多圈管冻结模型试验及人工冻土冻胀规律研究

发布时间：2018-04-04 03:19

本文选题：冻胀试验　切入点：多圈管冻结　出处：《安徽理工大学》2013年博士论文

【摘要】：目前以两淮地区为代表的新建矿井穿越的表土层厚度不断加大,为保证井筒掘砌的顺利进行,普遍采用三圈甚至四圈管冻结来增加冻结壁的厚度以抵抗较大的地压。当前国内外对深厚地层土体基本冻胀特性及多圈管冻结过程冻结壁内部特征参数变化规律掌握尚不够全面,需进一步开展相关方面基础研究。本文针对目前国内缺乏多功能、边界可以多变的冻胀试验装置,研制了一台功能完善,集温度、水分、压力控制于一体的微机控制多功能冻融压缩试验系统,通过设定相关外边界条件,能够达到试验外边界与冻结法凿井现场外边界条件一致。基于该试验系统,进行了大载荷作用下土体冻胀力(率)的测试,得出外载荷对冻胀力(率)影响最敏感区间；冻结锋面迁移高度h与冻结时间t呈良好的对数函数关系。通过单、双向冻结模式下冻胀力试验,得出两种冻结模式下冻胀力随冷源温度变化均可用指数函数来描述,双向冻结较单向冻结冻胀力增幅与冷端温度之间呈良好的二次函数关系,且冻结锋面迁移速率近乎是单向冻结的两倍左右。同时改变试验常规冻胀测试方法,通过试验仪器位移闭环控制,在预留不同冻胀空间下进行冻胀力量测,间接获得了土体冻胀力与冻胀率呈二次抛物线函数下降趋势关系,当土体冻胀空间大于最大冻胀率42%时,冻胀力下降速率加快。通过试验,更好掌握了深厚表土地层土体冻胀基本特性。针对多圈管冻结过程冻结壁内部温度场、应力场、水分场规律掌握尚不够全面问题,在室内调整内、中、外圈冻结孔布置圈径以及冻结孔间距,进行了两次共六个区域多圈管冻结模型试验,获得了大量冻结壁内部温度、水分、应力场变化数据。同时结合ADINA有限元软件对不同冻结方案进行温度场模拟比较分析,描述了多圈管冻结过程冻结壁厚度、平均温度等参数变化特征,得出在冻结管无偏斜条件下,冻结孔环向间距平均增大(减小)O.1m,冻结壁交圈时间相应增大(减小)4d；两圈孔布置间距增大(减小)1m,孔间土体交圈时间相应增大(减小)8-10d；外圈孔圈径(直径)增加1.0m,冻结壁有效厚度增加0.3-0.4m；内圈孔圈径(直径)增大1.0m,井帮温度增高1.3～1.7℃等规律。应力场分析结果表明,冻胀力沿径向方向分布不均,主要积聚在外圈孔内侧各冻结管附近,冻结孔布置圈径对环向冻胀力影响小于对径向冻胀力影响,而冻结孔间距对环向冻胀力影响大于对径向冻胀力影响,冻结孔间距增大(减小)0.1m,冻胀力减小(增大)10%左右。在冻结壁形成过程,水分迁移剧烈,主要发生在测点温度处于5℃左右降至结冰温度阶段,不同位置土体含水率差值达到11.25%,引起径向方向冻结壁强度分布不均。利用有限元计算软件还考虑了冻结管偏斜对冻结壁特征参数的影响,得出冻结管偏斜对冻结壁有效厚度影响较小,但对冻结壁平均温度及井帮温度均有较大影响,且极易在内、外圈孔之间形成封闭的未冻水仓,对冻结壁整体稳定性产生影响。本文基于多圈管冻结背景,开发了一套适用于深厚冲积层人工多圈管冻结壁温度场的分析及信息可视化计算软件,并应用至淮南某矿冻结进风井现场实际工程中,对关键层位温度场、应力场、水分场进行测试分析。将现场测试结果与数值计算、模型试验结果进行对比,得出三种不同分析方式所获得的冻结壁内部特征参数变化规律相一致。基于室内基础试验、模型试验、数值模拟、现场测试等手段所获得的结果,得出在冻结过程中冻结壁沿径向方向温度、含水率、应力是不断变化的,引起冻结壁沿径向方向强度不一,因此在冻结壁设计时应注意冻结壁属于非均质材料这一特性。同时提出多圈冻结孔布置方案相关建议,指出冻结设计时应充分发挥其冻结壁厚度、平均温度和井帮温度的共同作用。本文掌握了多圈管冻结壁内部特征参数变化规律,为深井冻结壁设计提供参考。
[Abstract]:At present , the thickness of the surface layer of the newly - built mine crossing in the two - Huai region is continuously increased , so as to ensure the smooth running of the shaft excavation , three or even four - turn tube freezing is adopted to increase the thickness of the frozen wall to resist the large ground pressure .

In this paper , a microcomputer - controlled multi - function freeze - thaw compression test system with perfect function , temperature , moisture and pressure is developed in this paper . By setting relevant external boundary conditions , the external boundary conditions of the external boundary and freezing method can be achieved . Based on the test system , the test of the frost heaving force ( rate ) of the soil under heavy load is carried out , and the most sensitive interval is obtained .
In this paper , the relation of freezing and heaving force with cold source temperature in two freezing modes is described by using the exponential function of freezing and heaving force under two freezing modes . The frozen heaving force and the frost heaving rate of the frozen front surface are almost twice the one - way freezing .

In order to solve the problem of temperature field , stress field and water field law of freezing wall in freezing process of multi - coil pipe , the temperature , moisture and stress field change data of freezing wall were obtained .
The spacing of the two turns of holes increases ( decreases ) 1m , and the time of interhole soil crossing increases ( decreases ) 8 - 10d ;
the diameter of the outer ring hole is increased by 1.0 m , and the effective thickness of the freezing wall is increased by 0.3 - 0.4m ;
The results of stress field show that the effect of freezing tube deflection on the frozen wall characteristic parameters is less than that of the frozen wall . The effect of freezing hole spacing on the frozen wall characteristic parameter is more than about 11.25 % .

Based on the background of multi - loop pipe freezing , a set of analysis and information visualization software for freezing wall temperature field of artificial multi - loop pipe in deep alluvium is developed .

Based on the results obtained by indoor basic experiment , model test , numerical simulation and on - site test , it is concluded that freezing wall is not uniform in radial direction due to the changing of temperature , water content and stress in the radial direction of frozen wall during the freezing process .

【学位授予单位】：安徽理工大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：P642.14

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