Extensive identification of landslide boundaries using remote sensing images and deep learning method

The frequent occurrence of extreme weather events has rendered numerous landslides to a global natural disaster issue.It is crucial to rapidly and accurately determine the boundaries of landslides for geohazards evaluation and emergency response.Therefore,the Skip Connection DeepLab neural network(SCDnn),a deep learning model based on 770 optical remote sensing images of landslide,is proposed to improve the accuracy of landslide boundary detection.The SCDnn model is optimized for the over-segmentation issue which occurs in conventional deep learning models when there is a significant degree of similarity between topographical geomorphic features.SCDnn exhibits notable improvements in landslide feature extraction and semantic segmentation by combining an enhanced Atrous Spatial Pyramid Convolutional Block(ASPC)with a coding structure that reduces model complexity.The experimental results demonstrate that SCDnn can identify landslide boundaries in 119 images with MIoU values between 0.8and 0.9;while 52 images with MIoU values exceeding 0.9,which exceeds the identification accuracy of existing techniques.This work can offer a novel technique for the automatic extensive identification of landslide boundaries in remote sensing images in addition to establishing the groundwork for future inve stigations and applications in related domains.

Restraint effect of partition wall on the tunnel floor heave in layered rock mass

The presence of horizontal layered rocks in tunnel engineering significantly impacts the stability and strength of the surrounding rock mass,leading to floor heave in the tunnel.This study focused on preparing layered specimens of rock-like material with varying thickness to investigate the failure behaviors of tunnel floors.The results indicate that thin-layered rock mass exhibits weak interlayer bonding,causing rock layers near the surface to buckle and break upwards when subjected to horizontal squeezing.With an increase in the layer thickness,a transition in failure mode occurs from upward buckling to shear failure along the plane,leading to a noticeable reduction in floor heave deformation.The primary cause of significant deformation in floor heave is upward buckling failure.To address this issue,the study proposes the installation of a partition wall in the middle of the floor to mitigate heave deformation of the rock layers.The results demonstrate that the partition wall has a considerable stabilizing effect on the floor,reducing the zone of buckling failure and minimizing floor heave deformation.It is crucial for the partition wall to be sufficiently high to prevent buckling failure and ensure stability.Through simulation calculations on an engineering example,it is confirmed that implementing a partition wall can effectively reduce floor heave and enhance the stability of tunnel floor.

冻结粗粒砂岩和中粒砂岩的力学行为及能量演化机制

复杂地应力和低温环境条件下白垩系弱胶结红砂岩的力学特性和变形本质是西北地区冻结井筒工程安全建设的关键。通过低温单轴和三轴压缩试验,研究了不同低温、不同围压条件下饱和白垩系粗粒砂岩和中粒砂岩的强度和变形特性,查明了冻结砂岩加载变形过程中的能量演化规律和影响因素,并基于扫描电镜(SEM)揭示了两种砂岩的微观结构特征。结果表明:冻结白垩系砂岩的应力-应变关系呈应变软化型,其受温度、围压和岩性的影响显著,具有明显的孔隙压密变形阶段;冻结砂岩的三轴压缩强度随着温度和围压的增加分别呈非线性减小和增大规律,且各因素之间相互影响。两种砂岩的弹性模量随着温度的降低而非线性增大,但泊松比的变化与之相反。此外,冻结白垩系弱胶结红砂岩的总应变能、弹性能和耗散能具有不同的演化规律,揭示了冻结砂岩的变形破坏内部机制;基于能量比提出了冻结砂岩的损伤因子,评价了两种冻结砂岩的损伤力学特征。最后,从宏观物理特性和微观结构特征等多角度解释了两种砂岩力学和能量特性差异的内在原因。研究成果将为我国寒区矿山建设和深部地下工程的稳定性控制提供理论依据。

Characteristics and dynamic analysis of the February 2021 long-runout disaster chain triggered by massive rock and ice avalanche at Chamoli, Indian Himalaya

A massive rock and ice avalanche occurred on the western slope of the Ronti Gad valley in the northern part of Chamoli,Indian Himalaya,on 7 February 7,2021.The avalanche on the high mountain slope at an elevation of 5600 m above sea level triggered a long runout disaster chain,including rock mass avalanche,debris avalanche,and flood.The disaster chain had a horizontal travel distance of larger than 17,600 m and an elevation difference of 4300 m.In this study,the disaster characteristics and dynamic process were analyzed by multitemporal satellite imagery.The results show that the massive rock and ice avalanche was caused by four large expanding discontinuity planes.The disaster chain was divided into five zones by satellite images and field observation,including source zone,transition zone,dynamic entrainment zone,flow deposition zone,and flood zone.The entrainment effect and melting water were recognized as the main causes of the long-runout distance.Based on the seismic wave records and field videos,the time progress of the disaster was analyzed and the velocity of frontal debris at different stages was calculated.The total analyzed disaster duration was 1247 s,and the frontal debris velocity colliding with the second hydropower station was approximately 23 m/s.This study also carried out the numerical simulation of the disaster by rapid mass movement simulation(RAMMS).The numerical results reproduced the dynamic process of the debris avalanche,and the mechanism of long-runout avalanche was further verified by parametric study.Furthermore,this study discussed the potential causes of disaster and flood and the roles of satellite images and seismic networks in the monitoring and early-warning.

Effect of seepage-induced erosion on soil macropore structure

Internal erosion is one of the important factors causing geological disasters.The microstructure of soil can change with seepage erosion,resulting in changes in the hydraulic and mechanical properties of the soil.The evolution of seepage erosion is investigated with X-ray computed tomography(CT)in this study.The change in macropore structure characteristics during the seepage erosion test is quantified and the influence of seepage erosion on soil deformation is analyzed.Moreover,a pore network model(PNM)is established for the specimens and the evolution of the connected pore size characteristics is assessed.The results show that the macropore structure is significantly affected by seepage erosion,especially in terms of the porosity and pore geometry characteristics.The changes in macropore structure characteristics are most obvious in the lower part of the specimen.The influence of seepage erosion on the pore size distribution(PSD)and soil deformation is heterogeneous and closely dependent on the spatial location of the soil.Moreover,seepage erosion enhances macropore connectivity and has a directional impact on macropore orientation.These findings can provide a reference for the theoretical modeling and numerical simulation of the seepage erosion and improve the understanding of the seepage erosion evolution in engineering practice.

An improved Mesri creep model for unsaturated weak intercalated soils

The weak intercalated soils in redbed soft rocks of Badong formation have obvious creep characters. In order to predict the unsaturated creep behaviors of weak intercalated soils, an unsaturated creep model was established based on the unsaturated creep tests of weak intercalated soils by using GDS triaxial apparatus. The results show that the creep behaviors of intercalated soils are apparent and significantly affected by matric suction. Based on this, an empirical Mesri creep model for intercalated soils under varying matric suctions was built. The fitting results show that the parameters Ed and m of this model are in good power relations with matric suction s and stress level Dr, respectively. An improved Mesri creep model was established involving stress-matric suction-strain-time, which is more precise than the Mesri creep model in predicting the unsaturated creep behaviors of weak intercalated soils.

A numerical method of combined SPF-MEM-LBM on the rockfall-induced surge and its application

Rockfalls in reservoirs are prone to induce surges, posing a severe threat to passing vessels and facilities. A scheme combined Single-phase freesurface method(SPF), momentum exchange method(MEM), and Lattice Boltzmann method(LBM) is proposed to predict the impact of rockfall-induced surges. First, the LBM-SPF model is used to simulate the motion of the free surface, and the MEM model is used to calculate the hydrodynamic force acting on rock mass. To address the incompatibility issue arising from the coupling of LBM-SPF model and MEM model, a correction scheme inside the solid is induced. The simulation results of the single particle and double particle sedimentation in cavity show the feasibility and accuracy of the method designed in this paper. Moreover, the validation experiments of Scott Russel’s wave generator show that the proposed scheme can simulate wave profile stably. The simulation results emphasize that the waves induced by rockfalls have a significant impact on the safe operation of the Laxiwa dam and the passing vessels in the reservoir.

Dynamic Response of Double-Sided Loess Slope under Vehicle Load

In order to verify and study the dynamic response law on the double-sided loess slope under the action of the waves generated by automobile traffic,we select a double-sided loess slope from the long section of Anzi Road as the research object.Both field investigations and on-site monitoring processes are conducted,for the purpose of providing robust basis for road protection in these conditions.In detail,vehicleinduced vibration signals are different according to different vehicle types,speeds,as well as positions,and thus are collected,respectively.Based on the statistical analysis of the signals,the vibration response law and frequency spectrum characteristics of the slope are summarized.The results show that:①The dynamic response of the doublesided loess slope increases as the vehicle load increases,and the strong vibration response area is located in the middle of the side slope;②When the vehicle load is small,the vibration wave amplification effect is obvious.On the contrary,when the vehicle load is large,the vibration wave amplification effect is weakened;③The spectrum distribution of the X-direction wave is single-peak shape,and the dominant frequency is concentrated in 30-50 Hz;the frequency spectrum distribution of the Zdirection wave shows a multi-peak shape,and the dominant frequency is concentrated in 20-180 Hz;④The vibration wave propagates in the slope.The frequency change shows little correlation with the type,speed and position of the vehicle,and instead,it is mainly determined by the slope itself.This study reveals the dynamic response on doubled-sided loess slopes and provides both theoretical and practical significance for the road protection in such situations.

Earthquake source parameters of the 2009 M_W7.8 Fiordland (New Zealand) earthquake from L-band InSAR observations

The 2009 M W 7.8 Fiordland （New Zealand） earthquake is the largest to have occurred in New Zealand since the 1931 M W 7.8 Hawke’s Bay earthquake, 1 000 km to the northwest. In this paper two tracks of ALOS PALSAR interferograms （one ascending and one descending） are used to determine fault geometry and slip distribution of this large earthquake. Modeling the event as dislocation in an elastic half-space suggests that the earthquake resulted from slip on a SSW-NNE orientated thrust fault that is associated with the subduction between the Pacific and Australian Plates, with oblique displacement of up to 6.3 m. This finding is consistent with the preliminary studies undertaken by the USGS using seismic data.

Electrical responses and classification of complex waterflooded layers in carbonate reservoirs: A case study of Zananor Oilfield, Kazakhstan

Experiments of electrical responses of waterflooded layers were carried out on porous,fractured,porous-fractured and composite cores taken from carbonate reservoirs in the Zananor Oilfield,Kazakhstan to find out the effects of injected water salinity on electrical responses of carbonate reservoirs.On the basis of the experimental results and the mathematical model of calculating oil-water relative permeability of porous reservoirs by resistivity and the relative permeability model of two-phase flow in fractured reservoirs,the classification standards of water-flooded layers suitable for carbonate reservoirs with complex pore structure were established.The results show that the salinity of injected water is the main factor affecting the resistivity of carbonate reservoir.When low salinity water(fresh water)is injected,the relationship curve between resistivity and water saturation is U-shaped.When high salinity water(salt water)is injected,the curve is L-shaped.The classification criteria of water-flooded layers for carbonate reservoirs are as follows:(1)In porous reservoirs,the water cut(fw)is less than or equal to 5%in oil layers,5%–20%in weak water-flooded layers,20%–50%in moderately water-flooded layers,and greater than 50%in strong water-flooded layers.(2)For fractured,porous-fractured and composite reservoirs,the oil layers,weakly water-flooded layers,moderately water-flooded layers,and severely water-flooded layers have a water content of less than or equal to 5%,5%and 10%,10%to 50%,and larger than 50%respectively.

GNSS techniques for real-time monitoring of landslides:a review

Currently,Global Navigation Satellite System(GNSS)Real-Time Kinematic positioning(RTK)and Precise Point Positioning(PPP)techniques are widely employed for real-time monitoring of landslides.However,both RTK and PPP monitoring techniques have their limitations,such as limited service coverage or long convergence times.PPP-RTK technique which integrates RTK and PPP is a novel approach for monitoring landslides with the advantages of rapid convergence,high-precision,and a wide service area.This study summarizes the limitations of RTK,PPP,and PPP-RTK monitoring techniques and suggests some improved strategies.Their performances are compared and analyzed using real monitoring data.The experiment results demonstrate that RTK is the best option for small-scale(the baseline distance<15 km)and real-time landslide monitoring without considering the cost.PPP technique converges to centimeter-level accuracy in tens of minutes,only suitable for the stability analysis of reference stations.Over a large area(the baseline distance<100 km),PPP-RTK can provide excellent horizontal accuracy and adapt the service range in response to the demand for monitoring accuracy,as the vertical accuracy is signifcantly impacted by the service range and elevation diference.Finally,the characteristics of three techniques are integrated to form a comprehensive landslide monitoring technique that considers intelligence,robustness,and real-time.

Stability analysis of reference station and compensation for monitoring stations in GNSS landslide monitoring

The Real-Time Kinematic(RTK)positioning method of the Global Navigation Satellite System(GNSS)has been widely used for landslide monitoring.The stability of its reference station is crucial to obtain accurate and reliable monitoring results.Unstable reference stations due to the geological environment and human activities are difficult to detect and in practical applications often ignored.As a result,it affects the positioning solutions and subsequently the interpretation and detection of landslide motions,which must be addressed in GNSS landslide monitoring.To solve this problem,we propose using the Precise Point Positioning(PPP)technique to analyze the stability of the reference station by verifying its position.The deformations of the monitoring stations are then compensated.First,the reference station coordinates are obtained by the PPP technique and tectonic motion is considered in data processing.The change or breakout of the reference station position is then determined using a cumulative sum control chart method.Finally,each monitoring station’s displacements are compensated according to the displacements of the reference station.According to the results of the Tengqing landslide experiment,the PPP technique can be used in GNSS landslide monitoring to analyze the stability of reference stations.With PPP,millimeter-level accuracy for the coordinates of reference stations is achieved.Compared to the traditional deformation series,the compensated displacement series more reliably reflects the landslide motions.This study will increase the reliability of monitoring results and contribute to implementing GNSS in monitoring landslides.

Improved Kalman filter method considering multiple factors and its application in landslide prediction

Landslides,seriously threatening human lives and environmental safety,have become some of the most catastrophic natural disasters in hilly and mountainous areas worldwide.Hence,it is necessary to forecast landslide deformation for landslide risk reduction.This paper presents a method of predicting landslide displacement,i.e.,the improved multi-factor Kalman filter(KF)algorithm.The developed model has two advantages over the traditional KF approach.First,it considers multiple external environmental factors(e.g.,rainfall),which are the main triggering factors that may induce slope failure.Second,the model includes random disturbances of triggers.The proposed model was constructed using a time series which consists of over 16-month of data on landslide movement and precipitation collected from the Miaodian loess landslide monitoring system and nearby meteorological stations in Shaanxi province,China.Model validation was performed by predicting movements for periods of up to 7 months in the future.The performance of the developed model was compared with that of the improved single-factor KF,multi-factor KF,multi-factor radial basis function,and multi-factor support vector regression approaches.The results show that the improved multi-factor KF method outperforms the other models and that the predictive capability can be improved by considering random disturbances of triggers.

Estimation of fractional cycle bias for GPS/BDS-2/Galileo based on international GNSS monitoring and assessment system observations using the uncombined PPP model

The Fractional Cycle Bias(FCB)product is crucial for the Ambiguity Resolution(AR)in Precise Point Positioning(PPP).Different from the traditional method using the ionospheric-free ambiguity which is formed by the Wide Lane(WL)and Narrow Lane(NL)combinations,the uncombined PPP model is flexible and effective to generate the FCB prod-ucts.This study presents the FCB estimation method based on the multi-Global Navigation Satellite System(GNSS)precise satellite orbit and clock corrections from the international GNSS Monitoring and Assessment System(iGMAS)observations using the uncombined PPP model.The dual-frequency raw ambiguities are combined by the integer coefficients(4,−3)and(1,−1)to directly estimate the FCBs.The details of FCB estimation are described with the Global Positioning System(GPS),BeiDou-2 Navigation Satellite System(BDS-2)and Galileo Navigation Satellite System(Galileo).For the estimated FCBs,the Root Mean Squares(RMSs)of the posterior residuals are smaller than 0.1 cycles,which indicates a high consistency for the float ambiguities.The stability of the WL FCBs series is better than 0.02 cycles for the three GNSS systems,while the STandard Deviation(STD)of the NL FCBs for BDS-2 is larger than 0.139 cycles.The combined FCBs have better stability than the raw series.With the multi-GNSS FCB products,the PPP AR for GPS/BDS-2/Galileo is demonstrated using the raw observations.For hourly static positioning results,the performance of the PPP AR with the three-system observations is improved by 42.6%,but only 13.1%for kinematic positioning results.The results indicate that precise and reliable positioning can be achieved with the PPP AR of GPS/BDS-2/Galileo,supported by multi-GNSS satellite orbit,clock,and FCB products based on iGMAS.

PPP-RTK considering the ionosphere uncertainty with cross-validation

With the high-precision products of satellite orbit and clock,uncalibrated phase delay,and the atmosphere delay corrections,Precise Point Positioning(PPP)based on a Real-Time Kinematic(RTK)network is possible to rapidly achieve centimeter-level positioning accuracy.In the ionosphere-weighted PPP–RTK model,not only the a priori value of ionosphere but also its precision afect the convergence and accuracy of positioning.This study proposes a method to determine the precision of the interpolated slant ionospheric delay by cross-validation.The new method takes the high temporal and spatial variation into consideration.A distance-dependent function is built to represent the stochastic model of the slant ionospheric delay derived from each reference station,and an error model is built for each reference station on a fve-minute piecewise basis.The user can interpolate ionospheric delay correction and the corresponding precision with an error function related to the distance and time of each reference station.With the European Reference Frame(EUREF)Permanent GNSS(Global Navigation Satellite Systems)network(EPN),and SONEL(Système d’Observation du Niveau des Eaux Littorales)GNSS stations covering most of Europe,the efectiveness of our wide-area ionosphere constraint method for PPP-RTK is validated,compared with the method with a fxed ionosphere precision threshold.It is shown that although the Root Mean Square(RMS)of the interpolated ionosphere error is within 5 cm in most of the areas,it exceeds 10 cm for some areas with sparse reference stations during some periods of time.The convergence time of the 90th percentile is 4.0 and 20.5 min for horizontal and vertical directions using Global Positioning System(GPS)kinematic solution,respectively,with the proposed method.This convergence is faster than those with the fxed ionosphere precision values of 1,8,and 30 cm.The improvement with respect to the latter three solutions ranges from 10 to 60%.After integrating the Galileo navigation satellite system(Galileo),the convergence time of the 90th percentile for combined kinematic solutions is 2.0 and 9.0 min,with an improvement of 50.0%and 56.1%for horizontal and vertical directions,respectively,compared with the GPS-only solution.The average convergence time of GPS PPP-RTK for horizontal and vertical directions are 2.0 and 5.0 min,and those of GPS+Galileo PPP-RTK are 1.4 and 3.0 min,respectively.