饱和软土大变形非线性自重固结模型

基于分段线性方法,建立了饱和软土一维自重固结模型（简称SWC模型）。该模型能考虑自重固结过程中土体的大变形效应和材料参数的非线性变化。将该模型的计算结果与相关解析解、现场试验及室内试验结果进行了对比验证,证明了SWC模型能准确计算出大变形和非线性条件下饱和软土的自重固结过程,包括沉降量、平均固结度、孔隙比分布和超孔隙水压力分布等参数随时间的变化过程。随后,以现场试验为基础,采用SWC模型对饱和软土自重固结的4个主要影响因素（即土体初始高度、边界排水条件、初始孔隙比和土粒相对密度）进行了参数分析。结果表明,上述4个参数对软土自重固结过程均具有重要影响：土体初始高度越高,则自重固结沉降量和最终平均应变值越大;边界排水条件对土体自重固结的速度有重要影响,但不影响自重固结的最终沉降量;初始孔隙比越大,则自重固结沉降量越大,其完成自重固结所需时间越短;土粒相对密度越大,则土体的最终沉降量越大,完成自重固结所需时间越短。     

饱和软土大应变自重固结非线性分析

饱和软土的自重固结涉及许多复杂的非线性问题,而现有分析方法一般基于线性假设,将固结控制方程简化,在沉降变形较大的情况下并不合理。基于Gibson大变形固结方程,推导在单面排水和双面排水条件下的边界条件,综合考虑饱和软土的自重特性与非线性压缩、渗透关系,采用稳定性较好的Crank-Nicolson型差分格式离散并求解非线性控制方程,并从孔隙比、沉降、孔隙水流速3个方面将数值解与CS2固结数值模型进行对比验证。结合工程实例,研究土层不同初始厚度和初始孔隙比对自重固结的影响。结果表明：初始厚度与初始孔隙比较大土层最终沉降也较大。与传统方法相比,该方法所得出的数值解精度较高,实现了高度非线性固结方程的快速求解,其成果更能广泛运用于实际工程的分析之中。     

碴土桩在黄土,杂填土及饱和软土地基中的应用

本文介绍了某工程采用碴土桩处理松散杂填上、Ｉ级非自重湿陷性典土及饱和软土设计、施工与检测结果,通过三种不同桩间距的对比试验,探讨了地基加固效果,从而分析桩间距与承载力关系。文中最后对在复合地基上所做的大小压板试验进行了对比,表明用小压板试验推算大压板复合地基承载力是可靠的,可取代大压板试验。     

饱和软土大变形非线性自重固结模型

基于分段线性方法,本文建立了饱和软土一维自重固结模型(简称SWC模型)。该模型能考虑自重固结过程中土体的大变形效应和材料参数的非线性变化。将该模型的计算结果与相关解析解、现场试验及室内试验结果进行了对比验证,证明了SWC模型能准确计算出大变形和非线性条件下饱和软土的自重固结过程,包括沉降量、平均固结度、孔隙比分布和超孔隙水压力分布等参数随时间的变化过程。随后,以现场试验为基础,本文采用SWC模型对饱和软土自重固结的四个主要影响因素(即土体初始高度,边界排水条件,初始孔隙比和土粒比重)进行了参数分析。结果表明,上述四个参数对软土自重固结过程均具有重要影响:土体初始高度越高,则自重固结沉降量和最终平均应变值越大;边界排水条件对土体自重固结的速度有重要影响,但不影响自重固结的最终沉降量;初始孔隙比越大,则自重固结沉降量越大,其完成自重固结所需时间越短;土粒比重越大,则土体的最终沉降量越大,完成自重固结所需时间越短。     

饱和软土大变形非线性自重固结模型

基于分段线性方法,本文建立了饱和软土一维自重固结模型(简称SWC模型)。该模型能考虑自重固结过程中土体的大变形效应和材料参数的非线性变化。将该模型的计算结果与相关解析解、现场试验及室内试验结果进行了对比验证,证明了SWC模型能准确计算出大变形和非线性条件下饱和软土的自重固结过程,包括沉降量、平均固结度、孔隙比分布和超孔隙水压力分布等参数随时间的变化过程。随后,以现场试验为基础,本文采用SWC模型对饱和软土自重固结的四个主要影响因素(即土体初始高度,边界排水条件,初始孔隙比和土粒比重)进行了参数分析。结果表明,上述四个参数对软土自重固结过程均具有重要影响:土体初始高度越高,则自重固结沉降量和最终平均应变值越大;边界排水条件对土体自重固结的速度有重要影响,但不影响自重固结的最终沉降量;初始孔隙比越大,则自重固结沉降量越大,其完成自重固结所需时间越短;土粒比重越大,则土体的最终沉降量越大,完成自重固结所需时间越短。     

西安市近期饱和黄土的工程地质特征

本文以西安市东郊某场地,在Q_3湿陷性黄土中,近期形成的饱和黄土为例,从土的一般物性指标和变形特征入手,分析讨论了近期饱和黄土复杂而多重的工程性质,以试验数据说明近期饱和黄土由于饱和度的差异和结构强度对土体变形性的影响;提示了确定近期饱和黄土承载力f_o值之变形参数的选择原则,同时提出了多种处理地基方法的组合应用是处理近期饱和黄土地基的发展方向。     

浅谈近期饱和黄土的工程特征

本文以西安市东郊某场地，在Ｑ３湿陷性黄土中．近期形成的饱和黄土为例，从土的一般物性指标和变形特征入手，分析讨论了近期饱和黄土复杂而多重的工程性质，以试验数据说明近期饱和黄土由于饱和度的差异和结构强度对土体变形性的影响；提示了确定近期饱和黄土承载力ｆｏ值之变形参数的选择原则，同时提出了多种处理地基方法组合应用是处理近期饱和黄土地基的发展方向。     

石家庄市及周围地区饱和粉土特征

在总结石家庄市及周围地区多个勘察及地基处理场地饱和粉土的物理力学性质基础上,讨论了饱和粉土实际较低承载力、变形较大与土工试验结果相矛盾的原因,为规范上未曾提及饱和粉土提出了综合评价办法及改良处理措施.     

复杂应力路径下流体饱和砂岩本构模型

高孔隙率砂岩在不同围压及被不同流体（水及油）饱和时表现出不同的应力-应变特性及不同的破坏过程。复杂应力路径下油和水饱和砂岩的力学试验表明,存在某一临界围压,随着围压的增加,饱和砂岩从以压剪破坏为主,逐渐转变为以孔隙坍塌破坏为主的破坏机制。通过力学试验结果的分析,以两种破坏理论对油和水饱和砂岩的破坏特征进行了力学解释,并应用经典塑性力学的盖帽模型建立了相应的本构模型,应用非线性有限元法进行了数值验证,研究结果表明,提出的模型与试验资料吻合良好,能较好地模拟复杂应力路径下油和水饱和砂岩的破坏机制及模拟注水采油引起的砂岩附加沉降。     

西安地区饱和软黄土工程地质特征研究

饱和软黄土是黄土地区一种特殊性岩土。结合西安城区和北环铁路工程勘察的结果,分析了西安地区饱和软黄土的分布规律及其物理力学性质,讨论了饱和软黄土分布上的差异,从地质环境角度探讨了北环铁路饱和软黄土分布的成因,提出了上层滞水含水层也存在饱和软黄土的观点。     

冻结黄土抗拉强度的试验研究

冻结饱水黄土的拉伸试验表明，拉伸破坏均属脆性破坏类型，拉断面上矿物颗粒剪移错粒，裂隙发育。拉伸的应力－应变过程，视荷载作用的快慢大致可分为粘弹－塑性、粘－弹性有脆性破坏三类，它们可用统一的方程形式加以描述，此外，对饱水冻结黄土的峰值应力、破坏应变和破坏时间等特性进行了分析，对抗拉、抗压强度作分析比较后指出，它们的比值为０．４４－０．６３，与负温和加载速率的关系不大。     

正常固结饱和粘性土的不排水强度

本文以有效应力强度理论和Henkel孔隙水压力公式为基础,建立了各种类三轴与平面应变试验条件下正常固结饱和粘土的不排水强度公式及相互关系;初步估计了粘土强度随固结增长的计算公式.     

Hydraulic Conductivity Prediction of Saturated Sand-Bentonite Mixtures

In this paper, models have been developed to predict the hydraulic conductivity of the saturated bentonite and saturated sand-bentonite mixtures. For these models, free swell void ratio of the bentonite is required which can be obtained using a simple test. It was observed that hydraulic conductivity of the saturated bentonite and saturated sand-bentonite mixtures could be predicted within 5 or 1/5 times of the measured values for most of the cases.     

饱水粘性土主固结理论

对饱水软粘土的预压排水主固结研究应从其排水的本质出发, 即从软土在预压过程的含水量变化上研究主固结量的变化规律, 利用土的基本性质指标导出主固结比基本公式及主固结量(沉降量)、绝对主固结量、绝对固结度等理论计算方法.与传统的算法不一样的地方是这些算法与预压荷载(即固结应力) 无关系, 直接计算出主固结的效果及评价预压排水固结地基处理卸载的可行性.利用上述基本公式亦可导出剩余主固结量、主固结速率等计算式.通过实例的分析, 证明上述理论方法与观测的数据基本相符.      

饱和粘性土地基固结沉降的变化规律

本文用计算饱和粘性土地基固结沉降量的归一化曲线法进行大量电算,探讨在总荷载和载荷面积保持不变的情况下,地基沉降量随载荷面形状和基础埋深变化的规律,并提出根据这些规律性来调整多层住宅建筑基础沉降量的建议,使基础设计更臻合理。最后用一个砂井堆载预压试验的观测成果进一步验证了所采用的计算方法的可靠性。     

An Elastoplastic Model for Partially Saturated Collapsible Rocks

A unified elastoplastic model for describing the stress–strain behavior of partially saturated collapsible rocks is proposed. The elastic–plastic response due to loading and unloading is captured using bounding surface plasticity. The coupling effect of hydraulic and mechanical responses is addressed by applying the effective stress concept. Special attention is paid to the rock–fluid characteristic curve (RFCC), effective stress parameter, and suction hardening. A wide range of saturation degree is considered. The characteristics of mechanical behavior in partially saturated collapsible rocks are captured for all cases considered.     

Regularities of Consolidation Settlement for Saturated Cohesive Subsoils

A great quantity of computer-sided data has been made by means of the normalized curve method of estimating consolidation settlement for saturated cohesive subsoils in this paper to research into regularities of subsoil settlement varying with the shapes of loading area and with the foundation depths while the total loads and the loading area are constant. A proposal of using the regularities to adjust the settlement of foundations of multi storied residence buildings is given which will make the design more reasonable. Finally, the estimating method is cheeked experimentally by the observed results of an in-situ loading test.     

Saturated permeability measurements on pumice and welded-tuffaceous materials

Fluid flows in consolidated porous media of volcanic origin are being investigated to support such diverse efforts as the modeling of thermal/outgassing phenomena at Mount St. Helens and the hydrological modeling of tuffaceous rocks in support of the Department of Energy’s (DOE) Nevada Nuclear Waste Storage Investigations Project An experimental apparatus was designed and built to allow water-saturated permeabilities as low as 10⁻¹⁸ m² to be measured on cores of diameter 5 cm and length 10 cm under steady-state flow conditions. This same apparatus can also be utilized in a transient (pressure-decay) mode in order to measure permeabilities several orders of magnitude lower than the steady-state limit. Tests were conducted on samples of pumice, fractured welded tuff, and welded tuff, representing a permeability range of seven orders of magnitude Pumice was found to have a permeability of ∼3×10⁻¹² m², sufficiently high to allow the complete Darcy-to-Ergun regime to be investigated Welded (unfractured) tuff was tested in the transient mode, yielding a permeability of ∼5×10⁻¹⁹ m². Two, long-time-scale, steady-flow experiments were conducted on a core of welded tuff containing a single, through-going fracture. For the first experiment, the core was an integral cylinder containing a naturally occurring fracture. For the second experiment, the core was separated into two pieces along the existing fracture plane, then rejoined. Effects of essentially constant, as well as rapidly varied, circumferential stress were studied in both tests. Results showed core permeability to decay to 2×10⁻¹⁸ m² in both cases, independent of the initial fracture state (closed versus open). With a naturally occurring fracture, core permeability decreased by a factor of 2 over a 200-h test period. With an initially open fracture, core permeability decreased by a factor of 4 under the influence of a comparable 200-h load-time history, after 700 h of testing, core permeability was reduced by an order of magnitude from its initial level. Final effective hydraulic fracture aperture was calculated to be 10⁻⁶ m, corresponding to a calculated effective fracture permeability of 10⁻¹³ m² Fracture flow was thus estimated to account for 80% of the total flow rate through this core under final test conditions.     

Heterogeneous Equilibria in Saturated Aqueous Solutions of Uranophane

Heterogeneous equilibria in the system Ca(HSiUO₆)₂ · 5H2O_(c)–aqueous solution were studied over broad ranges of pH, ionic strength, and ionic composition of the solution, and the pH range of stability of Ca uranyl silicate is determined. Hydrolysis products of Ca uranyl silicate are identified, and their solubility is determined. The equilibrium constant of the dissolution reaction and the standard Gibbs function of formation of Ca(HSiUO₆)₂ · 5H₂O are calculated from experimental data, and solubility curves of uranophane and equilibrium speciation diagrams for U(VI), Si(IV), and Ca(II) in coexisting aqueous solutions and solid phases are calculated.     

饱和多孔介质中的非均匀平面波

讨论了两相饱和多孔介质中的非均匀平面波,在所采用的多孔介质模型中,利用了每种组分的微观密度保持不变而与体积分数相关的宏观密度是变化的假设。针对理想无粘流体充填的弹性多孔固体,深入讨论了两种非均匀平面波的传播特性以及质点运动的轨迹线。