【作者】 于志强；

【导师】 闫澍旺；

【作者基本信息】 天津大学 ， 岩土工程， 2005， 博士

【摘要】 本文介绍了土工合成材料应用发展历史以及在港口工程中土工织物应用类型、范围,简要分析了土工织物材料种类、物理结构、添加剂等内部因素及紫外线、温度、化学生物、气候、机械磨损等外部因素对土工织物的耐久性与抗老化的影响,分析了土工织物耐久性及土工织物的研究现状。通过对长江界牌、汉江航道整治试验坝土工织物应用工程实地取样和收集国内外已有的试验成果,分析了不同使用目的、不同材质、织造类型对土工织物耐久性的影响,给出了工程上常用的土工织物的耐久年限。根据黄骅港防波堤土工织物加筋垫层孔隙水压力消散、地基沉降、土工织物拉应力、堤基土压力等现场实测结果,分析了土工织物加筋垫层拉应力分布大小、特点以及与堤底地基的沉降关系。实测结果表明基底土压力分布趋向均化,拉应力发挥水平远低于设计拉力值,这对土工织物加筋垫层稳定分析中如何考虑拉应力大小提出了新的问题。结合黄骅港防波堤实际工程,通过一组有、无土工织物加筋垫层及不同织物加筋条件的离心模型试验研究,分析了地基土质点运动位移场、孔隙水压力的发展过程、地基表面的沉降或隆起以及堤坝轴对称处织物的拉力。根据试验结果探讨了防波堤的填筑极限高度,研究了各种不同工况下地基的变形特性及稳定性,对土工织物的加筋机理与加筋地基稳定性作了分析和探讨。通过现场和室内离心模型试验,可以得出:(1)土工织物加筋垫层通过改变防波堤-垫层-地基体系的固结应力分布及地基表面的剪应力分布,抑制堤基的不均匀沉降,减小侧向位移,并能改善堤坝的稳定性从而提高堤基的极限承载力。(2)土工织物的加筋效果受织物铺设宽度、强度、模量和界面强度等诸多因素的影响。一般铺设宽度愈大、织物强度愈高,其加筋效果愈好。为了保证加筋效果的充分发挥,要求织物的强度及模量应与砂垫层的界面强度相匹配。土工织物加筋垫层所承受的力主要是由堤体产生的内力,假设堤体产生的内力部分由加筋垫层承担(承担比例为ηt),部分由地基承担,基于极限平衡理论条件,推导出了土工织物加筋垫层地基稳定性分析公式。计算表明:圆弧滑动面的简单条分法与对数螺旋面的本文方法能很好的反映加筋垫层的抗滑效果。加筋垫层的抗滑作用与滑动面位于地基的深度有关,浅层滑动时抗滑作用显著,深层滑动时抗滑作用较小。更多还原

【Abstract】 The paper expounds the development history of geosynthetics as well as the types of geosynthetics used in port works and the scope of application of geosynthetics. The internal factors affecting the geosynthetics such as the types of materials used, physical structure and additives used as well as the influence of ultraviolet rays, temperature, chemical organism, climate and mechanical wear upon the durability and ageing resistance of geosynthetics are analyzed briefly. Durability of geotextiles and present research and study of geotextiles are also analyzed.Based on the field sampling and tests of the geotextiles used in the pilot dams for the works training the waterways of the Changjiang River at Jiepai and the Hanjiang River as well as the available data and results of tests made both at home and abroad, the influence of different purposes of usage, different materials and different textures of geotextiles upon the durability of geotextiles is analyzed and by so doing the durable life of geotextiles commonly used on engineering projects is given.With the measured data of the dissipation of pore water pressure of the geotextile-reinforced course, settlement of foundation, tensile stress of geotextiles and pressure on the embankment of the breakwater for Huanghua Port, the magnitude and characteristics of the distribution of tensile stress of the geotextile-reinforced course and their relationship with the settlement of the foundation below the breakwater are analyzed. The measured data showed that the pressure distribution on the foundation soil tended to homogenize and the tensile stress developed was lower than the design tension force, thus raising a new problem in considering the magnitude of tensile stress when the stability of a synthetic-reinforced course is being analyzed.In combination with the construction of the breakwater for Huanghua Port and on the basis of the tests of the centrifugal models of bedding courses with and without reinforcing geotextiles and with different types of geotextiles, the displacement field of particle movement of foundation soil, process of development of pore water pressure, settlement or uplift of foundation surface and the tensile force of geotextiles at the axial symmetric point of the breakwater were analyzed. The ultimate height of the breakwater was discussed in accordance with the test results and the deformation characteristics and stability of the foundation under different working conditions werealso studied. The reinforcing mechanism of geotextiles and the stability of the geotextile-reinforced foundation were also analyzed and discussed. It can be concluded from the field and laboratory centrifugal model tests that,(1) By altering the distribution of the consolidation stress in the breakwater - bedding course– foundation system and the distribution of the shear stress of the foundation surface, the geotextiles-reinforced bedding course may restrain the uneven settlement of a foundation and reduce the lateral displacement and can also improve the stability of breakwaters and dams, thus increasing the ultimate bearing capacity of foundations.(2) The reinforcing effect of geotextiles may be affected by a number of factors like the width of laid geotextiles, strength and modulus of the geotextiles and interfacial strength. Generally, the wider the geotextiles is laid and the higher the strength of geotextiles is, the better the reinforcing effect of the geotextiles will be. To ensure the full play of the reinforcing effect of geotextiles, the strength and modulus of the textile should match the interfacial strength of the sand cushion.The load borne by the geotextile-reinforced bedding course is mainly the internal load generated by the body of the breakwater itself. Assuming that the internal load generated by the body of a breakwater itself is partially borne by the geotextile-reinforced bedding course (with a proportion of bearing ofηt) and partially borne by the foundation, an analytical equation is derived for the stability of a foundation with a geotextile-reinforced bedding course on the basis of the theory of ultimate equilibrium. The calculations thus made indicate that the simple slice method for circular slip surface and the logarithmic spiral surface method presented in this paper may well reflect the anti-sliding effect of the geotextile-reinforced bedding course. The sliding resistance of a geotextile-reinforced bedding course and the position of sliding surface is related to the depth of the foundation. The anti-sliding resistance is significant when the sliding develops in shallow strata, but the anti-sliding effect is less remarkable when the sliding develops in deep strata.更多还原