袁大滩矿主斜井冻结壁稳定性研究

发布时间：2018-06-02 12:19

本文选题：斜井 + 冻土　；参考：《中国矿业大学(北京)》2017年博士论文

【摘要】：本文充分运用冻土试验、理论分析、数值模拟及现场工程实测等研究方法,测试了袁大滩矿井筒检查孔地层样品的主要物理力学特性参数,分析了倾斜井筒冻结壁的应力场演化规律,提出了斜井冻结壁稳定性判别方法及塑性区分布和冻结壁厚度计算方法,推导出冻结壁内部温度分布方程和冻结壁外缘原始冻胀力计算方程。详细探讨了斜井冻结壁变形、塑性区分布与冻结壁力学参数、冻结壁几何参数、冻结壁外载以及暴露时间等影响冻结壁稳定的各主要因素之间的关系,并拟合出冻结壁收敛变形和塑性区分布的回归计算式。现场实测了袁大滩矿主斜井去回路盐水温度、测温孔温度、冻结壁两帮温度、冻结壁收敛变形及壁后冻土压力等参数,分析了冻结壁形成后至解冻期间的稳定性变化特征,总结出细砂层及粘土层的冻结壁径向收敛变形大于粉砂岩层和砂质泥岩层,主斜井冻结壁收敛变形产生差异的原因主要来自于冻结地层的强度特性变化等。本文以袁大滩矿主斜井冻结施工为背景,主斜井冻结壁稳定性研究内容及成果主要基于以下几个方面:1.对袁大滩矿主斜井穿过地层岩土体进行冻土物理力学特性试验,测试了冻结土样的质量比热、容积比热、导热系数、结冰温度、冻胀率等参数,并进行了单轴压缩和单轴蠕变试验。单轴试验结果表明,冻结表土单轴抗压强度随温度降低近乎呈线性增长,强度增长速率约为0.32~0.64MPa/℃。冻结岩石单轴抗压强度总体随温度降低而提高,-10℃~-15℃之间温度对冻结岩石强度影响较大。低温条件下冻结表土弹性模量受冻结温度影响明显,随温度降低不断增加,增长速率约为0.874~12.97MPa/℃。低温条件下冻结岩石弹性模量相对表土弹性模量要高,随温度降低总体呈现增长趋势且离散性较大。低温状态下,冻结地层蠕变变形整体较小,应力水平较低时,基本上属于衰减型蠕变,当应力水平较高时,逐渐转化为非衰减型蠕变。最后,通过建立冻土蠕变数学模型,并根据不同温度条件下的轴向蠕变应变与时间关系曲线获得了各试验地层在不同温度条件下各蠕变参数值。2.基于弹性力学理论,建立“倾斜弹性厚壁筒”力学模型,且考虑不同埋深条件,分析了冻结壁应力场演化规律,计算出冻结壁的径向应力σ_r、环向应力σ_θ、切向应力τ_(rθ)及轴向应力σ_τ的表达式,并从强度条件和变形条件两方面提出冻结壁稳定性判别方法。基于弹性状态下冻结壁的应力分布特征来确定其达到塑性状态时的边界线,并采用Mises屈服准则来确定塑性区的屈服条件,给出冻结壁的最大塑性扩展半径及其厚度计算方法。基于圆管稳定导热方程建立双孔冻结温度场数学模型,利用叠加原理,推导出竖向直排三孔冻结壁温度场分布方程和整排冻结壁内部温度方程,并对竖向多排斜井冻结壁的温度场分布做出预测。按照内缘冻胀力作用于外层井壁表面的方向,将其划分为法向冻胀力、水平冻胀力和切向冻胀力,并总结了其分布特点。基于弹性力学理论,结合竖向直排孔的冻结帷幕特点,建立冻胀力计算模型,根据冻结壁与未冻土之间的变形协调关系分析并得出冻结壁外缘原始冻胀力计算方法。3.通过对斜井冻结壁稳定性的数值模拟研究,分析了冻结壁收敛变形、塑性区分布与冻结壁力学参数、冻结壁几何参数、冻结壁外载以及暴露时间等影响冻结壁稳定的各主要参数之间的关系,拟合出计算指标与多因素回归方程。斜井冻结壁收敛变形和塑性区分布范围主要受冻结壁强度、冻结壁厚度、井筒掘进尺寸、开挖段长、冻结壁外荷载以及暴露时间等多重因素综合影响。影响斜井冻结壁收敛变形和塑性区分布范围的主要因素为冻结壁所承受的顶板荷载、水平荷载以及冻结壁的强度,其次是开挖段长和暴露时间,而冻结壁厚度对冻结壁收敛变形和塑性区分布范围的影响程度比较复杂,主要与外载水平和当前厚度相关。外载水平变化时,冻结壁厚度对冻结壁收敛变形的影响并不显著,但对冻结壁塑性区分布范围的影响则较大;开挖段长对冻结壁收敛变形和塑性区分布范围的影响与冻结壁外荷载水平相关;冻结壁暴露时间对冻结壁收敛变形和塑性区分布范围的影响主要体现在冻结壁暴露初期,随变形时间的增大收敛变形和塑性区分布成线性增长。在冻结壁空帮段上,冻结壁顶板变形大于底板变形,左右两帮变形对称,最大顶底板变形和最大两帮变形均发生在距离工作面迎头0.45倍段长处,且靠近工作面迎头和已支护段两端,变形量逐渐减小。冻结壁顶板塑性区分布范围较大,底板塑性区分布较少;左右两帮塑性区分布整体上对称,且靠近工作面迎头和已支护段方向上塑性区分布逐渐增大。为了获得更加安全、经济、稳定的冻结壁,当井筒的开挖尺寸确定时,必须明确不同地段、不同深度冻结壁所承受的外荷载,从而提高冻土强度,并结合施工工艺和进度安排合理确定开挖段长。井筒掘进开挖时,在距离工作面迎头0.45倍段长处,应对围岩采取加强支护措施,防止围岩发生突然垮落。同时,片面增加冻结壁厚度并没有太大意义,确定冻结壁厚度时,应对井筒掘进尺寸、开挖段长、冻结壁强度、外载水平及变形时间等因素进行综合分析。4.开展现场条件下的工程实测研究,实测内容主要包括:去回路盐水温度、测温孔温度、冻结壁两帮温度、冻结壁收敛变形及壁后冻土压力等指标,并结合实测结果对冻结壁稳定性进行分析。根据实测的去回路盐水系统温度、测温孔温度、冻结壁两帮温度计算出冻结壁的平均温度。监测结果表明,冻结壁温度基本满足工程设计要求。冻结壁收敛变形实测结果表明,冻结壁的径向变形不仅与冻结壁土层埋深有关,同时与土层性质密切相关。在细砂层与粉砂岩层附近及粘土层与砂质泥岩层附近,冻结壁的径向收敛变形均有大幅降低,细砂层及粘土层的冻结壁径向收敛变形大于粉砂岩层和砂质泥岩层。冻结壁的收敛变形速率实测结果与按照数值模拟回归公式计算得到的冻结壁收敛速率基本一致,(?)_v/V_v的波动范围为0.75~1.69,(?)_v/V_v波动范围为0.71~3.17,实测值与计算值相差不大。通过冻结壁的顶、脚、底三处的斜井井壁的受力监测,分析了内层井壁形成后至解冻期间冻结壁的稳定性变化特征。井壁最大压力出现在拱顶,底板与拱脚压力都很小。在压力测试元件埋设约70~80d左右之后,冻结壁承载能力逐渐下降,直至完全解冻后,承载能力完全丧失。袁大滩矿主斜井冻结壁收敛变形产生差异的原因主要来自于各冻结地层冻结壁的强度不同,在类似条件的冻结壁设计过程中,当冻结壁厚度、开挖段长和暴露时间等因素确定时,可按照强度条件来判定冻结壁的稳定性。
[Abstract]:In this paper, the main physical and mechanical properties of the samples are tested by the methods of frozen soil test, theoretical analysis, numerical simulation and field engineering measurement. The evolution law of the stress field of the frozen wall of the inclined shaft is analyzed. The stability discrimination method for the frozen wall of the inclined shaft and the distribution and freezing of the plastic zone are put forward. The equation of the temperature distribution inside the frozen wall and the calculation equation of the original frost heaving force on the outer edge of the frozen wall are derived, and the key factors affecting the stability of the frozen wall are discussed in detail, such as the deformation of the frozen wall, the distribution of the plastic zone and the mechanical parameters of the frozen wall, the geometric parameters of the frozen wall, the loading of the frozen wall and the exposure time. The regression calculation formula of the convergence deformation and the plastic zone distribution of the frozen wall is fitted, and the parameters such as the temperature of the salted water in the main inclined shaft of Yuanda beach, the temperature of the temperature of the temperature of the temperature of the temperature of the temperature of the freezing wall, the convergent deformation of the frozen wall and the pressure of the permafrost after the wall are measured, and the characteristics of the stability change during the freezing wall form to the thawing are analyzed. The radial convergence deformation of the frozen wall of the fine sand layer and the clay layer is larger than the silt rock and the sandy mudstone layer. The reasons for the difference of the convergence and deformation of the main inclined shaft are mainly due to the change of the strength characteristics of the frozen strata. Based on the following aspects: 1. the physical and mechanical properties of the main inclined shaft of Yuan datan mine through the stratum rock and soil were tested, and the parameters of the mass specific heat, the volume specific heat, the thermal conductivity, the freezing temperature and the frost heave rate were tested, and the uniaxial compression and uniaxial vermicular test were carried out. The uniaxial test results showed that the frozen topsoil was uniaxial compression. The strength increased almost linearly with the temperature, and the strength growth rate was about 0.32~0.64MPa/ C. The uniaxial compressive strength of the frozen rock increased with the temperature, and the temperature between -10 C and ~-15 C had great influence on the strength of the frozen rock. The growth rate is about 0.874~12.97MPa/ C. At low temperature, the modulus of elasticity of frozen rock is higher than that of surface soil. The overall growth trend and dispersion are larger with the temperature decreasing. Under low temperature, the creep deformation of frozen stratum is smaller and the stress level is low, it is basically attenuated creep, and when the stress level is high, the stress level is higher. In the end, by establishing the mathematical model of frozen soil creep, and according to the relation curve of the axial creep strain and time under different temperature conditions, the creep parameter values of each test stratum under different temperature conditions.2. are based on the elastic mechanics theory, and the mechanical model of "inclined elastic thick wall cylinder" is set up, and it is not considered. On the same buried depth condition, the evolution law of the stress field of the frozen wall is analyzed. The expressions of the radial stress Sigma _r, cyclic stress sigma, R theta and the axial stress sigma are calculated, and the formula for the stability of the frozen wall is put forward from two aspects of the strength condition and the deformation condition. The boundary line when it reaches the plastic state is determined, and the yield condition of the plastic zone is determined by the Mises yield criterion. The maximum plastic expansion radius and the thickness calculation method of the frozen wall are given. Based on the stable heat conduction equation of the circular tube, a mathematical model of the freezing temperature field of the double hole is established, and the vertical straight row three hole freezing wall temperature is derived by the superposition principle. The temperature field distribution equation of the degree field and the internal temperature equation of the whole frozen wall are predicted, and the temperature distribution of the freezing wall of the vertical multi row inclined shaft is predicted. According to the direction of the inner edge frost heaving force acting on the surface of the outer well wall, it is divided into the normal frost heaving force, the horizontal frost heaving force and the tangential frost heaving force, and the distribution characteristics are summed up. Based on the elastic mechanics theory, the conclusion is made. The frost heaving force calculation model is set up with the characteristics of the freezing curtain of vertical straight holes. According to the analysis of the deformation coordination relationship between the frozen wall and the unfrozen soil, the calculation method of the original frost heaving force of the outer edge of the frozen wall is obtained by the numerical simulation of the stability of the frozen wall of the inclined shaft, and the deformation of the frozen wall, the distribution of the plastic zone and the frozen wall force are analyzed by the numerical simulation of the stability of the frozen wall of the inclined shaft. The relationship between the parameters of the parameters, the geometric parameters of the frozen wall, the load of the frozen wall and the exposure time, etc., which affect the stability of the frozen wall, and fitting out the calculation index and the multiple factor regression equation. The convergence and the plastic zone distribution of the frozen wall of the inclined shaft are mainly frozen wall strength, the thickness of the frozen wall, the bore size of the shaft, the length of the excavation section and the freezing. The main factors affecting the convergence and plastic zone distribution of the frozen wall of the inclined shaft are the roof load, the horizontal load and the strength of the frozen wall, followed by the length of the excavation section and the exposure time, while the thickness of the frozen wall is distinguished from the convergence deformation and plasticity of the frozen wall. The influence degree of the cloth range is complex, mainly related to the load level and the current thickness. The effect of the thickness of the frozen wall on the convergence deformation of the frozen wall is not significant, but it has great influence on the distribution of the plastic zone of the frozen wall; the influence of the length of the excavation length on the convergence deformation and the plastic zone distribution of the frozen wall and the frozen wall The influence of the exposure time of the frozen wall on the convergence deformation and the plastic zone distribution of the frozen wall is mainly reflected in the early stage of the freezing wall exposure, with the increase of the deformation time and the linear growth of the plastic zone. On the frozen wall space section, the deformation of the roof of the frozen wall is greater than that of the bottom plate, and the two sides of the frozen wall are symmetrical. The deformation of the maximum top floor and the maximum two groups of deformation occur at the length of 0.45 times the length of the head-on face of the working face, and the deformation is gradually reduced. The plastic zone distribution of the roof of the frozen wall is larger, the plastic zone of the floor is less distributed, and the distribution of the plastic zone of the left and right two groups is symmetrical and close to the face of the working face. The distribution of plastic zone in the direction of the support section is increasing gradually. In order to obtain more safe, economical and stable frozen wall, when the excavation size of the shaft is determined, it is necessary to clear the external load under the frozen wall of different sections and different depths, so as to improve the strength of the frozen soil, and to rationally determine the length of the excavation section with the construction technology and schedule. During the excavation, 0.45 times the length of the face from the face of the working face, the strengthening measures should be taken to prevent the sudden collapse of the surrounding rock. At the same time, it is not of great significance to increase the thickness of the frozen wall unilaterally. When the thickness of the frozen wall is determined, the dimensions of the shaft heading, the length of the excavation section, the strength of the frozen wall, the level of the external load and the time of the deformation should be taken into account. On the basis of the comprehensive analysis of.4., the actual measurement research under field conditions is carried out. The main contents are as follows: the temperature of the salted water, the temperature of the temperature of the temperature of the temperature of the temperature of the temperature of the temperature of the freezing wall, the convergent deformation of the frozen wall and the pressure of the permafrost after the wall, and the stability of the frozen wall is analyzed with the measured results. The average temperature of the freezing wall is calculated at the temperature of the temperature hole and the freezing wall two. The monitoring results show that the freezing wall temperature is basically satisfied with the engineering design requirements. The measured results of the convergence deformation of the frozen wall show that the radial deformation of the frozen wall is not only related to the buried depth of the frozen wall soil, but also closely related to the soil layer properties. Near the clay layer and the sandy mudstone layer, the radial convergence deformation of the frozen wall is greatly reduced. The radial convergence deformation of the frozen wall of the fine sand layer and the clay layer is larger than the silt and the sandy mudstone. The convergence rate of the frozen wall is basically the same as the calculation of the convergence rate of the frozen wall calculated by the numerical simulation regression. The fluctuation range of (?) _v/V_v is 0.75~1.69, and the range of (?) _v/V_v fluctuation is 0.71~3.17. The measured value is different from the calculated value. The stability change characteristics of the frozen wall during the formation of the inner wellbore to the thawing are analyzed by the force monitoring of the wall of the inclined shaft at the top of the frozen wall, the foot and the bottom three. The maximum pressure of the shaft wall appears in the vault, the floor and the floor. The pressure of the arch foot is very small. After the pressure test element is buried about 70~80d, the bearing capacity of the frozen wall gradually decreases, and the bearing capacity is completely lost after the complete thawing. The reasons for the difference of the convergence deformation of the frozen wall of the main slope of Yuanda beach mainly come from the different freezing wall strength of the frozen strata and the frozen wall in similar conditions. In the design process, when the factors such as the thickness of the frozen wall, the length of the excavation section and the exposure time are determined, the stability of the frozen wall can be determined according to the strength conditions.
【学位授予单位】：中国矿业大学(北京)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TD265.3

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