A roof model and its application in solid backfilling mining

Through changing the axial load on backfilling material compaction test to reflect different overlying strata pressure on backfilling material, the stress-strain relations in the compaction process of backfilling material under the geological condition can be obtained. Based on the characteristic of overlying strata movement in backfill mining, a model of roof thin plate is established. By introducing the stress-strain relation in compaction process into the model and using RIZT method to analyze the bending deformation of roof, the bending deflection and stress distribution can be obtained. The results show that the maximum roof subsidence and maximum tensile stress occurring at the center are 255 mm and5 MPa, respectively. Tensile fracture of roof under the geological condition of Dongping Mine did not occur. The dynamic measurement results of roof in Dongping Mine verify the theoretical result from the aforementioned model, thereby suggesting the roof mechanical model is reliable. The roof thin plate model based on the compaction characteristic of backfilling material in this study is of importance to research on backfill mining theories and application of backfilling material characteristics.     

An improved method to assess the required strength of cemented backfill in underground stopes with an open face

Backfill is increasingly used in underground mines to reduce the surface impact from the wastes produced by the mining operations. But the main objectives of backfilling are to improve ground stability and reduce ore dilution. To this end, the backfill in a stope must possess a minimum strength to remain self-standing during mining of an adjacent stope. This required strength is often estimated using a solution proposed by Mitchell and co-workers, which was based on a limit equilibrium analysis of a wedge exposed by the open face. In this paper, three dimensional numerical simulations have been performed to assess the behavior of the wedge model. A new limit equilibrium solution is proposed, based on the backfill displacements obtained from the simulations. Comparisons are made between the proposed solution and experimental and numerical modeling results. Compared with the previous solution, a better agreement is obtained between the new solution and experimental results for the required cohesion and factor of safety. For large scale (field) conditions, the results also show that the required strength obtained from the proposed solution corresponds quite well to the simulated backfill response.     

Strength properties of fly ash based controlled low strength materials

Controlled low strength material (CLSM) is a flowable mixture that can be used as a backfill material in place of compacted soils. Flowable fill requires no tamping or compaction to achieve its strength and typically has a load carrying capacity much higher than compacted soils, but it can still be excavated easily. The selection of CLSM type should be based on technical and economical considerations for specific applications. In this study, a mixture of high volume fly ash (FA), crushed limestone powder (filler) and a low percentage of pozzolana cement have been tried in different compositions. The amount of pozzolana cement was kept constant for all mixes as, 5% of fly ash weight. The amount of mixing water was chosen in order to provide optimum pumpability by determining the spreading ratio of CLSM mixtures using flow table method. The shear strength of the material is a measure of the materials ability to support imposed stresses on the material. The shear strength properties of CLSM mixtures have been investigated by a series of laboratory tests. The direct shear test procedure was applied for determining the strength parameters Phi (angle of shearing resistance) and C(h) (cohesion intercept) of the material. The test results indicated that CLSM mixtures have superior shear strength properties compared to compacted soils. Shear strength, cohesion intercept and angle of shearing resistance values of CLSM mixtures exceeded conventional soil materials' similar properties at 7 days. These parameters proved that CLSM mixtures are suitable materials for backfill applications.     

杏山铁矿露天转地下覆盖层回填自然分级研究

露天转地下覆盖层的自然分级现象,对使用崩落法开采矿山的通风、温度、矿石损失贫化等指标都有较明显的影响,但对于覆盖层在回填时就形成合理自然分级,国内研究尚处于空白阶段。以首钢杏山铁矿为研究背景,采用理论分析、物理模拟试验、现场排土场试验等研究手段,对露天转地下覆盖层回填自然分级规律进行了深入系统的分析,研究结果得出杏山铁矿采用倒排排土场废石,人工回填形成合理结构和厚度的自然分级覆盖层是可行的。露天转地下|     

充填料浆沉缩性能试验研究

沉缩率是矿山充填工程的一项重要指标,严重制约着充填接顶的质量。以保山金厂河铅锌矿的全尾砂为试验材料,研究了全尾砂的泌水沉缩特性与规律,分析了不同料浆浓度、水泥添加量对沉缩性能的影响。结果表明：①胶结充填料浆沉缩率小于非胶结充填料浆。②在胶结充填料浆中,随着料浆浓度增大,料浆沉缩率会逐渐减小。③在充填料浆浓度为60%～68%范围中,随着灰砂比增大,料浆沉缩率会逐渐减小;在料浆浓度达到70%时,料浆沉缩率变化幅度很小,基本没有沉缩。     

金川二矿区膏体充填系统试运行有关问题的探讨

金川二矿区的膏体充填系统于1991年开始建设,1999年8月生产试运行成功,并通过了国家有色金属工业局的鉴定。本文对该系统的试运行作了概括介绍,对试运行状况及存在的问题进行了初步探讨。     

影响中深部充填质量的因素探讨及对策

金川二矿区是我国最大的充填法开采的大型铜镍矿,年产矿石突破400万t,其开采深度超过千米,随着开采深度的加深,矿区地压日益明显,充填质量的好坏直接影响到矿山的安全生产。本文介绍了金川二矿区深部开采的矿区应力状况,探讨了充填材料、充填材料制备及采场充填工艺对充填质量的影响,并研究了保证充填质量的策略,对矿山中深部开采具有一定的借鉴。     

采场结构参数及充填配比优化的FLAC3D数值模拟

为了保证矿山安全高效开采,通过分析影响采场稳定性关键因素及破坏机理,应用数值模拟法对二步矿柱在不同结构参数和两侧不同充填配比开采条件的稳定性进行分析,优选出安全高效的一步采场充填配比和二步采场的结构参数。采用FLAC3D数值模拟,计算和分析在开采过程中,不同结构参数和两侧不同充填配比的采场顶板的应力、应力分布区域面积及位移变化特征,得出各不同方案的采场顶板稳定情况。结果表明:采场受两侧充填体配比的影响较为明显,一步采场灰砂比由1∶6改变到1∶8时,对二步采场的稳定性影响较小;灰砂比小于1∶8和采场宽度大于18 m时,采场顶板的拉应力和位移的变化率逐渐变大,采场的稳定性迅速降低。因此,综合矿山生产安全、高效及成本考虑,建议一步采场充填配比为1∶8、二步采场的宽度为18 m。     

换填法处理地基及其效果分析

以由粘土、石灰、炉渣、石子组成的材料（四合土）对地基进行回填处理的工程为例,通过一系列四合土物理力学性能试验,分析影响四合土抗压强度的主要因素。对工程竣工后的沉降监测表明,四合土换填处理地基是一种实用的地基处理方法。     

高水压粉砂地层泥水盾构水下到达施工技术

结合武汉地铁二号线越江隧道工程水下到达的施工经验,介绍了如何创造条件实现泥水盾构水下到达,安全可靠地完成泥水盾构到达施工,重点论述了端头旋喷加固、冷冻加固以及基坑回填、盾构掘进等水下到达关键施工技术。该工程采用端头旋喷加固和冷冻加固技术相结合,洞门破除后实施基坑回填,成功地解决了盾构到达过程中高水压风险,可为类似工程提供一定的参考和借鉴。