选矿废水拌合尾砂胶结充填体强度演化规律及声发射特征

Strength evolution and acoustic emission characteristics of cemented tailing filling body mixed with mineral processing wastewater

尾砂胶结充填体是充填采矿中的核心承载单元,其稳定性关乎矿山生产安全。近年来,一些地下矿山为减少环境污染等问题,选择二次利用选矿排放废水进行充填,因此,对于采用选矿废水进行充填的矿山,明确选矿废水对尾砂胶结充填体强度的影响至关重要。为此,以3种pH选矿废水(pH=7、8、9)和普通自来水(pH=7)为拌合水制备4种养护龄期(7、14、21、28 d)的尾砂胶结充填体试件。利用声发射(AE)、扫描电镜(SEM)和X射线衍射(XRD)等试验手段,分析充填体试件的单轴抗压强度、微观结构及其破坏过程中AE振铃计数率、bi值、能量变化特征。研究表明:(1)在相同养护龄期下,选矿废水拌合的充填体强度低于普通自来水拌合的充填体强度,选矿废水拌合的充填体强度随pH的增大而减小,且CO_(3)^(2-)与充填体单轴抗压强度指标间的灰色关联性最好,而Ca^(2+)的关联性最差,阴离子的关联性整体好于阳离子;(2)在相同养护龄期下,选矿废水拌合的充填体内部C—S—H凝胶的质量浓度及衍射峰强度低于普通自来水拌合的充填体内部C—S—H凝胶的质量浓度与衍射峰强度,而选矿废水拌合的充填体中钙矾石的质量浓度及衍射峰强度高于普通自来水拌合的充填体中钙矾石的质量浓度和衍射峰强度;随着选矿废水pH的升高,充填体内部C—S—H凝胶的质量浓度减少、衍射峰强度降低,而钙矾石的质量浓度增多、衍射峰强度升高,从而导致充填体强度下降;(3)充填体破坏过程中AE振铃计数率及b^(i)值整体上分别呈现“升—降—突增—峰值”和“波动上升—剧烈下降—逐步上升”的变化规律;在相同养护龄期下,对于破坏过程中AE b^(i1)、b^(i2)、b^(i3)、峰值应力处每10 s累计振铃计数率及能量数值,选矿废水拌合的充填体均小于普通自来水拌合的充填体,且上述AE特征指标均随着选矿废水pH的增大逐渐减小。

The stability of cemented tailing filling body plays a core role in backfill mining as bearing body.In recent years,mineral processing wastewater is reused for filling mining to reduce a series of problems such as environmental pollution in some mines.It is extremely important to find out the impact of mineral processing wastewater which use it to filling on the strength of cemented tailing filling body in the mines.Therefore,cemented tailing filling body specimens(curing ages=7 d,14 d,21 d,28 d)have been prepared with mineral processing wastewater(pH=7,8,9)and ordinary tap water(pH=7).The uniaxial compressive strength,microstructure,and the process of failure of acoustic emission(AE)count rate,ib value and energy of cemented tailing filling body were analyzed by using AE,scanning electron microscopy(SEM)and X-ray diffraction(XRD)test.The results show that:①At the same age of maintenance,the strength of cemented tailing filling body which mixed mineral processing wastewater is lower than that mixed ordinary tap water,the strength decreases with the increase of pH value,and the grey correlation between CO_(3)^(2-)and the uniaxial compressive strength index of the filling body is the best,while the correlation of Ca^(2+)is the worst,and the correlation for anions is better than for cations overall;②Under the same curing age,the mass concentration and diffraction peak intensity of C—S—H gel in the filling body mixed with mineral processing wastewater are lower than those of the filling body mixed with ordinary tap water,while the mass concentration and diffraction peak intensity of ettringite are higher than those of the filling body mixed with ordinary tap water;With the increase of pH value of mineral processing wastewater,the mass concentration of C—S—H gel in the filling body decreases and the intensity of diffraction peak decreases,while the mass concentration of ettringite increases and the intensity of diffraction peak increases,which leads to the decrease of filling body strength;③AE count rate and ib value show the laws of“rise-drop-sudden increase-peak value”and“fluctant risesharp drop-gradual rise”during the failure process of the filling body;AE b^(i1),b^(i2),b^(i3),the cumulative counts rate per 10 s and energy value at the peak stress of the filling body which mixed mineral processing wastewater are less than those of mixed ordinary tap water,moreover,the above AE characteristic indexes gradually decrease with the increase of pH value of mineral processing wastewater.