【作者】 宋飞；

【导师】 张建民；

【作者基本信息】 清华大学 ， 土木工程， 2009， 博士

【摘要】 土压力问题是土力学和岩土工程领域的基本研究课题之一。本文在较为系统地总结了国内外已有刚性挡土墙土压力问题研究成果的基础上,从设备研制、材料试验、离心模型试验、机理分析、实用算法诸方面入手,对任意侧向变形条件下各向异性填土的土压力产生机理和随挡墙位移变化的基本规律进行了较为深入而系统的研究,提出了相应的计算方法。主要取得的新成果有:(1)研制开发了新的基于液压式三轴仪的应变路径控制试验系统和可控任意挡墙位移的离心模型挡土墙试验设备。两套设备性能稳定,运行可靠,易于操作,具有足够的控制精度和测量精度,可分别用于砂土的等应变增量比试验以及砂土和粘性土的主动侧土压力离心模型试验研究。(2)基于系列化的材料试验揭示了各向异性对土压力系数与应变增量比之间关系的定量影响,基于离心模型试验揭示了各向异性填土的土压力和位移场随挡墙位移的变化规律。试验表明,与沉积面铅直的情形相比,沉积面水平的滑动区域和土压力均较小;与各向同性的情形相比,各向异性使静止状态的土压力增加15～50%,但对极限状态影响较小。(3)阐明了压剪耦合效应的不同是土压力随应变约束条件变化的根本原因,采用渐近状态应力比概念反映填土沉积或压密到稳定状态时的土压力系数,建立了不同渐近状态应力比与用应变增量比表述的应变约束条件之间所具有的唯一性关系,提出了反映各向异性对上述关系定量影响的数学表达式,称之为各向异性砂土的渐近状态准则。亦给出了一个各向同性砂土的三维渐近状态准则。(4)改进了张建民等(1998)提出的考虑任意侧向变形的土压力计算公式及方法,使其在绕墙顶转动情形、被动侧土压力和填土为超固结等三种条件下的计算更趋于合理;提出了挡墙位移从静止到主动状态的各向异性填土的土压力计算公式及方法;采用本文与其他学者的试验研究成果对上述计算公式及方法进行了验证分析,初步表明了其有效性和合理性。更多还原

【Abstract】 Evaluation of earth pressures is of practical significance for the design of retaining structures such as retaining walls, sheet pile bulkheads, bridge abutments, and basement walls of buildings. It is one of the key research subjects in soil mechanics and geotechnical engineering. In this dissertation previous researches on earth pressures against rigid retaining structures are reviewed critically and systematically. Experimental and theoretical investigations are made on the mechanism of generation and methodologies of evaluation for the earth pressures induced due to anisotropic sandy backfill against rigid retaining walls that fall at an intermediate state from active to passive states. Several new main achievements obtained in such studies are as follows:1) A new strain-path controlled test system is developed based on a triaxial test apparatus. The devise can be well applied to the studies on the stress-strain behaviors of anisotropic sand under the condition where axial and lateral stresses are exerted along different constant strain increment ratio paths. A new centrifugal model test facility is developed to investiagte the variations in the earth pressure with the wall displacement from the at rest state to active state for the rigid retaining wall system. Experimental facts confirmed the good precision and effectiveness of the above two devises.2) Quantitative influence of the anisotropy of sandy backfill on the relationship of the earth pressure coefficient with the strain increment ratio is found from a series of soil element tests. Moreover, significant effects of the anisotropy on the variation of the earth pressure against a movable rigid retaining wall with the increasing lateral soil deformation are confirmed from the centrifugal model tests. Test results show that, in comparison with the backfill of isotropic sand, anisotropy can result in an obvious increase of the coefficient of earth pressure at rest from 15 to 50%, but it has a little effect on the coefficient of active earth pressure. It is postulated from experimental analysis that anisotropy leads to the decrease of the earth pressure at passive side.3) Compression-dilatancy coupling effect is found to be responsibe for the dependency of the change of the earth pressure on the strain increment ratio and also the lateral strain constraint of the backfill. The key issue in the study of earth pressure under any lateral deformation is to establish the quantitative relationship between stress ratio corresponding to the asymptotic state and strain increment ratio. New asymptotic state criterion is proposed to describe the effect of anisotropy on the above relationship. In addition, an asymptotic state criterion is suggested to determine the above relationship for isotropic sand under three-dimensional stress states.4) Methodologies and formulas proposed by Zhang et al (1998) to evaluate the earth pressure under any lateral deformation are extended to be more suitable and effective in the evaluation of earth pressures for three conditions including i) the wall rotation about some point above the top, ii) all the stress states at the passive side and iii) the backfill of over-consolidated sand. New methodologies and formulas are proposed to evaluate the earth pressure for anisotropic backfill from the state at rest to the active state, and their essential effectiveness are confirmed experimentally.更多还原