage, and the relatively quiet period of AE before the specimens failure is not obvious under confining pressure. The AE amplitude distribution with time and its envelope line can indirectly reflect the trend of stress. The AE events peak stress and elastic modulus decrease with the temperature increase, and the value of m which reflects the cumulative distribution of amplitude increases as the confining pressure rises. The results also show that the AE frequency distributes in three frequency domains, and the proportions of dominant frequency significantly increase while the specimens are broken.     

Influence of Motorcycle Noise on Gear Transmission

The study of motorcycle's acoustic signal shows that gears noise take a great proportion on the whole acoustic of motorcycle.So how to control the noiseof gears is very helpful for reducing the whole motor's acoustic.This paper discusses the engine matching with transmission system in reason,primary transmission and gear geometry design parameter & the mend of tooth body(tooth form & tooth direction) how to influence the acoustic of motorcycle.The study shows that the gear transmission System's matching with engine in reason can notable improve the efficiency of motorcycle.In the meaning time the exactly choosing the primary transmission gear geometry design parameter and the mend of primary transmission gear's tooth body can effectively reduce the acoustic of motorcycle.This paper has engineering practice sense.     

Acoustic emission behavior of shale under four point bending test

PXWAE Acoustic Emission System is useol to investigate the acoustic emission behavior of shale under four point bending test. In these tests, the maximum bending stress, bending strain, acoustic emission hits, acoustic emission energy and etc., are recorded. The results show that when vertical loads impose on the shale sample which has horizontal stratification planes, Kaiser effect does exist under four point bending tests. Kaiser point can be recognized directly from the stress vs. cumulative AE hits curve. But by the impact of shale’s stratifications and local failure during the tests, strain relaxation occur which makes it difficult to determine the Kaiser point only by the strain vs. acoustic emission curve. An accurate conclusion can be achieved by a comprehensive judgment combing with all test data, as well as the failure mode of rock sample. The research on acoustic emission behavior of rock in the stress state during bending tests to some extend can provide guidance to engineering practice for stability monitoring of mine roof or separation layer with acoustic emission monitoring technology.     

Damage Analysis on Coal and Rocks and the Method of the Checking Damage by the Deviator Stress

The characteristic of the original damage and the breaking of the coal and rocks under the loading has been discussed by a lot of microscopic structure analysis and by whole stress strain testing on the coal and rocks. The non homogeneity causes the stress locating in a small spot. It is the essential cause of the damage developing and causing the structure breaking of the coal rocks. The failure of brittle fracturing, rubbing later on and granulating should be a major pattern in the outburst of coal and gas. The method of the examining damage by the deviator stress, is proposed. It can be used to analyse the characteristic of the coal and rocks.     

Research of the Estimate of Our Country''s University Science Park Based on the Analytic Hierarchy Process Method and the Dynamic Clustering Method

The development of university science park is very rapid, its evaluation is a problem that to be solved. According to the feathers of university science park, the authors select the analytic hierarchy process as the basic evaluating method to develop elements of university science park, and then use the dynamic clustering to do the synthetical evaluation to the general developing status. The examples show this evaluating system is simple and practical. The system can provide decision-making functions to the development of university science park.     

The Research of Landslide Hazards Assessment System

Landslides caused substantial damage to property,which is seriously hampering social development.With the use of geographic information systems(Arcview),a risk assessment system is established in the paper.The failure probability of 3D-slope is calculated using the Monte Carlo method.The risk of life and economic losses were also calculated by the risk assessment system.By a case study,the results of the risk of life and economic losses may be crucial foundations for administrant branch.