In geotechnical engineering, empirical formulas and related relationships are site‐specific, and empirical formulas from different engineering sites cannot be universally applied to other sites. This paper proposes a Bayesian theory‐based correction method for soil parameter transformation models, constructs the likelihood function for the transformation model, and determines the prior distribution of the model parameters. This method can build a soil parameter transformation model with site specificity. The method proposed in this paper is applied to the correction of the soil unit weight transformation model, and the research results show that the method can effectively and accurately identify a soil parameter transformation model suitable for a certain geotechnical site. Moreover, by comparing the soil parameters estimated by the modified model with the true values, it demonstrates the effectiveness and correctness of this method.

Due to the heterogeneity of carbonate rocks, the pore-structure is typically characterized by low connectivity and high tortuosity. However, the previous studies on fractal permeability model assume that pore-structure is composed of impermeable capillary tubes. The effects of cementation on the reduction of capillary connectivity and the increase of tortuosity are neglected. This assumption makes it difficult to accurately evaluate the permeability characteristics of low-permeability carbonate rocks. For the overestimation of permeability, the capillary connectivity is used to characterize the area loss of inlet and outlet capillary flow. At the same time based on the relationship between geometrical tortuosity and porosity of fluid permeation path, the tortuosity index is introduced to reflect the actual cementation tortuosity. Finally, a new fractal permeability model of carbonate rocks considering capillary connectivity and cementation tortuosity is established, which adopts fractal geometry Apollonian packing models of a compact pile of equal diameter particles. Comparing with the experimental results, the calculated value of cementation tortuosity is more consistent with the experimental value of mercury intrusion method and the proposed model considering capillary connectivity and cementation tortuosity has a good agreement with the value of microscopic measurement and permeability test. It shows that the new fractal model can better predict the permeability of carbonate rocks. Through sensitivity analyses, it is found that the permeability of rocks with the same porosity and different particle sizes increases with the increase of diameter; on the other hand, the permeability of rocks with the same particle size increases with the increase of porosity. However, because both the minimum/maximum pore area and the pore area fractal dimension are related to porosity, the relationship between permeability and porosity is not a simple linear relationship, i.e., as the porosity becomes higher, the permeability increases but with a gradually reducing rate, while the sensitivity of permeability to porosity decreases.

The plastic potential surface and yield surface need to be established separately due to the difference between the plastic flow direction and loading direction in the soil modeling in traditional plasticity mechanics. However, the difference between the plastic flow direction and loading direction can be described by choosing one of the plastic potential surface and yield surface by introducing the fractional calculus. For that, the new modeling approach by using the fractional derivative of Riemann–Liouville is adopted in this study. First, a plane model for peak stress ratio considering the initial void ratio and confining pressure is proposed, and a dilatancy equation considering particle breakage for rockfill material is employed to derive a plastic potential function. Then, the fractional derivative direction and first derivative direction of the plastic potential function are deduced and developed as the loading direction and plastic potential direction, respectively. On this basis, a non-associated fractional-order plastic model without yield function is developed for rockfill material. Finally, a number of drained triaxial test results of rockfill materials are simulated to verify the capability of the proposed model. Good agreement between test data and model simulations indicates that the proposed fractional-order plasticity model can accurately capture the stress–strain behaviors of rockfill materials.

Outlier is attached importance in statistics and engineering, because it might result in misleading identification results. However, there is significant uncertainty in the outlier detection, when an outlying observation lies close to the boundary between outliers and regular data or there are sparse observations. The associated uncertainty of outlier mostly results from statistical uncertainty of parameters, such as mean value and standard deviation. However, it is unknown how the statistical uncertainty influences the outlier detection. This paper compares two outlier detection methods for influence study of statistical uncertainty on probabilistic outlier detection. One is based on Mahalanobis distance (MD) using the total probability theorem combining with the half-means method (RHM). The other is RHM method with Bayesian machine learning (BML), which can consider the statistical uncertainties of parameters in MD. The simulated dataset with outliers are used to comparative study. Different dimensional dataset and various numbers of observations and outliers are simulated. Thereinto, outliers are simulated through double-mode triangle distribution. The results show that it is necessary to consider the statistical uncertainty for sparse multivariate observations.

During the construction of large-scale hydropower projects in deep mountain gorge areas of the Western China, the difficulties, such as uncontrollable large deformation, great deformation caused by small disturbance, are often encountered in the process of implementation. In particular, due to the limitation of topography, geological conditions and the layout of structures, the slope and dense tunnel group with large section need to be excavated simultaneously in the toppling rock mass. The feedback action mechanism between slope and tunnel excavation is complicated and the deformation control of toppling rock is difficult, which leads to great challenges to engineering construction. In MW hydropower project in west of China, the intake slope, the spillway channel slope, four headrace tunnels, and the sand flushing tunnel, as well as the construction traffic tunnel are arranged in Huishi Ridge on the left bank, where two high slopes and six lager cross-section tunnels are simultaneously excavated and the excavation rate in the toppling deformation rock mass is over 50%, moreover, the lateral coverage thickness of tunnel body is less than the diameter of the tunnel, which leads to the great difficulty of stability control. The excavation stability and safe of the thin mountain ridge is the vital issue to the success of the whole project. Based on the study of the physical and mechanical parameters of toppling rock mass of MW HPP, the mutual feedback mechanism of toppling slope and tunnel group is revealed, an excavation method involving horizontal partitioning, vertical layering, reserving rock plug and reasonable skipping warehouse is proposed. Monitoring results shows that the slope and surrounding rock of the tunnels are stable during the operation period. The research of this paper based on the MW HPP can provide reference for other similar projects.

Two-dimensional soil layers profile inversion is usually based on the in-situ test and borehole information, such as the cone penetration test, standard penetration test, borehole data, which can provide one dimensional data along the depth direction. There are some methods proposed to predict the horizontal soil layers profile, such as Kriging interpolation method, sequential indicator simulation method and Markov chain simulation. However, there may be unknown soil types between adjacent boreholes, so it is impossible to accurately predict two-dimensional soil profile based on interpolation method. This paper proposed a two-dimensional soil layer profile inversion method based on surface wave exploration.

A constant head permeability test of the coarse-grained soil of an earth-rockfill dam was carried out and the gradation of the tested soil was determined based on the continuous gradation equation. Based on the test results, an empirical formula of permeability coefficient considering the influence of gradation was established. The formula can be used to assess the influence of gradation on permeability coefficient with respect to the area under the gradation curve. The applicability of the formula was verified based on the results of the permeability test from other studies. It was found that the empirical formula of permeability coefficient based on gradation area was suitable for coarse-grained soil. This paper provides a new perspective for the study of permeation behavior of coarse-grained soil.

根据NB 35047-2015《水电工程水工建筑物抗震设计规范》和《澜沧江苗尾水电站枢纽工程竣工安全鉴定工作大纲》规定要求,应按照设定地震法确定场地相关设计反应谱,作为人工合成地震波的目标谱,对苗尾水电站砾质土心墙堆石坝进行抗震复核计算.根据地震动参数复核结果,结合坝料动力试验成果,采用非线性动力有限元法对苗尾水电站砾质土心墙堆石坝进行抗震复核分析.复核结果表明,大坝抗震安全性能良好,满足规范要求.

采用邓肯E-B模型与椭圆-抛物双屈服面模型对两岔河心墙堆石坝进行有限元应力变形分析,比较两种本构模型在正常高水位的满蓄期计算得到的坝体应力应变差异.结果表明:(1)两种模型计算的坝体沉降较为接近,邓肯E-B模型计算最大沉降稍小;邓肯E-B模型计算的顺河向水平位移与双屈服面模型相比,上游位移与下游位移均偏大.(2)受心墙拱效应影响,无论邓肯E-B模型还是双屈服面模型,心墙内的主应力均比过渡层小,小主应力均为正,心墙内均未出现拉应力.相比于双屈服面模型,邓肯E-B模型计算的心墙应力受心墙拱效应更为明显.(3)满蓄期防渗墙小主应力在左右岸角部出现拉应力,两种模型计算的拉应力区分布规律基本一致,但双屈服面模型计算的拉应力的值及变化梯度均大于邓肯E-B模型.

Abstract Aiming at the large range and depth of toppling and cracked deformation occurred in a typical toppling slope during the excavation in Miaowei hydropower station on the Lancang River, through geological survey, the classification standard system for toppling deformation rock has been established based on the main characteristic indexes of rock mass, and the mechanism of the toppling and tensile deformation of the slope at Miaowei is revealed. Comprehensive rescue reinforcement measures were implemented to control the development of deformation and to maintained the stability of the slope, which included prestressed anchorage and systematic drainage. Numerical simulation was implemented to predict the deformation and guide the reinforcement. The numerical and monitoring results both show that the deformation has been effectively controlled and the slope is already in a stable state with the completion of reinforcement measures. The study on the deformation mechanism and the successful practice of treatment of typical toppling slope in Miaowei hydropower station provide a constructive reference for similar complicated slopes.

Dry density is known to be one of the primary factors affecting the behavior of granular materials. This study investigates dry density effects on shear behavior and particle breakage for rockfill materials. To achieve this, we conducted large-scale consolidated drained tests followed by sieve analysis for slate rockfill. Our results demonstrate that the stress–strain characteristics of the slate investigated depend on both dry density and confining pressure. Based on our observation of non-linear shear strength envelopes, we propose a failure criterion incorporating the effects of dry density to describe shear resistance. Our results also demonstrate that the peak friction angle increases with increasing dry density but decreases with increasing confining pressure. Moreover, the secant modulus depends on both dry density and confining pressure and is closely related to the void ratio after consolidation. Finally, our sieve analysis data indicate that dry density has a minor effect on particle breakage for this slate material.

利用砂土UH模型对两岔河水库工程心墙堆石坝进行了应力变形三维有限元计算,分析了坝体在竣工期和满蓄期的应力变形特性.结果显示:坝体在竣工期和满蓄期的最大沉降分别为73.8 cm和77.7 cm;坝体在竣工期和满蓄期的大主应力、小主应力均存在拱效应,大主应力的拱效应更显著,心墙内小主应力均为正,未出现拉应力;竣工期和满蓄期防渗墙左右两侧小主应力出现了拉应力区,防渗墙最大拉应力和压应力均在混凝土强度容许范围内.大坝应力变形的计算结果符合心墙堆石坝应力变形一般规律.有限元计算结果均在合理范围内,表明砂土UH模型在土石坝工程中有较好的适用性.

The left bank of Baihetan hydropower station is a high slope, which is a three-dimensional (3D) complex block system with strongly unloaded rock mass. The 3D geomechanical model test was adapted to investigate the slope deformation characteristic, failure process and mode, destruction mechanism, slope stability, and reinforcement effect. The model test shows that the slope failure exhibits the mode of the block sliding failure, which demonstrates the shear slipping among the bottom surfaces, the tensile crack along the trailing edge surface, and the block sliding along the bottom surface and side surface. The failure process basically experienced three stages, including the initially crack of discontinuities, crack expansion throughout the block boundaries, and the instability of the slope. The general safety factor of the left bank slope was obtained through the comprehensive geo-mechanical model test. The safety factors of given blocks were compared with the calculation results of both 3D-LEM and BEM, which shows good agreements. Simultaneously, the relative displacements at the interface of LS337 were monitored. From the results, we can see that by the reinforcement of the deep concrete replacement caverns, the sliding deformation among the bottom surfaces is effectively controlled, and the safety factors of the combination blocks of related discontinuities are improved, and the effect of slope reinforcement is more obvious. This paper provides significant guidance for the stability and reinforcement of the left bank slope of the 3D complex block system with the strongly unloaded area in Baihetan or other similar engineering slopes.

The protection provided by filter I for the corewall constitutes an important safety guarantee for the impervious bodies of corewall dams. In particular, the fine particle content (the content of particles < 0.075 mm in size) of filter I provides a filter protection effect for the corewall. Furthermore, this also determines its own drainage characteristics as an important gradation requirement for filter design. In practical engineering, due to the nature of the aggregate source, the crushing and screening process, and rolling construction, the fine particle content may exceed relevant standards. Relying on the field measured gradation envelope of the filter of a gravelly earth core rockfill dam project, this study prepared two classes of filter I (i.e., filter I of class I with a fine particle content of 8%, and filter I of class II with a fine particle content of 12%). Permeability property test, large-scale compression test, large-scale static triaxial test, and large-scale dynamic triaxial test were conducted. Furthermore, dynamic finite-element calculation of the dam under seismic action was performed, and the anti-seismic liquefaction property of the filter was analyzed. According to the permeability property test, the permeability coefficients of the two classes of filter I were both 1∼5×10−3 cm/s. Lower content of particles < 0.075 mm in size increased the permeability coefficient. According to the mechanical test, the stress-strain test curves of both classes of filter I presented nonlinearity, compressive hardening, elastoplasticity, and other general laws. The strength index and deformation resistance both increased with increasing relative density. Under the same relative density, both strength index and deformation resistance declined with increasing fine particle content. According to the dynamic finite-element anti-seismic liquefaction analysis on filter I of class II (with a content of particles < 0.075 mm in size of 12%) under seismic action, the liquefaction degree had a maximum value of 0.58 (less than 0.8), and the anti-liquefaction safety coefficient had a minimum value of 1.72, which would not trigger liquefaction of filter I. This experimental study and computational analysis offers references for the exploration of the gradation design of filter I of earth core rockfill dams and investigates the related engineering influence.

竹寿水库大坝加高工程拟采用面板堆石坝培厚加高原有粘土心墙石渣坝,加高高度38.4 m,加高后坝体高度98.1 m,为目前国内外类似工程中规模最大的工程.笔者简述了竹寿水库大坝加高的防渗形式选择、坝体结构设计、新老坝体防渗体系连接设计等.采用现场原位物理力学试验获得的新老坝料参数,对加高培厚施工、水库蓄水及地震工况下的加高坝体、尤其是防渗体系的应力应变情况进行了计算分析与探讨,得出在各工况下,大坝坝体及防渗体结构应力及变形在材料承受范围之内,大坝结构及防渗体安全满足要求.同时,针对竣工期河床段趾板受上部培厚坝体填筑影响而沉降差较大的问题,分别拟定了调整施工顺序方案、趾板断面分期施工方案、趾板下部基础超高填筑方案与趾板断面体型调整方案四种方案对比,经过对比得出适用于本工程最优方案.

苗尾水电站坝址区大范围发育由砂岩板岩互层的弯曲倾倒变形体,在水库蓄水后,地下水位升高,导致岩体和结构面软化,抗剪强度降低,容易引发倾倒体的持续变形甚至失稳破坏,进而可能威胁到大坝安全.针对蓄水作用下右岸坝后倾倒变形体稳定问题,采用UDEC离散元分析方法,分析了地下水位升高过程中该边坡的变形演化特征.结果表明,受坡体水位升高影响,边坡倾倒体变形将持续发展,当坡体水位达到1390 m时,坝头坡体浅层的变形可达到8～18 mm,对大坝变形及稳定性的影响有限.建议现场加强水库蓄水期间的变形监测和地下水位监测,进一步研究水库蓄水与边坡变形演化的内在机制.

Toppling slope is one of the complicated rock slopes.Deformation mechanism of toppling varies due to different geological conditions.To a certain extent,toppling slope is different from general sliding mode slope both in reinforcement idea and stability analysis method,which makes toppling become a difficult engineering issue in projects.Aiming at the wide range of toppling-crack deformation occurred at the right slope in Miaowei hydropower station,the deformation mechanism was studied by geological analysis and numerical simulation.Focusing on prestressed anchor and strengthening slope drainage,comprehensive rescue reinforcement measures were put forward.Both the results of numerical analysis and monitoring show that the treated slope is stable,which indicates the reinforcement measures is feasible and effective.The typical case of processing against complicated toppling slopes in Miaowei can be reference for similar projects.

介绍苗尾水电站坝址区边坡变形加固处理技术.左坝基1365m高程以下微型钢管组合桩,右坝基边坡采取"锚拉板或框梁+预应力锚索"为主的锚固方案,针对坡脚软岩分布区进行固结灌浆处理,同时在边坡上布置系统排水孔.监测成果表明目前左坝基处于稳定状态,右坝基变形趋于收敛,已安全度过了2013至2016年汛期,至今大坝左右坝坝基边坡稳定.

苗尾水电站砾质土心墙堆石坝,工程场地地震基本烈度为VII度,地形地质条件复杂.坝壳料主要采用的溢洪道开挖料,岩性偏软,粒型偏差;心墙砾质土料料源复杂,天然含水率变化大.结合"基础地质条件差、地震烈度高、土料含水率变化大和坝料岩性偏软"等工程特点和难点,从坝基处理设计、坝体结构设计、筑坝材料设计和抗震措施设计等方面进行了大量的专题研究.目前坝体监测成果表明坝体沉降变形、应力应变符合一般规律且数值合理,大坝安全是有保障的.

结合水工模型试验及技施阶段现场施工情况,对苗尾水电站岸边溢洪道布置、水力设计、结构设计及基础处理设计的优化情况进行介绍.苗尾水电站地处云南澜沧江中游峡谷,具有下泄流量大、水头高等特点.因下游消能区基岩抗冲能力差,故泄洪消能设计经多方案比选,泄洪消能建筑物采用岸边开敞式溢洪道全表孔布置方案,溢洪道采用差动式挑流鼻坎消能,下游防冲建筑物采用护岸不护底的方案.