【摘要】：道路路基作為承載和傳遞車輛荷載的關(guān)鍵結(jié)構(gòu),在服役期內(nèi)將承受數(shù)百萬次交通荷載作用,掌握大次數(shù)交通循環(huán)荷載下路基的剛度變化及累積變形發(fā)展規(guī)律是保障道路長期服役性能的前提。粗粒碎石填料因其良好的力學(xué)性能及透水性能,且易于就地取材被廣泛應(yīng)用于路基層填筑工程。目前學(xué)者們針對交通循環(huán)荷載下路基粗粒填料的動力特性開展了一系列研究,獲得了路基粗粒填料物理狀態(tài)、交通荷載大小與循環(huán)次數(shù)等因素對道路路基回彈與累積變形的影響規(guī)律。在交通運輸日益高速化、密集化趨勢下,荷載頻率作為反映交通荷載速度與密度的重要參數(shù),其對路基粗粒填料長期動力特性的影響不容忽略。此外,地基翻漿等原因?qū)⑹孤坊至Ｌ盍鲜艿讲煌潭鹊奈廴?細(xì)粒污染將改變路基的內(nèi)部結(jié)構(gòu)與級配,降低路基的排水性能,對路基強(qiáng)度與變形特性造成顯著影響進(jìn)而影響到道路的長期服役性能。因此,有必要采用公路路基粗粒填料層所對應(yīng)的典型頻率荷載對其動力特性進(jìn)行研究,并分析不同細(xì)粒污染程度下路基填料特性變化,以揭示荷載頻率及細(xì)粒含量對路基粗粒填料的長期動力特性影響規(guī)律。本文利用GDS大型三軸試驗系統(tǒng)進(jìn)行了一系列不同頻率與細(xì)粒含量下凝灰?guī)r碎石填料的排水循環(huán)荷載試驗,具體內(nèi)容包括以下幾個方面:1、針對不同車輛速度與行車密度等因素在道路路基中產(chǎn)生不同荷載頻率這一實際工程問題,利用大型三軸循環(huán)試驗系統(tǒng)在不同荷載頻率下對公路路基粗粒填料開展飽和排水循環(huán)荷載試驗。系統(tǒng)性地分析了荷載頻率、循環(huán)應(yīng)力比等對路基粗粒填料長期動力特性的影響規(guī)律,獲得了循環(huán)荷載頻率對路基填料體應(yīng)變、回彈模量和軸向累積應(yīng)變的影響規(guī)律。研究表明,在粗粒填料密實階段,提高荷載頻率使粗粒填料產(chǎn)生更大的體應(yīng)變而更為密實,從而使粗粒填料回彈模量隨荷載頻率增加顯著增大;在低循環(huán)應(yīng)力比下,土體軸向累積變形隨荷載頻率變化相對較小,但在高循環(huán)應(yīng)力比下,軸向累積變形隨荷載頻率增加明顯增大。當(dāng)粗粒土進(jìn)入穩(wěn)定變形階段,荷載頻率對路基粗粒填料體應(yīng)變與軸向累積變形基本無影響。因此,控制路基中的循環(huán)應(yīng)力比,可顯著降低荷載頻率對路基長期動力特性的影響。2、結(jié)合不同荷載頻率下路基填料軸向累積應(yīng)變試驗數(shù)據(jù),對路基填料大次數(shù)循環(huán)累積變形預(yù)測模型HCA模型(High-cycle Accumulation Model)進(jìn)行改進(jìn)。通過引入考慮荷載頻率影響的因子ff,提出了可考慮荷載頻率影響的路基填料軸向累積變形預(yù)測模型。研究表明,該模型可準(zhǔn)確預(yù)測公路路基在典型頻率荷載下的軸向累積變形,為更加全面地預(yù)測和控制道路工后沉降提供了有效工具。3、為研究交通循環(huán)荷載下受細(xì)粒污染的路基填料的動力特性,針對不同污染程度下的凝灰?guī)r碎石填料開展了一系列大型三軸循環(huán)荷載試驗研究。通過在粗粒填料中摻入不同含量高嶺土來模擬污染路基填料。為考慮荷載頻率與細(xì)粒含量對污染路基填料動力特性的耦合影響,開展了 5種不同污染程度下的路基填料在3種荷載頻率下的大三軸循環(huán)荷載試驗。著重分析了不同荷載頻率及細(xì)粒含量下粗粒填料的孔壓、體應(yīng)變、回彈模量及軸向累積變形的變化規(guī)律,總結(jié)了細(xì)粒含量在不同荷載頻率下對路基填料動力特性的影響規(guī)律。研究表明,細(xì)粒土對路基粗粒填料動力特性的影響分為三個階段。首先,少量細(xì)粒土對粗顆粒土的潤滑作用導(dǎo)致粗粒填料在循環(huán)荷載下的體應(yīng)變和軸向累積應(yīng)變增大;隨著細(xì)粒含量進(jìn)一步增大,粗粒填料孔隙被細(xì)粒填充而使其壓縮性減小,體應(yīng)變與軸向累積應(yīng)變隨之減小;當(dāng)細(xì)粒含量增加到一定值后,粗粒填料滲透性顯著降低,循環(huán)荷載下路基中孔壓迅速累積,進(jìn)而導(dǎo)致軸向累積應(yīng)變急劇增大,回彈模量大幅減小。此外,細(xì)粒含量對粗粒填料長期動力特性的影響受荷載頻率影響顯著,高頻荷載將加劇孔壓累積,導(dǎo)致路基長期服役性能劣化。
[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.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：U414

【參考文獻(xiàn)】

相關(guān)期刊論文 前10條

1 冷伍明;周文權(quán);聶如松;趙春彥;劉文R，

本文編號：2316786