Pre-stressed anchoring beam technique applicable in the reinforcement of high-steep slopes

During the construction of some large-scale rock engineering, high-steep slopes and insufficient slope stability induced by unloading fissures are often encountered. For the reinforcement of these slopes, some techniques (including conventional pre-stressed anchoring cable and unconventional anchoring hole) are usually utilized, however, having several obvious defects. Thus, it is very difficult for a designer to design an efficient reinforcement scheme for the high-steep slopes. For this reason, the authors develop the pre-stressed anchoring beam technique, in which tensile capacity of pre-stressed structures are fully utilized. It is analyzed that the new technique is characterized by multi-functions, including engineering investigation, efficient reinforcement, drainage, monitoring and urgent strength supplement, and hoped to be extensively applicable in the reinforcement of high-steep slopes.     

高压旋喷注浆法在建筑物桩基托换加固中的应用

针对兰州某小区商住楼已形成不均匀沉降的地基,根据场地施工条件、地基条件和建筑物的结构特征,对该工程地基选择了高压旋喷注浆法进行加固,加固结果表明:加固前及加固初期地基沉降速率较大,加固施工完成后沉降速率变小,加固完成两个月后沉降稳定,加固效果良好。通过该工程实践表明:高压旋喷注浆法在复杂地基中对既有建筑物的加固处理虽然是可行的,但同时必须根据地基土的特点采取相应的切实可行的技术措施,才能使地基加固处理达到预期的效果。其加固原理既有旋喷桩的托换加固之功效,又有静压注浆加固之作用。     

Assessment of rock slope stability by probabilistic-based Slope Stability Probability Classification method along highway cut slopes in Adilcevaz-Bitlis (Turkey)

Rock slope stability is of great concern along highway routes as stability problems on cut slopes may cause fatal events as well as loss of property. In rock slope engineering, stability evaluations are commonly performed by means of analytical or numerical analyses, principally considering the factor of safety concept. As a matter of fact, the probabilistic assessment of slope stability is progressively getting popularity due to difficulties in assigning the most appropriate values to design parameters in analytical or numerical methods. Additionally, the effect of heterogeneities in rock masses and discontinuities on the analysis results is minimized through the probabilistic concept. In this study, slope stability of high and steep sedimentary rock cut slopes along a state highway in Adilcevaz-Bitlis (Turkey) was evaluated on the basis of probabilistic approach using the Slope Stability Probability Classification (SSPC) system. The probabilistic assessment indicates major slope stability problems because of discontinuity controlled and discontinuity orientation independent mass movements. Almost all studied cut slopes suffer from orientation-independent stability problems with very low stability probabilities. Additionally, the probability of planar and toppling failures is significantly high with respect to the SSPC system. The stability problems along the investigated rock slopes were also verified by field reconnaissance. Remedial measures such as slope re-design and reinforcement at the studied locations should be taken to prevent hazardous events along the highway. On the other hand, the probabilistic approach may be a useful tool during rock slope engineering to overcome numerous uncertainties when probabilistic and analytic results are compared.     

延安市凤凰山东北麓滑坡危险斜坡的变形特征及稳定性分析

通过对凤凰山东北麓工程地质特征的分析．指出该区存在的不良地质问题有滑坡(滑塌)以及危险斜坡等，并对各滑坡(滑塌)以及危险斜坡的变形破坏特征进行了分析，最后运用斜坡(滑坡)稳定性计算中常用的瑞典法、毕肖普法和剩余推力法对其进行了稳定性验算，为凤凰山东北麓后期的治理设计提供了依据。     

Fuzzy-support vector machine geotechnical risk analysis method based on Bayesian network

Machine learning method has been widely used in various geotechnical engineering risk analysis in recent years. However, the overfitting problem often occurs due to the small number of samples obtained in history. This paper proposes the FuzzySVM(support vector machine) geotechnical engineering risk analysis method based on the Bayesian network. The proposed method utilizes the fuzzy set theory to build a Bayesian network to reflect prior knowledge, and utilizes the SVM to build a Bayesian network to reflect historical samples. Then a Bayesian network for evaluation is built in Bayesian estimation method by combining prior knowledge with historical samples. Taking seismic damage evaluation of slopes as an example, the steps of the method are stated in detail. The proposed method is used to evaluate the seismic damage of 96 slopes along roads in the area affected by the Wenchuan earthquake. The evaluation results show that the method can solve the overfitting problem, which often occurs if the machine learning methods are used to evaluate risk of geotechnical engineering, and the performance of the method is much better than that of the previous machine learning methods. Moreover,the proposed method can also effectively evaluate various geotechnical engineering risks in the absence of some influencing factors.     

断层破碎带条件下组合式圆截面抗滑桩加固边坡效果研究

随着我国公路建设不断向山区深入, 在地质构造复杂区公路边坡遇到断层破碎带的情况日渐增多, 亟需开展阻滑能力强的抗滑桩结构加固边坡研究。传统的人工挖孔桩施工模式存在高风险、低效率等缺点, 而组合式圆截面抗滑桩具有施工效率高、安全便捷等特点, 为此, 探究其对含断层破碎带边坡的加固效果具有现实意义。采用自主设计的边坡物理试验系统, 设计了5种不同破碎带厚度与组合式圆截面抗滑桩组合的物理模型, 采用坡顶逐级加载的方式模拟加载, 监测桩身应变、桩顶位移和桩后土压力, 采用高速相机捕捉滑体变形破坏图像, 并使用粒子图像测速(PIV)技术对图像进行处理。研究结果表明: 组合式圆截面抗滑桩通过限制桩后滑体水平位移, 并将滑体限制在前、后排桩间来达到加固边坡的效果; 滑体演化分为变形压密、加速变形和破坏滑移3个阶段; 前、后排桩桩后土压力比值介于1/3~1/2之间; 随断层破碎带厚度增加, 滑体水平滑移速率增大, 组合式圆截面抗滑桩的桩顶位移增大, 桩身最大正弯矩减小。模型试验与数值模拟计算的弯矩及桩顶位移较为吻合, 研究成果可为边坡工程组合式圆截面抗滑桩设计提供一定借鉴与参考。      

A new approach to plane failure of rock slope stability based on water flow velocity in discontinuities for the Latian dam reservoir landslide

The stability of slopes is always of great concern in the field of rock engineering. The geometry and orientation of pre-existing discontinuities show a larger impact on the behavior of slopes that is often used to describe the measurement of the steepness, incline, gradient, or grade of a straight line. One of the structurally controlled modes of failure in jointed rock slopes is plane failure. There are numerous analytical methods for the rock slope stability including limit equilibrium, stress analysis and stereographic methods. The limiting equilibrium methods for slopes under various conditions against plane failure have been previously proposed by several investigators. However, these methods do not involve water pressure on sliding surfaces assessments due to water velocity and have not yet been validated by case study results. This paper has tried to explore the effects of forces due to water pressure on discontinuity surfaces in plane failure through applying the improved equations. It has studied the effect of water flow velocity on sliding surfaces in safety factor, as well. New equations for considering water velocity (fluid dynamics) are presented. To check the validity of the suggested equations, safety factor for a case study has been determined. Results show that velocity of water flow had significant effect on the amount of safety factor. Also, the suggested equations have higher validity rate compared to the current equations.     

Cyclic load testing of pre-stressed rock anchors for slope stabilization

The objective of this research was to assess the characteristics of seismic induced damage and the deformation patterns of pre-stressed cement-grouted cables that are used for rock slope stabilization projects subjected to quasi-static cyclic loading. The experimental configuration includes the installation of 15 pre-stressed cables in a slope model made of concrete blocks (theoretically rigid rock mass) on top of a pre-existing sliding surface. The study showed that: (i) The pre-stressed cables exhibited great seismic performance. Rapid displacement of the model blocks was observed after the complete loss of the initial pre-stress load under continued applied cyclic loads and exceedance of the state of equilibrium, which implies the higher the initial pre-stress load, the better the seismic performance of the rock anchor; (ii) The failure of the pre-stressed cables was due to fracture at the connection of the tendons and cable heads under cyclic loading. The sequence of failure had a distinct pattern. Failure was first observed at the upper row of cables, which experienced the most severe damage, including the ejection of cable heads. No evidence of de-bonding was observed during the cyclic loading; (iii) The stress distribution of the bond length for pre-stressed cables was highly non-uniform. High stress concentrations were observed at both the fixed end and the free end of the bond length both before and immediately after the state of equilibrium is exceeded. The results obtained can be used to evaluate the overall performance of pre-stressed rock anchors subject to seismic loading and their potential as rockfall prevention and stabilization measures.     

某高等级公路路堑边坡预应力锚索加固设计

高等级公路穿越山区时 ,通常需要开挖而形成路堑边坡 ,其边坡的稳定性将危及公路施工和运营安全 ,故常需要对不稳定边坡进行加固处理。对具有大体积、大面积范围且存在滑动面的不稳定岩土体 ,加固方法以预应力锚索为佳。在结合某高等级公路路堑高边坡工程中 ,分析了已有地质条件的基础上 ,提出了预应力锚索加固边坡的设计方案     

Local scour and the laws of scour pit’s shape downstream of debris flow sabo dam

The erosion shape and the law of development of debris flow sabo dam downstream is a weak part in the study on debris flow erosion. The shape and development of scour pit have an important effect on the stability and safety of debris flow sabo dam, which determines the foundational depth of the dam and the design of protective measures downstream. Study on the scouring law of sabo dam downstream can evaluate the erosion range and reasonably arrange auxiliary protective engineering. Therefore, a series of flume experiments are carried out including different debris flow characteristics （density is varying from 1.5 t/m3 to 2.1 t/m~） and different gully longitudinal slopes. The result shows that the scour pit appears as an oval shape in a plane and deep in the middle while superficial at the ends in the longitudinal section, the position of the maximum depth point moves towards downstream with an increase of flume slope angle. The maximum depth of scour pit is mainly affected by the longitudinal slope of gully, density of debris flow, and the characteristics of gully composition （particle size and the viscosity of soil）. The result also indicates that the viscosity of soil will weaken the erosion extent. The interior slopes of scour pit are different between the upstream and the downstream, and the downstream slope is smaller than the upper one. For the viscous and non-viscous sands with the same distribution of gradation, the interior slope of non- viscous sand is smaller than the viscous sand.According to tbe regression analysis on the experimental data, the quantitative relationship between the interior slope of scour pit, slope of repose under water and the longitudinal slope of gully is established and it can be used to calculate the interior slope of scour pit. The results can provide the basis for the parameter design of the debris flow control engineering foundation.     

Rock slope stability evaluation using kinematic and kinetic methods along the Kamyaran-Marivan road,west of Iran

Interest in rock slope stability in mountainous regions has increased greatly in recent years.This issue has become a topic of major interest for geoscientists and engineering professionals,as well as for private citizens and local administrators,in many parts of the world.This paper evaluates the stability of seven rock slopes along the KamyaranMarivan tourist road,Kurdistan province,Iran,using various methods.The two main reasons for performing this research were to determine whether different methods of stability analysis provide the same results,and to determine how different factors such as the presence of water,tension cracks,and seismic forces affect the stability of these rock slopes.Firstly,field investigations were performed to obtain the engineering characteristics of the rock masses,discontinuities,and intact rocks of the slopes.Secondly,laboratory tests were carried out on rock samples obtained from the slopes,to determine the engineering properties of the intact rocks.Then for each rock slope,the contour diagram of discontinuities and slope face was drawn in the Dips v.5.1 software environment,and the failure mechanism was determined based on the kinematic or stereographic method.Next,the factors of safety of the rock slopes were calculated using the limit equilibrium method,based on the failure mechanisms resulting from the kinematic method.The accuracy of the results obtained by these two methods was investigated using SWedge v.4.0 software.The results indicated that four rock slopes have a potential for plane,wedge,and toppling failure,and three others are stable.Also,it was found that the stability of the studied rock slopes decreases greatly in the presence of water,tension cracks,and seismic forces.     

砼地基施工质量的CT检测技术

建筑工程板状砼地基属地下工程,其施工质量的检测与控制难度较大。根据该类工程的特点（面积大,厚度小）,可将其视为二维结构,采用弹性波ＣＴ成像方法检测其施工质量,在工程实践中取得了满意的效果。本文将结合工程实例介绍板状砼地基浇注质量的ＣＴ检测技术,包括弹性波ＣＴ的基本原理、野外数据采集系统的设计以及数据处理方法。     

A new method for the stability analysis of geosynthetic-reinforced slopes

This paper is concerned with the stability analysis of reinforced slopes. A new approach based on the limit equilibrium principle is proposed to evaluate the stability of the reinforced slopes. The effect of reinforcement is modeled as an equivalent restoring force acting the bottom of the slice and added into the general limit equilibrium (GLE) method. The equations of force and moment equilibrium of the slice are derived and corresponding iterative solution methods are provided. The new method can satisfy both the force and the moment equilibrium and be applicable to the critical failure surface of arbitrary form. Furthermore, the results predicted by the proposed method are compared with the calculation examples of other researchers and the centrifuge model test results to validate its correctness and effectiveness.     

Theoretical Analysis of Coral Reef Stability in South Sea

In this paper, we utilize the variational limiting equilibrium (LE) procedure to theoretically determine the slope stability of homogeneous coral sand in the South China Sea. By establishing a reasonable functional and calculating its extremum, we can deduce the stability factor of a coral reef identical to that obtained by upper bound analysis. To determine the accuracy of the results obtained using the variational LE procedure, we present some classical examples of homogeneous sand slopes without a hard shell and compare our results with those obtained by the upper bound theorem of plasticity. A series of extensive calculations and comparisons reveal that the results obtained by our proposed analysis method and those obtained using classical methods are slightly different, but the variational results are believable. On the other hand, our method solves some stability factors for reef slopes covered with a hard shell, which indicates that the existence of a hard reef shell may significantly enhance the stability of a reef slope, and that there is strong nonlinear relationship between reef stability and the mechanical characteristics of the reef shell, such as its thickness and strength. Finally, based on the variational results presented in this paper, we present a useful chart that offers a convenient and straightforward way to determine the maximum stability factor of reef slopes. Taking into account the influence of the hard reef shell, we found that, in some limit equilibrium cases, the limit stability factor and critical height of a coral slope could be improved significantly. Therefore, this issue deserves careful attention in engineering practice.     

含优势渗流层边坡降雨入渗下的可靠度分析

含优势渗流层边坡在降雨入渗的作用下其渗流场往往具有较高的不确定性,这给边坡的稳定性评价带来困难,通常采用概率的方法解决此类问题。针对含优势渗流层边坡降雨入渗下的可靠度问题,通过将应力分析中的点估计-有限元法引入到边坡渗流-稳定性分析,提出了考虑优势渗流层渗透特性不确定性的渗流概率分析和边坡可靠度分析方法;其次以广西某含碎石夹层土坡为例,分析了降雨入渗下碎石夹层的优势渗流效应及渗流概率,并基于此开展了该边坡降雨入渗下的可靠度分析。结果表明:①含优势渗流层边坡雨水沿优势渗流层渗入坡体内部的深度显著高于沿坡面渗入的深度;优势渗流层渗透特性的不确定性对渗流结果的影响较大,使得边坡稳定性分析具有较强的不确定性;②随着雨水入渗持时的增加,含优势渗流层边坡不同滑动面的失效概率总体呈现增加趋势,最危险滑动面的位置不断向边坡下部演化;依托工程滑动面位置的预测结果与工程实际吻合;③提出的概率分析方法适用于分析含优势渗流层边坡降雨入渗影响下的稳定性问题,而且具有计算量小的优势,可作这类边坡可靠度分析的一种新方法。      

蓬莱阁丹崖山安全监测与分析

丹崖山边坡稳定性是关系古文物蓬莱阁安全的关键问题。丹崖山边坡高差大、断层裂隙发育、岩体卸荷深度大,地质条件十分复杂,边坡在施工期和运行期的稳定性问题特别突出。该文介绍了丹崖山岩体加固后的监测布置,并对岩体表面变形趋势、空间分布形态、加固后变形趋势进行分析,通过对多点位移计、锚杆测力计、锚索测力计、表面裂缝计及地表变形等监测结果进行综合分析,得到边坡岩体的变形规律。     

土坡稳定性的极限分析方法

本文应用塑性力学中的极限分析法原理，建立了滑动面为折线时的土坡稳定性极限分析公式。通过工程实例证明，该公式具有使用简便、可靠性强等优点。它对于评价斜坡的稳定性，合理地进行滑坡治理等，都具有实际意义。     

岩质边坡平面滑动锚固方向角的三维优化方法

以岩质边坡中常见的平面滑动为研究对象,研究其最优锚固方向角的计算方法。将锚索自由段单位长度能提供的最大抗滑增量作为目标控制变量,将坡面和滑动面特征参数与锚索设计参数作为优化控制自变量,通过坐标系转换得到的线性方程组对锚索的预拉力进行分解,并根据锚索支护时的三维模型建立了锚索自由段长度的优化公式,进而推导了用于锚固方向角三维优化的新计算方程。在该方程的基础上借助MATLAB软件中的fmincon函数对锚索加固方向不受限制时的锚固方向角进行了优化。最后通过锚固方向角敏感性分析与工程实例分析相结合,证明了推荐的最优锚固方向角计算方法的有效性与先进性。新方法有效地解决了边坡坡面与滑动面走向存在夹角时最优锚固方向角的求解问题,可进一步提高锚索的锚固效益,降低边坡的支护费用。      

The formation of the Wulipo landslide and the resulting debris flow in Dujiangyan City,China

The Wulipo landslide, triggered by heavy rainfall on July 10, 2013, transformed into debris flow,resulted in the destruction of 12 houses, 44 deaths, and 117 missing. Our systematic investigation has led to the following results and to a new understanding about the formation and evolution process of this hazard. The fundamental factors of the formation of the landslide are a high-steep free surface at the front of the slide mass and the sandstone-mudstone mixed stratum structure of the slope. The inducing factor of the landslide is hydrostatic and hydrodynamic pressure change caused by heavy continuous rainfall. The geological mechanical model of the landslide can be summarized as "instability-translational slide-tension fracture-collapse" and the formation mechanism as "translational landslide induced by heavy rainfall". The total volume of the landslide is 124.6×104 m3, and 16.3% of the sliding mass was dropped down from the cliff and transformed into debris flow during the sliding process, which enlarged 46.7% of the original sliding deposit area. The final accumulation area is found to be 9.2×104 m2. The hazard is a typical example of a disaster chain involving landslide and its induced debris flow. The concealment and disaster chain effect is the main reason for the heavy damage. In future risk assessment, it is suggested to enhance the research onpotential landslide identification for weakly intercalated slopes. By considering the influence of the behaviors of landslide-induced debris flow, the disaster area could be determined more reasonably.     

Slope reinforcement for housing in Three Gorges reservoir area

The Three Gorges Project of the Yangtze River is the largest hydropower-complex project under construction in the world. Under the largescale relocation projects, 2874 engineered slopes are formed along with the construction of new towns. In this paper, the cutting slopes are mainly soil slopes and rock slopes. Soil slopes include residual soil slopes, colluvial accumulation slopes, swelling soil slopes, and artificial earth fill slopes, etc. Rock slopes include blocky structure rock slopes, layer structure rock slopes, and clastic structure rock slopes, etc. Varied protection measures have been used for slope protection in the reservoir area including shotcrete concrete-anchor bars, frame beams, retaining walls, slope stabilizing piles, sheet-pile walls, anchorage anti-shear tunnels, flexible protection grids, and drainage, etc. Besides, slope deformation monitoring systems have been set up to monitor deformation failure and the stability state of slopes. The protection measures have guaranteed slope safety and maintained a harmony with the urban environment and surrounding landscape.