GIS-based 3D limit equilibrium analysis for design optimization of a 600 m high slope in an open pit mine

Combining the GIS （geographic information systems） grid-based data with four proposed column-based 3D slope stability analysis models, a comprehensive solution of a high-steep open-pit slope has been obtained. For six searching ranges, 19 critical slip surfaces of different sizes have been studied, in which the minimum 3D safety factor is 1.33. Comparison of 3D safety factors of designed and proposed slope plans shows for all the critical slip surfaces for the proposed plan, the smallest 3D safety factor is 1.33 under the most unfavorable condition. This means that the proposed plan of the high slopes, about 600 m, of an open pit （2-5° steeper than designed plan） is feasible.

Experimental Study on Performance of Multidirectional Geogrid and Its Application in Engineering of High Slope

By analyzing the grille mechanical property, tensile strength and creep tests, and the fi eld tests, we investigated the characteristics and the reinforcement principle of multidirectional geogrid, and obtained the effect factors of grid characteristics, load and time curve and the shear stress of grille and sand interface. The reinforcement effect of geogrid in combination of typical project cases was illustrated and the following conclusions were presented. Firstly, multidirectional geogrid has ability to resist structural deformation, node distortion or soil slippage under stress, and can effectively disperse load. Secondly, with the increase of tensile rate, grille intensity increases and the creep value also increases with the increase of load. Thirdly, the frictional resistance balance between horizontal thrust of damaged zone and reinforced soil in stable region can avoid slope failure due to excessive lateral deformation. Fourthly, the multidirectional geogrid is able to withstand the vertical, horizontal and diagonal forces by combing them well with three-dimensional orientation, realizing the purpose of preventing soil erosion and slope reinforcement, which has a wide range of application and development in engineering fi eld.

Stability of High Slope Interbedded Strata with Low Dip Angle Constituted by Soft and Hard Rock Mass

Slopes consisting of interbedded strata of soft and hard rock mass, such as purplish red mudstone and grey brown arkosic sandstone of Jurassic age, are very common in Sichuan basin of China. The mudstone is soft while the sandstone is hard and contains many opening or closing joints with a high dip angle. Some are nearly parallel and the others are nearly decussated with the trend of the slopes. Many natural slopes are in deformation or sliding because of those reasons. The stability of cutting slopes and supporting method to be taken for their stability in civil engineering are important. In this paper, the stability and deformation of the slopes are studied. The methods of analysis and support design principle are analyzed also. Finally, the method put forward is applied to study Fengdian high cutting slope in Sichuan section of the express way from Chengdu to Shanghai. The results indicate that the method is effective.

Maintenance and Management of High Slope of the Mountain Expressway

In order to effectively reduce the incidence of expressway operation safety accidents,one should pay attention to expressway safety management,especially high slope maintenance and management.In conjunction,with the current situation of operation safety management of some expressways,many mountain expressways have high slope incidences from time to time,due to the extension of operating time,and inadequate maintenance management.Moreover,vehicle damage,and human death accidents caused by the high slope collapse,landslide,debris flow,and other disasters are often reported.Therefore,it is essential to strengthen the maintenance and management of high slope in the mountain expressways.This paper,will further elaborate the issues,which are related to the maintenance and management of high slopes in the in mountainous expressways.

Large deformation and failure mechanism analyses of Tangba high slope with a high-intensity and complex excavation process

The Tangba high slope is mainly composed of coarse soils and supplies core wall materials for the construction of the Changheba dam. Since the filling intensity of the Changheba dam is high, the Tangba high slope suffers from a high-intensity excavation process, and reinforcement measures are usually not implemented immediately. Moreover, the distribution of useful materials is uneven and insufficient, and the mixing of different soil materials is necessary; thus, multiple simultaneous excavations and secondary excavation are inevitable. In the construction period from 2012 to 2016, large deformations occurred in this area, and one of the largest monitored horizontal deformations whose direction points to the opposite side of the valley even reached more than 8000 mm. According to field investigation, site monitoring and theoretical analysis, the large deformation in the Tangba high slope can be divided into two phases. In the first phase, the excavation construction breaks the original stress equilibrium state; in the second phase, the precipitation infiltration accelerates the deformation. Thus, the excavation construction and precipitation infiltration are the two major factors promoting the deformation, and the high-intensity and complex excavation process is the fundamental cause. Notably, rate of slope deformation significantly accelerated in rainy seasons due to precipitation infiltration; the rate also accelerated in early 2016 due to the high-intensity, complex excavation process. Comprehensively considering the above factors, timely and effective reinforcement measures are essential.

Stability of loess high-fill slope based on monitored soil moisture changes

This paper aims to assess the influence of moisture content changes during rainfall on the stability of loess high-fill slopes by taking a loess high-fill slope in Lanzhou City as an example.First,according to the moisture content monitoring data collected from a slope online monitoring system,direct shear tests were performed on soil samples of different moisture content to determine the relationship between the shear strength parameters and moisture content.Next,a coupled hydro-mechanical model with soil shear strength related to moisture content was established and used to analyze 16 working conditions with various rainfall intensities and durations for two cases:shear strength parameters from the site exploration report and those from this study.Finally,the results from the two cases were compared regarding the changes in stresses and displacements after rainfall infiltration to analyze the influence of moisture content on the stability of loess high-fill slopes.The conclusions are as follows:(1)Segmental relationship equations of cohesion and angle of internal friction were established for loess with various moisture content.(2)Under the conditions of different rainfall intensities,significant differences were observed in the trends of slope stress and displacement changes.(3)The slope displacement occurred in the shallow soil layer within about 12.5 m from the slope top,and the plastic strain concentrated in the soil layer within about 6 m from the slope top.(4)The results of slope stability analyses based on moisture content monitoring data are more in line with the observed.

Inversion analysis of the shear strength parameters for a high loess slope in the limit state

It is difficult to obtain reliable shear strength parameters for the stability analysis and evaluation of high loess slopes.Hence,this paper determines slope elements and physical parameter of 79 slopes with heights of[40,120]m based on the measured loess slopes in the Ganquan and Tonghuang subregions of northern Shaanxi Province,China.In the limit state of the loess slope(stability factor Fs is 1.0),a fitting equation for the slope height and width is established.Then,the model is developed by stability analysis software-SLOPE/W,and the comprehensive shear strength parameters corresponding to different slope heights of the high slope in the study area are obtained by inversion using the Morgenstern-Price method.The results show that when the height of the slope increases,the cohesion c increases in the soil,and the internal friction angle j decreases.This change is consistent with the characteristics reflected in the composition and physical properties of the slopes,and the comprehensive strength parametric curves are very similar between the Ganquan subregion and the Tonghuang subregion.A landslide that occurred in Miaodian-zaitou of Jingyang County,Shaanxi Province,is selected to verify this inversion method,and the results show that the calculated shear strength parameters of the inversion are consistent with the measured value of the actual slope.

Dynamic Response of Shallow-Buried Tunnels Traversing High Loess Slopes

Considering the existence of numerous shallow-buried tunnels traversing high slopes in the loess area in western China and the fact of high seismic intensity there,we investigate the dynamic response rules of a shallow-buried loess tunnel and its slope under the action of seismic waves with different intensities.Through large-scale shaking table model tests,we successfully analyze the characteristics and process of the destabilization of tunnels and slopes,and propose valuable suggestions regarding the reinforcement parts of a tunnel for reducing seismic damage.The results show that the main seismic damage on a slope include the failure of the sliding surface between the top and foot and the stripping of the soil around the tunnel entrance,while the damage on a tunnel is mainly manifested as the seismic-induced subsidence at the portal section and the cracking deformation at the joint areas.Finally,we propose that the“staggered peak distribution”phenomenon of the maximum acceleration values at the vault and inverted arch area can be considered as a criterion indicating that the tunnel enters into the threshold of dynamic failure.

Application of Three-Dimensional Laser Scanning and Surveying in Geological Investigation of High Rock Slope

The appearance of 3D laser scanning technology is one of the most important technology revolutions in surveying and mapping field. It can be widely used in many interrelated fields, such as engineering constructions and 3D measurements, owing to its prominent characteristics of the high efficiency and high precision. At present its application is still in the initial state, and it is quite rarely used in China, especially in geotechnical engineering and geological engineering fields. Starting with a general introduction of 3D laser scanning technology, this article studies how to apply the technology to high rock slope investigations. By way of a case study, principles and methods of quick slope documentation and occurrence measurement of discontinuities are discussed and analyzed. Analysis results show that the application of 3D laser scanning technology to geotechnical and geological engineering has a great prospect and value.

Deformation and failure of a high-steep slope induced by multi-layer coal mining

During underground mining,accurate revelation on the deformation and failure mechanisms of a high-steep slope under multi-layer mining conditions facilitates the prevention and control of geological disasters in mines.Numerical simulation based on discrete element theory can be used to explore the characteristics and mechanism of action of deformation and failure of a slope under complex geological and multi-layer mining conditions.By utilising PFC2 D(particle flow code) software,the deformation and failure characteristics of a high-steep slope in Faer Coal Mine in Guizhou Province,China were investigated.Additionally,the mechanism of influence of different numbers of mining layers on the deformation and failure of the high and steep slope was elucidated.The result showed that after the goaf passed by the slope toe,multi-layer mining aggravated the subsidence and deformation of the slope toe:the slope toppled forward as it sank.The toppling of the slope changed the slope structures:the strata in the front of the slope were transformed from anti-dip to down-dip features.Extruded by collapsedtoppled rock mass,the slope toe and the rock mass located in the lower part of the slope toe generally exhibited a locking effect on the slope.Multi-layer mining degraded the overall stability of the slope,in that the total displacement of the slope was much greater than the total mining thickness of the coal seams.Based on the aforementioned research,ideas for preventing and controlling geological disasters during mining operations under a high-steep slope were proposed.

Mechanical response of bridge piles in high-steep slopes and sensitivity study

The bridge piles located in high-steep slopes not only endure the loads from superstructure, but also the residual sliding force as well as the resistance from the slope. By introducing the Winkler foundation theory, the mechanical model of piles-soils-slopes system was established, and the equilibrium differential equations of pile were derived. Moreover, an analytic solution for identifying the model parameters was provided by means of power series method. A project with field measurement was compared with the proposed method. It is indicated that the lateral loads have great influences on the pile, the steep slope effect is indispensable, and reasonable diameter of the pile could enhance the bending ability. The internal force and displacements of pile are largely based upon the horizontal loads applied on pile, especially in upper part.

Simulation analysis of construction process of high rock slope's stabilization

A self-developed elasto-plastic finite element program was used to analyze the construction sequence of high rock slope's stabilization in a coal-coking plant, and the result was compared with that employing the ultimate equilibrium method. Based on the results of finite element analysis, the stress contour graphs and displacement vector graphs at different construction steps were obtained, and the behavior of the slope during stabilization construction process was analyzed quantitatively. Based on the analysis of safety factors of three different schemes of stabilization and two different construction schemes, the assessment of stability and bracing design of the construction process were performed. The results show that the original reinforcement design is improper; the stability of the rock slope is controlled by a developed structural plane, the stability factor after excavation is less than 1, and the free surface should be braced in time; for stability, the construction sequence should adopt that bracing follows excavation step by step up to down; the local slide occurred during the construction process agrees with the dangerous slide determined by the numerical analysis, which proves the validity and rationality of the adopted method.

Research on Deformation and Force of Bridge Pile Foundation on High and Steep Slope in Mountainous Area

With the rapid development of my country’s economy, the demand for infrastructure construction is also increasing. However, in most areas of China, the terrains are mountainous and hilly. Some projects have to be built on steep slopes. Choosing viaducts or half-bridges on high-steep slopes is not only conducive to the protection of the surrounding environment, but also conducive to the stability of the slope. Bridges usually choose the form of pile foundation-high pier bridge. This paper uses numerical simulation to study and analyze the bridge pile foundation of the slope section. Relying on actual engineering, use the finite element software ABAQUS6.14 to establish a three-dimensional finite element model to study the bearing mechanism and mechanical characteristics of the pile foundation under vertical load, horizontal load and inclined load, discuss the influence of the nature of the soil around the pile and the stiffness of the pile body on the deformation and internal force of the bridge pile foundation in the slope section. The analysis results show that the horizontal load has a great influence on the horizontal displacement of the pile, but has a small influence on the vertical displacement, and the vertical load is just the opposite. Inclined load has obvious “p-Δ” effect. The increase in soil elastic modulus and pile stiffness will reduce the displacement of the pile foundation, but after reaching a certain range, the displacement of the pile foundation will tend to be stable. Therefore, in actual engineering, if the displacement of the pile foundation fails to meet the requirements, the hardness of the soil and the stiffness of the pile can be appropriately increased, but not blindly.

Study on the sunny-shady slope effect on the subgrade of a high-speed railway in a seasonal frozen region

The temperature distributions of different parts of a subgrade were analyzed based on the results of three years of moni- toring data from the Harbin-Qiqihaer Passenger Dedicated Line, a high-speed railway, including the slope toes, shoulders, and natural ground. The temperature variation with time and the maximum frozen depths showed that an obvious sun- ny-shady effect exists in the railway subgrade, which spans a seasonal frozen region. Development of frost heave is af- fected by the asymmetric temperature distribution. The temperature field and the maximum frozen depths 50 years after the subgrade was built were simulated with a mathematical model of the unsteady phase transition of the geothermal field.

Deformation Monitoring and Result Analysis on the High Excavated Slopes of TGP's Permanent Shiplock

To ensure the stability of the high rock slopes of the permanent shiplock of the Three Gorges Project is the key to the successful construction and normal operation of the shiplock. In the course of the slope excavation, effective deformation monitoring, well understanding of the deformation characteristics, and reasonable analyzing and predicting of the deformation trend of the high slopes are important aspects of work for the slope excavation and dynamic design of the shiplock. The optimized design, successful implementation of deformation monitoring and accurate monitoring results are the important guarantee for carrying out the project. The monitoring design of the permanent shiplock was conducted in accordance with the general principles of "laying stress on the key points, considering parts as well as the whole, planning uniformly and conducting in stages". The deformation monitoring system of the permanent shiplocks is composed of survey network for horizontal and vertical displacements, monitoring points, inverted plumb lines, tension wires, extensimeters, etc.

Rock engineering property of the high-steep open-pit slope and its stability

According to the rock engineering property and stability of high-steep open-pitslopes, various factors were collected on the basis of rock engineering system (RSE) theory,and the interaction matrix of stability evaluation was established.Then, the stabilityevaluation index (S_p) of the slope was put forward.Ranges of the S_p value and the correspondingstable state were given on the basis of thirty-six samples.It is found that the followingrelationships exist: unstable (easy landslide): S_p<-0.20; mid-stable (may be landslide):-0.20<S_p<0.63; stable (no landslide): S_p>0.63.Finally, the stability evaluation indexwas applied on the high-steep open-pit slope of one mine.Analysis results and monitoringdata indicate that the index meets the necessity of the property of slope engineering, and ithas an important engineering purpose for landslide forecasting of high-steep slopes.

Semi-solid Casting of High Speed Steel Ingots Using Inclined Slope Pre-crystallization Method

Semi-solid casting of M2 high speed steel ingots was investigated by inclined slope pre-crystallization method. Effects of casting temperature and slope length on the microstructure of M2 HSS ingots were investigated. M2 cast ingots of non-dendritic primary austenite and fine eutectic ledeburite network carbide structure were obtained, with the casting temperature, slope length and angle of 1480 ℃, 500 mm and 60° respectively. Meanwhile, the microstructure of cast samples was quantitatively assessed by Image tool software. Results show that optimum mean equivalent diameter of primary austenite crystal grain is 50.8 μm, shape factor is 0.83, and mean thickness of network carbide is 5.21 μm.

高边坡下方管廊基坑支护设计方案比选

人工填土高边坡的坡体稳定性差,因其土体未经压实,开挖极易引起坍塌,对周边建(构)筑物的基坑开挖产生严重的安全隐患。根据人工填土高边坡下南宁凤岭管廊基坑开挖的工程地质条件,分析了基坑设计的难点。对钻孔灌注桩、SMW工法桩、钢板桩3种管廊基坑常用的支护形式进行了对比,在综合考虑整体刚度和强度、基坑安全性、费用、施工速度等因素后,最终确定采用具有降低施工成本、可对施工材料重复利用、地下空间资源污染低的SMW工法桩作为该基坑的最佳支护方案。此方案可对今后类似工程的设计施工提供借鉴和参考。