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工程中应用土工合成材料时必需考虑其流变特性的影响,流变特性一般指蠕变、松弛、长期强度等方面的性质。当前在土工合成材料设计强度值的选择中,为考虑蠕变影响,往往对其极限强度乘一个蠕变折减系数后加以使用。这个系数如何取值对工程的安全性和经济性影响很大。由于对该系数研究不够,国际和国内都存在很大分歧,一般都取得十分保守。土工合成材料蠕变试验成果表明,蠕变的影响与作用的荷载水平关系很大,当荷载水平小于某一临界值时,材料的变形将渐趋稳定,不会导致蠕变破坏。而根据国内外大量工程实测资料表明,加筋土结构中筋材所受的力很小,仅及设计预测值的几分之一,甚至只有5%,变形也远低于预测值,筋材最大的受力和变形发生在施工结束时。同时,实测资料表明,土体中筋材存在松弛现象,它将减轻蠕变的影响。根据有关的机理分析、试验数据和实测资料,对筋材强度折减系数的合理取值提出了建议。
Engineering geocomposite materials must consider the impact of its rheological properties, rheological properties generally refers to creep, relaxation, long-term strength and other aspects of the nature. Currently in the selection of geosynthetics design strength values, in order to consider the effect of creep, it is often used after the ultimate strength is multiplied by a creep reduction factor. How the value of this factor has a great impact on the safety and economy of the project. Due to the lack of sufficient research on this factor, there have been great differences both at home and abroad, and they have generally been very conservative. The creep test results of geosynthetics show that the influence of creep has a great relation with the load level of action. When the load level is less than a critical value, the deformation of the material will become stable without creep damage. According to a large number of engineering surveying data at home and abroad, it shows that the strength of the reinforced material in the reinforced earth structure is very small, only a fraction of the predicted value of the design or even only 5%, the deformation is much lower than the predicted value, The force and deformation occurred at the end of the construction. At the same time, the measured data show that there is slack in the soil material, which will reduce the impact of creep. According to the relevant mechanism analysis, test data and measured data, the reasonable value of strength reduction coefficient of tendons is put forward.