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1.
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
2.
To explore the characteristics of deformation of sandstone under cyclic pore water pressure, the experiments with different axial stresses (60%, 70% and 80% of peak intensity) of sandstone subjected to cyclic pore water loading are investigated by using MTS815 rock mechanics testing system, and irregular small deformation in deformation curve of sandstone are also processed by wavelet transformation of Matlab. The results show that with the increase of constant axial stress, fatigue deformation under cyclic pore water pressure will accelerate the failure of the sandstone. With the increase of the number of cyclic pore water pressure, the deformation evolution of the plastic-loop is illustrated as sparse-dense-sparse. The deformation curves of sandstone under cyclic pore water pressure affected by many factors are decomposed, reconfigurable processed and evaluated by using wavelet transformation, which indicates that the basic curve with optimal decomposition scale fits well with the experimental curves and reveals the deformation evolution of sandstone. 相似文献
3.
大型渠道水荷载加载过程中渠床变形特性 总被引：1，自引：1，他引：0
为了研究改建后的大型渠道在首次加荷过程中产生的沉降位移量是否会对灌溉设计产生较大影响,笔者基于大型梯形渠道弧形底混凝土防渗渠加荷与卸荷过程中变形观测原位试验,分析了改建后的大型渠道在首次加荷与卸荷过程中渠床的变形特性。结果表明：改建后的大型渠道在首次加荷与卸荷过程中,会发生一个较大的弹性变形及塑性变形,渠道在垂向上的沉降量与回弹量的大小随外荷载不断变化具有一定特征;改建后的大型渠道在首次加荷过程中产生的沉降位移量与渠底以下非饱和土壤的厚度有较大关系;由于渠道在首次加荷与卸荷过程中在垂向上有较大的沉降量,则为满足灌溉条件,应在渠道的设计与施工中采取一定的必要措施。 相似文献
4.
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
5.
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
6.
The destruction of rock mass arises from opening rock possibly, the main outside-factor of influence rock slope stability is groundwater and water seepage. To analyze the relationship of unloading and permeability coefficient, the method and step of experiment of unloading rock mass are put forward. The curve relationship of the seepage-unloading of different phase is found by experiment. According to the experimental result, the equation of the seepage-stress of unloading is established, the variational rule of the unloading and permeability coefficient is discussed. The permeability coefficient is almost unchanged in the elasticity phase of unloading process. The permeability coefficient changes very much in the plastic phase of unloading process, as the unloading is 80% of ultimate unloading especially, and the permeability coefficient is increasing very much. 相似文献
7.
A full-scale model test was conducted on the low silt soaking subgrade of the alluvial flatlands flooded by the Yellow River. The test mainly studied the mechanical characteristics and vertical deformation of the silt subgrade under grade cyclic loading in different water immersion conditions. The test demonstrates that the silt subgrade has intense capillarity and water sensitive characteristics; the additional stress is large in the roadbed of the new and soaking silt subgrade, and it decreases sharply as the depth increases; the phenomenon of strength degradation is obvious in the soaking subgrade; the elastic and plastic deformation is large under overloading force and the deformation increases as the water immersion level ascending; The plastic deformation of the subgrade is easy to accumulate in water-saturated areas, where large plastic deformation still occurs in low stress level. 相似文献
8.
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
9.
Peng Xianghe Gao zhihui Zeng Xiangguo 《保鲜与加工》1998,(2):46-50
Using the theory of non classical elastoplasticity with finite deformation theory and the corresponding finite element program,the compression and spring back of an O Ring,the sealing element between flanges of a pressure vessel,was analyzed,and then the relaxation of pressure of the O Ring during cyclic loading and unloading process was investigated.The comparison between the analytical and experimental results is quite satisfactory.It is also showed that the adopted method possesses good convergence and is convenient to engineering application. 相似文献
10.
采用消(耗)能元件的结构在遭受地震作用时,元件芯材首先屈服进入塑性阶段,利用其滞回变形消耗地震输入能量,保护主体结构,元件芯材本构关系的数值模拟是对采用消(耗)能元件结构进行抗震分析与设计的基础。为更真实地模拟结构消(耗)能元件芯材在单调和循环荷载下的本构响应,更准确地对采用消(耗)能元件结构进行结构弹塑性地震响应分析,对常用作消(耗)能元件芯材的日本高延性钢材SN490B的单调、循环加载本构及循环骨架曲线进行了数值模拟,包括：采用Esmaeily-Xiao二次流塑性模型模拟材料在单调荷载作用下弹性段、屈服段、强化段和二次流塑段4个阶段;采用混合强化模型模拟材料循环荷载作用下的本构响应,运用大型通用有限元软件ABAQUS结合数值模拟参数对16种不同循环加载制度下的循环加载试验进行模拟,并与试验结果进行对比;采用Ramberg-Osgood模型、无量纲化的Ramberg-Osgood模型及两段式模型模拟循环骨架曲线。研究结果表明：所采用数学模型可以较好地模拟SN490B钢材单调、循环加载本构响应及循环骨架曲线,数值模拟与试验结果拟合较好。 相似文献
11.
The investigations on the deformation mechanisms, estimation of stability and technique of disasters controlled of brittle rocks excavated under high geostress are difficult points for rock mechanics and engineering geology. The evolutionary rule of mechanical parameters and deformation failure of brittle rocks are discussed based on unloading under high geostress, and the obvious characteristics of strain strength for brittle rocks under high geostress is found. It is presented that the brittle rock yielded follows Griffith rule of strain strength at peak. The elasto brittle plastic numerical calculation method is established considering the dynamical variation of mechanical parameters in course of unloading yield, and it is validated by practical engineering. 相似文献
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13.
In this paper,several calculation methods for hawser cables as the crane stability system in loading and unloading forces is put out by coordinating principle of deformed body.It is convenient for adjustment of crane in unloading state to benifit accurance of the equipment installation and safrty of device during hoisting.It is also a more accurate and practical method for choice of the cable. 相似文献
14.
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
15.
In order to discuss the influence of stress history on the constitutive relations for soils,a series of drained conventional triaxial compression tests for normally consolidated and overconsolidated clays have been carried out.It is found through comparing the stress-strain relation curves under the different stress histories that the overconsolidated ratio is the determining factor for volumetric strain.The volumetric strain is less sensitive to consolidation pressure,however.For the shear capacity,the consolidation pressure is the determining factor,but the influence of the overconsolidated ratio can not be neglected since it determines whether there will be strain hardening or strain softening as well as the grade of strain softening.Despite that,the soil specimens will finally reach a unified critical state and approximately the same residual strength.According to the principle of interaction between plastic volumetric and shear strains,the mechanism of generating two types of stress-strain relation curves for clays is explained.It is shown that the critical state is a pure process of shearing deformation in which the interaction between plastic volumetric and shear strains completely disappears.The critical state is independent of the previous stress history. 相似文献
16.
Based on the small deformation assumption, the equations of the laterally loaded piles influenced by the axial load were established. The effect of axial load on the lateral response of piles was studied with parameter analysis. The analysis shows that internal force and deformation of laterally loaded pile under axial loading is actually closely linked with the values of axial and lateral loads. In general, the high level axial load should be focused on. It is more significant that the effect of axial load on the internal force and lateral deflection of the upper part of flexible piles, while there is little effect on deep of long-thin pile foundation. The effect of axial load on the lateral response of pile is the largest as coefficient form of subgrade reaction increases linearly, while the effect is minimal as coefficient form of subgrade reaction is a constant. Except in case of buckling, the changes of axial load along the pile direction have little influence on the magnitudes of deflection and moment. The assumption that the axial load is constant with depth can meet the requirements of engineering. 相似文献
17.
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
18.
A one dimensional creep and stress relaxation response of cancellous bone to instant loading is investigated based on the studies with scanning microscope, can cancellous bone be viewed as a cellar solid consisting of an interconnected skeleton filled with medulla. A two phase poroelastic model is introduced to describe the cancellous bone, in which the tissue(material) densities of the skeleton and medulla are assumed to be unchangeable while the corresponding apparent densities are changeable due to the change of volume fraction. The governing equations are derived for the case of a linear poroelastic solid skeleton saturated with an inviscid medulla. Under the loading, responses of the skeleton stress as well as the medullary pressure are obtained with Laplace transform technique. The computational result shows that the cancellous bone is provided with certain features similar to those appearing in viscoelastic solids, which means the responses do not only depend on time, but furthermore depend on previous loading history. It is worth paying attention to the result that the medullary pressure can be negative. This point is due to the recovery of the skeleton after unloading whereas the medulla is not squeezed out but absorbed into the pores by suction. 相似文献
19.
Zhu Caicao Wang Hongen Gong JianxiaoYu Shixing 《保鲜与加工》1993,(6):51-57
In this paper,the mill stand and the rolled piece were studied as a system. Based on the disoreted masses and the deformation of bending curve of the roller and roll housing, according to Rayleigh method,the equivalent mass and and the equivalent stiffness of the mode were solved,and set up a multiple degree of freedom vibration dynamic model. And also did theoretical analysis and calculation with an exapmle of the 4200 thick plate rolling mills. 相似文献