Law Of Displacement Research Articles

Development of a field condition monitoring system in high speed railway turnout

To study the law of wheel set lateral displacement (WSLD), a test system is equipped with lasers for the switch and crossing panel instrumentation. Some measurements including passing a train with different speeds of 250, 270, 290 and 310 km/h were performed to prove the feasibility of this arrangement of sensors, establish the relation between measured lateral displacement and frequency in the switch and crossing panels and specify the critical wheel set. The results determine the critical spots in the switch and crossing panels. The lateral dominant frequency ranges of the wheel set are 50 and 200 Hz at the switch panel and 50 and 300 Hz at the crossing panel while the train is passing. Moreover, the first wheel set should be considered a critical one for the switch panel at all speeds and the last wheel set in the crossing panel with a speed less than 290 km/h.

Stability evaluation of flat large-span cavern in jointed rock mass

The excavation of the rock mass will have a great influence on the characteristics of the caverns under extremely bad geological conditions. According to the characteristics of the engineering geology, several groups of the caverns are designed to be excavated in the rock mass with three sets of through joints. Based on the summary of the failure mechanism and the failure pattern, the classification method of the failure modes is done for the flat large-span underground cavern with three sets of through joints. The classification method takes into account the control factors of the surrounding rock instability, failure mechanism, distribution of the disturbed zone, and characteristics of the rock weakness, etc. The failure modes of the flat large-span caverns contain six types: the relatively stable, the partial area falling, and the partial collapse of vault, the zigzag failure of rock stratum, the V-shaped failure, and the large-scale collapse. The change law of the vertical stress is first increasing and then decreasing for the surrounding rock in the disturbed zone. The horizontal stress shows an exponential change trend with an increase in the distance from the vault. Influenced by the failure degree of the caverns, the change law of the vertical displacement for the vault can be divided into two types. The horizontal displacement decreases with an increase in the distance from the sidewall, and there is an exponential relationship between them.

Study on the shear movement law of overlying strata by slice mining

AbstractBased on the analysis of shear movement characteristics of overlying strata under mining effect, a quantitative calculation model for shear displacement in the along‐strike and down‐dip directions of the overlying strata is established. The shear displacement at any point on the interface of overlying strata in composite rock beam under slice mining is analyzed. The evolution law of shear displacement and deformation of the overlying strata with the advancement of working face was inverted by physical simulation test. The results show that the shear movement of the overlying strata is characterized by a repeated pattern of "increase → decrease →increase → decrease.” The shear displacement of the overlying strata increases gradually after slice mining. The shear displacement of the overlying strata is in the shape of “W” after the lower seam mining, and the maximum shear displacement of the overlying strata by the lower seam mining is 1.67 times of that of the overlying strata after the upper seam mining. Field test of shear movement of the overlying strata was conducted on the panel 4308 of Chengzhuang coal mine. The results show that the shear displacement of the overlying strata above the coal seam increases with the burial depth. And the shear displacement of the overlying strata movement after mining has "time‐delay" effect. The larger the depth of the measuring point is, the larger value of the along‐strike shear displacement is. The breakage of the key strata of the overlying strata will cause the shear displacement of the overlying strata to increase rapidly. And there is a demarcation depth (127.98 m) for the shear displacement of the overlying strata. The shear movement of the overlying strata above the dividing point is not obvious, while the shear movement of the overlying strata below the dividing point is in the shape of "S" (amplitude of 50 mm). When the working face advanced beyond the test well, the overlying strata would experience multiple shear movement. When the working face advanced 34‐100 m ahead of the surface test well, the overlying strata experienced the most severe shear displacement. When the working face advanced to 74 m away from the surface test well, the shear displacement of the overlying strata between 10# (depth of 192.01 m) and 16# (depth of 300.07 m) is larger than that at the upper position, and down‐dip shear displacement is the most severe(about 315 mm). The shear displacement of the overlying strata is coincident with the along‐strike shear displacement, and the down‐dip shear displacement is smaller than the along‐strike shear displacement. This research provides theoretical guidance for the design of shale gas or coalbed methane surface wells and coal mine shaft under slice mining.

Analysis on Deformation and Stress Characteristics of a Multibraced Pit‐in‐Pit Excavation in a Subway Transfer Station

As an important part of subway transfer station construction, pit‐in‐pit (PIP) excavation has always been a key object of monitoring and control. In this study, taking the PIP excavation project of Hefei metro line 4 and line 7 transfer station as the background, combined with on‐site monitoring and numerical simulation, the variation law of lateral wall displacement, ground surface settlement, and strut force during the PIP excavation were analyzed. The results showed that the maximum lateral deformation of the pile caused by the excavation of the external pit accounted for 80%–90% of the total deformation and the surface settlement accounted for 70% of the total settlement. The excavation of the inner pit only made the maximum lateral wall displacement of the outer pit and the surface settlement behind the wall increase slightly, the growth rate tended to zero, and the maximum lateral deformation depth was all above the excavation surface, which indicated that, for this project, the inner excavation had little effect on the outer pit retaining structure. In addition, the increased exposure time of the soil at the bottom of the pit and the presence of the corner effect will cause the further development of the structure displacement and the surface settlement. Based on strut force measurements, using the tributary area load distribution procedure, it was obtained that 0.3γHe was used as the upper limit index of strut force in the region, where γ is the weight of the soil and He is the excavation depth of the foundation pit. The research conclusions were helpful for the construction and sustainable development of the PIP project.

Experiment Investigation on Stress Characteristics of Grouting Microsteel Pipe Piles with Cement‐Soil Wall

Microsteel pipe piles are widely used in excavation support owing to their excellent bearing capacity, flexural rigidity, construction speed, and adaptability. In this study based on a project in soil‐rock layers in Qingdao, China, a new type of support combining microsteel pipe piles mounted in cement‐soil piles and anchors was adopted and studied. The inner force change laws and bearing capacity of microsteel pipe piles were discussed through in situ stress measurement and laboratory antibending tests on three microsteel pipe piles. It was found that the bending moment of the piles gradually increased with the foundation excavation and maximized at the pile head. The bending moment was larger at the upper and smaller at the lower part along the depth direction, indicating it is reasonable to design and calculate microsteel pipe piles by the pile‐anchor system. The variation law of the foundation pit displacement with the excavation depth was monitored. The horizontal displacement of the foundation pit is the maximum at the base top, which is 6.5 mm. The flexural strength of the miniature steel tube pile after grouting is 40% higher than that of the miniature steel tube pile without grouting. It was indicated that the grouting microsteel pipe piles could be implanted in cement‐soil piles, which improved the flexural rigidity of cement‐soil piles and limited the deformation of foundation pits. This study provides reference for the design and construction of soil‐rock foundation pit supporting projects. At the same time, it provides reference for the application of miniature steel pipe piles in other fields.

Semianalytical Solution for Large Deformation of Salt Cavern with Strain‐Softening Behavior

A semianalytical solution of stress and displacement in the strain‐softening and plastic flow zones of a salt cavern is presented. The solution is derived by adopting the large deformation theory, considering the nonlinear Hoek–Brown (H‐B) strength criterion. The Romberg method is used to carry out numerical calculation, and then, the large deformation law of displacement is analyzed. The results are compared with those obtained by former numerical methods, and the solutions are validated. The results indicate that the displacement of the plastic zone decreases with the increase in distance away from the salt cavern. Similarly, it decreases with an increase in the geological strength index or running pressure, with the running pressure having a more significant effect on the displacement. It increases with the dilation angle, and the impact degree gradually increases. Compared with the softening parameter, h, of the plastic zone, the flow parameter, f, has little impact on the displacement. The displacement of the plastic zone obviously increased when considering the strain‐softening of salt rock. When considering the shear dilation and softening behaviors of salt rock, the analytical solution obtained by employing the experiential regression Hoek–Brown (H‐B) criterion, which considers many factors such as the structural characteristics of the salt formation and the rock mass quality, is safer and closer to the actual situation. This study can provide reference for many applications, including but not confined to analyzing the deformation of the surrounding rock of an underground salt cavern storage facility during construction.

The determination of the rate of heat release in the diesel cylinder taking into account the change in the composition of the working substance

The thermodynamic efficiency of the cycle of the internal combustion engine and its efficiency are related to the law of supply of heat to the working fluid. The characteristics of heat release allow us to evaluate and improve the combustion process from the point of view of the thermodynamic efficiency of the cycle, from thermodynamic positions. To optimize the combustion process in compression-ignition engines, including when working on unconventional fuels, it is necessary to develop an algorithm for determining the rate of heat release, taking into account the current composition of the working fluid, since when working on fuels with a changed chemical composition, the ratio of gases in the combustion products can significantly change. The type of heat dissipation characteristic is determined by the regularities of the combustion of fuel in the cylinder e and the law of displacement of the piston and depends, inter alia, on the composition of the working fluid, which continuously changes during combustion of diesel fuel, increasing volume and mass. Existing methods for calculating the heat dissipation characteristics consider a working body consisting of two components - a fresh charge and combustion products. Such an approach reduces the accuracy of calculations when determining the heat input from the diesel fuel indicator chart operating on fuels with modified chemical composition or on non-traditional fuels, since it does not take into account the change in the heat capacity and internal energy of the combustion products. In this article, a mathematical model to compute the heat dissipation in the cylinder of a diesel engine when operating on diesel fuel for the changes in the working fluid composition. The presented results of calculations for a diesel engine of 2CH10.5/12.0 when operating on diesel fuel at the nominal operating mode correspond to the results of the determination of the integral and differential heat dissipation rate obtained by the well known CNIDI method.

Wind-Load Response and Evacuation Efficiency Analysis of Marine Evacuation Inflatable Slide

Flexible inflatable membrane structure has the characteristics of light weight, large span, and small stiffness, and it is very sensitive to wind load. Aiming at the dynamic response of marine evacuation inflatable slides under complex and changeable wind loads at sea, the response law of the inflatable slide under different wind directions, wind speeds, and internal pressure conditions is studied by using fluid–solid coupling theory. The most dangerous conditions of evacuation system installation and the ideal internal pressure of the inflatable slide meeting the stability requirements are deduced. The LS-DYNA module is used to simulate the inflation process of the slide. The evacuation sliding is rationally simplified. By changing the inflatable internal pressure of the slide, the variation law of displacement, deformation, and sliding speed of the slide is obtained, and the optimal inflation internal pressure satisfying the evacuation efficiency requirement is obtained. The results show that the inflow wind direction angle of 30° is the most dangerous condition for slideway installation, and the internal pressure of 4000 Pa is the ideal internal pressure to meet the double standards of stability and evacuation efficiency. The numerical results obtained are valuable for analyzing wind resistance of offshore inflatable membrane structures and their practical design and application in evacuation systems.

Design and construction monitoring and deformation analysis of super-large deep foundation pit

Using the large and deep foundation pit of Metro Line 1 of Jinan west railway station as an example, this paper elaborated the design scheme of its retaining structure, formulated a monitoring scheme for foundation pit. In addition, through the real-time on-scene monitoring of horizontal displacement of pile top and pile body, and the monitoring data, we found the law of displacement of deep foundation pit supporting structure. The maximum horizontal displacement of pile body moves down gradually with the advancement of excavation support and the main construction. The maximum displacement occurs around 0.684H. This study has implications for similar engineering geological conditions of foundation pit supporting structure.

Study on Size Design of Shaft Protection Rock/Coal Pillars in Thick Soil and Thin Rock Strata

To prevent serious shaft deflection disasters under asymmetric mining conditions, it is urgent to solve the problem of designing shaft protection rock pillar (SPRP) sizes in thick soil and thin rock strata. In this paper, based on the parallel mining model and the perpendicular mining model, a dynamic prediction model that can describe the horizontal movement of the shaft was established by the probability integration method and the Knothe time function. Next, according to the measured data of the shaft deflection in the Guotun Coal Mine, a back analysis was used to calculate the prediction parameters that were suitable for the deep soil strata. Based on the mining model, the variation law of the horizontal deflection displacement of the shaft and SPRP size was obtained. The results showed that the final displacements of the shaft under the two ideal mining models were equal, while the parallel mining model was superior to the perpendicular mining model at the initial stage of mining. The horizontal displacement of the shaft head had a nonlinear negative correlation with the SPRP, and the SPRP size in thick soil and thin rock strata calculated by the parallel mining model was more reasonable. For the Guotun Coal Mine, when the soil movement angle was 57.8% of the actual value, the horizontal displacement of the main shaft head was reduced by 87%. The results have important theoretical and practical value in preventing shaft deflection in thick soil and thin rock strata.

Calculation and Analysis of Mechanical Characteristics of Transformer Windings Under Short-Circuit Condition

Accurate calculation of short-circuit (SC) dynamic characteristics of power transformer windings is of great significance to the safety of transformers. A 110 kV power transformer model is established, and SC electromagnetic characteristics and dynamic characteristics of the transformer windings are obtained through magnetic-structural coupling analysis by the finite-element method, considering the nonlinear mechanical characteristics of spacers. The distribution of leakage magnetic field and electromagnetic force (EF) and dynamic stress and displacement of windings are calculated due to SC fault. The SC EF of windings decreases exponentially with time. The axial EF of the disks at both ends of the winding is larger, while the radial EF is smaller, compared with that of central disks. The variation law of winding stress and displacement is similar to dynamic EF. The stress and displacement at both ends of the winding are larger while that in the middle part is smaller. The maximum stress and displacement of the end of windings are nearly 60% and 90% higher than that of the middle part, respectively. The axial displacement is the major part of the total displacement. The analysis method can provide a reference for checking the SC strength of the transformer.

The Law (and Politics) of Forced Displacement: Toward a History of the Present

It is a tremendous honor being here today and participating in this esteemed panel on the “Law (and Politics) of Displacement,” which Jill Goldenziel has organized. I would like to share some research Umut Özsu and I are working on. This is a work in progress, but I still think its outlines are worth discussion, by way of historical background. I hope the project also demonstrates quite well why several of us at the International Migration Law Interest Group at the American Society of International Law have been thinking that migration should become more central to the discipline of international law; as central, say, as international humanitarian law.

Remarks by Daniel Sullivan

Today, the world is facing the highest numbers of internally displaced persons and refugees since at least World War II. Addressing this crisis involves several challenges regarding the law and politics of displacement. To see how this plays out, it is helpful to zero in on a particular case. The case of the Rohingya minority from Myanmar who have been pushed out into Bangladesh is a particularly acute case, one involving atrocity crimes and ethnic cleansing.

Mechanical Behavior of Supporting Structure of Rectangular Deep Ventilation Shaft in Rail Transit

In order to analyze the mechanical behavior of surrounding rock and initial support during shaft excavation and support process, reveal the law of stratum displacement, the stress characteristics of surrounding rock and the internal force of supporting structure during construction, this paper establishes a three-dimensional finite element numerical model relying on the construction process of a ventilation shaft in Chongqing Rail Transit. The results show that the stress of shotcrete, the bending moment of supporting structure, the axial force of bolt and the axial force of I-beam are all within the allowable range. The "S" shape bending occurs in the range of 60m~70m for the axial force of bolt and cross brace I-beam. According to the results of model test, there is inflection point in the pressure distribution of rectangular deep ventilation shaft in rail transit, which provides a basis for the support design of deep ventilation shaft.

Research on Deformation Characteristics of Foundation Pit Support Structure

Based on the theory of Bolton system stiffness, the factors of foundation pit excavation in Changsha area are analyzed, and an empirical formula is proposed. Taking Changsha Metro Line 3 as the background, Finite difference software Flac3D is adopted to simulate the excavation and analyze the law of horizontal displacement, the relationship between the system stiffness and the lateral displacement of the retaining structure is discussed. The results show that: 1) With the increase of the excavation depth of the foundation pit, the horizontal displacement of the l retaining structure is small at both ends, and the middle is large, showing a “bow” type; 2) Based on the data of foundation pit excavation of six stations in Changsha, the empirical formula for predicting the lateral displacement of retaining structure is given.

Geomechanical Model Test and Energy Mechanism Analysis of Zonal Disintegration in Deep Surrounding Rock

With the decreasing of shallow resources, underground roadways of resources exploitation have reached into deep rock mass with high geostress. A series of new failure phenomena such as zonal disintegration phenomenon were discovered in deep surrounding rock, which is completely different from shallow caverns. To reveal the formation mechanism of zonal disintegration, the geomechanical model test and energy mechanism analysis of zonal disintegration were carried out respectively. Taking the deep roadway of Dingji coal mine in China’s Huainan coal mine as engineering background, a 3D geomechanical model test was carried out relying on the high stress 3D loading test system. The zonal disintegration phenomenon was observed, and the oscillation law of displacement was measured. Based on the strain gradient theory and continuum damage mechanics, the elastoplastic damage model was established. An energy failure criterion was proposed by principle of energy dissipation and release. The ODE45 function in Matlab software was used to solve the displacements and stresses of excavated model roadway. The analytical solutions the and the geomechanical model test were basically consistent. The applicability of theoretical model and energy failure criterion were confirmed to explain the mechanism of zonal disintegration and it can be used to provide theoretical support for the failure and supporting design of surrounding rock in deep underground engineering.

Multidisciplinary design optimization of the belt drive system considering both structure and vibration characteristics based on improved genetic algorithm

The dynamic performance of a belt drive system is composed of many factors, such as the efficiency, the vibration, and the optimal parameters. The conventional design only considers the basic performance of the belt drive system, while ignoring its overall performance. To address all these challenges, the study on vibration characteristics and optimization strategies could be a feasible way. This paper proposes a new optimization strategy and takes a belt drive design optimization as a case study based on the multidisciplinary design optimization (MDO). The MDO of the belt drive system is established and the corresponding sub-systems are analyzed. The multidisciplinary optimization is performed by using an improved genetic algorithm. Based on the optimal results obtained from the MDO, the three-dimension (3D) model of the belt drive system is established for dynamics simulation by virtual prototyping. From the comparison of the results with respect to different velocities and loads, the MDO method can effectively reduce the transverse vibration amplitude. The law of the vibration displacement, the vibration frequency, and the influence of velocities on the transverse vibrations has been obtained. Results show that the MDO method is of great help to obtain the optimal structural parameters. Furthermore, the kinematics principle of the belt drive has been obtained. The belt drive design case indicates that the proposed method in this paper can also be used to solve other engineering optimization problems efficiently.

Research on Formation Process of Zonal Disintegration in Deep Rock Mass Based on Field Monitoring and Geomechanical Model Test

The zonal disintegration phenomena in deep rock mass will appear with the increase of underground engineering depth which is widely different from shallow cavern. In order to reveal the formation process and production mechanism of zonal disintegration, the field monitoring is carried out in the deep tunnel of China’s Huainan mining area. With the help of borehole television, the zonal disintegration is observed which is alternation phenomenon of the rupture zone and non-rupture zone. At the same time, using the multi-point displacement meter, the whole process change law of the deep displacement in surrounding rock is tested. Taking the field monitoring deep tunnel as engineering background, the 3D geomechanical model test is carried out based on the high stress 3D loading test system. The typical zonal disintegration phenomenon is observed, and the whole process change law of displacement and strain is measured. Based on comprehensive analysis of the whole process test data of the model test and the field monitoring data, the following conclusions are obtained. Under certain stress conditions, zonal disintegration will appear in the surrounding rock of deep tunnel. The zonal disintegration will not occur at the moment of tunnel excavation, but it will be gradually formed after the excavation completion for a period of time.

Research on Correlation Between Abutment Pressure and Gas Drainage Flow of Coal Seam

In this paper, based on the field test of No.S3012 working face of Shan Mushu Coal Mine in Sichuan Coal Group, monitoring the abutment pressure and gas drainage flow during the mining process, studying the change law of the abutment pressure and gas drainage flow of the coal seam, and using the numerical simulation method research on the evolution of abutment pressure and displacement of coal seam during the mining process. The results shown that: with the advance of coal mining face, the abutment pressure of coal seam can be divided into stress decreasing area, stress increasing area and original stress area, and the stress state of coal seam and the pore, crack structure and permeability of coal body are obviously changed. With the advance of the mining face, the abutment pressure in front and back of the coal mining face is the moving abutment pressure, and the coal mining face to be in the pressure relief area, the front abutment pressure peak value deep into the coal body 5–10 m, the influence scope reaches the front coal mining face to 90–100 m, this area is the stress increasing area. And the evolution law of the roof displacement of goaf is similar to the elliptical with the axial ratio changes, when the ratio is close to 1, the roof subsidence affected area is similar to the shape of “O”.

УСТРАНЕНИЕ КОЛЕБАНИЙ ТВЕРДОГО ТЕЛА, ПОДВЕШЕННОГО НА ТРОСЕ ПЕРЕМЕННОЙ ДЛИНЫ, ПРИ УПРАВЛЯЕМОМ ГОРИЗОНТАЛЬНОМ ПЕРЕМЕЩЕНИИ ПОДВЕСА

The paper considers a passive force (dynamic) and kinematic control problem of a heavy cargo movement (an undeformed solid) suspended on an inextensible inertia-free variable length cable with a controlled horizontal displacement of the suspension point. Differential equations with variable coefficients for small translational-rotational vibrations of the body are obtained. The following problem is stated: to move the body from the initial rest position to a given final equilibrium rest position for a preset time with oscillations elimination at the stop. In this case, the law of changing the cable length is considered to be prescribed, and the law of displacement of its suspension point is unknown. The integral conditions are established for required unknown control actions (force or acceleration of the suspension point), which should be satisfied. An approximate solution of the kinematic control problem described by two differential equations with variable coefficients for the angles of rotation of the cable and body is sought in series with unknown coefficients by the Bubnov-Galerkin method with the use of the given approximating functions of time satisfying certain initial and final conditions. Acceleration of the suspension point of the cable is sought in the form of a series of sines with unknown coefficients. A coupled system of linear algebraic equations for all unknown coefficients is obtained, which includes equations of the Bubnov-Galerkin method, equations for the initial and final conditions that are not satisfied in the choice of given functions, and one equation representing the integral condition in the form of the dependence of the acceleration of the cable suspension point on its specified finite displacement. The proposed approach for solving the problem of the oscillations finite control for a system with variable parameters is new. By using the examples of a system with a cable of constant and variable length, we performed the calculations with an analysis of the convergence and accuracy of solutions for two different sets of given functions and for different numbers of them by comparing them with numerical solutions of differential equations of the direct problem by the Adams method with the control laws found.