Abstract:An approach to maximize the fundamental frequency of free-form FRP shells using the multiisland genetic algorithm is proposed in this paper. The geometry of free-form FRP shells is generated by the NURBS technique. The creation of structural finite element model and the calculation of the fundamental frequency are carried out by ANSYS. The multi-island genetic algorithm is embedded in Isight and stacking sequence of the free-form FRP shell is optimized by using Isight to integrate ANSYS. Finally,three free-form FRP shells with the positive,negative,positive and negative Gaussian surface are optimized to obtain the optimum stacking sequence. The numerical examples show that the proposed method for stacking sequence optimization of free-form FRP shells is accurate and effective.

Abstract:In order to study the effect of interaction between soil and structure on the natural vibration characteristics of the structure, the calculation model of the soil - parallel foundation isolation system is established.,The ABAQUS software is used to establish the common structure and the parallel base isolation structure under different foundation conditions based on the principle of finite element method. The natural vibration frequency and the law of variation of the natural vibration period is discussed. The results show that the interaction between soil and structure on the natural vibration characteristics of the parallel base isolation structure is much smaller than that of the common structure,and the weaker the soil conditions of the site,the greater the degree of influence.

Abstract:In order to study the lap joint performance of the new reserved hook rebar at the vertical seam of the prefabricated shear wall under the influence of earthquake,the ANSYS discrete model was set up based on the research results of monotonous one-time loading. Under the bond-slip constitutive relationship and loading regime,numerical calculations of low cyclic loading under different steel bar diameter and concrete grades were conducted. The results show that compared with monotonous onetime loading,the overlap hook length of reserved hooks under low cyclic load increases by 30%. Under different steel bar diameters and concrete grades,the reliable overlap length of the reserved hooks is close to 0.9labE considering seismic requirements.

Abstract:Based on field investigations and simulations of stress and displacement characteristics of loess cave dwelling under different water content conditions of loess,this paper studies the sensitive parts of loess cave dwelling and their deformation and destruction processes. The process of the deformation of loess caves is summarized into four stages. It is concluded that the resistance of the loess cave dwelling comes mainly from the loess' own structure and the resistance provided by the arch structure of the cave. Finally,the economically feasible protective measures are put forward.

Abstract:The experimental study of the engineering properties for 3D printing concrete materials used in pile foundation engineering is carried out. 42.5R rapid hardening sulphoaluminate cement,smalldiameter construction dry sand and gravel are used as the main materials. Through the slump test and compressive strength test,it shows that the larger the water-cement ratio is,the larger the slump of material is;when the sand rate is larger,the slump of the material decreases firstly and then increases. Finally,when the water-cement ratio is 0.39 and the sand rate is 0.536,the fluidity is relatively good;at the same time,the setting time of the material is controlled by adding sodium gluconate retarder. When the proportion is 0.71%,the material can maintain a longer time plasticity,which is beneficial to the better control of the setting time of the concrete after mixing. By adding polycarboxylate superplasticizer,it can increase the fluidity and compressive strength of the material,the addition ratio0.48% is the best. Through a series of laboratory tests,a new type of concrete material suitable for 3D printing of pile foundation engineering is given.

Abstract:In order to study the effect of different fly ash replacement ratio on the fracture performance of brick-rich recycled concrete,four sets of brick-recycled concrete three-point bending beam specimens with dimensions of 100mm×100mm×515mm were produced. Recycled concrete was based on RC25, and the replacement ratio of fly ash was 0%,10%,20% and 30%.. Through the fracture toughness test of three-point bending beam,the variation law of the replacement rate of brick-rich recycled concrete with fly ash was studied. The results show that when the replacement ratio of fly ash is 10%,the increase of cracking toughness and instability toughness of brick-rich recycled concrete is 4.61% and 7.44%, respectively. When the replacement rate of fly ash exceeds 10%, with the increase of the replacement rate of fly ash,the fracture toughness decreases gradually,and the reduction maximum is 12.21%. The relationship between double K fracture toughness and fly ash replacement ratio of brick-rich recycled concrete is given.

Abstract:The traditional temperature sensor has some shortcomings in measuring the temperature of underground soil,such as poor corrosion resistance,vulnerable to electromagnetic interference and easy to be damaged. It is difficult to accurately and comprehensively obtain the long-term variation of soil temperature. In this paper,several distributed optical fiber temperature measurement techniques are compared and analyzed. It is proposed to use optical frequency domain reflection technology to monitor the temperature of underground soil. According to the characteristics of high precision and high spatial resolution of optical frequency domain reflection technology,the detailed monitoring scheme of optic fiber and the analysis of monitoring data are presented. In order to verify the advantages and feasibility of optical frequency domain reflectance technology in soil temperature monitoring,an indoor simulation monitoring test of soil temperature is carried out,and a set of fine temperature measurement device of soil temperature using optic fiber is designed. The optical frequency domain reflectance technology is used to monitor the temperature of soil and water in different containers. It shows that the result of optic fiber is basically consistent with the result obtained from the traditional method,but the distributed measurement can be realized by the optical fiber temperature measurement. It is remarkable compared with the traditional method. The good result of the soil temperature measurement is achieved.

Abstract:In this paper,the water stability is studied by adding different proportions of lime and water glass to the silty soil in Taizhou. The results show that the water stability of the improved soil is very poor when the content of lime is low (1%),and that the water stability of silt can be improved by increasing the content of lime or the amount of water glass after soaking 24h. The increase of lime content is more significant for the improvement of the water stability of silty soil. The amount of lime content is the same,the higher the amount of water glass,the higher the capillary water absorption rate of lime and water glass modified soil,the higher the amount of lime content,the better the capillary water absorption speed of lime and water glass improved soil. When the amount of lime content is low (1%),the erosion resistance of the modified soil is poor. The damage of the specimen after 4h erosion is serious,so the increase of lime content can effectively improve the erosion resistance of the soil.

Abstract:Four consolidated drained triaxial tests of an island calcareous sand were carried out to research its shear behavior,the confining pressure was 50 kPa,100 kPa,200 kPa and 400 kPa respectively. The stress and strain curves show that the calcareous sand body is shrinkage and dilatancy in turn,accompanied by the phenomenon of strain softening during the development of dilatancy. In order to further explore the reason of the strain softening of calcareous sand,then,particles smaller than 0.5mm are removed and the tests are repeated. The results show that there is no strain softening phenomenon in the calcareous sand of large particles. This paper convinces that:(1) the position of strain softening occurs relatively later,and with the increase of confining pressure,the position of the peak strength will gradually move backward;(2) the possibility of strain softening induced by particle breakage of calcareous sand under low confining pressure is very low;(3) fine particles are the key factors to induce the directional slip of flat calcareous sand;(4) the higher the confining pressure is, the higher the difficulty of the strain softening is,the peak strength is move backward gradually, accompanied by the appearance of the shear band.

Abstract:Anti-slide pile has been used widely in constructing embankments on sloped weak ground,but the application of rigid group piles to strengthen embankments on sloped weak ground is still insufficient. Based on the numerical simulation,a comprehensive investigation on the sloped weak ground reinforced by rigid piles was conducted by using software ABAQUS. The paper studies the influence of piles design parameters such as pile spacing,elastic modulus on its internal forces and deformation. Compared with the reinforcement without piles,the maximum settlement value of the embankment decreased by 1.5-1.93 times,and the lateral deformation value of the foundation decreased by 1.46-2 times. With the increase of the elastic modulus of rigid piles and embedded depth,the stress state of rigid piles does not significantly increase. The impact of pile spacing on rigid piles is significant. With the increase of elastic modulus and pile spacing,the reinforcement effect is improved in some extent. It is found the pile spacing is more effective to reduce the pavement settlement value of the embankment compared with the elastic modulus. Under the consideration of the factors such as the stability of embankment,force,economy etc,the pile group spacing of rigid pile group is 2 m,and the elastic modulus is 10GPa in this project.

Abstract:A series of one-dimensional compression tests were carried out under different loading processes of Yanglin shiplock. Different consolidation loading steps were studied. The time-hardening creep model and extended D-P model were used to obtain the subgrade settlement after construction in different loading methods and the subgrade was taken from the highway near Yanglin shiplock. The results show that under the multistage loading test,the time between the main and secondary consolidation points is larger,which indicates that the completion time of the main consolidation is higher than that of the first loading test. Simulation results show that the subgrade settlement without considering the creep situation is smaller than that with considering the creep situation. In the case of considering the creep situation,the settlement of the single loading is greater than the multi-stage loading. The correction of multi-stage loading for reducing subsidence settlement is verified.

Abstract:In order to clarify the mechanical response characteristics of adjacent tunnels during excavation,the deformation and internal force of tunnel segments were analyzed by finite element numerical simulation software. The influence of groundwater seepage on adjacent tunnels during excavation was analyzed by controlling the change of water head and pressure during excavation. The results show that the excavation of foundation pit will lead to the deformation and internal force changes of adjacent tunnels. The deformation and internal force of the tunnel will increase significantly when the seepage of groundwater is considered. This study can provide a reference for evaluating the safety of adjacent tunnels and the design and construction of related projects.

Abstract:Taking the landslide in AnKang reservoir as the research object,we adopt field investigation,laboratory test and numerical simulation to analyze the physical indexes and mechanical properties parameters of the rock under different water-dehydration cycles,and verify the rationality and safety of the supporting design. The effect of periodic fluctuation of reservoir water level on the reinforcement effect of anti-slide piles is studied. The main conclusions are as follows:(1) Under the water-dehydration cycle,the physical and mechanical properties of the strong weathering phyllite show the deterioration phenomenon,and there is a tendency to decrease slowly after the first rapid descent; (2) The stability of slope with the pile installed is improved greatly. With the increase of water level, the effect of anti-slide piles is weakened,and the speed is fast and then slow;(3) As water level cycles increases,the displacement and plastic strain bands gradually move to the trailing edge of the landslide,and the maximum force of the pile at the sliding zone is increased slowly.

Abstract:Taking Yangzonghai Lake as the research object,using landsat-8 OLI remote sensing image and chlorophyll a concentration measured data,based on band sensitivity analysis,a chlorophyll a concentration estimation regression model was constructed. The results show that the polynomial regression model with the band combination (B5-B4))/((B5+B4) as the parameter has the best result with a fit of 0.7201. The inversion obtained the spatial distribution map of chlorophyll a concentration and eutrophication index of Yangzonghai Lake on March 1,2018. The results showed that the Yangzonghai Lake was in a medium nutrient state.

Abstract:In order to accurately determine the extent of the ground fissure and the extent of the hazard of the Longyao ground fissure,the influence width of the ground fissure activity zone in the area was analyzed through the field survey results combined with trenching and physical simulation tests. The results show that the Longyao ground fissure has a total length of about 35 km and is distributed in a linelike manner. It has the characteristics of normal tensile extension,left-lateral rotation and east-lateral right-lateral strike-slip movement. The distribution of fractures in the ground fissure disaster area and the Neiqiu-Julu (Longyaonan) is basically coincident,indicating that the Neiqi-Julu (Longyaonan) fault is the main fault of the Longyao ground fissure. The cracks in the Longyao ground fissures are distributed along the ground. The main deformation zone of the ground fissure is 0~15m on the upper plate and 0~11m on the lower plate. The micro-deformation zone is 16~46m on the upper plate and 12~28m on the lower plate.

Abstract:As is a kind of layered silicate minerals,kaolinite could be intercalated by some organic compounds to form kaolinite organic intercalation complexes. Functional materials based on kaolinite organic intercalation composites have received widespread attention,and which is one of the research hotspots of applied mineralogy. This paper introduces the research history and current status of kaolinite organic intercalation composites and nano-kaolinites. Also,the main influencing factors,intercalation mechanism,characterization of kaolinite organic intercalation composites,and preparation of nanokaolinite based on kaolinite organic intercalation were summarized. The outlook was made in this research field.

Abstract:There are abundant halite resources with reserves about 100 billion tons in the strata of Paleogene System at Shahejie Formation in Ningjin area of Jizhong plain. However,the mined-out areas formed by solution mining of halite deposits may easily lead to geological disasters and environmental problems such as excessive surface subsidence,collapse,land salinization and so forth. So,how to effectively predict and control roof fall of salt cavities has become the most pressing problem. Based on the rectangular plate theory and the non-porous elastic circular plate theory,the stability of the overlying strata in Ningjin Halite Mine is analyzed. The results show that the critical horizontal stresses of the overlying strata of cavity are and under the two theories,respectively. The stability and reliability of the overlying strata in Ningjin Halite Mine under the above two models are also analyzed.

Abstract:In order to explore the long-term variation characteristics of PM_2.5 concentrations in Handan and their potential source of pollution,the statistical analysis of the PM_2.5 concentrations obtained from online monitoring of Hebei University of Engineering site from December 2012 to February 2018 was carried out. Source analysis of PM_2.5 was performed by HYSPLIT model,potential source contribution factor method (PSCF) and concentration weight trajectory analysis (CWT). The results show that the average annual values of PM_2.5 in Handan city from 2013 to 2017 are 108.4,98.3,92.2,81.2,66.3μg·m^-3,respectively. The trend is declining year by year;the pollution is more serious in autumn and winter,followed by spring and summer;the monthly mean value of PM_2.5 is unimodal,and the highest in January (167.4μg·m^-3),The lowest value appears in July (59.2μg·m^-3). The results of the backward trajectory show that the near-surface air pollution air mass transport path is dominated by close-range trajectories,and the path with shorter trajectories accounts for more than 40%. In addition to winter, there are spiral turns in the short-distance transport path,and the trajectory direction turns to the southdirection and east-direction paths. The main pollution source areas are large,and trajectories from central central and southern Hebei,northern Henan,south-central Shanxi,north Shaanxi,and southern Inner Mongolia contribute a lot to the mass concentration of PM_2.5.

Abstract:This study used a two section type sampler for single particle sampling,analyzed the particle morphology,size,influencing factors of diesel engine particulate emission,and compared the characteristics with other diesel engines. It finally found:Chain particles are the primary number of diesel emissions with the ratio of 72%,the second is mineral particles,existing in two forms of single particle and adherent to secondary pollutants,with their sizes ranged mostly in 0.2~0.6 μm. The polygon particles are the main material in the surrounding atmospheric particles,mainly concentrated in the size of 0.3~0.5 μm. The number of particles gradually increased along with the loading of diesel engine, and the organic particles increased first and then decreased.

Abstract:Municipal solid waste(MSW) produce plenty of leachate in the process of landfill after hydrolysis and degradation,which leads to the moisture content of the MSW along the depth direction very different. Most of the MSW is below the liquid level of leachate,which makes the degradation rules complicated. The samples from Wu Xi Tao hua shan Landfill were crushed by scissors and mixed, and the water content was carried out by using leachate,leachate (pH=7.45) and water(pH=7.45). The changing external temperature was simulated by adjusting the water tank in the apparatus,and he temperature of the tank water was monitored to keep 41℃ during this degradation test. The following conclusions were drawn:Under the same moisture content,the first peak of gas generation rate, the start time of secondary gas production and LFG cumulative volume have the same rule,which is specimen with leachate > specimen with leachate (pH=7.45) > specimen with water(pH=7.45),and correlated with leachate (water) rate.

Abstract:Boundary layer transition is of great significance in many applications of CFD engineering based on the Fluent software,this paper uses the existing RANS solver and the SST k-omega turbulence model to simulate the flow around the Aerospatiale-A airfoil. The velocity and pressure distributions of airfoil flow field under different attack angles are analyzed. Under the condition of attack angle of 13.1 degree and 13.3 degree,the simulation results are compared with the experimental data of wind tunnel abroad. The results show that the boundary layer transition can be observed under this condition and the results of direct numerical simulation agree well with the experimental data of wind tunnel. The simulation study of this model provides a theoretical reference for the subsequent research and prediction of the boundary layer transition phenomenon.

Abstract:In order to reduce the abrasion of the vehicle planetary gear bidirectional rotary axial sliding support,this paper introduces the bionics concept to the design of the micro texture on the supporting end face,and simplifies the fine aerodynamics of the bird wing structure to the parabolic groove,the double parabolic triangular groove and the double parabolic trapezoid groove. A numerical model of cavitation effect is established based on the boundary condition of mass conservation. The numerical model of the cavitation effect of the boundary conditions is established to analyze and compare the influence of the operating parameters and structural parameters of different groove types on the lubrication characteristics. The results show that the oil film bearing capacity and friction coefficient of the double parabolic triangular groove are the best in the three types of grooves based on bionic. The lubricating oil flow and cavitation rate of the double parabolic trapezoid groove are the best,and the lubrication performance of the parabolic groove is not too good or too poor,but the comprehensive lubrication performance is the best in the three.