Abstract:In this paper， a landslide displacement prediction model integrating extreme gradient boosting and optimized support vector regression is proposed by using extreme gradient boosting and support vector regression， and combining the advantages of hunter-prey optimization algorithm. Firstly， extreme gradient boosting （XGBoost） is used for the preliminary prediction of landslide displacement， and then hunter-prey optimizer （HPO） is used to optimize support vector regression （SVR）. A combined prediction model （HPO-SVR） is constructed by optimizing the hyperparameters of SVR using HPO to correct the prediction results of XGBoost. The validation of two sets of landslide displacement measured data shows that the HPO algorithm obtains a more reasonable hyperparameter of SVR through the dynamic optimization strategy of constantly updating the positions of the hunter and the prey. Relative to the combined prediction models of XGBoost， SVR， and its combination with particle swarm optimization algorithm， genetic algorithm， and HPO， the combined XGBoost-HPO-SVR model achieves good results in predicting the displacements of Yangwashan landslide and Tuojiashan landslide， with mean square errors of 3.505 and 0.550， and mean absolute errors of 1.357 and 0.538， respectively.

Abstract:The research background focused on the occurrence of loess roadbed landslides in northwest China in recent years. The test datas of solidified loess with different geopolymer content were measured through compaction and direct shear tests. Additionally， the microstructure of steel slag-fly ash geopolymer solidified loess was examined using the scanning electron microscope （SEM） test and X-ray diffraction （XRD） test， and the pF-Meter instrument was used to measure the matrix suction and volumetric moisture content of the solidified loess with different geopolymers content. The test datas were then imported into COMSOL Multiphysics based on the strength reduction method， and the finite element model of the solidified loess roadbed slope was created using the Richards equation of the saturated-unsaturated theory. The impact of geopolymer content and slope ratio in the roadbed layer on the overall stability of the roadbed slope before and after rainfall was analyzed. The results indicate that when the solidified loess contains 25% geopolymer， the internal friction angle increases by 62.5% compared to reshaped loess， reaching 31.2°. The cohesion exhibits a trend of initially increasing and then decreasing as the geopolymer content increases. The highest peak is reached at 81.09 kPa when the geopolymer content is 20%， which is 75.86% higher than the cohesion of reshaped loess. The stability of the roadbed slope initially increases and then decreases with an increase in geopolymer content， while it increases with a decrease in slope ratio. Under specific conditions， slope stability decreases with prolonged rainfall duration and reduces with higher rainfall intensity.

Abstract:The Benchmark model of the floor response spectrum established by our study group was used to study the effect of different friction coefficients of the elastic slide bearing on the floor response spectrum. ETABS software was used to establish the finite element model of the seismic isolation structure， and the elastic slide bearing was arranged between the bottom of the ground floor column and the foundation. To make the floor response spectrum practical and representative， the 22 far-field vibrations recommended in ATC-63 were inputted to carry out the nonlinear time-distance analysis for the four friction coefficients of the base seismic isolation structure， respectively， and to study the effect of the friction coefficients of the elastic slide bearing on the floor response spectrum， which was compared with that of the friction coefficient of lead core rubber bearing seismic isolation. The results show that the friction coefficient affects the spectral value of the floor response spectrum but does not change the period of the peak value of the floor response spectrum and does not affect the spectral characteristics of the floor response spectrum； in the period of 0~6 s， the spectral value of the floor response spectrum of the four friction coefficients of elastic slide bearing structure in the paper is less than that of the lead core rubber bearing， which indicates that the seismic isolation performance of this structure of elastic slide bearing is better than that of the lead core rubber bearing.

Abstract:Whether the bridge pile structures adjacent to the slopes can support the threats of the landslides im?pact determines that the bridge can provide safe service. Therefore，the research on the slope instability mechanismand the law of sliding mass impact on bridge pile structure under earthquake and rainfall is an urgent need for bridgeengineering design and construction. Based on the advantages of Smoothed Particle Hydrodynamics method，such astracking the time change of particle characteristics and simulating large deformation，a parallelized Smoothed Particle Hydrodynamics algorithm was proposed to simulate the process of earthquake-induced landslides impact onbridge pile structure. The effects of seismic acceleration amplitude，frequency spectrum，duration on analyzing lawof impact by rainfall-induced landslide and earthquake-induced landslide on bridge pile structure were analyzed，and the effect of different number of threads on the efficiency of parallel computing were studied. The results showedthat the increase of seismic acceleration amplitude can accelerate the soil sliding impact on bridge pile structure andincrease the impact volume. There was a seismic acceleration critical value for the increase of soil sliding impact vol?ume. If it was greater than the critical value，the increase of soil sliding volume was larger. In a certain frequencyrange，the sliding velocity and impact volume of soil increased with the increase of the peak frequency of seismic re?sponse spectrum，and the impact of sliding soil on bridge pile structure was accelerated. With the increasing propor?tion of the earthquake duration，the displacement of the middle and rear edge of the slope increased obviously，andthe impact volume of the sliding soil on the bridge pile structure also increased. The optimization algorithm can makefull use of threads and greatly improve the computing efficiency.

Abstract:In terms of the range of sliding mass resulting in landslide thrust on stabilizing piles， firstly， this paper established the range of soil-arching effect of sandy-slope behind anti-slide piles based on the pole point theory of Mohrs circle. Moreover， on the basis of Coulombs theory， the analytical solutions for Coulombs coefficient of active earth pressure considering the influence of slope angle and lateral stress nearby pile sides with consideration of soil-arching effect were obtained. Furthermore， the analytical solutions for distributed model and resultant force of landslide sliding force acting on anti-slide piles were obtained by adopting the improved solution of the theory of partial plastic deformation which takes account of soil-arching effect. Success of the proposed methods in this paper is illustrated by good comparison with the results of available analytical approach and numerical simulation，which verifies the correctness of the derived Coulomb′s coefficient of active earth pressure considering the influence of slope angle and analytical solution for landslide thrust on anti-slide pile. Finally，the performed parametric study on landslide thrust reveals that landslide thrust and corresponding resultant force increase with the increasing slope angle β， internal friction φ and decreasing the ratio of D1/d.

Abstract:After the excavation of the cutting slope at DK324 of Huaishaoheng line， a slope slump was formed. Through analyzing the spatial morphology， the composition and structural characteristics of the slope slump， and the hydrogeology of the area based on field exploration， investigations and surveying， in-situ test and laboratory test， the cause and mechanism of the slope slide were clarified. Comparing the differences of stress and deformation among single row piles， double row piles and rigid frame anti-slide piles using finite element method， it was found that the rigid frame anti-slide piles performed the best. And the structure of safe and convenient construction was adopted to treat the slop slump. The long term monitoring results shows that the treatment effect of rigid frame anti-slide piles obviously surpasses others. It is of important guiding significance for slope slump treatment in similar projects.

Abstract:The relationship between the deformation and stability of the ancient landslide is studied in this paper. The necessity of considering the stiffness degradation in the process of reducing the mechanical parameters of the landslide is proved by the formula derivation, and a new method that considers the coupling effect of stiffness- and strength- degradation is presented. The deformation curve of the instability in the ancient landslide is drawn by a large number of engineering experiences, and the concepts about the warning displacement value of self-stabilizing ability and the ultimate displacement value of ancient landslide are put forward and defined by a determined method. Comparing with the methods of global strength degradation and slide zone strength degradation and the method in this paper applied to actual engineering example, it is seen that the method in this paper is more realistic to analyze the deformation field of the ancient landslide.

Abstract:At present， most scholars at home and abroad usually focus on the stress and deformation of landslide body caused by tunnel excavation. There are few studies on the force， deformation and reinforcement of existing tunnel structures under the influence of landslide. Based on the issue， a new combined reinforcement system of pile and cable in existing tunnel is proposed，where the anti-slide piles， anchor cables and tunnel lining are integrated， which is very different from the traditional study by the separated type between tunnel reinforcement and landslide treatment. However， due to its theoretical research lags far behind engineering practice， it limits the application in engineering practice. In order to study the stress and deformation of the reinforcement measures of the existing tunnel in landslide scope， three geo-mechanical model tests in case of vertical crossing direction are established to study the interaction rules between the landslide and the tunnel structure. It includes the ones without reinforcements，with anti-slide pile reinforcements and with combined anti-slide pile and anchor cable reinforcements. It is found that the test data change significantly after the reinforcement measures are applied. Especially in the combined anti-slide pile and anchor cable reinforcement system， the tunnels， the anti-slide piles and the anchor cables form a new structural system with higher carrying capacity and stability， which can ensure the operational safety of the existing tunnel. The results can provide a theoretical basis for the service reinforcements of the tunnel in the landslide mountain scope.

Abstract:According to the phenomenon of statistical relationships showing different distributions, between the area and cumulative frequency of landslides in Ⅹ,Ⅺ seismic intensity of Ms 8.0 Wenchuan earthquake, 6 sandpile model tests under seismic were conducted with the increase of seismic peak ground acceleration ranging from 0.075 g to 0.450 g. The phenomenon of statistical relationships was reproduced by the tests between the amount and cumulative frequency of sand changing from power-law distribution to lognormal distribution, then to normal distribution, with increase of seismic loading. By mathematical analysis, the decrease of the coefficient of variation is the cause of probability distribution shift between power-law, lognormal distribution and normal distribution. Observed through experiments, the performance of grains on the surface of sandpile will show different models with the increase of seismic loading. Under weak vibration, the probability that the activity will die is overall balanced with the probability that the activity will branch. A large-scale collapse occurs when there is a chain interaction between neighboring grains. It has the greatest uncertainty. Under strong vibration, most grains start independently. A large-scale collapse becomes a certain event. Therefore, the scale of collapse is transformed from the chain reaction of unstable grains triggered by self-organized effect to the independent falling of unstable grains triggered by vibrating force effect, which is the physical mechanism of the reducing of Cv. According to the above realization, the phenomenon of the relation between area and cumulative frequency changing from power-law distribution to lognormal distribution with the increase of seismic intensity of Ms 8.0 Wenchuan earthquake may be universal.

Abstract:A method for the tendency prediction of collapse-landslide caused by earthquake was developed, which meets the precision requirement of railway location principle stage. Based on the theory of the erosion cycle (youth-maturity-old age), this paper discussed the sequence of within-reaching-deviation from the critical slope in one ideal cycle, then put forward the principle that the tendency prediction of collapse-landslide induced by earthquake could be estimated by judging the development stage of the drainage basin. Based on the feedback mechanism of the valley and valley slope, the method of distinguishing different stages of the basin by selecting the profile feature was proposed. This method eliminates the spatial dependency on small drainage basins. At last, the method was validated with the field data of Yushu earthquake, Wenchuan earthquake and Lushan earthquake, which are the three strong earthquakes with M≥7.0 within 21st century in China. The tendency of collapse-landslide caused by earthquake is most serious when the Strahlers Integral is between 0.5~0.6. The gap to the value is bigger and the tendency is minor.