共查询到18条相似文献,搜索用时 140 毫秒
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深表土冻结壁变形规律 总被引:1,自引:0,他引:1
利用ANSYS软件建立数学模型,分析不同地压、不同冻结壁厚度、不同冻结壁平均温度、不同开挖段高与冻结壁变形之间的关系。通过研究发现,井帮位移随冻结壁平均温度的降低、冻结壁厚度的增大而减小,随施工段高增大、地层地压值的增大而增大,且地压值的变化对冻结壁的变形影响最为显著。据此提出了深表土冻结壁应按变形条件进行设计,且施工段高是影响冻结壁稳定性的极为重要的参数,在施工中应严格控制。研究提出当冻结壁厚度为10 m左右,平均温度达到-20℃时,采取降低冻结壁平均温度的方式比增加冻结壁厚度能更加有效地提高冻结壁的稳定性。研究成果对于指导深表土冻结工程设计与施工,实现矿井冻结工程安全、优质、高效、节能,具有重要的参考价值。 相似文献
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本文在潘集矿区冻结壁形成的试验实测和理论计算的基础上,结合作者长期从事冻结法凿井的体会,对冻结管的单位热流量和影响冷冻站装机能力的主要因素进行了分析研究,提出了冷冻站合理装机能力的确定原则。这样,既能满足井筒开凿的需要,又能大幅度地降低冻结费用。 相似文献
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基于三维连续黏性阻尼介质理论和径向多圈层复刚度传递模型,综合考虑桩周土径向非均质效应和纵向成层性,建立双向非均质土体中桩基扭转振动简化分析模型。采用拉普拉斯变换和复刚度传递法求解得出土体位移形式解,进而利用桩-土耦合条件将该形式解耦合进桩身动力平衡方程中,并通过扭转阻抗传递法推导得出桩顶扭转阻抗解析解答。将该解退化并分别与均质土及径向非均质土中的解答进行对比验证其合理性。在此基础上,通过参数化分析探讨了桩周土施工扰动程度和扰动范围、扩颈及缩颈缺陷对桩顶扭转阻抗的影响规律,可为具体工程实践提供理论指导和参考作用。 相似文献
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考虑表皮层和未扰动承压层的非均质性、各向异性以及竖向越流补给作用,建立了径向双层承压三维井流的数学模型,采用Laplace变换和矩阵理论求得表皮层和未扰动承压层的水头降以及井壁流量的半解析解.应用所求解编制计算程序,分析了表皮层沿竖向随机变化的渗透性对承压层井流的影响,结果表明:表皮层非均质变化形态决定了表皮层内和其附近处的水头降以及井壁流量的竖向分布规律,表皮层对承压层渗流产生的影响范围与承压层的竖向渗透系数大小有关;改善井周岩土介质渗透性或增大"负表皮层"厚度可提高抽水井产量;表皮层径向渗透系数较小时,承压层的水头降幅度主要取决于承压层径向渗透系数的大小,而当表皮层径向渗透系数较大时,承压层径向渗透系数和竖向渗透系数均对承压层水头降有较大影响. 相似文献
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栗伟 《制冷与空调(北京)》2022,(1)
传统带法兰椭圆形封头设计方法设计周期长、试错成本高。本文采用ANSYS有限元应力分析技术对带法兰椭圆形封头进行建模仿真分析,并与其他研究人员进行的带法兰椭圆形封头的验证性实验结果进行对比,结果表明有限元应力分析技术可以满足工程应用要求。最后利用ANSYS软件中的优化设计功能,对带法兰椭圆形封头的壁厚进行设计优化,壁厚为8.03 mm时,最大等效应力和最小总质量分别为312.3 MPa和26.2 kg,相比壁厚为10 mm时最小总质量下降了16.5%,可以达到节省工程材料、提高经济效益的目标。 相似文献
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The effect of supercooling on ice structure in tuna meat observed by using X-ray computed tomography
Several studies have reported that freezing a homogeneous food such as soy bean curd with deep supercooling (supercooled freezing) results in the formation of many particle ice and homogenous ice structure. However, ice crystal morphology may be affected by the cellular structure of the food. In this study, the ice crystal structure in tuna meat, a cellular food, frozen by the supercooled freezing method was investigated by X-ray computed tomography and compared with ice structures in tuna meat frozen by conventional freezing methods. The results showed that rod-like ice crystals grew parallel with the myofibers, and inhomogeneous ice structures formed in tuna meat frozen by the supercooled freezing method regardless of the degree of supercooling, in contrast to the ice structure in frozen soy bean curds. These ice crystals linked with each other to form rod-like ice structures due to mobility limitations imposed by the cellular structure. 相似文献
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Freezing is a valuable method to increase food shelf life and to ensure high quality standards during long-term storage. Additional benefits to frozen food quality can be achieved by freezing at very low temperatures (< −50 °C): small ice crystal formation during fast freezing reduces food cell wall rupture, preventing water and texture loss during thawing. This paper presents the design of an innovative food freezing system operating at very low temperatures, based on a modified reversed Brayton cycle (rB cycle). The plant is composed of two interconnected sub-systems: a primary thermodynamic closed loop, operated by an rB cycle, and a secondary airflow loop which is devoted to food freezing by batch process. Relevant features of the designed rB cycle rely on the adopted environmentally safe working fluid, the optimised thermodynamics working conditions and the innovative cycle layout. A modelling framework for the system was developed to identify and design efficient operative settings for the plant components (turbo-machineries, heat exchangers, etc.) and to assess, via sensitivity analysis, the influence of the main design parameters on the global energy performance. The proposed system configuration, designed to maximise the coefficient of performance (CoP) value of the plant, was determined by means of nonlinear multivariable optimisation. In addition, the energy performance of the system can be increased by recovering waste heat available from the rB cycle. 相似文献
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《Cold Regions Science and Technology》2009,58(2-3):116-122
High frequency ground-penetrating radar direct ground waves were used to monitor the seasonal development of a thin, high velocity frozen soil layer over a wet low velocity unfrozen substratum. During the freezing process, the progressive attenuation of a low velocity direct ground wave and the subsequent development of a high velocity direct ground wave were observed. Numerical simulations showed that low velocity direct wave event occurring after freezing commences is due to energy leaking across the frozen layer from the spherical body wave in the unfrozen half space. This leaky phase progressively dissipates until the frozen layer reaches a thickness equivalent to one quarter of the dominant wavelength in the frozen ground. The appearance of the high velocity direct wave is governed by its destructive interference with the reflection events from the base of the frozen layer. This interference obscures the high velocity direct wave event until the frozen layer thickness reached one half of the dominant wavelength in the frozen ground. These changes in direct wave transmission permit frozen layer monitoring for thicknesses that are significantly less than those feasible using the reflection event from the frozen–unfrozen boundary. 相似文献
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Shunsuke Takagi 《Cold Regions Science and Technology》1980,3(1):57-81
Presented in this paper are the theorization of a traditional concept of the mechanics of frost heaving, as well as a critical review of the recent developments in this field. The key to the theorization is the following: (1) the film water adsorbed on soil particles can build up an internal solid-like stress, and (2) the flow of film water is different from the conventionally accepted flow of pore water. It is expected that modern continuum mechanics will, in the future, improve the theory of film water which, in this paper, has been formulated by use of the classical method.The freezing film water, trying to retrieve the loss of its thickness to the frozen ice, generates a suction force that draws water to the freezing front where the frost-heaving pressure pushes up the overburden. The temperature of the freezing film water that has generated the solid-like stress, is lower than the temperature of the freezing pore water. This distribution of freezing temperatures in the region of film and pore waters explains the observation that the freezing front causing frost heaving is not a planar surface but a three-dimensional zone diffused in the direction of heat transfer. Frost-heaving pressure can be derived as part of the solution of the boundary-value problem of the frost-heaving differential equations. 相似文献