Great damage has been done to the earth’s surface as a result of mining. An important concern is whether power-law occurrence rate–scale statistics that are used to study many natural hazards, such as landslides and volcanic eruptions, can be used to study mine subsidence. The ground subsidence in Longshou Mine, China, is analysed using data from a 12·5-year-long (May 2003–November 2015) continuous field investigation with 488 global positioning system monitoring points. The results of occurrence rate–scale statistical analysis fit well with a power-law relationship – that is, M (S) ∼ S −β . The subsidence power-law parameter varies between 1·06 and 2·18 for settlement between 2 and 257 mm. Additionally, the uplift parameter varies between 1·01 and 2·45 for uplift between 1 and 123 mm, regardless of changes in the goaf geometry and rock mass integrity. The power-law model of the results of the occurrence rate–scale statistical analysis is established, and the underlying controls of the power laws, the self-organised criticality of the subsidence system and the application of power laws are discussed. The spatial self-similarity and long-range spatial correlations of mine subsidence are expressed by significant power-law dependencies, which suggests that both large- and small-scale mine subsidence may follow the same physical and mechanical principles.

Several studies have simulated and studied the phenomenon of toppling failure caused by open-pit excavation. However, these studies do not involve or neglect the interpretation of some special geometric characteristics and laws of this deformation. Only by understanding the subtle geometric characteristics and geometric laws of slope toppling failure, can we understand the conditions, processes and mechanisms of such deformation. In this study, a soft material, small model, deformable element method is successfully used to simulate the phenomenon of the bending each layer element from the lower part of the slope to the upper, with the dislocation distance (scraps on the slope) being bigger. This method overcomes the shortcoming of the rigid body element that traditional methods cannot simulate. Finally, the conditions and mechanism of this phenomenon are further analysed and explained by structural unit of inclined composite cantilever and elastic theory. Under the action of the body force component f(x) which is parallel to the longitudinal direction of the cantilever, the geometric characteristics of the single cantilever in the composite cantilever are changed such that the upper part of it is narrowed and the lower part of it is widened. Under the action of the body force component f(y) which is perpendicular to the longitudinal direction of the cantilever, the cantilever is bent. Under the action of these two body force components, the composite cantilever is bent as a whole after open-pit excavation. Because of the change in the geometric shape of the cantilever, any single cantilever has a larger deflection than the other single cantilever below it; that is, greater the deflection of each cantilever along the slope upwards, greater is the curvature of the corresponding point. Finally from the lower part of the slope to the upper, the scraps on the slope are bigger.

Mine subsidence is a regional geological hazard in China. To evaluate whether a power law describes the frequency–size statistics of mine subsidence, as for earthquakes and floods, we studied the frequency–size statistics of mine subsidence at three metal mines in China (Jinchuan Nickel Mine, Sanshandao Gold Mine, and Jingerquan Nickel Mine). Data sets for these mines consisted of 1088, 345, and 101 Global Positioning System (GPS) monitoring points, covering monitoring periods of 14.5, 4, and 3.5 years, respectively. Although these mines had different geological and hydrological settings, mining methods, and stress fields, their noncumulative frequency–size distributions for subsidence and uplift events can be described using power laws. The subsidence power-law exponent for these three mines ranged from 1.20 to 1.67, 1.49 to 1.94, and 1.01 to 1.17, with mean values of 1.46, 1.76, and 1.09, respectively. The power-law scaling for each mine was valid over the range from 2 to 455 mm, 2 to 566 mm, and 2 to 277 mm, respectively; scaling was positively correlated with the power-law exponent. The frequency–size statistics for subsidence events having different time scales showed an identical power-law dependence. The power-law behavior of uplift events was similar to subsidence events. This power-law behavior, its underlying mechanisms, factors influencing the power-law exponent, and the threshold between normal and extreme subsidence events are discussed herein. We conclude that the power-law distribution of mine subsidence events reflects the scale invariance of the subsidence system. This has important practical applications for subsidence hazard assessment and subsidence event prediction.

喷气锥(碟)是五大连池世界地质公园内重点保护的熔岩地貌,它们是熔岩喷发冷却后形成的.目前,许多喷气锥(碟)表壳上分布有裂隙.这些裂隙造成了喷气锥(碟)的破坏.本文根据喷气锥(碟)的形成过程,分析了熔岩的温度变化.建立喷气锥(碟)的三维模型,通过数值计算得到熔岩降温后的温度应力分布.在此基础上,运用断裂力学理论分析喷气锥(碟)上裂隙的形态及分布特征.研究表明:熔岩喷发冷却形成喷气锥(碟)时会产生温度应力,并且最大主拉应力迹线呈环状分布.该温度应力作用下形成的裂隙具有竖直、相互平行、近似等距、由表及里等特征.故此认为喷气锥(碟)竖直状裂隙为熔岩冷却过程中产生的原生裂隙.本文还分析了喷气锥(碟)上裂隙尖端钝化现象以及裂隙密度差异现象的原因.

This paper is based on the observation and the analysis of the geological phenomena of the rock mass in engineering states.It has studied and summarized some results of physical and numerical models and developed the 12 kinds of qualitative effects of the discontinuities on the mechanical behavior and actions,and then explained and discussed them respectively.

Laboratory simulation experiment is an important method for studying roadway deformation condition and mechanism.Based on the theory of solidification pressure,we built a vertical experimental model used by low strength material.This model,which initial strain energy equaled zero,simulated the solidification pressure.And this model made up for the deficiency of displacement field of horizontal solidification method.According to similarity theory,the material is desirable.In solidification process,this experimental model simulated physical and mechanical property in different depth.The simulated object was ore-body in 14-exploration line used two-sublevel mining under self-weight stress.Experiment results matched numerical simulation.Roadway deformation mechanism has been analyzed based on experiment results and numerical simulation.

Based on GPS monitoring data, the movement and deformation rules of surrounding rock of open pit in the Longshou Mine of Jinchuan Company have been analyzed. The monitoring results show that underground mining has caused rock mass movement and large-range deformation, with two subsiding troughs separated by a central uplifting zone formed on the surface.The maximum settlement of the hang-ing wall sink area and footwall sink area are 767 mm and 1 078 mm respectively as well as the maxi-mum uplift amount of the rising area in the open pit bottom are 648 mm. And physical simulation ex-periment has been conducted to simulate the movement and deformation process of surrounding rock mass of open pit from open-pit mining to underground mining. The experimental results are consistent with the monitoring results.And the uplift phenomenon of the bottom of open pit in both open-pit mining and underground mining stages has been clearly observed.Moreover, the uplifting mechanism of the open pit bottom after the transformation from open-pit mining to underground mining has been theoretically analyzed, from which a conclusion has been drawn that the earlier movement and defor-mation of slope rock mass caused by open-pit mining would be activated again by the underground mining activities. And when the uplifting amount of the open pit bottom caused by the activation is larger than its settlement caused by underground mining, the open pit bottom will rise because of the extrusion.

Backfill mining could induce noticeable ground movement when it is applied to be mining of large-scale metal orebody.The paper aims to grasp the deformation mechanism of the surface movement and destruction in Jinchuan Nickel Mine Area caused by underground mining.It uses the GPS monitoring system that is built covering the whole area.The range and the characteristics of the surface movement area are quantified using the data from the site investigation and monitoring.The condition and law that are related to the rock mass movement and deformation are analyzed.Besides,a number of predictive points of view are made.Consequently,this paper can be used as a reference for technicians and researchers when facing the mines that have a similar engineering and rock mechanics conditions as this mine area.

Based on the derived general expression for the displacement of a point in a surrounding rock mass caused by excavating under the action of self-weight volume forces from similarity theory,by means of dimensional analysis,and comparing with the results of the numeral simulations,an empirical formula of parametric ratios expressed in geometric,physical and mechanical parameters is proposed,which shows the quantitative relationships between the displacement of a point in a surrounding rock mass caused by excavating in a linearly elastic semi-infinite body and any one of the parameters,including the specific weight of a rock material,the modulus of elasticity for the material,the size of a cross section of a tunnel and the distance from the earth surface to the center of the cross section.And the conditions under which the formula holds and its applications are discussed,and the methods for use it are given.A main conclusion says that,in the case that the geometric similarity law is not completely satisfied,under the given other conditions the displacement of a point in the rock mass surrounding a tunnel is proportional to the product of the distance from the center of cross section to the earth surface and the size of the cross section and is independent of the shape of the cross section.

Fault reactivation is a common and important engineering geological phenomenon. However, the surface expressions and intensity of reactivated faults adjacent to open-pit mines can vary with the engineering geological conditions. In this study, several types of fault reactivation were identified and studied based on geological investigations conducted at an open-pit mine in China. Based on these studies, a comparatively simple physical simulation method was employed to analyze the causes of fault reactivation under self-weight stress conditions. For a steeply dipping fault which outcrops in the tensile zone of an excavated slope, the tensile stresses generated perpendicular to the fault surface usually result in normal fault-style movement, regardless of the orientation of the fault. For a steeply dipping fault which outcrops in the compressional zone of an excavated slope, an outward-dipping fault usually generates reverse fault-style movement, whereas an inward-dipping fault usually generates normal fault-style movement. For a low-angled and inward-dipping fault, reverse fault-style movement could be induced because of the self-weight body forces of the hanging wall slope. Flexural toppling failure of an excavated slope was simulated by a series of inward-dipping faults. The simulated scarp sizes and deflections of the reactivated faults increased along the excavated slope.

► The increased tensile stresses and the decreased and shear strength of the fault plane caused the occurrence of the fault reactivation. ► The shear displacements on the fault plane decrease with the depth of the fault, ending off downward to the end of the reactivated section. ► Under the assumption of linear elasticity , the ratio of the scarp lengths in any two stages is equal to the squared ratio of the reactivated lengths. ► The preliminary research are verified and discussed based on physical experiments.

The vertical shaft plays an important role in underground tunnel mining mines. However, few attempts have been done on the deformation and failure mechanics of shafts suffering from rock mass movement in metallic mines undergoing mining activities. Numerical simulation methods and geomechanical methods are applied in the study of deformation, failure and stability of the line No. 14 ventilating shaft in Jinchuan No. 2 Mine under the conditions of different kinds of mining design. The results show that the shaft is seated in the scope of the depression induced by the underground mining, and the displacement of rock mass keeps increasing. Therefore the underground mining is the main factor for the safety and stability of the shaft. Moreover, whether mining of the rich ore body or combined mining of the rich ore body and lean ore body, the distribution regularities of displacement and stress of the shaft are similar, and the section of the faults is still the vulnerable zone of the shaft in which it influences the size and distribution of the displacement and stress greatly. Consequently, it is the faults which cross the shaft and lead to reactivation due to underground mining are the trigger factor, and the rock mass movement, rupture and fall are the primary form of the shaft deformation and failure mechanism, and this kind of fault effects will be aroused again in the future under the present circumstances of mining.

Based on a series of experiments in numerical simulation, the model boundary conditions for in situ stress field inversion and excavation are discussed. Study results indicate that roller boundary conditions are reasonable for the in situ stress field inversion before excavation simulation, while, as a closed system, changing the roller boundary conditions to fixed boundary conditions in the subsequent excavation is optimal when the dimensions of the model borders are greater enough than the zone of influence of the excavation. As a case study, a comparative study of the mining-induced ground movement in a steeply dipping mine is carried out in two different stress fields. The results show that the mining-induced ground movement in the high-level tectonic stress field clearly differs from that in the ideal self-weight stress field. Because of the steep occurrence and large thickness of the ore body, the mining-induced ground subsidence exhibits different characteristics at different mining stages in the practical tectonic environment. Further studies elucidate the causes of these differences and clarify the effects of high-level tectonic stresses on rock mass movement and deformation. Finally, based on GPS monitoring results on the ground surface, the current ground subsidence is evaluated and its development trend is predicted.

We derived the relation between surrounding rock displacement of shaft prototype and that of model on its body force condition of self-weight based on the similarity theory. According to the results of discussion of the equation, we derived dimensional expression of surrounding rock displacement of shaft. And we analyzed the relation between displacement and diameter(d) and cross-sectional depth(h) by numerical methods.

To enhance understanding of the mechanism of slope stability,this paper investigates some of the mechanical characteristics of the slope mass only subjected to its self-weight body force.It uses the FLAC numerical simulation software and similarity law.It studies the relationships between them and the related physical or mechanical parameters.At the ground surface,the principal stresses must be either parallel or normal to the topography in the absence of surface loads.As the depth increases,the principal stress directions approach either vertical or horizontal.There are tensile stress and compressive stress at the slope surface.And the tensile stress in the toe of a slope is also very high.These are some general characteristics for the distribution of stresses in a slope,shown both in this paper or some other articles.This paper emphasizes that when the angle of a slope increases linearly,the changing velocity of maximum tensile stress on the top of the slope behaves fastly,then slowly and then fastly.The tensile stress decreases linearly with the depth on a line from the top of the slope downward vertically to the inner of the slope.Under the condition of small deformation,the stress field does not depend on the Young's modulus value.When meeting the similarity law,the magnitudes of displacement ratios at the corresponding points are square times of their sizes' ratios of a slope.This paper complements to existing knowledge.It further offers a base for further studies on more complicated slopes.It is meaningful in both theory and practice.

Because of the suspects on the theory of unloading rebound,three experiments are performed;and it is noticed that some interesting phenomena that are not understood previously are discovered.Based on the observed phenomena,a hypothesis on the original state of strain energy in a geological body after diagenesis,which is different from present theories,is advanced.On the hypothesis,there is no strain energy in a geological body after diagenesis unless other external forces act on it.This new hypothesis gives a possible reason for the surface subsidence around an open pit.The constitutive equation by which the behavior of the cast material body is characterized in one of the three experiments is established.A new computer program is developed;and it is employed in trial examples of simulation of displacement fields from excavation;and satisfactory results are obtained.The achieved results agree well with in-situ measurements in direction of displacement vectors as well as in relative magnitude.The question when a geological body after tectonic movement(s)is excavated,is discussed,whether or not its original state of strain energy will cause up-rebound strain.

1 前言 大量的现场位移监测资料表明, 在边坡、露天矿与基坑的开挖中, 相当多的情况是开挖后位移方向指向坑内, 即坡体的较上部分以及地表的垂直位移分量向下, 水平分量指向采坑.

Overcoming the model defects due to the simplification occuring in slope stability analysis, this is a study of the thermodynamics of nonlinear dissipative solid materials with mass moving resulted from the transport of its liquid and gas. After obtaining the system distinct postulates of specific entropy with energy rate equilibrium, and based on the assumption that the fluid is incompressible and gas is perfect, we find the general restrictions in four different affinity conjugation space at finite deformation which the Clausius-Duhem inequality places on response to these functions. The exhibition and difference between these restriction equations and the internal state variables established by Coleman and Gurtin which is the essential principles of thermoplasticity are also discussed.

The results of the experiment proved the first author's supposition that when a body changes from the liquid to the slolid state there is a quontity difference of a regularity in the mechanical properties in their different depthes of it because the solidification pressure gradient is not equal to zero; and there is no elastic potential energy to change from others to in the body, in otherwords, the density of the strain energy equals zero anywhere in the body, and therefore no relaxed-rebound phenomenon to occur in any lower part of the body no matter how cut off the upper part. The material used in the experiment is a soft elastic material. It is made from fusing gelatine, glycerin and water in the ratio of 3 to 5 to 12, and is of the phatoelastic property. And when a body of the material acted on by its self-weight volume force, its deformation will be observed easily with the naked eye alone. The repeated experiments show that the cast mould body of the soft elastic material has a property of 'memory' of its solidifacation confining pressures from the self-weight volume force of the body (from the hiquid to the solid state) in a long vertical cast tube. If a confining pressure p acting on a small unit of the material is more than its salidification cofining pressure p(s), the volume of the unit will be reduced; if 0≤p≤p(s), the valume will not change, and if p<0, by the first author's inference, the volume will expand. According to the experimental results, the first author proposed 'materials haveing a proerty of 'memory' of their solidification confining pressures'. And according to the characteristic of the displacement field caused by the open excavation, the fiest author inferred that the rock in a rock-forming geological body can also be of the property of 'memory' of its rock-forming confining pressure. It is easy for us to determine the confining pressure that acts on a sample of rock and makes its volume reduse using hydraulic pressure method, so it is possible to determine rock-forming pressure p(s) of a sample of rock.

Considering the influence of self-weight volume force during phase transition of deformation behaviour of rock mass after its solidification or consolidation, the authors applied vertical casting instead of the horizontal to cast a model slab memorizing solidification pressures in the different depths, did an experiment to simulate the slope deformation caused by open pit excavtion and obtained a good and different result from what is obtained with the traditional methods.