中国冻土力学研究50a回顾与展望

中国多年冻土和季节冻土面积分别占国土面积的 21.5% 和 53.5% 。在这些地区,地表层都被一层冬冻夏融的冻结–融化层覆盖,作为地基的冻结–融化层,在其冻融过程中土体性质受气温的变化直接影响着上部建筑物的稳定与安全,因此,在冻土地区进行水利工程、工业与民用建筑及交通运输工程的建设,就必须对冻土及其与工程建筑物相互作用的一系列工程冻土学理论和实践问题做出解答,以确保冻土地基上工程建筑物的稳定性、耐久性及经济合理性。简要回顾了中国冻土力学的创始和发展过程,阐述了冻土力学在强度与变形、本构模型研究、水热过程研究、冻土与结构物相互作用研究及冻土力学测试技术的发展等 5 个方面的成就,并根据冻土力学学科特点、工程建设对冻土力学发展的要求以及相关学科的发展趋势,展望了冻土力学未来的发展方向。     

新疆皇吉220 kV输电线路天山段多年冻土工程特性研究

多年冻土和季节性冻土属于不良工程地质条件,其物理特性、力学和热学性能决定了冻胀和融沉工程病害对线路基础稳定性的影响程度。系统介绍了新疆皇吉220 kV输电线路天山段多年冻土原位直剪试验、融化压缩试验、静载荷试验试验方法及其研究成果,从而为该地区输变电线路基础型式选择与设计优化提供了具有较高价值的参考资料。     

季节性冻土和多年冻土对场地地震反应的影响

季节性冻土和多年冻土的存在，对场地的地震反应将产生一定的影响。根据一维波动理论，应用水平层状场地地震反应的等效线性化有关程序，对季节性Ⅰ，Ⅱ类场地的冻土区和多年冻土区在不同地震波作用下的反应进行计算，分析冻土层的变化对场地地震反应的影响。计算结果表明：在季节性冻土区，冻土层使自由场地的地面峰值加速度减小，且随冻土地温降低，冻土厚度增大、地面的加速度减小。对Ⅱ类场地的冻土层影响大于Ⅰ类场地；在多年冻土区，冻土层厚度越大，Ⅱ类场地的地面加速度越小，而在Ⅰ类场地上没有此规律。多年冻土上界以上为融土时，地表面的加速度峰值比上界以上为季节性冻土时要大。     

多年冻土和人工冻土的爆破试验与方法研究

阐述了冻土爆破方法研究的必要性 ,介绍了冻土爆破漏斗、掏槽爆破及光面爆破试验的研究成果 ,根据近几年的理论研究和现场实验研究 ,总结了我国多年冻土和季节冻土的爆破方法及矿山冻结法施工的冻土爆破方法。     

Modeling the thaw boundary in broken rock zones in permafrost in the presence of surface water flows

The behavior of the thaw boundary of a permafrost rock zone is investigated in connection with the melting of frozen highly fractured rock zones that is caused by water movement across these zones. This behavior is different from that of frozen earth due to the large frozen pore volumes. A computational method to track the movement of the thaw boundary on the basis of the finite element analysis is presented and the method for determining some of the appropriate input parameters is discussed. The differences in thaw boundary movement is shown clearly by the analysis of heat flux in the two cases considered. The computational method is used to predict the melting depth of a frozen fractured rock mass in a permafrost region, and the comparison of the computed results with engineering cases in practice is used to verify the computational method.     

Boring piles and a new design of pile-driving machine

A rational technology for the boring of piles in unfrozen and seasonally frozen soils and permafrost, as well as in rock is presented. Prospects for the use of boring piles and a new design of machine are substantiated in construction. Experimental investigations of piles with multiple-turn helical blades and a machine for their boring indicated high accuracy of pile installation and machine productivity (18 piles per shift). Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 4, pp. 21–24, July–August, 1996.     

Increasing the Bearing Capacity and Durability of Building Foundations on Frozen Soils

Soil Mechanics and Foundation Engineering - The article considers the behavior of pile foundations of buildings constructed on permafrost soils with the preservation of the frozen state, depending...     

Grundwasserschutz in Permafrostgebieten

The peculiarities of anthropogenic impacts under the specific hydrological conditions of the permafrost are described using examples from Eastern Siberia. The hazards for these groundwaters depend on their situation relative to the frozen water-tight permafrost bodies. The human activities influence the groundwater in permafrost areas mainly by deterioration of the natural landscape, by contamination of suprapermafrost water and of seasonal melt water in surficial soils, by man-induced formation of ice sheets, especially at extrusion points of intraperma-frost waters, and by destruction of the permafrost body due to the disposal of brines.     

多年冻土区灌注桩桩–冻土相互作用有限元分析

 基于ANSYS有限元软件平台，建立多年冻土区灌注桩桩–冻土相互作用有限元模型。通过面–面接触实现桩与冻土间黏结、滑移和开裂的状态模拟，给出接触参数的合理取值，并将其对P-S曲线的影响进行分析。结合工程实例，对多年冻土区灌注桩基础在垂直静载作用下的内力和沉降进行分析研究。研究结果表明：多年冻土区桩基的承载力主要由桩侧冻土层的黏聚力提供；三维高阶接触单元能较好地模拟桩与冻土系边界条件的非线性，真实地反映多年冻土区单桩的实际受力状态；有限元计算值与实测值吻合较好，从而证明模型建立的正确性。     

Determination of the deformation characteristics of thawing permafrost soils in the construction of the urengoiskii grés complex

Conclusions 1. The test thawing of soils in the test area in the Urengoiskii GRéS construction sites made it possible to determine the deformation characteristics of permafrost in their natural occurrence and to estimate the rate of consolidation and distributive properties of preliminarily thawed soils. 2. The calculation for the settlements of thawing soils with the use of results of compression tests and visual determination of the ice content led, in the given case, to values with are twice as much as the actual values. 3. Permanently frozen sandy soils in the construction areas are practically noncompressible with thawing, whereas clayey soils are highly compressible with thawing and cannot be made use of as per principle II without preliminary thawing. Deceased. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 1, pp. 16–18, January–February, 1989.     

Method of using permafrost as foundation elements

A method of using compacted permafrost as bearing foundation structures on nonuniformly deforming beds, which encloses weak interlayers of unfrozen or plastically frozen saline soils that exist both on the surface and within the frozen stratum is discussed. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 2, pp. 34–37, March–April, 1996.     

冻结状态青藏粉质黏土的渗透系数测量研究

粉质黏土在青藏高原多年冻土地区广泛分布,为了充分认识其在冻结状态下的渗透性质,开展了一系列渗透试验测量了在-0.6℃~0.1℃条件下含水率为50%的青藏粉质黏土的渗透系数。结果显示:在高负温区间内,冻结粉质黏土的渗透系数处于8.22×10~(-11)~7.19×10~(-9) cm/s之间;另外,渗透系数与土温之间呈现出幂函数关系,土温越接近于0℃,渗透系数增大越快;冻土的渗透系数表现出随着未冻水体积含量的增加而快速增大的趋势。渗透性的存在可测意味着高温冻土在外荷载下会存在固结作用。     

冻融循环条件下土的融沉性质试验研究

多年冻土地区路基病害主要由冻土土体在季节变化条件下的冻融循环造成的。因此,本文结合青藏铁路清水河、北麓河试验段土质条件,通过室内试验探讨和研究了不同土质在不同含水率、密实度、荷载条件下,反复冻融过程中的融沉特性。并探讨了循环融沉系数与融沉系数的关系及表达式,为进一步深化对融沉特性的认识提供了参考。     

多年冻土区单桩承载力研究

多年冻土中的桩,在垂直荷载作用下地基土将产生三项反力：季节融化层与桩周的摩阻力、多年冻土层与桩周的冻结力、桩端承载力。基于规范中的计算方法,探讨了上述三项反力的取值,可供工程设计参考。     

Effect of gas-temperature regime on pipeline condition in permafrost

The problem of ensuring operational stability of cold gas pipelines in permafrost stands out among the diverse problems encountered in the construction of gas-pipeline systems. Based on the Yamburg-Novyi Urengoi gas pipeline as an example, it is demonstrated that heaving of enclosing soils is the basic cause of the deformation and floating of pipelines. The influence exerted by the gas-temperature regime on heaving processes in frozen and frozen-through soils and gas-line deformation is examined.     

冻土原位旁压蠕变试验粘弹性模型分析

研究高温高含冰量冻土的蠕变特性,采用Menard旁压仪在青藏高原多年冻土区开展了大量的旁压蠕变试验,利用Merchant粘弹性模型对蠕变曲线进行回归分析并得到模型参数。结果表明,温度对高温冻土力学性质的影响要大于含水量。随着压力的增加,每级压力下冻土的瞬时应变在总应变中所占的比例逐渐减小。回归分析发现,瞬时剪切模量与负温的绝对值呈线性关系,而延迟剪切模量和粘滞系数与负温的绝对值之间为幂函数关系;当冻土的含水量达到46%时,各参数均出现峰值,而后缓慢减小,此结果与低温冻土有所差别。     

大型多功能冻土-结构接触面循环直剪系统研制及应用

在天然冻土区和人工冻土工程中存在着大量冻土与结构物接触面问题,而目前尚无有关此类接触面剪切行为的试验研究手段。为此,研制了大型多功能冻土-结构接触面循环直剪系统DDJ—1,该系统性能优异：能实现0～-20℃范围内对接触面温度的精确控制;能精确施加常刚度、常位移、零法向应力和常应力4种法向边界条件;能够模拟多种粗糙度的接触面实现循环和单调两种剪切形式;能够观测接触带的破坏状态和厚度,同时可以测量接触带土体内部的剪切位移;应力施加、位移控制和温度调节精准。试验结果表明：该系统能准确地再现冻土与结构接触面的力学行为、变形行为,可为系统开展冻土-结构接触面的研究提供试验基础和重要思路。     

人工冻土帷幕的冻结过程研究

人工冻土帷幕具有广泛的应用前景。研究表明,冻土的均匀性和冻结状态是影响人工冻土帷幕强度的重要指标。冻结方向、受力方向、冻结时间影响下的冻结锋面发展情况和温度场规律是描述冻土力学性能差异的四个重要特征。该文通过分析这些指标和特征,完善了人工冻土帷幕的分析计算内容,有助于验证冻结时间、冻结位置等重要工程指标的正确性。     

寒区路基工程与多年冻土间相互作用问题研究进展

多年冻土地区兴建的道路、工业设施以及大型土木工程建筑工程等,都会受到多年冻土稳定性问题的影响。土壤中的热状况、水分状况及其变化是引发冻害及严重程度的主要因素。基于工程稳定性、耐久性及积极性考虑,建立可靠的路基工程冻土热环境评价方法和合理准确的路基温度场计算模型对指导寒区工程建设有重要意义。本文从冻土介质热质耦合输运过程的机理及理论模型、温度场相关问题的计算方法及工程应用等几个方面简要综述了近年来国内外有关多年冻土地区路基工程与冻土间相互作用问题的研究现状和进展。     

Compressibility of sandy permafrost during thawing

Conclusions 1. The compressibility of sandy permafrost deep deposits with a medium texture density is, as a rule, close to the compressibility of similar thawed deposits.2. The degree of saturation of frozen sandy soils may serve as an indicator of their compressibility during thawing. When G_f<0.91, the compressibility of frozen sands during thawing is equal to the compressibility of similar thawed soils.3. The compressibility of frozen sandy deposits during thawing, which increased as compared with ordinary thawed sands, should be expected in zones adjacent to the roof of soils with a low permeability.4. The refinement of the method and the high quality of the testing of thawing soils increases significantly the technicoeconomic effectiveness of construction on permanently frozen sandy soils, making it possible to reduce the volume of special measures taken to ensure the stability of buildings and structures, or eliminate them entirely.All-Union Scientific-Research Institute of Foundations and Underground Structures. Northern Branch of the All-Union Scientific-Research Institute of Foundations and Underground Structures. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 3, pp. 20–22, May–June, 1988.