【作者】 冷毅飞；

【导师】 孙友宏； 张喜发；

【作者基本信息】 吉林大学 ， 地质工程， 2011， 博士

【摘要】 为了保障能源供给,我国目前正从俄罗斯大量进口的原油。漠河一大庆段原油输送管道工程需要穿越东北大小兴安岭和嫩江平原北部、大约500 km的多年冻土区和465m的季节冻土区。该地区冻土正处于逐渐消退过程中,所经过多年冻土地带冻土工程地质条件复杂,不良冻土现象发育,沿线多年冻土工程地质特征存在较大的差异,可能对管道工程安全造成严重威胁。冻土区的输油管道设计和施工具有许多特殊性,管道油温对其周围和沿线冻、融土的水热状态将会产生巨大的影响,进而直接影响到冻、融土的物理力学特性,威胁着管道的整体稳定性和结构完整性。由此,开展对管道沿线冻土区工程地质性质及其相关的工程地质问题的研究具有重要意义。为了满足该管道初勘阶段勘察评价和设计施工的需要,我院冻土实验室受大庆石油工程有限公司的委托,对所送冻土样品按照中国石油管道公司在《中俄原油管道(漠河一大庆段)工程多年冻土工程地质勘察技术规定(试行)》中对冻土指标提出的各种技术要求进行了相当数量的冻土专项试验。本文首先通过各种实验方法对取自中俄管道沿线的地基土进行了相关的物理指标测试,主要包括冻土未冻水、骨架比热、体积热容、导热系数与导温系数。这些物理参数都是冻土热物性研究与工程设计中的重要指标。这一部分内容中重点论述冻土未冻水的测试研究。从理论上分析测定未冻水含量的测温法与量热法,得出测温法原理存在混淆温度概念问题,即测温法通过Wu=aθ-b预报模式衍生而来,实际上是将起始冻结温度下的未冻水含量当成任意负温下的未冻水含量。从模拟试验数据的对比分析,测温法试验结果存在不确定性。相比之下,量热法根据能量守恒原理进行试验与计算公式的推导,试验原理清晰明确,并且经过大量试验验证,量热法的测试精度较高,满足工程设计使用要求。采用量热法对管道冻土区六大类原状土样进行了综合试验研究,归纳了温度、土质和含水量对未冻水含量的影响规律。温度是影响未冻水含量的主要因素,随温度降低,未冻水含量均减少,不同土的未冻水含量剧烈变化的温度区间范围有所不同；六种土质类型在各温度下平均未冻水含量与温度关系反映出,随着土质分散性的增大(塑性增强),未冻水含量增加。在相同负温下有机土比无机土未冻水含量高,有机土随着有机质含量的增大,未冻水含量增大；初始含水量对有机质土的未冻水含量有非常明显的影响。初始含水量对未冻水含量的影响程度依次是粘土>粉土、粉质粘土>砾砂。通过对未冻水影响因素的分析,本文总结了石油管道工程沿线各类土在给定负温下的未冻水含量代表值(平均值)以及冻土未冻水通用公式幂函数wu=at-b中的参数a、b数值。在此基础上,拟合得出粘土、粉质粘土、粉土和泥炭质土的wu-wp-t经验计算公式和在给定温度下的wu-wo-wp关系的二元一次线性回归方程式。这些经验公式不但反映出了土质、含水量和温度对未冻水的综合影响规律,同时也可供工程快速确定未冻水含量提供参考依据。本文完成的冻土基本热物理参数包括导热系数、体积热容量、导温系数,冻土骨架比热。这些参数是冻土热工计算的应用指标,在现场很难直接获得,主要是在实验室内测定。本次冻土热物理参数采用的试验方法是：导热系数采用稳定状态热流计法测定,导温系数用正规状态法测定。冻土体积热容和冻土骨架比热采用量热法。对大兴安岭多年冻土区泥炭草炭、泥炭质土、粘土、粉质粘土、粉土和各种砾砂等一系列土样的进行冻土骨架比热测试,经统计分析和比较可知,随颗粒变粗和塑性减弱,冻土骨架比热逐渐减小。冻土骨架比热值不仅与颗粒和塑性大小有关,而且与土中有机质含量有关。随土中有机质含量增加,骨架比热值增大：根据-10℃条件下的体积热容试验和计算结果,分土类讨论其与总含水量和干容重的关系。对四类土Cvf_W_γd试验数据进行二元一次线性回归分析,得到冻土体积热容随总含水量和干密度增加而增大且线性相关性均很好。结合未冻水与骨架比热测试结果连同土样总含水量与干容重,从而可以计算出任一负温下的冻土体积热容；冻土导热系数的测定采用热流计法,通过试验给出了大兴安岭多年冻土区五种典型土料的λ_w_γd线性回归方程式,相关性较好。热流计法能较好地揭示冻融状态、含水量、干容重和土质条件等因素对导热系数的影响和规律。大多数在北半球的国家为冻胀和融沉问题所困。但是,对冻土这个特殊环境的科学和技术难题,特别是寒区岩土和管道工程的研究却非常不足。本文第二部分通过室内试验对各种不同土质进行冻胀敏感性分析与管道区冻土融沉性分析。对典型土料进行室内冻胀模拟试验,找出土质条件、含水量、饱和度、密实状态、等因素与冻胀率之间的经验关系。分别对影响细粒土与粗粒土的冻胀敏感性的主导因素进行分析。细粒土冻胀性,在含水量相同时塑性指数越大,所需起始冻胀含水量越高,而冻胀性也越弱；粘性土和粉土的冻胀性随超塑含水量(W-WP)变化的规律基本相同,可统一按土的η～(W-WP)关系进行细粒土冻胀敏感性分类；细粒土的冻胀性还受饱和度和压实度的影响,在同一饱和度下.土的冻胀性随着压实度的增加而降低,当含水量一定时,细粒土的冻胀率都随着压实度或饱和度的增加而增大；对η～(W-WP)～Kd/Sr进行回归分析.(W-WP)对土体冻胀性的贡献要比Kd或Sr大,说明超塑含水量是影响细粒土冻胀性大小的主导因素。在对粗粒土冻胀敏感性及分类的研究中可知,土中的含水率是使其产生冻胀最主要的因素,而含泥量的影响有限。从粉砂到粗砂,冻胀率随含水率的增长而显著增长。通过与规范对比研究,可得出规范规定的含泥量界限值是不合适的,含泥量低于规定的界限值在一定含水率的情况下仍然存在冻胀,甚至可达到强胀；规范在除粉砂外的粗粒土冻胀性分类面,在土类划分、含泥量界限、冻率与含水率关系及界限值规定上,都存在许多问题明显偏于不安全方面,值得商榷。对引起管道冻胀变形的2-6m范围的地基土冻胀性的分析中可知,AB段沿线在2-6m深度范围内粉质粘土的冻胀是引起该段管道冻胀破坏的主要原因。从实验资料看,沿线粉质粘土的冻胀性没有明显规律,很可能是各段水分补给条件的影响不同所致。AB段分布的粗粒土主要是砾砂和圆砾角砾,砾砂大多数属于弱冻胀性,冻胀强弱取决于含水量(补水条件),考虑到管道运营后可能改变下部水分条件,对一些天然含水量较低的弱冻胀性地区,也需要考虑水分充足后演变成冻胀甚至强冻胀类型的可能性。该段含有的圆砾角砾土层可按不冻胀处理。本文完成了细砾、砂土、粉土、粘性土、泥炭化粘性土、泥炭质土六种共345个土样的融沉试验,通过对大量的试验数据进行分析,提出了多年冻土融沉系数与融化压缩系数的经验确定方法,并对冻土融沉性分类做了进一步的研究。总结了各类土融沉系数a0与含水量和干容重关系。各类土的融沉敏感性是不一样的。粉土的融沉敏感性最大。砾石土在条件具备时亦可产生可观沉降,但总体上看融沉较小,一般是良好的冻土地基；在冻土融沉性分类研究中本文比现有规范增加了泥炭化粘性土和泥炭质土这两种土类。在回归分析基础上提出了各融沉等级界限含水量和界限超塑含水量；融化压缩系数在实验荷载范围(200KPa)以内并非常数,而是随着荷载的增大而减小,所以冻土融化后体积压缩系数mv不应取定值,而应根据实际压力段大小取相应值；总结出来六类土mv-rd回归关系和数字化表格,可供工程上估计mv时使用。冻土是一种对温度十分敏感的土体,随着温度的不同其物理力学性质会发生很大的变化。在多年冻土区埋设常温输油管道必然会破坏冻土与大气间已经建立的热量平衡状态,使地基土的温度状况及冻融过程发生较大的改变,从而对管道基础的稳定性造成不良影响。因此,针对管道工程的施工和运行特点,对管道地基土在设计使用年限内的温度场做出预报有重要意义。论文对管道周围土壤温度场建立一理想物理模型,给出一定的模型假定条件,根据相关文献和设计资料给出相应的边界条件,计算管道周围土壤温度场的变化。不考虑油温的影响与给定一负温油温两种情况对冻土温度场进行预测。从管道横截面轴心的地温冻融过程线看,管道在运行前25年左右,季节冻土深度在7米左右变化,而在计算的后25年,季节性冻土的冻结深度逐年减小,说明季节冻土也在逐年消退。计算的前25年,多年冻土上限呈逐年降低趋势,同时多年冻土的下限在逐年抬升,说明多年冻土在逐年退化；计算到27年,多年冻土完全退化为季节性冻土。因此,在全球变暖的气候大条件下,使得高温极不稳定冻土受到较大影响,多年冻土退化至季节冻土直至完全退化。油温在整个计算过程中是随着地温场的变化而变化,并不是恒定温度。由管道横截面轴心深度方向作出温度一深度关系曲线可知,管道界面中心地温随运行时间的变化规律,同一深度处的地温成递增趋势,10m以上范围内温度变化梯度较大,10m一下温度变化梯度逐渐减小。冻土人为上限随着运行年限在减小,说明在油温的影响下,人为上限逐年抬升。更多还原

【Abstract】 China is importing oil from Russia to ensure energy supplies. The oil transportation pipe engineering, Mohe to Daqing, is covering about 500 kilometers permafrost areas and 465 kilometers seasonal frozen soils areas through Da Hinggan Ling,Xiao Hinggan Ling in northeast and the north of Nenjiang plain. The frozen soil in this area is subsidizing gradually, and the geological condition is complex, while badness of frozen soil growing, characters of frozen soil-along the line are greatly different, so it is possible to result in serious harm for security of pipe engineering. As particularities the design and construction of pipe for oil transportation in frozen soil areas have, the temperature of oil transported impacting water-heat state of frozen or melt soil all around and along the line, even impacting physical mechanics specialities of frozen or melt soil, it would have been threatening stability of whole and integrality of structure. Therefore, it is a significance to carry on research on the engineering characters of frozen soil along the line and all geological problems related to.In order to meet the demands for evaluation of survey and design of construction at the beginning of the pipe engineering, frozen soil lab of Jilin University accept the commission from Daqing Oil Engineering limited Company to take large numbers of frozen soil special experiments on indices for frozen soils according to various requirements referred by permafrost technical requirements for engineering geological investigation ofChina-Russia Oil Pipeline.The text tests physical indices of groundsill soils got along the line with various experiment measures first. It includes unfrozen water content, aggregate specific heat, volumetric specific heat, coefficient of thermal conductivity, and thermal diffusivity. These physical parameters are all important indices for heat-matter quality research on frozen soil and design of construction. In this content, it stresses the testing research on unfrozen water in frozen soil, and analyses unfrozen water content measurement of initial freezing temperature and unfrozen water content measurement on testing unfrozen water content in frozen soil in theory, indicating that there is a problem confusing the concept of temperature existed in unfrozen water content measurement of initial freezing temperature. The unfrozen water content measurement of initial freezing temperature come out from the forecast mode of Wu=αθ-b, actually, it makes unfrozen water content at the initial freezing temperature be that in random minus temperatures. Comparing the simulation test data, the results of unfrozen water content measurement of initial freezing temperature experiment are uncertain. Contrarily, unfrozen water content measurement of heat can carry on the experiment according to conversation of energy theory and deduce the calculation formula, the test principle being legible, it is substantiated by a great lot of experiments that the precision of unfrozen water content measurement of heat is higher, and well met with the use requirement for construction design.The text also makes the general experiment research on six kinds of original soils in this area by taking unfrozen water content measurement of heat, and makes a conclusion of the effect law of unfrozen water with temperature, soil, and liquid water content. The temperature is the most important factor to effect on unfrozen water content. With temperature falling and unfrozen water content decreasing following, the ranges which unfrozen water contents in different soils change violently in are different. The relationships to temperature and average unfrozen water content in each temperature with six kinds of soils reflect that, as decentralization of soils growing (plasticity growing), the unfrozen water content increases. In the same minus temperature, unfrozen water content in organic soils is higher than that in non-organic soils, and the more organic matter in organic soil is. the more unfrozen water content is. The influence of beginning liquid water content on unfrozen water content in organic matter soli is greatly obvious. The degree in turn that beginning liquid water content effects on unfrozen water content is clay, silty soil, clayey silt and gravelly sand.The text summarizes representative unfrozen water content value (average value) in certain minus temperature in each kind of soil along the oil pipe engineering and numerical value of parameter a, b in currency formula, the power function wu=at-b, of unfrozen water in frozen soil by analyzing the effect factor on unfrozen water. On this basis, it concludes the experience calculate formula of wu-wp-t of clay, clayey silt, silty soil, peat soil and simple regression equation with two unknown of relationship with wu-wo-wp in certain temperature. These experience formulas reflect not only the general law of unfrozen water that soil, liquid water content and temperature effect on, but also offer references to fix on unfrozen water content for engineering.The basic physical parameters of frozen soil that the text finishes include coefficient of thermal conductivity, volumetric specific heat, thermal diffusivity and aggregate specific heat. These parameters are application indices of frozen soil thermodynamics, and it is hard to get directly at site, mostly in lab. The ways we get parameters are. heat-flow meter in steady-state technique to test coefficient of thermal conductivity, normal state techniques to test thermal diffusivity. unfrozen water content measurement of heat to test aggregate specific heat and volumetric specific heat.While testing aggregate of several kinds of soils, such as turf, peat soil. clay, clayey silt, silty soil and various gravelly sands in frozen area in Da Hinggan Ling, analyzing and comparing, we get to know that aggregate specific heat of frozen soil is minishing, as granule turning thick and plasticity weakening. It is concerned not only with the size of granule and plasticity, but also with the content of organic matter in soil. The more content of organic matter is. the bigger value of aggregate specific heat is. According to results of volumetric specific heat experiments under the condition of-10 degree, it is discussed by classification of soil with the relation to the chief liquid water content and dry bulk density. It is found that volumetric specific heat of frozen soil is always growing with the chief liquid water content and dry bulk density increasing, and the linearity relativities are all fine, while analyzing Cvf_W_γd test data of four kinds by simple linearity regression equation with two unknown. Combining unfrozen water content with aggregate specific heat, the chief liquid water content and dry bulk density also being in connection with, it can figure out the volumetric specific heat of frozen soil at any minus temperature. The heat-flow meter is used to test coefficient of thermal conductivity of frozen soil. It comes out theλ_ω_γd linearity regression equation of five typical soil in Da Hinggan Ling, and the linearity relativities are better. It is well proved to use the heat-flow meter that the law and influence on coefficient of thermal conductivity that state of frozen or melt, liquid water content, dry bulk density and soil condition affect.There are many countries in the northern hemisphere locked into the problem of frost heave and thawing settlement, and it is very deficient to study the special science and technique of frozen soil, especially geotechnical engineering and piping engineering in cold areas. The second part of the text is to analyze frost heaving susceptibility of different soils and thawing settlement in piping areas by experiments indoors.Carrying on the frost heaving simulation experiment on typical soils indoors and finding out the connection between frost heaving ratio and each factor, soil condition, liquid water content, saturation, green density and so on, it analyzes the chief factors respectively that affect on the frost heaving susceptibility of fine-grain soil and coarse grained soil. For the frost heaving of fine-grain soil, the higher initial frost heaving water content needed is, the weaker frost heaving is, while plasticity index is greater in the same liquid water content. Because the law of frost heaving of clay and silty soil is almost the same to the changing of over-plasticity water content(W-Wp), it can be classified by the relationη～(W-Wp) which fine-grain soils classification of the frost heaving susceptibility is according to. As the frost heaving of fine-grain soils being affected by saturation and green density, it is falling while the green density is growing at the same saturation, and growing while the green density or saturation is growing at the same liquid water content. While analyzing the regression equation ofη～(W-Wp)-Kd/Sr, the contribution of (W-Wp) to the frost heaving of soil is bigger than that of Kd or Sr. It is showed that the over-plasticity water content is the chief factor that affects the frost heaving value of fine-grain soil.With the research on the classification and frost heaving susceptibility of coarse grained soil, we can get to know that the liquid water content in soil is the most important factor to make it frost heaviy, and the effect of the mud content is limited. The frost heavy ratio is growing while the water content of it is growing from silt sand to coarse sand. It can be concluded by comparing to the criterion that the limited value of criterion is ill-suited, and the soil whose mud content is below the limited value is still to frost heave at some liquid water content, some even heavily. Criterion of the frost heave of coarse grained soil except silt sand has a lot of problems obviously on insecurity in the regulating the limited value of soil classification, mud content, and connection between freezing ratio and liquid water content, and it is worth being discussed.In the analyse on range which cause the frost heaving anamorphic of the pipe between 2 to 6 meters of groundsill frost heaving, it is shown that the frost heaving of clayey silt in the range between 2 to 6 meters along the AB sect is the main reason to cause the damage of the pipe in this sect. According to the experiment data, the frost heaving of clayey silt along the line is no obvious regulation. It is possibly caused by water supplying condition of each sect. There are coarse grained soils in the AB sect, the most are sands, thick pellet soils and breccias, and sands are belong to the weak frost heaving, which lies on the water content, considering the change of water condition probably caused after pipe operation. For some lower inartificial water content in weak frost heaving area, it is needed to consider the probability of turning frost heaving or harder if water enough. The thick pellet soils and breccias contained in this sect can be dealt with non-frost heaving.The text finished 345 in six kinds soils thawing settlement experiments, including pebble, sand, silty soil, clay soil, peat clay soil and peat soil. It indicates the experience measurement of thawing settlement coefficient and thawing compressing coefficient for perennial-frost soil, and research further on classifying the thawing settlement of frozen soil by large numbers of experiments.It summarized the connection of thawing settlement coefficient a0 for each kind of soil with the liquid water content and dry density, and each of thawing settlement susceptivity is different. That of silty soil is the biggest, and gravel, while the condition having, can be caused a considerable settlement, but thawing settlement is smaller as a whole, commonly a fine frozen groundsill. There is two kinds of soils added, peat clay soil and peat soil, comparing to the criterion in research on the classification of frozen soil thawing settlement. It indicates the limited water content and limited over-water content in each thawing settlement grade on the basis of regression analyse. It is not a constant within the load range (200 KPa) in experiment of the thawing compressing coefficient, but minishing while the load growing. So it should not be a fixed value for the volumetric compressing coefficient mv after frozen soil thaw, moreover, it should be the value according to the practical pressure. The mr-γd regression connection and digital diagram of the six kinds of soils summarized can be used in practical engineering.Frozen soil is a kind of soil impressible to the temperature, and the physical mechanics of it was to change while the temperature is changing. It is a necessity to destroy the heat balance founded between frozen soil and atmosphere by laying the oil transportation pipe in perennial-frost area, and make the big change for temperature of groundsill and process of freezing and thawing, thereby, cause the blight for basal stability of pipe. In allusion to the character of construction and running of pipe engineering, it is most meaningful to make the forecast for groundsill of pipe within the service life of temperature field.The text sets up a ideal physical model for soil temperature field around the pipe, and indicates a certain assuming condition, according to the limit condition offered in literatures and design information correlated, figures out the change of temperature field around pipe. It can be carried on testing the temperature field of frozen soil without considering the effect of the oil temperature and a minus oil temperature offered. Watching the freezing and thawing process of ground temperature on cross section axes. season-frost deepness is changing within seven meters while pipe is running the former twenty-five years around. It is minishing year after year when the later twenty-five years, showing the season-frost soil is subsidizing year after year. In the former twenty-five years, the upper limit of perennial-frost soil is a falling trend year after year, meanwhile, the lower limit of it is a rising trend, showing the perennial-frost is retrogressing. By the 27th year, the perennial-frost soils turn to the season-frost soils completely. Therefore, in the condition of the global warming, frozen soil is rather affected, causing the perennial-frost turning to the season-frost until the whole. The oil temperature is not invariableness in the process of ground temperature changing. The changing law of ground temperature in the center of the pipe interface changes with the runtime,and increasing by degrees in the same depth, known from the temperature-depth curve made in the deepness direction of pipe cross section axes. Above 10 meters, the temperature changes obviously, and minishes gradually below 10 meters. The artificial limit ofˉfrozen soil minishes with the service time, showing it will rise year after year in the effect of oil temperature.更多还原