Maximum Horizontal Movement Research Articles

Optimization of Physical Parameters and Analysis of Rock Movement and Deformation Patterns in Deep Strip Mining

China’s shallow coal resources are gradually diminishing, and deep coal resources have slowly become the main energy source. However, the destruction mechanism and evolution of deep rock formation structure are not clear, which seriously restricts the exploitation and utilization of deep energy. Here, the optimization of the physical parameters and the deformation law of the overlying rock in a deep mine in Shandong Province were studied with an integrated approach including similar simulation, mechanical analysis, numerical simulation, and measurement verification, etc. First, the paper simplified the rock formation and developed a numerical model using the field exploration data; second, we analyzed the mechanical properties of each rock formation, obtaining the key rock formation that affects the surface deformation of the mining area. Furthermore, we tested the physical parameters of rock formation by using the orthogonal test, optimizing the physical parameters of rock formation with the extreme difference, and variance analysis of the orthogonal test results. Then, using FLAC3D, we conducted numerical calculations for strip mining of deep wells with numerous working faces, analyzing the maximum surface subsidence value, the maximum horizontal movement value of ground surface at different mining depths, and the change in the subsidence coefficient. By analyzing the linkage relationship between the surface phenomenon and deep mining, we obtained the optimal mathematical model of the three and the coal seam mining depth, which revealed the linkage law of “deep formation–earth surface”. Finally, the model relationships of the influence boundary value, maximum subsidence value, maximum horizontal movement value, and mining depth for each rock layer were separately established.

Overlying Strata Movement and Mine-Pressure Weakening Law of High-Efficiency Longwall Paste Backfilling of Thick Coal

This work focused on the serious coal compression under buildings, railways, and water bodies in central and eastern China; the wide range of rock formation damage during the collapse mining process; the high pressure of mines; and difficulties in controlling surface subsidence after mining. The E1302 working face of Shanxi Gaohe Energy was taken as the engineering background in the work. The mechanical properties of gangue paste-filling materials were studied through laboratory tests, and the critical conditions for bending and fracture of the coal seam roof were analyzed. Discrete-element numerical simulation software was used to study the fracturing process of the roof, and the reasonable filling rate to ensure roof stability was determined to be 95%. Meanwhile, overlying stratum movement and mine-pressure weakening law were studied through numerical simulations and field measurement. The results showed that fracture development during the mining process of thick-coal paste filling was divided into the advanced development, re-compaction, and steady-state maintenance of fractures. Fractures advanced in a “sail shape” and developed only in the main-roof rock strata after recompaction. The maximum subsidence angle of the working face was 87.13° after mining, with a subsidence factor of 0.034 and a maximum horizontal movement coefficient of 0.71. The advanced stress value was weakened by 40%, and the influenced area was reduced by 13%. Overlying stratum movement was controlled, and mine pressures were significantly weakened. The work can provide a scientific basis for green backfill mining, roadway support design, and backfill mining equipment selection.

D-InSAR Monitoring Method of Mining Subsidence Based on Boltzmann and Its Application in Building Mining Damage Assessment

Monitoring and predicting mining area subsidence caused by coal mining help effectively control geological disasters. Information regarding small surface deformations can be obtained using a differential interferometric synthetic aperture radar (D-InSAR), which exhibits high monitoring accuracy and can cover large areas; thus, D-InSAR are being applied for mining area settlement monitoring. However, mining areas are prone to large gradient deformations in short durations; obtaining information regarding such deformations is outside the scope of D-InSAR monitoring. To adapt to the characteristics of D-InSAR monitoring, this study selected a Boltzmann function model with a slow boundary convergence rate to address the problem of probabilistic integration methods exhibiting a high boundary convergence rate. The three-dimensional surface deformation of the mining area can be accurately obtained. According to the projection relationship between D-InSAR line of sight (LOS) directional deformation, subsidence, and horizontal movement, a D-InSAR monitoring equation for mining subsidence assisted by Boltzmann is derived. This equation is combined with the shuffled frog leaping algorithm (SFLA) to obtain the parameters to be estimated from the equation. The D-InSAR LOS deformation information of the 13121 working face in the Huainan mining area was obtained from July 14 to October 30, 2019. The proposed method was then used to obtain the predicted parameters of the working face under insufficient mining. The predicted parameters of mining subsidence were calculated to obtain the predicted parameters when it was fully mined. Then, the revised parameters were used to predict the subsidence and horizontal movement of the mining area and compared with the actual leveling observations. The results show that the mean square error of predicted subsidence is 97.1 mm, which is about 3.09% of the maximum subsidence value; the mean square error of predicted horizontal movement is 46.1 mm, which is about 4.1% of the maximum horizontal movement value. The predicted results of the aforementioned method were used to analyze the damage to the buildings above the working face and determine the damage level of the buildings to provide a reference for the demolition and maintenance of the Zhaimiao village.

Height of overburden fracture based on key strata theory in longwall face.

Among the three overburden zones (the caving zone, the fracture zone, and the continuous deformation zone) in longwall coal mining, the continuous deformation zone is often considered to be continuous without cracks, so continuum mechanics can be used to calculate the subsidence of overburden strata. Longwall coal mining, however, will induce the generation of wide cracks in the surface and thus may cause the continuous deformation zone to fracture. In this paper, whether there are cracks in the continuous deformation zone as well as the height of overburden fracture in longwall face and the subsidence and deformation of strata of different fracture penetration ratios were studied by means of physical simulation, theoretical analysis and numerical simulation. The results show that: (1) Rock stratum starts to fracture as long as it has slightly subsided for only tens of millimeters, and the height of fracture development is the height of working face overburden. (2) With the increase of fracture penetration ratio, the subsidence of key strata remains basically unchanged; the surface deformation range and the maximum compression deformation decrease, while the maximum horizontal movement and maximum horizontal tensile deformation increase. Therefore, the subsidence of overburden strata which have fractured but have not broken can be calculated through the continuum mechanics method.

Study of the behavior of mechanically stabilized earth (MSE) walls subjected to differential settlements

The limit equilibrium (LE) analysis has been used to design MSE walls. Presumably, the deflection of MSE walls can be limited to an acceptable range by ensuring sufficient factors of safety (FOSs) for both external and internal stabilities. However, unexpected ground movements, such as movements induced by excavations, volume changes of expansive soils, collapse of sinkholes, and consolidations of underlying soils, can induce excessive differential settlements that may influence both the stability and the serviceability of MSE walls. In this study, a numerical model, which was calibrated by triaxial tests and further by a specially-designed MSE wall tests, investigated the behavior of an MSE wall as well as the influence of various factors on the performance of the MSE wall when the wall facing settled relatively to the reinforced zone. The numerical results showed that the differential settlement would cause substantial vertical and horizontal movements for the MSE wall, as well as an increase in lateral earth pressure and geosynthetic reinforcement strain. The maximum horizontal movement and increase of the lateral earth pressure occurred at about 1.0 m above the toe. The differential settlement resulted in a critical plane that coincided with the plane of 45°+ϕ/2. The maximum increase of the strain for each geogrid layer occurred in that plane, and the bottom layer had the greatest strain increase among all layers of reinforcement. The study further indicated that the surcharge, backfill friction angle, tensile stiffness of geogrid, reinforcement length and MSE wall height had noticeable influences on horizontal and vertical movements, and strain in geosynthetics. According to the results, the MSE wall that had a higher factor of safety would have less movements and geosynthetic strain increase. In contrast, only the friction angle, tensile stiffness and MSE wall height showed some degree of influence on the lateral earth pressure due to differential settlements.

The relationship between movement speed and duration during soccer matches.

The relationship between the time duration of movement (t(dur)) and related maximum possible power output has been studied and modeled under many conditions. Inspired by the so-called power profiles known for discontinuous endurance sports like cycling, and the critical power concept of Monod and Scherrer, the aim of this study was to evaluate the numerical characteristics of the function between maximum horizontal movement velocity (HSpeed) and t(dur) in soccer. To evaluate this relationship, GPS data from 38 healthy soccer players and 82 game participations (≥30 min active playtime) were used to select maximum HSpeed for 21 distinct t(dur) values (between 0.3 s and 2,700 s) based on moving medians with an incremental t(dur) window-size. As a result, the relationship between HSpeed and Log(t(dur)) appeared reproducibly as a sigmoidal decay function, and could be fitted to a five-parameter equation with upper and lower asymptotes, and an inflection point, power and decrease rate. Thus, the first three parameters described individual characteristics if evaluated using mixed-model analysis. This study shows for the first time the general numerical relationship between t(dur) and HSpeed in soccer games. In contrast to former descriptions that have evaluated speed against power, HSpeed against t(dur) always yields a sigmoidal shape with a new upper asymptote. The evaluated curve fit potentially describes the maximum moving speed of individual players during the game, and allows for concise interpretations of the functional state of team sports athletes.

Finite Element Analysis of the Movement of the Tie-Back Wall in Alluvial-Silty Soils

Excavations in urban–developed areas were commonly supported by diaphragm walls with internal braces or tieback anchors. There are still required the necessary civil works to serve the demands and also to solve the environmental problems. Wales and cross-lot struts are by far the predominant method for wall support, the large working space inside the excavation provided by a tieback anchor system has a significant construction advantage. This paper aims to evaluate the soil stiffness parameters of the alluvial Taipei soil for tie-back diaphragm wall based on back analysis of case study. The case histories of the Taipei County Administration Centre (TCAC) and NTU Hospital (NTUH) were studied in this paper. The deformation analysis was carried out by available finite element analysis tool using PLAXIS. In the analysis, beam element method together with an elastic perfect plastic soil model was used to design the diaphragm wall and the tieback anchor system. The soil was modelled as Mohr-Coulomb model. According to the basic design, the clay deposits are modelled as undrained behaviour while silty-sand behaves in drained condition. The simulation results show that the maximum horizontal movement occurred at around the bottom of wall. At the final stage of construction, the root mean square deviation (RSMD) between measured and calculated the wall movement was 4% and 7% respectively at TCAC and NTUH sites. It was concluded that tied-back diaphragm wall can be satisfactorily modelled using elasto-plastic Mohr-Coulomb soil model. The predicted soil's modulus of elasticity can be obtained from the SPT-N relationship, for clay deposit layer and for silty-sand deposit.

Comparison between responses of reinforced and unreinforced embankments due to road widening

The objective of this work is to compare the responses of geosynthetically-reinforced embankment and unreinforced embankment due to road widening by using the centrifuge model tests and a two-dimensional (2D) finite element (FE) model. The measured and calculated responses of the embankment and foundation exposed to road widening include the settlement, horizontal displacement, pore water pressure, and shear stresses. It is found that the road widening changed the transverse slope of the original pavement surface resulting from the nonuniform settlements. The maximum horizontal movement is found to be located at the shoulder of the original embankment. Although the difference is small, it is clearly seen that the geosynthetic reinforcement reduces the nonuniform settlements and horizontal movements due to road widening. Thus the reinforcement reduces the potential of pavement cracking and increases the stability of the embankment on soft ground in road widening.

FINITE ELEMENT ANALYSIS OF EMBANKMENTS ON SOFT CLAYS - CASE STUDIES

In order to design structures on soft soils, it is necessary to predict the behavior of the soft soilunder imposed structure load. The high excessive settlements of the soft soil can cause manyproblems for the structures built on the soil like cracking and breakup of pavements, railway,highway embankments, etc...In this work, the finite element method is utilized as a tool for carrying out differentanalyses of embankments on soft ground with different conditions. The computer program CRISP(CRItical State Program) is developed to suit the problem requirements. CRISP uses the finiteelement technique and allows predictions to be made of soil deformations using the critical statetheory.Eight-node isoparametric quadrilateral element has been added to the program. The programwas used to analyze fully coupled (Biot) consolidation of two-dimensional plane strain problems.The finite element predictions of displacements and excess pore water pressures were comparedwith field measurements.It was concluded that the maximum vertical movement occurs below the centerline of theembankment. The settlement decreases slightly as the toe of the embankment is approached anddecreases rapidly as the distance away from the toe increases. Upward movement of the surface farfrom the toe is observed. The maximum horizontal movement occurs near the top boundary. Therate of horizontal movement at the top of the foundation is greater than at the bottom. This behaviormay be due to the flexibility and free movement condition of the vertical boundary in the top half

Ground movement due to longwall mining in high relief areas in New South Wales, Australia

Abstract The theoretical pattern of ground movement observed in flat terrains was modified by surface topography and geological structures. In high relief areas, e.g. creeks and gullies, the observed pattern of movement was asymmetrical about the centre of the extraction panel. The lateral movement of both sides of the valley caused large compressive strains and a hump at the creek bed. The strains were three–four times those normally observed in flat or fairly gentle topographies. The hump was due to the rock mass in the creek bed being pushed up by the lateral forces from the valley sides. A major geological fault caused both sides of the valley to move laterally away from the fault plane. The magnitude of the maximum horizontal movement was as large as 40% of the observed vertical movement. Outside the goaf, the horizontal movements were generally larger than the corresponding vertical movements. However, the horizontal movements outside the goaf appeared to be rigid body type movements with small deformations which may only have insignificant surface consequences.

Palaeoseismologic and geomorphic investigations along the middle portion of the Ovindoli-Pezza Fault (Central Italy)

his paper presents the results of a detailed investigation performed along the central part of the Ovindoli- Pezza Fault with the aim of improving our understanding of the seismic behaviour of this fault within Central Italy seismogenesis. Results of the trenching investigations we performed across the central part of the fault confirm and strengthen the results obtained at other sites located in the northern part. There is clear evidence that the two most recent surface faulting events occurred within the same interval of time at the different trench sites and thus, at least during these two events, the fault was activated for its entire length. The most recent surface faulting event occurred between 860 and 1300 A.D. Geomorphic and microtopographic investigations indicate that although the trace of the fault shows an important bend, the kinematics of the fault seem to be prevalently normal, consistent with the other seismogenic faults that accommodate the NE-SW extension in this part of the Apennines. The maximum horizontal movement derived using geomorphic methods along the central part of the Ovindoli-Pezza Fault did not exceed 30% of the vertical movement. Slip rate and average recurrence interval were obtained using data both from trenching and Late Pleistocene-Holocene geomorphology. Resulting slip rate ranges between 0.7 and 1.2 mm/year whereas the average recurrence time varies between 1000 and 3000 years.

Horizontal and Vertical Movements of Two Expansive Soils in Mississippi

AbstractExpansive soils create severe problems for road construction and maintenance, building foundations, and agricultural and industrial operations. Quantification of soil movement under natural field conditions has received little attention and is not well understood. Horizontal and vertical movements were measured for 20 mo by surveying rods placed at various depths in field plots of Typic Chromuderts and Vertic Hapludalfs of the Mississippi Blackland Prairie. Vertical soil movement was a function of soil depth, soil water content, and rainfall. Greatest vertical soil movement occurred in the upper 50 cm of both soils, with a maximum of 27 mm in the Vertisol and 24 mm in the Alfisol. Soil swelling occurred in winter and shrinking occurred in late spring and summer. Horizontal soil movement was not related to soil depth, but was related to soil water content and rainfall. Maximum horizontal movement was 36 mm in the Vertisol and 20 mm in the Alfisol. Horizontal and vertical movements in expansive soils are reversible, dynamic processes under natural field conditions. Horizontal movement appears more dynamic than vertical movement, and it reflects short‐term response to precipitation events followed by drier periods. Vertical movement reflects long‐term precipitation‐evapotranspiration distribution and is probably related to movement along master slickensides.