Influence of Load Path and Effective Stress on One-Dimensional Deformation of Cemented Paste Backfill (CPB) During Deposition and Curing

Geotechnical and Geological Engineering - Pore water pressure and effective stress development within cemented paste backfill (as one of the most popular local and regional underground mining...     

Influence of Acid Attack on Physical Characteristics of Cemented Tailings Backfill

Geotechnical and Geological Engineering - The strength of backfill plays an important role in the stability and safe mining of goaf. Considering the influence of underground acid environment, the...     

Influence of Water Pressure on the Stress State in Stopes with Cohesionless Backfill

The rapid increase of backfill use in underground mines requires a better understanding of the interaction between the fill material and the surrounding rock mass. This is a fairly complex issue as backfill materials are weak compared to the rock mass. This difference in the mechanical behavior induces a stress transfer along the contact area. Previous work conducted on backfilled trenches and mining stopes has shown that basic arching theory can be used to estimate earth pressures in narrow, vertical openings. In this regard, most existing solutions have been developed for dry backfills. However, in many cases, water is present in mine stopes, so its effect should be assessed. In this paper, the authors present a solution to evaluate the stress state in submerged or partially submerged backfilled stopes. The proposed analytical solution is validated against numerical modeling results.     

圆环试样内径对抗拉强度的影响

运用RFPA2D软件对岩石的单轴拉伸强度试验、不同内径的圆环试样的劈裂试验进行了模拟。比较模拟结果 ,重点研究了圆环试样内径对试件抗拉强度的影响 ,确定了最接近单轴拉伸试验结果内径的范围 ,利用回归分析确定了内径与试样抗拉强度之间的关系。     

Undrained Strength of Deposited Mine Tailings Beds: Effect of Water Content, Effective Stress and Time of Consolidation

An understanding of the geotechnical behaviour of mine tailings is imperative when evaluating the stability and erosional resistance of sedimented tailings beds; as well as for the design and long-term management of tailings disposal facilities. Laboratory testing was conducted on mine tailings beds of various ages and thicknesses, deposited from concentrated slurries. Measured index properties allowed classifying the tailings as a coarse grained and non-cohesive material. The results obtained from the performed sedimentation experiments showed that the primary consolidation of the tailings beds was complete in approximately 1 h and negligible volume changes occurred in the beds during secondary compression. The undrained shear strength of the tailings beds was measured using an automated fall cone device at a depth interval of 1 cm and a profile of the shear strength variation with depth was obtained. At each tested surface, moisture content specimens were taken to determine the moisture content profile of the tested tailings beds. The undrained shear strength of the beds varied between 0.008 and 0.975 kPa for effective stresses below 1.19 kPa and increased with depth. Correspondingly, the moisture content decreased with depth and varied between 17 and 27%. The factor controlling the undrained shear strength of the tested beds was the vertical effective stress, with the water content also having some secondary effect. The correlation between the undrained shear strength and the vertical effective stress was expressed with a second order polynomial function. Consolidation time did not appear to influence the observed shear strength.     

Laboratory Characterization of Cemented Tailings Paste Containing Crushed Waste Rocks for Improved Compressive Strength Development

This paper aims at investigating some physical and mechanical characteristics of cemented tailings paste incorporating different amounts of crushed waste rocks (hereinafter called paste aggregate fill, PAF) for underground stope filling. Different mixture formulations were prepared with three classes of crushed waste rocks (or aggregate) grain size, namely 0/10, 0/15 and 0/20 mm. The amount of crushed waste rocks in the PAF mixtures ranges from 10 to 50% by volume (% v/v) (or 8–45% by mass, %m) of dry mill tailings and crushed waste rocks. The results show that the addition of crushed waste rocks in cemented tailings paste mixtures allows a significant unconfined compressive strength (UCS) development after 28 and 90 days of curing. The highest UCS was obtained from the mixtures containing 50% v/v of crushed waste rocks of class of size 0/15 mm. The PAF mixtures with the coarser crushed waste rocks (class of size of 0/20 mm) exhibit some particles segregation.     

应力路径及初始固结条件对强度的影响

该文主要分析了应力路径以及初始固结条件对固结不排水强度指标的影响，并建立了卸荷状态下强度指标与应力路径及初始固结条件之间关系的理论公式。     

Research on the Mechanical Properties of 3D Printing Polymer Reinforced Cemented Tailings Backfill Under Uniaxial Compression

Geotechnical and Geological Engineering - The brittle damage of the cemented tailings backfill (CTB) seriously threatens the safety of underground workers and equipment. To improve the toughness...     

Influence Mechanism of Mine Pressure on Coal Seam Gas Emission During Mining

Geotechnical and Geological Engineering - Gas is one of the main factors causing coal mine accidents in China. Understanding the mechanism of the influence of mine pressure on coal seam gas...     

Influence of an Inclined Rock Stratum on In-Situ Stress State in an Open-Pit Mine

In-situ stress plays a major role with respect to deformation and stability around underground or surficial excavations located at significant depth. Many sedimentary rock masses are more or less horizontally bedded. However, a possibility exists to have one or few inclined rock strata such as dikes in these horizontally bedded formations. It is important to know how the in situ stress changes from a purely horizontally bedded situation to a horizontally bedded rock mass that contains one or few inclined rock strata. This paper presents such an investigation using the largest open-pit metal mine in China—as a case study. This mine has a bedded rock mass with one steeply inclined rock stratum. For the bedded rock mass, the vertical stress was calculated based on the overburden above each lithology. The available in situ stress measurements conducted at the mine were used to estimate the ratios of horizontal to vertical stress. Numerical modeling was performed for the two scenarios: (a) the horizontally bedded system subjected to both the in situ and boundary stresses and (b) the mine lithological system that includes an inclined stiffer (denser) stratum intruding softer horizontally bedded system subjected to only boundary stresses to investigate the influence of an inclined rock stratum on the computed stress field. Thirty points were selected to compute the stresses on six planes of the inclined rock stratum. Due to the discontinuous nature of the geologic system at the interface between the stiffer inclined stratum and softer horizontally bedded system, one principal stress has become normal to the interface plane and the other two have become parallel to the interface plane with all three being perpendicular to each other. Presence of the stiffer inclined rock stratum has given rise to (a) increase in normal stresses up to about 120 % in the inclined rock stratum and (b) new shear stresses approximately in the range ?10.0 to 15.0 MPa. This means, because most of the rock masses are not purely horizontally bedded, estimation of in situ stress through measurements as well as application of in situ stress in numerical modeling associated with underground or surficial excavations located at significant depth is a difficult exercise. A better way to estimate the in situ stresses for complex geologic systems may be through application of appropriate boundary stresses to the geologic system in a numerical model.     

榆神矿区矿山开发对水环境的影响及防治措施探讨

榆神矿区属我国内陆干旱区,水资源贫乏,生态环境十分脆弱,矿山开发对水环境的影响主要可以归结为地下水位下降、地下水补排平衡状态的破坏和水质污染的问题.针对影响水环境变化的因素提出开展采煤保水研究、调整矿山开发规划、矿水污染治理的措施.     

Determination of the Effective Stress Law for Deformation in Coalbed Methane Reservoirs

Effective stress laws and their application are not new, but are often overlooked or applied inappropriately. The complexity of using a proper effective stress law increases when analyzing stress variation in coal as a result of gas production or mining. In this paper, an effective stress law is derived analytically for coalbed methane reservoirs, combining the concepts of matrix shrinkage/swelling and external stress by including the effect of sorbing gas pressure on the elastic response of the reservoir. The proposed law reduces to that of Terzaghi when the compressibility of bulk material is sufficiently greater than the compressibility of the solid grain, and without the strain associated with matrix shrinkage/swelling effect. Moreover, it is shown that the Biot coefficient (α) can have a value larger than unity for self-swelling/dilation materials, such as coal. The proposed stress–strain relationship was validated using experimental results. Overall, the effective stress law for deformation was extended for sorptive materials, providing a new and unique technique to analyze the elastic behavior of coal by reducing three variables, namely, external stress, pore pressure and matrix shrinkage/swelling along with the associated stress, down to one variable, “effective stress”.     

含盐量对冻土强度的影响特征

Is shown that the durability of frozen salted soil is caused by concentration of porous solution formed during freezing of soil moisture     

应力波在毛洞周围绕射时的波长-洞径比效应

本文用动力有限元数值模拟法研究了应力波在毛洞周围绕射时的波长-洞径比效应。采用了较普遍的三角形脉冲荷载,对七种波长-洞径比进行了计算分析,获得了比较完整的结果.除得到了洞边动应力集中系数随波长-洞径比变化的完整曲线外,还获得了整个应力场的变化情况,特别是洞周围径向和环向拉伸应力的数值及所出现范围的变化规律,并考察了荷载脉冲上升前沿长度 (从零到峰值)所造成的影响.另外,对两种波长的应力波峰值通过毛洞时所产生的动应力分布与相应的静态情况也作了比较.     

平顶山矿区影响煤层气含气量的地质因素研究

通过对研究区煤层气含气量的研究,揭示了影响研究区煤层气含气量的地质因素。沉积因素对煤层气有重要影响：煤层厚度与含气量之间的正相关关系;构造因素对含气量具有控制作用;水文地质因素有利于煤层气的保存。     

应力松弛作用对未固结砂岩等效弹性性质的影响

未固结碎屑砂岩储层是国内外重要的油气储层类型之一,其物理本质是由离散颗粒组成的软凝聚态物质.在地震勘探中通常使用Hertz-Mindlin等效介质模型来计算未固结砂岩的地震弹性特征,但该模型在使用中通常会得到明显偏高的剪切模量值.基于3D离散元技术,对颗粒介质在单轴压缩与纯剪两种过程中的力学响应进行离散元数值模拟,从微...     

不同接触面模型对评估地下结构震害的影响

对土 -结构之间相互脱离、滑移现象提供了一个有效的分析方法。在分析中 ,用二维有限元和无限元耦合对地铁隧道进行动力时程分析。同时 ,在分析中考虑了混凝土材料的塑性。研究比较地铁箱体结构在完全约束模型、经典库仑摩擦模型和 goodman单元三种不同的土 -结构相互作用方式下最大主应力、塑性铰的分布以及土 -结构之间的脱离、滑移程度。     

Sandbox Experimental Study on the Influence of Rock Strength and Gravity on Formation of Thrusts

INTRODUCTIONRock deformation is normally explained by tec-tonic stress as rock deformation results fromthe tec-tonic stress field. The classic tools that explainedfracture mechanisms were the Coulomb shear fracturerule and the Anderson mode derived fromit (Zhu,1999) . More and more studies have shown that it isdifficult to explain rock deformation in a large strainrange using only the Coulomb shear fracture rule( Waltham,2002 ; Gutscher et al .,2001 ; Tikoff andWojtal ,1999) . As a ver…