基于FWD的半刚性基层开裂状况无损评价模型

为无损判别半刚性基层开裂状况,以落锤式弯沉仪(FWD)为平台反演基层模量,分析弯沉盆匹配法和规律法模量反演结果的差异,进行基层反演模量与开裂状况的相关性分析,以基层模量比为评价指标,建立基层开裂状况无损评价模型和评价标准。研究表明：铣刨后的半刚性基层表面可视化损坏模式主要为裂缝;与弯沉盆匹配法相比,弯沉盆规律法的模量反演结果唯一且土基模量变异性较低;基层模量比与基层开裂状况在半对数坐标下具有良好的线性关系;基层开裂状况可分为四类,基层模量比分界值分别为0.68、0.47、0.30。该评价模型适用于不同强度的半刚性基层损坏状况的无损判别,可为路面大中修设计是否翻修半刚性基层提供决策支持。     

基于多种群遗传算法考虑浅层基岩及粘弹性的路基模量反演方法

提出一种考虑浅层基岩和粘弹性的路基模量反算新思路。对于路基模型,分别采用位移边界条件和开尔文模型来描述浅层基岩深度和粘弹性,并利用有限元软件对便携式落锤弯沉仪现场试验进行模拟,采用多种群遗传算法对路基模量最优值进行迭代。有限元模拟计算结果表明,新方法考虑浅层基岩的正算模型的反演模量平均误差为7.0%,而考虑半空间的正算模型却高达16.2%,说明忽略浅层基岩会使反演模量产生较大误差;随着浅层基岩深度的增加,误差减小,当深度为3 m时,影响几乎不存在。对于考虑粘弹性的有限元模型,在正算模型中忽略该特性的最大误差可达27.9%,而考虑粘弹性的最大误差仅为7.4%。由于浅层基岩深度勘探难度大,仅从理论方面进行研究。     

刚性路面结构参数反演弯沉盆衍生指标法综合分析

为解决刚性路面结构参数反演方法的适用性问题,综合分析刚性路面结构参数反演中3类代表性的弯沉盆衍生指标法.在系统梳理弯沉盆面积指数法、惰性点法、弯沉盆重心距离法的模型体系的基础上,采用理论数值分析的方法,定量分析3类衍生指标的规律特性,并从工程适用的简单、易操作性出发,提出惰性点法的计算图表和弯沉盆面积指数法及重心距离法的回归公式.以典型的刚性道面结构形式为例,对比分析3类弯沉盆衍生指标法的参数反演结果的准确性和鲁棒性,检验所提出模型或图表的有效性.计算结果表明:提出的计算图表或公式大幅简化了参数反演中衍生指标的计算,3种衍生指标法的参数反演结果存在明显差异,弯沉盆重心距离法充分利用各测点的信息并以拟合误差最小化为原则,显著提高参数反演的精确性和鲁棒性.     

FWD在道路使用性能评价中的应用

在研究现有国内外技术成果的基础上，结合工程实际，应用落锤式弯沉仪（FWD）对改建路面进行了弯沉、模量反算及接缝传荷能力的测试，详述了测试过程和结果，其分析成果在实践中得到了良好的应用。     

Application of semi-analytical finite element method to evaluate asphalt pavement bearing capacity

Bearing capacity is a key index in pavement management systems in many countries, which reflects the essential material properties of asphalt pavements. Many stationary measuring methods have been undertaken in the past; current assessment of the bearing capacity tends towards fast and continuous measurements at traffic speed for a network analysis. The conventional evaluation using stationary loads do not represent real traffic loading condition; therefore the results will inevitably lead to discrepancies from reality. A specific computational program SAFEM based on semi-analytical finite element method is proposed to overcome the difficulty. The reliability and efficiency of the SAFEM is proved by verification with commercial FE software ABAQUS and field measurements. The variation tendency of the back-calculated bearing capacity has a quite good negative linear relation with the number of loading cycles in the experiment. The investigation shows this proposed assessment system is a feasible option for the fast and reliable analysis of the pavement bearing capacity at a network level for road administrations.     

Systematic back-calculation protocol and prediction of resilient modulus for MEPDG

A research focusing on the characterisation of representative local material properties was conducted to facilitate the full implementation of the Mechanistic-Empirical Pavement Design Guide for roadway designs in Wyoming. As part of the test program, falling weight deflectometer deflection data were collected from 25 test sites in Wyoming for back-calculation of subgrade resilient modulus. Also, subgrade materials from these test sites were sampled for laboratory resilient modulus measurement in accordance with the AASHTO T 307. The back-calculation is a user-dependent procedure and produces a non-unique resilient modulus estimation. To alleviate this limitation, this paper focuses on the recent development of a systematic back-calculation protocol for subgrade resilient modulus using MODCOMP6 software. The protocol is intended for use on a flexible pavement with a crushed base. The proposed procedure discusses pre-analysis checks, seed modulus adjustment, pavement structure adjustment and program termination criteria. A correlation study was conducted to correct back-calculated resilient modulus to laboratory-equivalent values. The results conclude that a non-zero intercept linear regression model provides a better correlation than the widely used zero intercept linear regression model. Furthermore, better correlations are achieved when the back-calculated resilient modulus of a lower subgrade layer and resilient modulus measured at higher laboratory test sequences Nos. 11 to 15 are considered. The non-zero model based on M_r test sequence No. 14 and lower subgrade layer yields the best correlation. For the zero model, a C-factor of 0.645 based on M_r test sequence No. 15 and lower subgrade layer yields the best correlation.     

高频燃烧红外吸收法测定黑龙江典型鳞片石墨矿区浮选流程样品中固定碳

鳞片石墨矿浮选流程样品中的固定碳含量是确定浮选实验条件以及浮选实验所能达到选矿指标的重要依据。由于矿样中的碳酸盐、有机物,以及残留在样品表面的碳酸盐浮选药剂、有机浮选药剂等都会对固定碳含量的测定产生干扰,所以实验先将样品在高温下灼烧除去其中的有机碳,用酸将碳酸盐中的碳转化为二氧化碳挥发除去,然后以铁屑和钨锡混合助熔剂进行助熔,以人工配制的石墨矿校准物质绘制校准曲线,建立了高频燃烧红外吸收法测定鳞片石墨矿浮选流程样品中固定碳含量的方法。对称样量、灼烧温度、灼烧时间、酸处理条件和助熔剂用量进行了优化,确定实验条件如下:称样量为0.040 00～0.120 0g,灼烧温度为470℃,灼烧时间为60min,采用王水(1+4)分解样品中碳酸盐;采用0.5g铁屑和0.8g钨锡混合助熔剂进行助熔。在选定的实验条件下,固定碳质量在1.51～36.24mg范围内与其对应红外吸收信号的积分面积呈良好的线性关系,相关系数为0.999 2,方法检出限为0.005 3%,定量限为0.015%。将实验方法应用于黑龙江典型鳞片石墨矿浮选流程样品的原矿、粗精矿、中矿、尾矿中固定碳含量的测定,测定值与行业标准JC/T ...     

永磁同步伺服系统速度调节器抗饱和补偿器设计

针对永磁同步伺服系统速度调节器积分饱和问题,按照反计算思想,提出一种新型的Aw设计方法.该AW方法可根据PI调节器输入输出状态确定反计算支路的增益,为其提供一套整定原则.通过仿真和实验对比传统反计算AW与该新型AW设计方法,仿真和实验结果验证了该新型AW设计的可行性及优越性.在保证系统响应速度的前提下,新型AW设计的P...     

Assessing artificial neural network performance for predicting interlayer conditions and layer modulus of multi-layered flexible pavement

The objective of this study is to evaluate the performance of the artificial neural network (ANN) approach for predicting interlayer conditions and layer modulus of a multi-layered flexible pavement structure. To achieve this goal, two ANN based back-calculation models were proposed to predict the interlayer conditions and layer modulus of the pavement structure. The corresponding database built with ANSYS based finite element method computations for four types of a structure subjected to falling weight deflectometer load. In addition, two proposed ANN models were verified by comparing the results of ANN models with the results of PADAL and double multiple regression models. The measured pavement deflection basin data was used for the verifications. The comparing results concluded that there are no significant differences between the results estimated by ANN and double multiple regression models. PADAL modeling results were not accurate due to the inability to reflect the real pavement structure because pavement structure was not completely continuous. The prediction and verification results concluded that the proposed back-calculation model developed with ANN could be used to accurately predict layer modulus and interlayer conditions. In addition, the back-calculation model avoided the back-calculation errors by considering the interlayer condition, which was barely considered by former models reported in the published studies.     

含软弱结构面的岩质高边坡稳定分析研究

本文根据有限单元法和刚体极限平衡原理,探讨了岩质高边坡稳定分析新途径。在分析已有的参数反演原理基础上,进一步完善了参数反演原理,提出了新的参数反算方法.同时,文中阐述了三维弹塑性有限元变“Kp”迭代法解题原理,在有限元计算成果的基础上,探讨并提出了计算稳定安全系数的新方法.