非线性M-C强度准则下预应力锚索加固边坡时效稳定性分析M-P法

拓展传统极限平衡方法在复杂条件下边坡稳定性分析中的适用性一直是岩土工程界的研究热点。众所周知,边坡岩土体剪切失效一般服从于非线性强度准则,而传统极限平衡方法仅适用于线性强度准则下边坡稳定性分析。此外,预应力锚索作为一种主动防护措施,可极大地即时提高边坡稳定性而被广泛应用于中、大型边坡工程加固。然而,在应力松弛、蠕变效应以及腐蚀环境影响下预应力锚索加固边坡稳定性时效特征往往被忽视。由此,基于Morgenstern-Price(M-P)法,嵌入非线性Mohr-Coulomb(M-C)强度准则,并融入应力松弛与蠕变效应下锚索预应力损失模型以及腐蚀环境下锚索性能劣化模型,从而,建立非线性强度准则下预应力锚索加固边坡安全系数时程表达式。进一步,为了解决非线性强度准则下隐式嵌套公式难以求解的问题,归零化条间法向力初始值,并应用迭代循环求解策略,在引入循环终止允许误差判别条件后,可实现边坡稳定性理论真实结果的逼近求解。经过后续算例对比分析,验证了所提方法的可行性和合理性,与此同时,还研究了不同预应力损失速率和不同锈蚀环境下预应力锚索加固边坡稳定性的时效变化规律。

基于Hydrus-1D对西坝镇农田土壤重金属迁移模拟及空间解析

为了研究区域内土壤重金属迁移规律及分布特征,在基于整体土壤重金属背景值的基础上,选用四川西坝镇高产农田作为研究对象,通过对研究区所取土样进行淋滤实验,得到不同时间渗漏液中Cd、Cu、Zn、Cr离子浓度变化量,并运用Hydrus-1D对研究区土壤建立非饱和带一维水流溶质运移模型,模拟在稳定水流作用下,垂向上各迭代时间土壤重金属的迁移量;同时借助地下水建模系统(groundwater modeling system,GMS)对研究区建立空间模型,分析区域内土壤重金属空间分布特征。模拟结果表明:随淋滤时间增加土壤重金属含量逐渐降低,淋滤第4 d四种离子迁出量都已接近最小值,Cd、Cu、Zn、Cr离子变化量实验值均能与模拟值较好拟合,线性回归R2分别为0.932、0.951、0.936、0.965;空间分布特征显示:研究区重金属分布与地下水流向和土壤重金属的初始含量相关,外界污染源及浅层地下水水流路径迁移过程中的溶滤作用是造成研究区域内不同土壤重金属分布差异的主要因素。此次研究结果为进一步研究区域重金属迁移特征提供了理论依据及分析方法。

Limit equilibrium method(LEM) of slope stability and calculation of comprehensive factor of safety with double strength-reduction technique

When the slope is in critical limit equilibrium(LE) state, the strength parameters have different contribution to each other on maintaining slope stability. That is to say that the strength parameters are not simultaneously reduced. Hence, the LE stress method is established to analyze the slope stability by employing the double strengthreduction(DSR) technique in this work. For calculation model of slope stability under the DSR technique, the general nonlinear Mohr–Coulomb(M–C) criterion is used to describe the shear failure of slope. Meanwhile, the average and polar diameter methods via the DSR technique are both adopted to calculate the comprehensive factor of safety(FOS) of slope. To extend the application of the polar diameter method, the original method is improved in the proposed method. After comparison and analysis on some slope examples, the proposed method's feasibility is verified. Thereafter, the stability charts of slope suitable for engineering application are drawn. Moreover, the studies show that:(1) the average method yields similar results as that of the polardiameter method;(2) compared with the traditional uniform strength-reduction(USR) technique, the slope stability obtained using the DSR techniquetends to be more unsafe; and(3) for a slope in the critical LE state, the strength parameter φ, i.e., internal friction angle, has greater contribution on the slope stability than the strength parameters c, i.e., cohesion.

Limit equilibrium analysis for stability of soil nailed slope and optimum design of soil nailing parameters

Reinforcement of slopes using soil nailing can effectively improve slope stability, and it has been widely used in upgrading cut slopes. Based on the assumptions of stresses on the slip surface, a new method for analyzing the stability of a slope reinforced with soil nails was established in the limit equilibrium theory framework, by considering that slope sliding occurs owing to shear failure of the slip surface, which subjects to Mohr–Coulomb(M–C) strength criterion. Meanwhile, in order to easily analyze the stability of a soil nailed slope in actual engineering and facilitate optimum design of parameters for soil nailing, factor of safety(FOS) contour curve charts were drawn on the basis of the established linear proportional relationship between the spacing of soil nails and slope height, and the length of soil nails and slope height. Then, by analyzing and verifying the results obtained from classic examples, some conclusions can be got as follows: 1) The results obtained from the current method are close to those obtained from the traditional limit equilibrium methods, and the current method can provide a strict solution for the slope FOS as it satisfies all the static equilibrium conditions of a sliding body, thus confirming the feasibility of the current method; 2) The slope FOS contour curve charts can be used not only to reliably analyze the stability of a soil nailed slope, but also to design optimally the parameters of soil nailing for the slope with a certain safety requirement.

非线性Mohr-Coulomb破坏准则下浅埋三维圆形锚板极限抗拔力上限分析（英文）

基于非线性Mohr-Coulomb强度准则及相关流动法则,构建了浅埋水平圆形锚板承受极限抗拔力时上方土体的三维轴对称破坏机制;利用变分原理,推导出三维轴对称破坏曲面在平面上投影函数的导函数。利用差分原理迭代获得了满足边界条件的破坏面原函数及其与之对应的极限抗拔力函数数值解答;进一步分析了非线性MC参数变化对圆形浅埋锚板极限抗拔力和破坏模式的影响规律。结果表明:圆形锚板极限抗拔力随无量纲参数m的增大而减小,锚板埋深、锚板半径、地表超载、初始粘聚力、土体重度以及土体摩擦角的增大而增大,随土体单轴抗拉强度的增大而减小;圆形锚板上方土体破坏面呈对称的空间漏斗形态,且其形状主要取决于无量纲参数m;地表破坏范围随锚板半径、锚板埋深、初始粘聚力的增大而增大,随土体单轴抗拉强度、土体重度的增大而减小。在无量纲参数m=2.0时的特殊条件下,极限抗拔力精确解与数值解对比分析证明了本文基于差分法原理数值解答的可行性和有效性。同时,对比分析了变分法与上限法的极限抗拔力计算结果,表明在极限分析上限法理论框架内,变分分析方法结果优于上限法结果。

卵巢黏液性囊腺瘤患者的磁共振成像影像学特征及临床应用价值分析

目的 探讨卵巢黏液性囊腺瘤患者的磁共振成像(MRI)影像学特征及对良性黏液性囊腺瘤和交界性黏液性囊腺瘤的诊断价值。方法 选取2020年4月-2023年8月湖州市中医院收治的92例卵巢黏液性囊腺瘤患者,依据病理结果分为良性组(50例)和交界组(42例),对所有患者进行MRI检查。分析两组患者MRI影像学特征和信号强度;比较单房和多房的卵巢良性黏液性囊腺瘤和交界性黏液性囊腺瘤的瘤壁及间隔厚度;对比MRI诊断卵巢良性黏液性囊腺瘤和交界性黏液性囊腺瘤的准确度;分析MRI对卵巢交界性黏液性囊腺瘤的诊断价值。结果 与良性组比较,交界组蜂窝状子房(20.00%vs. 45.24%)、囊壁及分隔不规则增厚≥5 mm(10.00%vs. 35.71%)、结节或乳头状突起≥5 mm(8.00%vs. 69.05%)、T1WI含高、等信号(18.00%vs. 59.52%)、T2WI含低、等信号(18.00%vs. 45.24%)出现率显著更高,T1WI单一低信号(72.00%vs. 19.05%)、T2WI单一高信号(70.00%vs. 45.24%)出现率更低(均P<0.05)。与良性组比较,交界组多房囊腺瘤间隔厚度[(3.14±1.03)mm vs.(6.23±1.15)mm]显著更高(t=13.590,P<0.05)。MRI对卵巢交界性黏液性囊腺瘤的检出正确率为90.48%,显著高于卵巢良性黏液性囊腺瘤检出正确率(72.00%),差异有统计学意义(χ^(2)=4.951,P<0.05)。MRI诊断卵巢交界性黏液性囊腺瘤的曲线下面积(AUC)为0.812。结论 MRI可以详细显示卵巢交界性黏液性囊腺瘤患者的病理特征,有效鉴别卵巢良性黏液性囊腺瘤和交界性黏液性囊腺瘤,具有一定临床应用价值。