不同荷载频率与细粒含量下路基粗粒填料动力特性研究
发布时间：2018-11-07 15:31
【摘要】：道路路基作为承载和传递车辆荷载的关键结构,在服役期内将承受数百万次交通荷载作用,掌握大次数交通循环荷载下路基的刚度变化及累积变形发展规律是保障道路长期服役性能的前提。粗粒碎石填料因其良好的力学性能及透水性能,且易于就地取材被广泛应用于路基层填筑工程。目前学者们针对交通循环荷载下路基粗粒填料的动力特性开展了一系列研究,获得了路基粗粒填料物理状态、交通荷载大小与循环次数等因素对道路路基回弹与累积变形的影响规律。在交通运输日益高速化、密集化趋势下,荷载频率作为反映交通荷载速度与密度的重要参数,其对路基粗粒填料长期动力特性的影响不容忽略。此外,地基翻浆等原因将使路基粗粒填料受到不同程度的污染,细粒污染将改变路基的内部结构与级配,降低路基的排水性能,对路基强度与变形特性造成显著影响进而影响到道路的长期服役性能。因此,有必要采用公路路基粗粒填料层所对应的典型频率荷载对其动力特性进行研究,并分析不同细粒污染程度下路基填料特性变化,以揭示荷载频率及细粒含量对路基粗粒填料的长期动力特性影响规律。本文利用GDS大型三轴试验系统进行了一系列不同频率与细粒含量下凝灰岩碎石填料的排水循环荷载试验,具体内容包括以下几个方面:1、针对不同车辆速度与行车密度等因素在道路路基中产生不同荷载频率这一实际工程问题,利用大型三轴循环试验系统在不同荷载频率下对公路路基粗粒填料开展饱和排水循环荷载试验。系统性地分析了荷载频率、循环应力比等对路基粗粒填料长期动力特性的影响规律,获得了循环荷载频率对路基填料体应变、回弹模量和轴向累积应变的影响规律。研究表明,在粗粒填料密实阶段,提高荷载频率使粗粒填料产生更大的体应变而更为密实,从而使粗粒填料回弹模量随荷载频率增加显著增大;在低循环应力比下,土体轴向累积变形随荷载频率变化相对较小,但在高循环应力比下,轴向累积变形随荷载频率增加明显增大。当粗粒土进入稳定变形阶段,荷载频率对路基粗粒填料体应变与轴向累积变形基本无影响。因此,控制路基中的循环应力比,可显著降低荷载频率对路基长期动力特性的影响。2、结合不同荷载频率下路基填料轴向累积应变试验数据,对路基填料大次数循环累积变形预测模型HCA模型(High-cycle Accumulation Model)进行改进。通过引入考虑荷载频率影响的因子ff,提出了可考虑荷载频率影响的路基填料轴向累积变形预测模型。研究表明,该模型可准确预测公路路基在典型频率荷载下的轴向累积变形,为更加全面地预测和控制道路工后沉降提供了有效工具。3、为研究交通循环荷载下受细粒污染的路基填料的动力特性,针对不同污染程度下的凝灰岩碎石填料开展了一系列大型三轴循环荷载试验研究。通过在粗粒填料中掺入不同含量高岭土来模拟污染路基填料。为考虑荷载频率与细粒含量对污染路基填料动力特性的耦合影响,开展了 5种不同污染程度下的路基填料在3种荷载频率下的大三轴循环荷载试验。着重分析了不同荷载频率及细粒含量下粗粒填料的孔压、体应变、回弹模量及轴向累积变形的变化规律,总结了细粒含量在不同荷载频率下对路基填料动力特性的影响规律。研究表明,细粒土对路基粗粒填料动力特性的影响分为三个阶段。首先,少量细粒土对粗颗粒土的润滑作用导致粗粒填料在循环荷载下的体应变和轴向累积应变增大;随着细粒含量进一步增大,粗粒填料孔隙被细粒填充而使其压缩性减小,体应变与轴向累积应变随之减小;当细粒含量增加到一定值后,粗粒填料渗透性显著降低,循环荷载下路基中孔压迅速累积,进而导致轴向累积应变急剧增大,回弹模量大幅减小。此外,细粒含量对粗粒填料长期动力特性的影响受荷载频率影响显著,高频荷载将加剧孔压累积,导致路基长期服役性能劣化。
[Abstract]:As the key structure for carrying and transferring the load of the vehicle, the road subgrade will bear millions of traffic loads during the service period, and master the change of the stiffness and the cumulative deformation of the subgrade under the large number of traffic cycle loads, which is the premise to guarantee the long-term service performance of the road. The coarse-grained gravel packing material has good mechanical property and water permeability, and can be widely applied to the road-base filling project. The current scholars have carried out a series of research on the dynamic characteristics of the coarse grain filling of the subgrade under the traffic cycle load, and obtained the influence of the physical state, the traffic load size and the number of cycles of the subgrade coarse grain filler on the rebound and the cumulative deformation of the road subgrade. Under the trend of increasing traffic and transportation, the load frequency is an important parameter reflecting the speed and density of traffic load, and its influence on the long-term dynamic characteristics of the coarse-grained filler of the subgrade is not negligible. In addition, the cause of foundation turning and so on will cause the coarse grain filler of the subgrade to be polluted by different degrees. The fine-grained pollution will change the internal structure and grading of the subgrade, reduce the drainage performance of the subgrade, and have a significant impact on the strength and deformation characteristics of the subgrade, thus affecting the long-term service performance of the road. Therefore, it is necessary to study the dynamic characteristics of the subgrade with the typical frequency load corresponding to the coarse grain filler layer of the highway, and to analyze the change of the characteristics of the roadbed filling under different particle pollution levels, so as to reveal the influence of the loading frequency and the fine particle content on the long-term dynamic characteristics of the coarse grain filler of the subgrade. In this paper, a series of experiments on the drainage cyclic loading of tuff-gravel packing with different frequency and fine particle content are carried out by using a large-scale three-axis test system of GDS. The concrete contents include the following aspects: 1. In view of the actual engineering problems of different load frequencies in the road subgrade, such as the speed and the running density of different vehicles, the heavy-grain filling of the highway subgrade is tested by the large-scale three-axis cyclic test system at different load frequencies. The influence of the load frequency and the cycle stress ratio on the long-term dynamic characteristics of the coarse-grained filler in the subgrade is systematically analyzed, and the influence of the cyclic loading frequency on the strain, the rebound modulus and the axial cumulative strain of the subgrade filler is obtained. The results show that, in the dense phase of the coarse grain filling, the loading frequency is increased to make the coarse grain filler produce larger body strain and more compact, so that the rebound modulus of the coarse grain filler is increased significantly with the load frequency, and at the lower cycle stress ratio, The axial cumulative deformation of the soil is relatively small with the change of the load frequency, but the axial accumulative deformation is obviously increased with the load frequency under the ratio of high cycle stress. When the coarse grain soil enters the stable deformation stage, the load frequency has no effect on the strain and axial accumulative deformation of the coarse grain filler body of the subgrade. therefore, the influence of the load frequency on the long-term dynamic characteristics of the subgrade can be obviously reduced, the influence of the load frequency on the long-term dynamic characteristics of the subgrade can be obviously reduced, In this paper, the high cycle cumulative deformation prediction model HCA (High-cycle Model) model is improved. By introducing the factor ff which takes into account the influence of the frequency of the load, the prediction model of the axial cumulative deformation of the roadbed filling which can take into account the influence of the loading frequency is put forward. The research shows that the model can accurately predict the axial cumulative deformation of the highway subgrade under the typical frequency load, and provides an effective tool for the more comprehensive prediction and control of the post-work settlement. A series of large-scale three-axis cyclic loading test was carried out for the tuff-gravel packing of different degree of pollution. The contaminated subgrade filler is simulated by incorporating different amounts of kaolin into the coarse grain filler. In order to consider the coupling effect of the loading frequency and the fine particle content on the dynamic characteristics of the contaminated subgrade, a three-axis cyclic load test of the roadbed filling under the three loading frequencies is carried out. The changes of pore pressure, body strain, rebound modulus and axial cumulative deformation of coarse grain filler in different load frequency and fine particle content are analyzed, and the influence of fine particle content on the dynamic characteristics of the subgrade filler under different load frequency is summarized. The study shows that the influence of fine-grained soil on the dynamic characteristics of the coarse-grained filler in the subgrade is divided into three stages. first, a small amount of fine-grained soil is used to lubricate the coarse-grained soil, resulting in an increase in the bulk strain and the axial cumulative strain of the coarse-grain filler under the cyclic load; as the fine-particle content is further increased, the coarse-grained filler pores are filled with fine particles to reduce its compressibility, The body strain and the axial cumulative strain are reduced accordingly; when the fine particle content is increased to a certain value, the permeability of the coarse grain filler is obviously reduced, and the pore pressure in the subgrade under the cyclic load is rapidly accumulated, and further, the axial accumulative strain is rapidly increased, and the rebound modulus is greatly reduced. In addition, the influence of the fine particle content on the long-term dynamic characteristics of the coarse-grained filler is affected by the load frequency, and the high-frequency load will increase the pore pressure accumulation, leading to the deterioration of the long-term service performance of the subgrade.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U414
[Abstract]:As the key structure for carrying and transferring the load of the vehicle, the road subgrade will bear millions of traffic loads during the service period, and master the change of the stiffness and the cumulative deformation of the subgrade under the large number of traffic cycle loads, which is the premise to guarantee the long-term service performance of the road. The coarse-grained gravel packing material has good mechanical property and water permeability, and can be widely applied to the road-base filling project. The current scholars have carried out a series of research on the dynamic characteristics of the coarse grain filling of the subgrade under the traffic cycle load, and obtained the influence of the physical state, the traffic load size and the number of cycles of the subgrade coarse grain filler on the rebound and the cumulative deformation of the road subgrade. Under the trend of increasing traffic and transportation, the load frequency is an important parameter reflecting the speed and density of traffic load, and its influence on the long-term dynamic characteristics of the coarse-grained filler of the subgrade is not negligible. In addition, the cause of foundation turning and so on will cause the coarse grain filler of the subgrade to be polluted by different degrees. The fine-grained pollution will change the internal structure and grading of the subgrade, reduce the drainage performance of the subgrade, and have a significant impact on the strength and deformation characteristics of the subgrade, thus affecting the long-term service performance of the road. Therefore, it is necessary to study the dynamic characteristics of the subgrade with the typical frequency load corresponding to the coarse grain filler layer of the highway, and to analyze the change of the characteristics of the roadbed filling under different particle pollution levels, so as to reveal the influence of the loading frequency and the fine particle content on the long-term dynamic characteristics of the coarse grain filler of the subgrade. In this paper, a series of experiments on the drainage cyclic loading of tuff-gravel packing with different frequency and fine particle content are carried out by using a large-scale three-axis test system of GDS. The concrete contents include the following aspects: 1. In view of the actual engineering problems of different load frequencies in the road subgrade, such as the speed and the running density of different vehicles, the heavy-grain filling of the highway subgrade is tested by the large-scale three-axis cyclic test system at different load frequencies. The influence of the load frequency and the cycle stress ratio on the long-term dynamic characteristics of the coarse-grained filler in the subgrade is systematically analyzed, and the influence of the cyclic loading frequency on the strain, the rebound modulus and the axial cumulative strain of the subgrade filler is obtained. The results show that, in the dense phase of the coarse grain filling, the loading frequency is increased to make the coarse grain filler produce larger body strain and more compact, so that the rebound modulus of the coarse grain filler is increased significantly with the load frequency, and at the lower cycle stress ratio, The axial cumulative deformation of the soil is relatively small with the change of the load frequency, but the axial accumulative deformation is obviously increased with the load frequency under the ratio of high cycle stress. When the coarse grain soil enters the stable deformation stage, the load frequency has no effect on the strain and axial accumulative deformation of the coarse grain filler body of the subgrade. therefore, the influence of the load frequency on the long-term dynamic characteristics of the subgrade can be obviously reduced, the influence of the load frequency on the long-term dynamic characteristics of the subgrade can be obviously reduced, In this paper, the high cycle cumulative deformation prediction model HCA (High-cycle Model) model is improved. By introducing the factor ff which takes into account the influence of the frequency of the load, the prediction model of the axial cumulative deformation of the roadbed filling which can take into account the influence of the loading frequency is put forward. The research shows that the model can accurately predict the axial cumulative deformation of the highway subgrade under the typical frequency load, and provides an effective tool for the more comprehensive prediction and control of the post-work settlement. A series of large-scale three-axis cyclic loading test was carried out for the tuff-gravel packing of different degree of pollution. The contaminated subgrade filler is simulated by incorporating different amounts of kaolin into the coarse grain filler. In order to consider the coupling effect of the loading frequency and the fine particle content on the dynamic characteristics of the contaminated subgrade, a three-axis cyclic load test of the roadbed filling under the three loading frequencies is carried out. The changes of pore pressure, body strain, rebound modulus and axial cumulative deformation of coarse grain filler in different load frequency and fine particle content are analyzed, and the influence of fine particle content on the dynamic characteristics of the subgrade filler under different load frequency is summarized. The study shows that the influence of fine-grained soil on the dynamic characteristics of the coarse-grained filler in the subgrade is divided into three stages. first, a small amount of fine-grained soil is used to lubricate the coarse-grained soil, resulting in an increase in the bulk strain and the axial cumulative strain of the coarse-grain filler under the cyclic load; as the fine-particle content is further increased, the coarse-grained filler pores are filled with fine particles to reduce its compressibility, The body strain and the axial cumulative strain are reduced accordingly; when the fine particle content is increased to a certain value, the permeability of the coarse grain filler is obviously reduced, and the pore pressure in the subgrade under the cyclic load is rapidly accumulated, and further, the axial accumulative strain is rapidly increased, and the rebound modulus is greatly reduced. In addition, the influence of the fine particle content on the long-term dynamic characteristics of the coarse-grained filler is affected by the load frequency, and the high-frequency load will increase the pore pressure accumulation, leading to the deterioration of the long-term service performance of the subgrade.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U414
【参考文献】
相关期刊论文 前10条
1 冷伍明;周文权;聂如松;赵春彦;刘文R，
本文编号：2316786
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