采场充填体的三维应力解析及其强度设计理论

Empirical analogy methods or equations are mainly employed for the cemented backfill strength requirement design by many mines with open stoping and delayed backfill mining method in China, which leads to a condition that the cement consumption of domestic mining backfill is generally double higher than the similar mines abroad. The overly high cement cost severely restricts the application and development of backfill mining method. In this application, the studies will be focused on the cemented tailings backfill in the primary stopes within relevant mining method. And the following key points will be investigated in detail based on the previous theories about the backfill stress and strength requirement calculation around the world: The strength properties of the interfaces between backfill and side rock walls together with their influences on the stresses distribution in backfill; The lateral pushing mechanism and analytical methods of the pressure from the adjacent uncemented tailings on the exposed cemented backfill backside surface; The three dimensional analytical models and formulations for the stresses within the backfill in primary stopes considering arching effect; The potential failure mechanism and modes of the exposed cemented backfill under the combined effects of side rock walls constraints and backside pressure from uncemented tailings; The design theory for the required strength of the cemented backfill in primary stopes and the random predicted results validation with physical model tests. After these researches, two key scientific problems will be thoroughly overcome, including the three dimensional analytical methods of the stress changes in backfill considering different interface contacts and exposing process, and the failure mechanism of exposed cemented backfill within the excavating and filling processes and its strength requirement evaluation. And these investigations are supposed to achieve innovations about the contact properties between backfill and side rock walls, pushing mechanism and pressure analytical method from backside uncemented tailings, and the analytical solutions about three dimensional arching stresses in backfill. The strength requirement design theory and methods for cemented backfill with wide applicability in mines will be established eventually. All of these achievements will provide beneficial theoretical supports for the development of backfill mining method.

我国空场嗣后充填矿山基本采用经验类比或经验公式法确定充填体强度需求，导致国内矿山充填水泥单耗普遍高于国外一倍以上，严重制约了我国充填采矿法的发展应用。项目以该采矿法中一步骤采场尾砂胶结充填体为研究对象，在国际相关理论研究的基础上，开展充填体与侧壁围岩的接触作用及其对充填体应力分布的影响；相邻采场非胶结尾砂对胶结充填体的侧压作用机制及其表征；采场充填体的三维应力成拱解析模型及计算方法；侧壁约束与后壁推压共同作用下胶结充填体潜在破坏机制及表征；采场胶结充填体的强度需求计算理论及其试验验证等方面研究，重点解决采场充填体揭露前后的三维应力演化及其解析、采充时序过程中采场充填体的破坏机制及强度需求等关键科学问题，在充填体与侧壁围岩的接触作用机制研究、后壁尾砂的推力作用研究及三维拱应力解析分析方面形成创新，最终建立具有广泛适用性的充填体强度需求设计理论与方法，为我国矿山充填技术发展提供有利理论支撑。

地下金属矿山阶段空场嗣后充填采矿法中，一步骤采场胶结充填体成本占充填总成本70%以上，如何在确保充填体侧向揭露稳定性的同时，优化控制胶充成本是制约安全经济充填采矿的瓶颈。为此，以一步骤采场胶结充填体为对象，探究了充填体-围岩力学接触作用、非胶尾砂对胶结充填体侧压机制，研究了充填体三维应力解析方法，分析了侧向揭露充填体破坏模式，建立了采场充填体稳定性分析方法及其强度需求设计理论。主要创新成果如下：.（1）充填体与侧壁围岩间考虑接触单元后，充填成拱作用及应力分布主要受接触面内摩擦角和黏聚力所控制。当充填体与围岩接触面强度低于相应充填体强度时，考虑接触单元及其物理力学性质是必要的，否则会高估充填成拱效应、充填体应力偏小。.（2）二步骤采场非胶结充填体中，靠近采场中部的竖向应力大于同一埋深靠近采场边壁的竖向应力，呈“中间大、两端小”不均匀分布；同一埋深处采场中部与采场边部的水平应力基本相等，呈均匀分布模式。.（3）一步骤采场胶结充填体中，成拱作用下应力分布服从“揭露前三维拱应力<揭露后三维拱应力<揭露后二维拱应力<覆重法自重应力”变化规律。.（4）用于单侧揭露充填体强度需求计算的经典Mitchell法，适用不固结不排水短期强度状态的胶结充填体，其针对的充填体强度性质接近c=cu、φ=φu=0，导致该法进行固结排水长期强度条件下的强度需求计算结果偏保守。.（5）不同采场尺寸及充填体物理力学参数条件下，当胶结充填体底部潜在滑动面与水平面夹角为α=45°+φ/2、且胶结充填体与侧壁围岩接触面摩擦力方向角为β=45°‒φ/2时，得出了相对最优的充填体强度需求计算模型与方法。.（6）以矿山原位采场充填体中钻孔取芯试样的强度实测数据为样本，建立了定量表征采场充填强度分布离散性的浮动安全系数计算方法，形成了采场充填体“强度需求理论解→实际充填质量评估→浮动安全系数选取→实际强度需求”的动态优化设计模型。