共查询到20条相似文献，搜索用时 156 毫秒
1.
为进一步优化超声波提取胡萝卜中β-胡萝卜紊的工艺条件,在超声功率、超声时间、提取温度、物料粒度、料液比及提取次数6个单因素试验结果的基础上,采用二水平部分因子析因设计（2—level fractional factorial design）法,筛选出了影响β-胡萝卜素提取的主要因素为提取时间（p=0．0145）、温度（p=0．0189）、料液比（p=0．0180）和提取次数（p=0．0114）。 相似文献
2.
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. 相似文献
3.
A mathematical model of rock breaking under pulsed jet is established by introducing the Johnson-Holmquist-Concrete constitutive relation and the smoothed particle hydrodynamics method. Based on this model, the formation, propagation and attenuation of stress wave during rock breaking by pulsed jet are simulated. The relations between pressure and time at different points on rock surface and the curve of peak stress wave versus distance to action spot are obtained. Destruction behaviors of rock under pulsed jet and effects on stress wave effect from jet velocity and lithology are studied according to the above calculation results, analysis results show that stress wave effect of pulsed jet acts locally and the peak stress wave shrinks sharply as the acting distance increases. The rock breaking mechanism of stress wave is tensile failure during the high speed process of load-unload. Power and effect range of stress wave is in high direct proportion with jet velocity. There is a threshold velocity before the macroscopic failure. Rocks of different lithologies have different destruction types under pulsed stress wave of pulsed jet. Destruction type of low strength rock like sandstone is crack propagation under the tensile stress during the high speed process of load-unload, while the destruction type of high strength brittle rocks like granite and limestone is vertical failure of stress concentration. 相似文献
4.
Elasto-plastic analysis on surrounding rock of roadways based on seepage, strain softening and dilatancy 总被引：1，自引：0，他引：1
According to seepage body force, strain softening and rupture expansion of rock mass, elastic-plastic mechanics theory, distribution laws of stress and displacement of surrounding rock in seepage field are derived, and relationships between different zonation range of the surrounding rocks, pore water pressure, strain softening and rupture expansion are established. The results show that the pore water pressure and rupture expansion rock mass have a more obvious impact on the surrounding rock rupture area than the plastic zone. Both the plastic zone and the rupture area are larger when the seepage field is considered. The impact of strain softening on both the plastic zone and the rupture zone of surrounding rock is very significant, and both seepage and strain softening rupture expansion affect deformation of surrounding rock of roadways obviously. It provides certain reference values for the roadway support engineering in seepage field. 相似文献
5.
Elastic-Perfectly Plastic Solution of Tunnel Surrounding Rocks Using Mogi-Coulomb Strength Criterion
Lyu Caizhong 《保鲜与加工》2014,(6):54-59
Reasonable choice of rock strength criteria is crucial for stress and displacement prediction and support design in tunnel engineering. Based on Mogi-Coulomb strength criterion and elastic-perfectly plastic model, analytical solutions of stress and displacement for surrounding rocks around a circular tunnel were derived The intermediate principal stress coefficient was used to present the intermediate principal stress effect. The results in this study were compared with the current solutions in the literatures and the influence of intermediate principal stress and shear strength parameters of surrounding rocks was discussed. The results showed extensive applicability and the Mohr-Coulomb strength criterion and Matsuoka-Nakai criterion are two special cases; when the intermediate principal stress coefficient b was equals to 0.5, the results indicated that the intermediate principal stress effect and its range for rock strength; the influence of cohesion and internal friction angle on the plastic radius and tunnel wall displacement was significant; Care should be taken to the effects of intermediate principal stress and shear strength parameter variations of surrounding rocks on tunnel design and construction. 相似文献
6.
Experimental results of the basic mechanical properties and failure mode performed on rock salt demonstrate that rock salt is a typical and peculiar soft rock , whose" Young' s modulus/strength(E/S)"ratio is extremely small,and whose failure follows the deformation failure criterion. With these results,this paper develops a theoretic breakdown criterion of hydraulic fracturing in rock salt,which is based on the greatest tension strain failure theory and includes the vertical stress effects. It has been suggested that the critical tension strain should be determined from uniaxial compression tests. This theoretic criterion exceedingly agrees with experimental results and is applicable for every soft rock with small E/S ratio under various stresses. 相似文献
7.
The deformation characteristics and the plastic-loop of the fine-sandstone is studied under the loading and(unloading) condition at the three different deformation-rates and the two different stress-levels,the results show: 1) There is really the plastic-loop in the deformation curve for the loading deformation curve is different form the unloading deformation curve.But the plastic-loop is nearly unchangeable since the second circulate loading.2) There is different for every imitational parameter between the first deformation curve and the second deformation curve at the different stress-levels and the different deformation-rates,but every imitational parameters become more and more invariable gradually since the second circulate curve.3) With the change of the deformation-rates and stress-levels,the imitational(parameters) will change with it.4) The imitational parameters are different for loading section and unloading section of the fine-sandstone deformation curve at the same circulate curve under the same deformation-rate and stress-level. 相似文献
8.
The Relationship among Rock Crushing Energy, the Protodyakonov Coefficient and Rock Strength 总被引：1，自引：0，他引：1
将巨峰、玫瑰香以及红地球葡萄,分别包装在聚乙烯微孔保鲜袋内,置于（20±1）℃温度条件下,用臭氧消毒机每天分别向袋内通气0．5min（臭氧浓度150mg／m^3）和1min（臭氧浓度300mg／m^3）,进行模拟货架期臭氧处理对品质影响的试验。试验结果表明,2种浓度的臭氧处理显著地减轻了巨峰葡萄果梗霉变、果实腐烂率及失重率;显著地降低了红地球葡萄腐烂率及果实失重率,而对可溶性固形物和可滴定酸含量的影响较小;对降低玫瑰香葡萄腐烂率有一定作用,而对其它指标的影响不明显。 相似文献
9.
Tunnel portal section mostly faces unfavorable geologic and topographical conditions, such as broken surrounding rock, shallow and unsymmetrical loadings. The current Chinese code for design of road tunnel provides the load calculation method of tunnel under unsymmetrical. However, according to the mechanic and deformation characteristics of the tunnel lining on site, the assumption is not suitable for the shallow tunnel under unsymmetrical loadings in broken surrounding rock. Therefore, through engineering case analysis and results of three-dimensional numerical analysis, the failure mechanism of shallow tunnel under unsymmetrical loadings in broken surrounding rock is presented firstly, that is, deep buried side broken surrounding rocks slump down after excavation and squeeze the lining, which makes the lining deform outward and bear passive earth pressure. Through the failure mechanism, the surrounding rock mainly includes slumping area and passive area. Then the corresponding formulas are deduced based on limit equilibrium theory. Finally, a case study is adopted to verify the feasibility of the new method. It is show that the new method is more reasonable than the method of current code. 相似文献
10.
Geological conditions of Jinping I Hydropower diversion tunnel is very complicated, it has the following characteristics, such as high geostress and developmental faults and joints, several collapse occurred in the construction process. A brief introduction is given to the geological conditions of Jinping I Hydropower diversion tunnel, based on discrete element method, Major joints and faults were simulated, and calculation models were built. By calculation and analysis, Rules and characteristics of deformation and failure for rock diversion tunnel has been obtained. After the diversion tunnel was excavated, high geostress were released, structural surface relaxation and slip. Side wall generated vertical cracks, vault take place chipping. With deformation increasing, the structural plane was further slip and open, dome support weakened, leading to collapse. 相似文献
11.
In order to study the mechanical properties and structural properties of soft dredger fill under lateral deformation. Based on true triaxial and WF stress path apparatus, lateral unloading undrained tests were carried out. The results derived from true triaxial test, WF stress path test and routine triaxial shear test were analyzed. The contrastive conclusions are as follows: The stress-strain curve of true triaxial unloading test shows a softening behavior, which is different from the hardening behavior for that of conventional triaxial shear test. With the increase of initial confined pressure, the dilatancy of soil transfers from shrinkage to expansion. The structural yield stress of the unloading soil with true triaxial test method is dramatically larger than that with the latter two tests due to the effect of intermediate principal, which exhibits a nonlinear growth as the coefficient of intermediate principal bd stress jumps. The shear strength indexes of unloading soil with true triaxial test is larger than that with WF stress path test. Compared with the results of routine triaxial test, the internal friction angle of true triaxial test is bigger while the cohesion is smaller. 相似文献
12.
on the basis of the experimental studies of mechanical properties in brittle rock,the generalized elastic modulus,generalized elastic Poisson ratio,irreversible deformation Poisson ratio and damage deformation characteristic arediscussed.And then,a new damage variable is defined.A new nonlinear elastic-damage constitutive equation is built and the damage evolution equation is proposed.The nonlinear elastic-damage constitutive equation is verified in the uniaxialcompression test of quartz sandstone in Chongqing.The results show that reasonableagreement exists between the theoretical analysis and the experimental data. 相似文献
13.
By the experimental study about the effect of a circulate loading on the deformation and the Young's model of Sanjome andesite at the distinct strain rate in a low stress state, the viscoelasticity of Sanjome andesite in a low stress state is researched by means of the effect of the circulate loading on the deformation of rocks. It is found that the natural material such as rocks has obvious viscoelasticity, and the mechanical property of rocks has a direct bearing on the size, direction and loading rate, but also on the way of loading and the organization attribute of rocks. 相似文献
14.
Sand is a typical particle structure. The effective stress and corresponding deformation are both determined by the particle characteristics of the medium skeleton, and the changeable condition of the particles will further affect the mechanical response of the earth pressure cell in the test process. To correctly measure the earth pressure value, micromechanical method was applied to analyse the force chain formed by the particles contact under loading unloading condition, and the transferring process, the force strain curve and relationship between the cell mechanical response and the ideal response curve were analyzed in detail, which verified the above mechanical response model based on Particle Flow Code (PFC) method. According to the structural characteristics of the sand and above numerical model, the loading condition, porosity, friction coefficient between the particles and stiffness of the earth pressure cell affecting mechanical response of the earth pressure cell were deeply investigated, the numerical results indicated that there were obvious hysteresis and strain irreversibility for the response curve, and the measured value was sensitive to the above factors. Therefore, research on the force chain structure and corresponding evolution law brings forward a scientific base and new research means for understanding its micromechanical characteristics, and different factors influencing the earth pressure cell are also important for cell calibration and practical monitoring to get more correct earth pressure value. 相似文献
15.
In this paper, on the basis of the compressive tests of composte rock, the different kinds of mechanical properties of composite rock under different bond states are discussed. Authers found that all mechanical properties of composite rock relate to the bond strength between layers and are dilferent when the layers'' bond strength is changed. With increasing the bond strength between layers of the composite rock, the limiting strength, elastic modulus, and breaking energy increase, and this phenomenon is to be stability gradually when they reach some volue, with increasing the layers'' bond strength, the poson ratio reduces. 相似文献
16.
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. 相似文献
17.
Guo Yingzhong 《保鲜与加工》1997,(2):87-93
Using basic principles of stereographic projection,block theory and rock mechanics,this paper tries to find a simple and easy method for determination of an optimum scheme for bolting unstable rocks on a rock slope in design of slope engineering.finally, examination and analysis is made of the completed project for bolting the unstable,high and steep rock slope on the campus of Chongqing University. 相似文献
18.
Mechanical Properties of Concrete Cylinders Confined with CFRP Sheets Subjected to Axial Compression
Based on Drucker-Prager criterion with non-associated flow rule, numerical analysis of mechanical properties of concrete cylinders were carried out by using non-linear finite element method. The effect caused by various parameters such as wrap thickness, fiber orientation and concrete strength on axial mechanical properties of concrete cylinders is discussed. The results show that the results calculated by non-associated flow rule conform to that in the test. It is demonstrated that there is significant enhancement both in compressive strength and ductility of cylinders with the increase of wrap thickness. Moreover, the gain in axial compressive strength is observed to be higher for lower strength concrete and be highest in the cylinders wrapped with the hoop orientation. 相似文献
19.
To analyse size effect of high-strength concrete column under small eccentric loading, experimental analysis was carried out on 3 categories of different sizes of high-strength concrete columns under small eccentric loading. The columns' section size was 200 mm × 200 mm, 400 mm × 400 mm and 800 mm × 800 mm, respectively. Failure mode, ultimate strength, deformation capacity and cross-sectional strain distributing rules were compared to get the size effect law. The results show that the compressive failure mode and cross-sectional strain distributing rules of HSC column under small eccentric loading are basically the same, and the size effect isn't obvious. Ultimate strength and deformation capacity of HSC column under small eccentric loading have size effect obviously. With increase of section size, safety reservation of ultimate strength is reduced and deformation capacity also reduces. 相似文献
20.
Field test and deformation controlling for single tunneling lining stability 总被引：1，自引：0，他引：1 
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下载免费PDF全文 The construction process of anchor,fiber concrete and its mechanical principle of interaction with surrounding rocks is studied by field tests from the view of researching stability of single layer tunneling lining. The mechanical properties of single layer lining in the practical application of tunnel engineering are measured. On the basis of this study,the mechanism of single layer tunnel lining is discussed,which is finally applied to the engineering practice,formatting a set of theoretical support for the design method of single layer lining. Studies found that close effect between fiber reinforced concrete and rock is well,which shows that the single layer lining design method to ensure quality and safety proposed in this paper is feasible,and construction characteristic of retaining structure is reliable. The method can be widely applied in engineering practice,and has remarkable economic benefit and social benefit. 相似文献