陈湘生：再说地层冻结法.ppt

再说地层冻结法 纪念地层冻结法150周年 Some New Words On Ground Freezing Method in memory of 150th anniversary application of GFM,深圳市地铁集团有限公司 陈湘生博士 上海，05. 2012 CHEN Xiangsheng, Ph. D. Shenzhen Metro Co. (Group), Ltd. Shanghai, 05. 2012,目录 Contents,概述 Overview 地层冻结法关键要素 The key elements for GFM 人工冻土力学参数试验注意事项 The main points for tests of artificial frozen soil mechanical properties 地层冻胀融沉问题及对策 The countermeasure to ground freezing heave and thaw settlement 最新地层冻结案例 Some new cases interested of GFM,1.概述 Overview,追索求源 Originating 地层冻结法源于天然冻结现象。1850年代蒸汽压缩式冷冻机发明后，人类第一次使用地层冻结法是1862年在Wales基坑中；1880年德国工程师Poetch首先提出地层冻结法原理，并于1883年在德国阿尔巴里德煤矿成功地采用冻结工法建造103m深的竖井。我国第一次应用地层冻结法是1955年开滦煤矿林西风井（直径5m，冻深105m）。 Ground freezing method (GFM) originated from natural freezing phenomenon. It was the first time in 1862 that GFM was used in Wales foundation pit after invention of steam compression refrigerator in1850 s. The German engineer, Poetch, proposed first the principle of GFM in 1880, and then this method was successfully used in sinking a shaft in depth of 103m in Germanys coal mine in 1883. It was in 1955 that GFM was used in sinking Linxi air shaft (dia. 5m and frozen depth of 105 m) in Kailuan Coal Mine first in China.,1.概述 Overview (Cont.),核心是把地层里的水变成冰 The key of GFM is to change the water in soil into ice. 地层冻结的核心是把地层里几乎“没有强度”的水变成“强度极高且可以粘结土颗粒”的冰，而且冰的强度和弹性模量随负温度降低而增大。由此可以根据对冻土结构要求而随时调节冻结温度来确保冻土结构的稳定。 The core of GFM is to change “no strength“ of water the strata into ice of “high strength and power bonding soil particle“. Moreover, both strength and elasticity modulus of ice increase with decrease in negative temperature. This may, according to the requirements of frozen soil structure, adjust the freezing temperature in frozen soil structure to ensure its stability at any time.,1.概述 Overview (Cont.),核心是把地层里的水变成冰(Cont.) The key of GFM is to change the water in soil into ice. 所以，要了解水冻成冰的要素：地层里水的冰点、含盐、地层温度、水力联系和周边影响温度的边界条件等，还有冻土结构相关连影响稳定的边界条件。 在设计冻土结构时，要充分了解其受力状态、简化的受力模型、需要的力学指标等。还有土壤的冻胀和融沉特性 First things first is to understand the freezing temperature of the water in the stratum, its salt, stratum formation temperature, hydraulic relationship and surrounding heat influence, the boundary conditions of temperature, and moreover the boundary conditions of the frozen structure. Then all these elements must fully be understood when a frozen structure is designed: its stress state, the simplified model, the mechanics index needed, and etc. Meanwhile, the characteristics must be kept in mind of freezing heave and thaw settlement of soil.,1.概述 Overview (Cont.),带领全球的中国地层冻结 Ground Greezing in Mainland China Leading the global 截至2011年年底，中国大陆地区利用地层冻结法完成凿井约790个，总里程约180km；最大冻结深度达到955m。完成市政工程冻结项目98个（其中地铁工程超过70个），最长水平冻结长度到达147m。各项指标领先全球。 By the end of 2011, GFM has successfully been used in China mainland sunk shafts 790 with total mileage more than 180km and maximum frozen depth of 955m, and finished municipal engineering projects 98 (including the subway frozen projects more than 70) with the longest horizontal freezing length of 147 m. All technical indexes lead in the world.,2. 地层冻结法关键要素 The key elements for GFM,工程地质和水文地质及关键物理力学指标 The information of engineering geology and hydrogeology, and the key physical and mechanical indexes 设计要素 The key factors of design 施工要素 The key elements for execution 管理等关联要素 The key points for management,2. 地层冻结法关键要素The key elements for GFM (cont.),工程地质和水文地质及关键物理力学指标 The information of engineering geology and hydrogeology, and the key physical and mechanical indexes 1.施工范围内及关联的地层分布、水位（含气?）含水层及水力联系、流速流向、含盐量、隔水层、土的基本力学性质、比热、热传导系数、潜热、结冰温度等 The related strata distribution, stage (air ball?), aquifer location and hydraulic connection, Flow velocity and direction, salt concentration in the soil, aquiclude, the basic mechanical properties of soil, specific heat and thermal conductivity, the latent heat, freezing temperature, etc 2.土壤冻胀和融沉（冻土解冻）；单轴抗压、抗拉、抗剪(粘聚力、内摩擦角)、三轴强度、变形模量、泊淞比（受温度、含水量、未冻水含量、粒径、孔隙率、荷载、时间等影响） Frost heaving and thaw settlement (thawing); Uniaxial compressive, tensile and shear strength (cohesion, friction angle), triaxial strength, deformation modulus and poisson ratio (influenced by temperature, water content, unfrozen water content, particle diameter, pore ratio, loading, and loaded time, etc),2. 地层冻结法关键要素(cont.) The key elements for GFM,设计要素The key factors of design 首先是建立冻土结构受力模型（纯冻土结构、和其它结构共同承载、作为其它结构承载的封水等） First step is to chose a frozen structure bearing model (pure frozen soil structure, or other structure jointed with frozen soil, or as water shutoff (frozen soil) for other structure) 其次是在所选结构模型下全面考量全过程可能影响冻土强度、冻土结构本身可能影响周边环境或者影响维护结构本身稳定和安全的可能性 Second is to comprehensively consider the possibility of affecting the permafrost strength in the chosen frozen structure model through the process, frozen soil structure itself may affect the related environment or influence the stability and security of the frozen structure itself.,2. 地层冻结法关键要素(cont.) The key elements for GFM,设计要素The key factors of design (cont.) 再次是按所选冻土结构受力模型进行对应的冻土力学性能试验而获得必要的计算参数、并对冻土结构的冻胀融沉进行量化、针对计算结构进行措施补充（包括所有检测监控） Once again is to obtain the necessary parameters of the frozen soil by carrying out the corresponding mechanical test according to selected frozen soil structure bearing model, to quantitatively calculate freezing heave and thaw settlement of the related strata, and to supplement measures for the frozen soil structure （including all the detection monitoring） 最后就是实施这一设计进行施工组织设计 The last is to carry out the construction organization design.,2. 地层冻结法关键要素 The key elements for GFM (cont.),施工要素 The key elements for execution 冻结孔施工、冻结管安装以及质量的检测； Freezing pipe hole drilling, the pipe installation, and the final result inspection 地层内温度检测和盐水等检测系统的可靠性； Inspection of the system reliability of both the temperature measuring in the frozen soil and the brine data logging (temperature and flow) 达到冻结设计要求的检测和确认 Inspection and confirmation realizing the frozen structure design requirements 冻胀检测和控制、融沉监测和控制； Frost heaving measuring and control, thaw settlement monitoring and control; 开挖和支护，冻土结构变形实时检测 Excavating and lining, frozen soil structure deformation monitoring in situ,2. 地层冻结法关键要素(cont.) The key elements for GFM,管理等关联要素 The key points for management 冻结法是面对高风险地方的工法，故对于上述各个环节必须进行多次反复检查和检验，动态监测控制、精细化施工、严格监理管理,达到安全可靠。 Ground freezing method is a some kind of anagraph to high-risk problems, therefor the above each procedure must be inspected and confirmed repeatedly in order to realize safety and reliability by monitoring and controlling in time, elaborately constructing and consultant managing strictly.,3.人工冻土力学参数试验注意事项 The main points for tests of artificial frozen soil mechanical properties,矿山冻结凿井中冻土试验 Frozen soil mechanical property tests for frozen shaft lining 市政工程中地层冻结冻土试验 Frozen soil mechanical property tests for municipal frozen engineering 上述两个方面对冻土物理力学指标的要求是不完全相同的。The requirements for the above two aspects are not completely the same of the frozen soil physical and mechanical indexes,3.人工冻土力学参数试验注意事项(cont.) The main points for tests of artificial frozen soil mechanical properties,矿山冻结凿井中冻土试验 Frozen soil mechanical property tests for frozen shaft lining 全面正确认识冻土：冻土是由固相（土壤颗粒、冰）、液相（未冻水）、气相（气泡）组成多相介质（非饱和土） 。土样取样、冻土试样是否固结、是否达到固结度就是关键了。 Overall correct understanding of frozen soil: frozen soil is composed of solid phase (soil particles, ice), liquid (not cold water), air phase (bubble), that is a some kind of a multiphase medium （unsaturated soil）. The key is how to sample natural soil, whether consolidate the frozen soil samples and if to meet the degree of consolidation.,3.人工冻土力学参数试验注意事项(cont.) The main points for tests of artificial frozen soil mechanical properties,矿山冻结凿井中冻土试验 Frozen soil mechanical property tests for frozen shaft lining 由于矿山凿井深度比较深，土样取样后应力释放而体积和容重都发生变化。如果在冻土试验前不尽可能恢复到原来指标，显然所得结果不能反映真实情况。因此，在冻结前对式样进行固结并尽可能到达原来的固结度是非常必要的。到目前，试验和工程应用人员还没有充分认识到这一点。 The appearance density and volume of samples are changed because of stress release after sampling and depth of a shaft. If the soil samples do not regain their original index as far as possible before the frozen samples are tested, the test results can not reflect the true facts obviously. Therefore, it is essential to consolidate the samples to the original degree of consolidation as far as possible before freezing them and testing. The test and application personnel have not fully realize this key point yet.,ZJ290冻结粘土在-5、-10、-15、-20 和-25五种试验温度、排气排水条件下试验所得瞬时3、q值。将这些数据绘于p-q坐标平面如图所示,p=(1+23)/3 q=1-3,本试验仅限于 313.25MPa,3.人工冻土力学参数试验注意事项(cont.) The main points for tests of artificial frozen soil mechanical properties,ZJ290 frozen clay triaxial tests under drainage and un-drainage condition Constant axial strain rate 0.1%/min,3.人工冻土力学参数试验注意事项(cont.) The main points for tests of artificial frozen soil mechanical properties,兰州冻砂瞬时三轴剪切强度结果。随着p值增加，剪应力峰值后都开始下降并不断加速，即有冰融化发生。图中看到，剪应力峰值过后随着p值不断升高而加速这种冰的融化。高压p值下冰融化到最后就会导致不同温度下的这种剪应力曲线应全部趋向接近，而不是本图中的这种曲线最后相互远离。这种最后远离说明负温和“冰融”作用都很大，这与实际情况不符。,Frozen Lanzhou sand Triaxial tests at temperature -2, -3.5, -5 and -7 Constant axial strain rate 6.7%/min,3.人工冻土力学参数试验注意事项(cont.) The main points for tests of artificial frozen soil mechanical properties,国内某冻土研究机构对冻结粘土进行了不同负温、不同围压下的三轴剪切试验如图.,Some results of triaxial shear tests on frozen clay under different confining pressure in different negative temperatures by a domestic research oganization,3.人工冻土力学参数试验注意事项(cont.) The main points for tests of artificial frozen soil mechanical properties,图中显示在同一负温下，其试验冻结粘土在110MPa下的三轴强度试验结果呈现不同寻常的特点：峰值偏应力(或三轴抗剪强度)基本不变，莫尔圆包络线几乎呈水平线，三轴剪切强度可取作定值。图显示：冻结固结粘土在-5，-15试验温度下的内摩擦角0；即其三轴抗剪强度与围压无关。这和我们所在温度-10、不排气条件下试验所得的三轴剪切强度数据相近(图1中虚线)，其实是正常的。 Some unusual features can be found that triaxial strength of the clay are almost constant, or Mohrs circle envelope is almost horizontal, under confined pressure from 1 to10 MPa in the same negative temperature. And its internal friction Angle at -5, -10 ,-15 is equal to or less than 0, or the triaxial strength is not related to confined pressure. These kinds of so called “unusual features ” are just usual, all are the same as the triaxial shear strength data that we found under un-drainage of air and water at -10 (the dotted line).,3.人工冻土力学参数试验注意事项(cont.) The main points for tests of artificial frozen soil mechanical properties,在深冻结井中除了冻土抗压强度外，长时强度、蠕变特性极为重要，这些指标决定着冻结凿井的成败。 Both the long-term strength and creep property of frozen soil are very important except the compressive strength, these parameters decide the success of the freeze shaft lining. 而在市政工程的地层冻结中，除了冻土抗压强度外，有时候的抗拉强度、抗剪强度、抗弯强度极为重要。 While the tensile strength, shear strength and bending strength of frozen soil are sometimes very important except the compressive strength in municipal ground freezing engineering .,4.地层冻胀融沉问题及对策 The countermeasure to ground freezing heave and thaw settlement,在市政工程的地层冻结中，土壤的冻胀和融沉大小对关联建/构筑物影响至关重要。因此，在那些冻敏性土壤中应用冻结法，要特别注意相关联建/构筑物安全要求和土壤本身冻胀和融沉特性，通过试验和工程类比估算出冻胀和融沉量。根据这种估算采取必要的措施。 The magnitude both soil frost heaving and thaw settlement is very important to the related buildings/structures in municipal ground freezing. Therefore, more attention must be paid to the related buildings/structures safety requirements and soil itself frost heaving and thaw characteristics while GFM is applied in the freezing sensitive soil. Some necessary measures may be taken for the safety on the base of the estimated quantity of frost heaving and thaw settlement through test and engineering analogy.,4.地层冻胀融沉问题及对策 The countermeasure to ground freezing heave and thaw settlement,冻胀的主要原因是液态水冻结后变成固态冰,其体积增加9%产生“冻胀”。对于冻结时那些土壤内产生水分不断向冻结锋面迁移而不断集聚冻结成冰镜体（冻敏性土），对于原土体来说体积增加了迁移来的水的体积加上这些液态水变成固态冰体积增加9%，即增加了新迁移水109%的体积（迁移水冻胀）。前者叫土体“原位冻胀”，后者叫“迁移水冻胀”或者叫 “分凝冻胀” The main reason of frost heaving is because its volume increases 9% when the water (liquid) changes into ice (solid) after freezing. The volume of the new migrated water increases 109% (the volume of the new migration water 100% plus its frost heaving 9%) for those kinds of freezing sensitive soils in which water migrates continuously to the freezing fringe where some ice lens come out constantly by water gathering. The former is called “original frost heaving“, the latter is called “migrated water frost heaving“ or “segregating condensation frost heave“,4.地层冻胀融沉问题及对策 The countermeasure to ground freezing heave and thaw settlement,在工程中原位冻胀很难消除（除非对土壤孔隙水做某种处理），主要是尽可能减少迁移水冻胀。这种冻胀是一种在土壤冻结时形成一种势（能量）使水能在连通的非常细小的土壤孔隙里不断向冻结封面迁移，所谓“土水势”。它是一项目前还不能完全清晰表达的物理量。它由重力势、压力势、渗压势、温度势、电力势和磁力势中的某些和组成。 It is very difficult to eliminate the original frost heaving (unless doing something with the soil pore water) in the engineering, while mainly to reduce migrated water frost heaving. This kind of frost heave is caused by a kind of a potential (energy) gathered when freezing which drives water migrating to the freezing fringe through micro hydraulic capillary in freezing sensitive soil. This potential is so-called “water potential in soil” , which has not yet distinctly expressed some kind of physical quantity. It consists of some sum of gravity potential, pressure potential and seepage pressure potential, temperature differential, electric potential and magnetic potential.,4.地层冻胀融沉问题及对策 The countermeasure to ground freezing heave and thaw settlement,速冻法：快速降温使冻结速度超过水分迁移所需势形成的速度，使水分来不及迁移 Instant frozen method: fast freezing causes water freezing speed faster than that of the potential formed for migration in order to make water too late to migrate. 动态平衡式冻结法：达到冻结厚度后控制制冷量使冻土不再发展，从而减小水分迁移 Balanced freezing in time method: to control refrigerating capacity when the freeze thickness has been formed for reducing water migration 土壤改良法：冻结前对土壤进行某种改良，达到阻碍水力通道的目的 Soil improvement method: to conduct some improvement on soil before freeze to block the hydraulic capillary.,4.地层冻胀融沉问题及对策 The countermeasure to ground freezing heave and thaw settlement,把冻胀控制了，融沉就基本控制了8090%。对于沉降要求很严的地方，可以采取跟踪注浆等方式控制沉降量。 The thaw settlement will be reduced by 80-90% if migrated water frost heave has been totally blocked. Sometimes settlement tracked grouting may be carried out for the place where settlement control is strict.,5.最新地层冻结案例(竖井) Some new cases interested of GFM（shaft）,我国最深冻结井(也是世界最深冻结井，下部冻结) 核桃峪矿井位于甘肃省庆阳市正宁县周家乡，矿井建设规模为1200万吨/年。副立井井筒施工到472米深处发现岩层下部含水量很大而无法继续施工，决定下部施工前先对开挖荒径外进行冻结封水，也就是从472米深处往下冻结到深度955m。 Heitaoyu Service shaft, located in Zhoujia Disitrict, Zhengning County, Gansu Province, is 955m deep, the deepest frozen in the world with annual output 12 million tons/year. The shaft, lining to depth of 472m where underground water was encountered, have to be sunk by GFM from the depth of 472m to 955m. However, the freezing holes were drilled from the surface to the depth of 955m.,5.最新地层冻结案例（竖井） Some new cases interested of GFM (shaft)（cont.）,井筒净直径9m，开挖荒径10.413.4m，冻结孔布置圈径19.4m冻结孔深度(深孔/浅孔) 955/856m，冻结孔(深孔/浅孔)个22/22冻结孔开孔间距1.385m，冻结管规格168mm，岩石冻结的冻结壁设计厚度4m，冻结壁平均温度-8盐水温度-30。现在已经开始冻结。 The excavated diameter is about 10.4 13.4 m with net diameter 9 m and freezing hole arranged circle diameter 19.4 m. The freeze hole depths are 955/856 m (22 deep holes/22 shallow holes), respectively, and freezing hole spaces 1.385 m with total 22+22 freezing holes. The diameter of freezing pipe is 168 mm. The rock designed thickness of frozen rock wall is 4m and frozen wall average temperature is -8 with the brine temperature is about -30 . The refrigerator station has started operation.,核桃峪矿井地质柱状图The service shaft geologic col