【作者】 何伟；

【导师】 李成江；

【作者基本信息】 北京科技大学 ， 岩土工程， 2016， 博士

【摘要】 临涣矿区的地下水中,普遍含有高浓度的S042-和Ca2+离子。该矿区部分立井的基岩段,有大量腐蚀性水流淌的部位腐蚀程度较轻,而有少量渗水的部位却腐蚀严重。以童亭副井为例,对这种腐蚀现象的机理进行研究后,建立了一种基于室内加速腐蚀试验的,对腐蚀井壁进行可靠性评价和剩余寿命预测的方法。使用超声平测法和混凝土回弹法,对童亭副井典型部位的腐蚀程度进行评价后,通过腐蚀性水的离子成分分析和腐蚀产物、过水面井壁及其附着致密层的物相分析,对井壁腐蚀机理进行了研究。研究结果表明：腐蚀性水中的CaSO4已经饱和,当这种腐蚀性水在井壁表面流淌时,CaSO4结晶形成的致密层,有效减少了混凝土与腐蚀性水的接触,延缓了腐蚀性水中S042-对井壁的腐蚀；当腐蚀性水从浇筑缝流出时,由于渗水量小且蒸发作用大,CaSO4在浇筑缝内结晶膨胀,促进了硫酸盐腐蚀的发生。腐蚀发生后,井壁结构是否安全以及还能服役多久,是最令人关心的问题,这显然与其强度相关。目前腐蚀结构剩余强度的时间预测,多基于加速腐蚀试验,需要解决加速腐蚀试验的当量加速关系,以及加速腐蚀试验中混凝土强度劣化规律这两个关键问题。为了解决这两个问题,分别进行了三点弯曲梁和立方体试件的加速腐蚀试验。三点弯曲梁加速腐蚀的试验环境,包括三种浓度(清水、9%和15%)的浸泡腐蚀和一种浓度(15%)的干湿循环腐蚀。腐蚀试件的物相分析表明,这三种加速腐蚀环境下发生的硫酸盐腐蚀反应基本与井壁腐蚀相同,加速腐蚀对现场腐蚀具有代表性。使用GM(1,1)模型建立试件腐蚀厚度和弹性模量的时间函数,将干湿循环腐蚀厚度的时间函数与现场腐蚀深度的对比,得到干湿循环腐蚀的当量加速关系。再结合15%浸泡与干湿循环弹性模量时间函数的相互对比,得到了15%浸泡腐蚀试验的当量加速关系。立方体试件在进行0、14和21MPa的加载后,分别放入清水和15%硫酸盐溶液进行浸泡腐蚀试验。利用不同腐蚀龄期时的单轴抗压试验,使用GM(1,1)模型建立了腐蚀试件轴心抗压强度的时间函数。假设以抗压强度与弹性模量为指标的当量加速关系相等,结合15%溶液浸泡腐蚀的当量加速关系,建立起了井壁腐蚀段轴心抗压强度的时间函数。以童亭副井四个腐蚀段为研究对象,以等比例降低材料参数的方式,使用FLAC3D对不同腐蚀程度井壁的应力分布进行了数值模拟。结果表明腐蚀段全部失效时,井壁应力的最大改变率也不超过10.2%,并且影响范围有限。忽略腐蚀对井壁应力分布影响后,结合井壁腐蚀段轴心抗压强度的时间函数和圆形井壁的弹性力学解,建立了童亭副井结构可靠度指标的时间函数。若服役环境不发生改变,童亭副井的结构失效概率达50%时的服役时间为47.3年,自2014年起还有22.3年,目前可不急于进行加固。而如果在施工期,井壁经历了相当于14MPa或21MPa的损伤,那么其结构失效概率达50%时的服役时间将会分别降低至24.4和20.2年。当地下水中含硫酸盐等腐蚀介质时,应当特别注意施工节奏,避免早期受力对混凝土形成损伤,造成井壁服役寿命降低。更多还原

【Abstract】 The groundwater of the Linhuan Mining Area contains high concentrations of SO42- and Ca2+, and several vertical shafts at the bedrock section have been seriously corroded. At those shafts, the sidewall has varying degradation degrees in different parts. The part on which water flowed is barely corroded, whereas the moist part near the pouring joints is seriously corroded. After the mechanism of this phenomenon was studied, based on accelerated corrosion experiment, a remaining life prediction method for corroded sidewall was established.Taking the auxiliary shaft of the Tong-ting Coal Mine as the research object, the corrosion degree of typical parts was tested by ultrasonic and rebound test, and the corrosion mechanism was studied by chromatography, X-ray diffraction, and energy-dispersive X-ray spectroscopy. The results showed that gypsum in corrosive water was supersaturated. The part on which water flowed was protected by the crystallized precipitation on the concrete. By contrast, the corrosion of the part where water flowed through pouring joints was aggravated by internal crystallization.When a sidewall is corroded by sulfate attack, the reliability and remaining service life are both essential questions. In order to solve those problems, accelerated corrosion experiment is usually needed to obtain the degeneration law of strength parameters and the acceleration corrosion factor. In accelerated corrosion experiment, there were two kinds of specimens, three point-bending beams and cube specimens.The corrosion environments of the three point-bending beams included immersing (0,9 and 15 wt% sulfate solution) and drying-wetting (15 wt% sulfate solution).The phase analysis indicated that the corrosion reaction in accelerated corrosion experiment and corroded sidewall were similar. After a predictive function of the corrosion layer in drying-wetting accelerated corrosion experiment was built by GM(1,1) model, by comparing to the corroded sidewall, the acceleration corrosion factor of drying-wetting accelerated corrosion experiment was obtained. After the predictive functions of elastic modulus were built by GM(1,1) model, the corrosion speed rate between immersing and drying-wetting accelerated corrosion experiment was acquired. Then, the acceleration corrosion factor of immersing accelerated corrosion experiment was obtained.After the cube specimens were divided into three groups, and separately loaded 0,14 and 21 MPa, they were immersed in 0 or 15 wt% sulfate solution. As we assumed that the acceleration corrosion factor based on corrosion depth, elastic modulus and compressive strength are equal, combining with the acceleration corrosion factor and the predication functions of the axial compressive strength of the corroded pre-damaged and normal cube specimens built by GM(1,1) model, a predictive function of the axial compressive strength of corroded sidewall was established.When a sidewall is corroded, the degeneration of the elastic modulus may cause stress redistribution. Thus, simplified models was built to analyses how increasing corrosion degree affects stress distribution. The results showed that, as to the auxiliary shaft of the Tong-ting Coal Mine, corrosion barely influent on stress distribution. Based on the predictive function of the axial compressive strength and the elasticity solution of the circular sidewall, a predictive functional of the reliability index for corroded sidewall was established.As to the auxiliary shaft of the Tong-ting Coal Mine, the service life is 47.3 years. In 2014, the residual life was 24.7 years, and the degradation parts have no need of immediately reinforcement. But if the pre-damaged degree of the sidewall was equivalent to 14MPa or 21MPa, the service life decreased to 24.4 or 20.2 years. It shows that damge by early loading on young concrete should be avoided during construction period, especially in sulfate corrosion environment.更多还原