Abstract:In order to study the seismic performance of H-shaped SRC column under bidirectional horizontal loading,the fiber model is used to simulate the existing tests,and the simulation results applicability the correctness of the model. Based on this model,the effects of axial compression ratio,steel ratio and steel strength on the bearing capacity,energy dissipation and ductility of H-shaped SRC column under bidirectional horizontal loading are investigated,and compared with those under unidirectional horizontal loading. The results show that the axial compression ratio has a significant influence on the seismic performance of H-shaped SRC column. As the axial compression ratio increases,the bearing capacity of the column first increases and then decreases,while the energy dissipation and ductility gradually decrease with the increase of the axial compression ratio;The steel ratio has a certain influence on the seismic performance of H-shaped SRC column,and the The bearing capacity,energy dissipation and ductility of the column increase obviously with the increase of the steel ratio;The bearing capacity,energy dissipation and ductility are all improved slightly with the increase of steel strength. In addition,the bearing capacity,energy dissipation and ductility of the SRC column under bidirectional loading are lower than those under unidirectional horizontal loading.

Abstract:Based on the traditional steel tube lead damper,a new type of steel double-core damper was obtained through improvement.Based on this,the ABAQUS finite element simulation software was used to simulate the seismic performance.The simulation results show that the limit load of the new steel double-core damper is 183kN,the limit displacement is nearly doubled,and the hysteresis curve area obviously increases compared with the single lead damper.And the equivalent damping coefficient increases by 15%.The simulation results show that the energy consumption is better.

Abstract:This paper is aimed at the durability of underground concrete structure,and the influence of water pressure (0,0.1 and 0.2 MPa) and fly ash content (10%,25% and 40%) on sulfate corrosion of concrete which were studied by means of laboratory simulation test technique.In the experiment,the sulfate corrosion depth and mechanical properties (compression strength and dynamic elastic modulus) of concrete after 60 days of corrosion were measured.The results show that the sulfate corrosion depth of concrete decreases linearly with the increase of fly ash content,and increases linearly with the increase of water pressure.The compression strength and dynamic elastic modulus of concrete decrease with the increase of fly ash content,and slightly increase with the increase of water pressure.In addition,the relationship between the compression strength and ultrasonic pulse velocity of concrete was analyzed.The result indicates that the influences of fly ash content and water pressure are not obvious.Based on the regression analysis,an exponential model between the compression strength and ultrasonic pulse velocity of concrete exposed to sulfate attack is established.

Abstract:In order to understand the relationship between the parallel bond parameters in the PFC2D and the direct shear strength parameters when simulating laboratory direct shear test,a model was established based on the particle size distribution after the disintegration of mudstone in the Jianghuai test project.The influence of the parallel bond parameters in the PFC2D on the strength parameters of mudstone direct shear was studied by using the control variable method.The results show that the effects of the parallel bond parameters on the shear strength parameters are not monotonic and should be divided into different sections for discussion.The sensitivity of parallel bonding parameters to cohesion and internal friction Angle is different.

Abstract:Through the indoor direct shear test,the influence of different calcareous tuberculosis content on the strength and deformation characteristics of the sample was tested,which provides theoretical guidance for engineering construction.It was found through experiments that calcareous tuberculosis has a great influence on the shear strength index of the sample.As the calcium tuberculosis content increases,the cohesive force of the sample decreases and the internal friction angle increases.The skeleton effect of calcareous nodules in the sample under high normal stress can be fully exerted,and the higher the content is,the greater the strength will be.Under low normal stress,the calcium-containing tuberculosis samples are strain-softened,while the calcium-free tuberculosis samples are strain-hardened.With the increase of calcareous tuberculosis content and normal stress,the curves in the ideal plasticity stage are significantly different.

Abstract:For the foundations of sand drains with different permeability coefficients,different depths and different radii,the finite element consolidation calculation of the sand drain foundation was carried out. The finite element simulation results of the consolidation of the sand drain foundation considering the drain resistance are compared with the ideal solution of the Barron ideal drain. The influence degree of drain resistance on the consolidation of sand drain foundation was analyzed,and the necessity of properly considering drain resistance or drainage capacity when designing sand drain or drainage board foundation was demonstrated.The research shows that,(1) The smaller the permeability coefficient of the sand drain is,the smaller the degree of consolidation achieved under the same time conditions will be;similarly,the longer the time required for the same consolidation degree is,the more obvious the drain resistance effect will become. And the deeper the soil reinforcement is,the more significant influence of the drain resistance effect will be;(2)The influence of drain resistance on the consolidation degree of foundation and the consolidation time of foundation can not be ignored. Under the finite element simulation parameters of this paper,corresponding to the same consolidation time,when the ideal drain consolidation degree reaches 80%,the consolidation degree considering the drain resistance is 13%~67%,and the relative error relative to the ideal drain consolidation degree is 16%~83%. Corresponding to the same degree of consolidation,when the degree of consolidation reaches 80%,the relative error of the consolidation time relative to the ideal drain is greater than 50%.

Abstract:In order to demonstrate the scientificity and rationality of grass-wrapped silt technology widely used in Liangzhu period,unconfined compressive strength test and large-scale consolidation test were carried out on single grass-wrapped silt and grass-wrapped silt stack block.The experimental results show that the deformation of grass-wrapped silt can be divided into three stages,and the strip will be broken when the strain of grass-wrapped silt reaches 20%.The unconfined compressive strength of single grass-wrapped silt is not significantly different from that of open-joint stacking,but the unconfined compressive strength of single grass-wrapped mud can be improved obviously by staggered joint stacking.The drainage layer between grass-wrapped silt will accelerate the consolidation of silt,and the compaction and embedding of reed grass and strip will lead to the increasing of vertical deformation.The contribution of the deformation of reed grass and strip to the vertical deformation mainly occurred 3 hours ago.With the increasing of load,most of the deformation tended to be completed in the early stage,and the density of silt in the consolidated grass-wrapped silt was 2.50% higher than the undisturbed silt.Its cohesion and friction angle are 38.7% and 20.5% higher than the undisturbed silt respectively.

Abstract:This paper takes the developed landslide in Langao County of Shaanxi Province as the research object with the help of geotechnical experiments,physical simulation and numerical simulation,reveals the deformation and infiltration law of landslide under rainfall conditions,and studies the deformation and failure characteristics and formation mechanism of rainfall-induced accumulation landslide. The physical model test shows that:The relationship between seepage rate and time is exponential,and the relationship is y=6.658 83x^{-0.900 34};With the rainfall and changes of groundwater level,the accumulation of landslides is mainly characterized by traction whose development process can be summarized as follows:the generation of cracks→ the expansion of cracks→ the penetration of cracks→ secondary sliding→ overall sliding five stages;It is found that the binary structure of the landslide is the decisive factor in the formation of the landslide. The rainfall infiltration leads to the enrichment of the water flow near the bedrock surface,which is an important predisposing factor for the landslide.Numerical simulation results show that the slope stability decreases with the duration of groundwater,and the shear strain and the slope deformation increase gradually.

Abstract:In order to study the shear strength characteristics of an assembly of many Expanded Polystyrene beads,direct shear tests were carried out to investigate the relationship between shear stress and shear displacement under different normal stress conditions.The effects of particle size and compressibility on shear strength were analyzed for the beads with particle sizes of 1mm,3 mm and 5 mm.The results show that the shear strength of an assembly of many EPS beads decreases with the increase of particle sizes.The cohesion of the assembly decreases and the internal friction angle decreases from 8.1 kPa to 2.75 kPa when the particle sizes of EPS increases from 1 mm to 5 mm.The reason is that the compression of an assembly of EPS beads increases with the increase of particle sizes.

Abstract:In order to study the disaster-causing process of hydraulic fracturing of rock mass and reveal the microscopic mechanism of hydraulic fracturing,three-dimensional analysis platform for hydraulic fracturing of rock mass is performed,using VB compilation platform,which can finish the implementation of different business soft-wares including PFC,SURFER,GAMBIT and FLUENT,and achieving data information exchange and specific functions between different software based on FORTRAN.Subsequently,the reliability of the platform is verified by establishing the same hydraulic fracturing cylinder model of rock mass as in the literature and comparing with the test results.Finally,depending on the platform,a research on crack growth of outlet tunnel is carried out to analyze the failure process of crack initiation,expansion,extension and penetration in surrounding rock under high internal water pressure.The result shows that the platform can accurately reveal the hydraulic fracturing process of tunnel lining and dynamically obtain the distribution characteristics of corresponding fracture flow field.For this tunnel model,only when the pressure of the surrounding rock outside the lining is greater than 0.6MPa can the lining of the tunnel be safe under the action of the current high-pressure internal water and this conclusion has important guiding value for the design of outlet tunnel.

Abstract:Taking the sand-soil tower foundation slope of Dingbian County in northern Shaanxi as the research object,the physical and mechanical properties of sand loess were studied by means of laboratory tests,and compared with the physical and mechanical properties of Xi'an sticky loess. On this basis,the finite element software MIDAS was used to simulate the stress-strain characteristics of the tower foundation slope under different working conditions,and the failure mechanism of the towe foundation slope in the sand loess area is revealed. The results show that the natural density and dry density of sand loess are lower,the pores are higher,the coarse silt content is more,the friction strength is obviously larger,and the cohesive force is smaller. The finite element simulation shows that with the increase of influencing factors,the tensile stress of the slope shoulder increases continuously,the shear stress of the slope foot is continuously concentrated,the stability of the slope is gradually reduced,and the potential sliding surface is finally formed and destroyed,wherein the wind load and rainfall is are major factors affecting slope stability and stress strain.

Abstract:For the end restraint in the drained triaxial test,the program ABAQUS is used to simulate the drained triaxial test to study the effects of different end restraints on the behavior of soft soil under different confining pressures.The results show that without the end restraint,the stress-strain behavior of the specimen can well represent the constitutive model of soil.The end restraints lead to the non-uniformity of stress and strain in the specimen,and the greater the degree of end restraint is,the more obvious the inhomogeneity becomes.The effects of end constraint on the behavior of specimen is not great when the strain is small,but the effects under large strain condition can not be ignored,and the effects of different degrees of end restraint are the same.

Abstract:In order to accurately predict the rock burst level,five factors of rock burst occurrence were selected from three aspects of lithology,stress,and surrounding rock as the prediction evaluation index,and the importance of evaluation index was calculated by using the improved entropy weight formula.Combined with the multi-dimensional Indian huts model in the catastrophe progression method,the data of rock burst samples after dimensionless processing were normalized to obtain the catastrophe sequence value,and the rock burst interval was divided.Finally,this method is applied to the rock burst prediction of Jiangbian hydropower station tunnel.The results show that the method is objective,accurate,and consistent with the actual engineering situation and has certain advantages over other aspects.

Abstract:Strong toppling deformed bodies in reservoir area often destabilize in a specific mode during storage period. According to the instability characteristics of site slope,the failure mode is analyzed as "upper tension-lower shear" failure and sliding surface obviously segmented. Based on the traditional Sarma method,considering the strength reduction of saturated rock mass and hydrostatic pressure,the Sarma method is improved by adjusting the strength reduction coefficient of rock strata. Fortran is used as a platform to compile a program for stability analysis of strongly toppling deformed bodies. The mechanical model and analysis method are validated by a slope example of Miaowei Hydropower Station,and its accuracy is verified by comparing with the results of discrete element simulation. The parameter analysis results show that the stability of the toppling deformation body is negatively correlated with natural slope angle and the stability of the slope with more soft rock will be greatly reduced after impoundment.

Abstract:In view of the problems caused by expansive soil roadbed,this paper,combined with the related research of solid waste modified soil,put forward the research idea of using magnesium slag to improve expansive soil.The effects of magnesium slag on relative density,liquid plastic limit,free expansion rate,unconfined compressive strength and shear strength of expansive soil were studied by laboratory tests.The results show that the liquid limit,plasticity index and free expansion rate of the modified soil decrease with the increase of the content of magnesium slag.In addition,with the increase of mg slag content,the unconfined compressive strength and shear strength of mg slag modified soil showed a trend of first increasing and then decreasing,and reached the peak when the content of mg slag was 15%.

Abstract:With the development of urbanization,the number of school-age children in rural areas is gradually decreasing. Under the "Withdrawal and Merging School Policy",educational resources have been integrated nationwide,and the rural primary and secondary schools have been re-arranged which resulted in a large number of rural school buildings being idle. Taking the reuse of rural idle school buildings as the starting point,based on the investigation of Weizengzhai Town,Guantao County,Handan City,this paper classifies and summarizes the use of school buildings,analyses the current situation of idle school buildings,and combined with the wishes of the villagers,puts forward some suggestions for renovation.

Abstract:Through core observation and description and sedimentary facies analysis,and with rich core data,logging information and logging data, the sedimentary facies types and facies patterns of the reservoir in the Chang 6 formation are studied in depth. Based on the analysis of rock type,sedimentary structure,sedimentary tectonics,paleontology and sedimentary environment,it is concluded that the sedimentary period of Chang 6 formation mainly developed the terrestrial lacustrine turbidite fan facies in deep water,and could be divided into three subfacies:inner fan,middle fan and outer fan. The turbidite fan facies model of Chang 6 reservoir in the study area was finally established through the analysis of sedimentary facies and logging equivalence to clarify the planar distribution and vertical evolution of sedimentary facies.

Abstract:In order to deeply study the mechanism of machining accuracy detection for high-grade CNC machine tools,in this paper,Adams and Matlab/Simulink software was used to simulate the movement of S-shaped test piece produced by five-axis CNC machine with AC dual rotary table.Firstly,the mechanical system and control system model of the machine tool were built.Then the 6 input variables and 12 output variables of the mechanical model were docked with the control model established by Simulink through Adams/Control module respectively,and the settings of input and output in the system were completed,and the co-simulation of electromechanical coupling was realized.The simulation results show that the motion of each axis for the five-axis machine tool presents a non-linear change in the machining S-shaped test piece process,which is consistent with the actual engineering experience.

Abstract:The 7050 aluminium alloys are widely used in the aviation and aerospace for their higher strength,fracture toughness property and anti-fatigue performance. The effects of single-stage aging on alloy tissue and performance were studied by the hardness test,corrosion test and transmissive electron microscopic analysis (TEM) of 7050 aluminum alloys. The experimental results show that the 7050 aluminum alloys have a strong aging hardening effect. When the single-stage aging temperature rises from 120℃to 160℃,the speed of alloy aging hardening accelerates significantly,and the time required for alloys to enter the peak aging state is significantly shortened,but the hardness of the peak point of the alloys reduces. After aging treatment,the alloy precipitates abundant of fine η' phase dispersing in the matrix. A coarse equilibrium phase is precipitated at the grain boundary of the alloy with MgZn2 as the component and PFZ appears. With increasing aging temperature,the precipitation phase on the grain boundary is continuous and coarse,PFZ is widened and the intergranular corrosion resistance of the alloy continues to decrease. For exfoliation corrosion,the degree of alloy corrosion is related not only to the structure of the grain boundary but also to the number of it. As the temperature rises,the grain size of the alloy increases rapidly,and the number of the grain boundary reduces significantly,the interaction of which results in the improvement of the alloy's anti-corrosion property.

Abstract:Pipeline collision technology of BIM can effectively simulate the collision problem of HVAC pipes,electrical pipelines,water supply and drainage pipelines in complex construction projects. However,this technique cannot give an optimized solution according to the location of the pipeline collision currently. Motivated by this,BIM pipeline collision optimization model is established based on the intuitionistic fuzzy analytic hierarchy process (IFAHP). Firstly,a pipeline collision evaluation index system is given by construction costs,construction difficulty,construction safety,and construction aesthetics in accordance with construction pipeline construction specifications. Secondly,different intuitionistic fuzzy judgment matrixes are given according to IFAHP and the position of the collision point,corresponding intuitionistic fuzzy decision optimization models are established,and then the pipeline optimization solution for different pipeline collision points is given. Finally,the effectiveness and feasibility of the BIM pipeline collision optimization model are verified by an example.