Papers by Keyword: Fissure

Abstract: Among all kinds of environmental geological factors, the water permeability has the most significant influence on grottoes. The main reason for the destruction of caves is the recurrence and persistence of water seepage. Longmen grottoes mainly used epoxy resin and superfine cement grouting materials in the early seepage prevention. Superfine cement has the problem of efflorescence. The epoxy resin material has a large shrinkability and poor durability. Laboratory tests of the impervious materials were carried out. The results shown that the modified epoxy resin, compared with the waterborne epoxy resin, demonstrated higher strength, lower shrinkage and less volatile. Among all the laboratory test schemes, two samples of the modified epoxy resin which were added several adjuvants had the lower shrinkage and volatile, the higher strength and the stronger acid and alkali resistance, which possessed favourable comprehensive performance and were proved to be the best impervious materials in this study.

Abstract: When loaded over their yield strength, materials suffer significant plastic deformations. In such zones, the degree of plastic deformation depends on the characteristics of the material and also on the nature of the loading. As known, the degree of plastic deformation may be correlated with the value of hardness, determined in the plastically-deformed zone. The present paper discusses the three types of testings applied, which led to the fracture of some specimens and, consequently, to plastic deformations in the immediate vicinity of the fractured surfaces. The testings, performed on Compact Tension Specimens, aimed at determining the following characteristics developed by the Mechanics of fracture: the crack growth rate, da/dN, fracture toughness for materials with brittle behavior, K_Ic, and fracture toughness for the materials with a preponderantly ductile character, J_Ic. Along the surfaces fractured during these testings, plastic deformations occur, differentiated exactly by the load differences. Under such conditions, testings were made upon the 1C45 (1.053) steel, with the characteristics established by the manufacturer, as well as upon the same steel, yet subjected to an annealing thermal treatment, and the variations of Vickers hardness were recorded both along the fractured surfaces and from one specimen to another.

Abstract: In this paper we present the experimental results obtained after determining hardness on samples previously subjected to fatigue. Firstly, 6 identical samples have been subjected to stress fatigue in the elastic range a number of 10⁵, 5∙10⁵, 10⁶, 2∙10⁶, 3∙10⁶ and 4∙10⁶ cycles. For all samples we used the same form of stress cycle, respectively, sinusoidal, and the same values of maximum, minimum force and the amplitude of the cycle (50 kN, 30 kN and 10 kN). It is noted that the maximum value of the load was less than that at which samples fall within the plastic deformation. Therefore, the original loading of samples was performed in the elastic range. For each of the six samples determinations of levels of hardness were performed, with the value of indentation load of 10 kgf. Indentations were made on the samples, along the length of the calibration, at a distance of 10 mm one within the other. As it will be seen below, in the areas with the highest hardness were performed several indentations, in order to determine the highest hardness area, which, in our view, also presents the largest degree of plastic deformation.

Abstract: Fissure is one of the most important characteristics in expansive soil. It’s an important factor affecting slope stability in the expansive soil area. With the study of expansive soils typical channel slope fissured characters in the South-to-North Water Diversion Project, different impaction on slope stability such as location and inclination of the fissure are analyzed. By using the limit equilibrium method, the stability of expansive soil slope is analyzed; the most adverse condition of expansive soil slope is concluded. Then anti-slippery pile reinforcement in expansive soil channel slope is studied by using finite difference method. The research is of great significance to the construction and reinforcement of expansive soil slopes in South-to-North Water Diversion Project.

Abstract: Based on the analysis of influence of fissures and accumulation rainwater at toe of slope under rainfall condition on expansive soil slope, A limit equilibrium method was proposed based on former studies by dividing the slope into fully fissures area A , partially developed fissures area B , accumulation rainwater influence area B′, without fissures area C, and considering the top slope tension crack to reflect influence of fissures on expansive soil slope under rainfall condition. The depths of every layer and strength indexes were determined. The computed results of an engineering example using bishop method showed that the proposed method can not only reflect the characteristics of expansive soil landslide but also evaluate the long-term stability of the slope at ultimate state.

Abstract: Based on saturated-unsaturated seepage mechanism, the features of pore-water pressure, strain and displacement of fissured and fissureless slope are analyzed by using the finite element method. At the same time, pore-water pressure, displacement and safety factor of fissured and fissureless slope as well as fissured slope with different depth and width are comparatively analyzed under the condition of rainfall and evaporation. The research results show that, under rainfall condition, the existence of fissures could change the boundary of soil infiltration and seepage filed distribution, lead to stress concentration and make plastic strain around the fissures area. In addition, as the rainfall response time increasing, the plastic zone around the fissures will spread to the surrounding, thus, the new micro-fissures would be produced during the process of the fissures expansion. Evaporation will reduce the shallow soil water content, increase suction and slope stability. Under the condition of rainfall and evaporation, slope stability is affected more seriously by the fissure depth, but less by the width.

Abstract: The relation of tensile strength ＆ temperature stress and concrete fissure was researched firstly , then it showed the causes of late cracks on concrete by theoretical calculation, the result provided a simple theoretical calculation method to avoid concrete fissure. The construction methods to control the fissure was proposed: early strengthening cooling, managing maximum temperature of concrete through lately heat preservation, and overtime to preserving concrete moisture for controlling the late strain on mass concrete. This research has a great significance for controlling the fissure.

Abstract: Rock is a type of natural material containing microcracks. The evolution of mining-induced fracture field is one of the main problems of gas comprehensive control and rock mass seepage. The distribution of fissures and porosity in overlying strata under the mining influence were studied in this paper. The stratum subsidence was represented quantitatively using elastic thin plate theory and key strata theory. Based on the stratum subsidence, a program calculating porosity in overlying strata was developed based on VB. The results demonstrate that the porosity increase with face advances. The porosity becomes small with the decrease of strata depth, and the bigger separation is located in the strata below the key strata. The amount of the fissures in the middle part of overlying strata is more than that in two ends, and the porosity curves present symmetric arch shape in the initial stage. With face advances, the curves of porosity in the strata located the upper position change symmetric arch shape into saddle shape.

Abstract: Three types of corrosion attack frequently suffered by type Cr18Ni10 stainless steel in the heat-affected zone of welds were studied – knife-line, fusion-line, and fissure corrosion. Possible mechanisms and selected preventative measures were discussed in the light of microstructural findings.