土壤腐殖物质特征及其对有机碳长时间尺度稳定性的指示：以陕西洛川黄土剖面为例

在长时间尺度上研究土壤中腐殖物质的组成和腐殖化特征对于正确评价土壤有机质的稳定性具有重要意义。文中对洛川黄土/古土壤剖面S8以上的17个黄土和古土壤样品中的胡敏酸（HA）、富里酸（FA）和胡敏素（HM）进行定量研究,并对HA和FA的E465、E665值等进行了测定。结合该课题组对矿物组成、总有机碳（TOC）及其各组分含...     

Composition and geochemistry of clay sediments offshore the northeastern Sicilian coast (Southeastern Tyrrhenian Sea,Italy)

Grain-size, mineralogical and chemical analyses were carried out on fine fraction of sediments collected in the Gulfs of Patti and Milazzo, two borderland basins in the Southern Tyrrhenian extending offshore the northeastern Sicilian coast.     

Probing deep weathering in the Shale Hills Critical Zone Observatory,Pennsylvania (USA): the hypothesis of nested chemical reaction fronts in the subsurface

Weathering is both an acid‐base and a redox reaction in which rocks are titrated by meteoric carbon dioxide (CO₂) and oxygen (O₂). In general, the depths of these weathering reactions are unknown. To determine such depths, cuttings of Rose Hill shale were investigated from one borehole from the ridge and four boreholes from the valley at the Susquehanna Shale Hills Observatory (SSHO). Pyrite concentrations are insignificant to depths of 23 m under the ridge and 8–9 m under the valley. Likewise, carbonate concentrations are insignificant to 22 and 2 m, respectively. In addition, a 5–6 m‐thick fractured layer directly beneath the land surface shows evidence for loss of illite, chlorite, and feldspar. Under the valley, secondary carbonates may have precipited. The limited number of boreholes and the tight folding make it impossible to prove that depth variations result from weathering instead of chemical heterogeneity within the parent shale. However, carbonate depletion coincides with the winter water table observed at ~20 m (ridge) and ~2 m depth (valley). It would be fortuitous if carbonate‐containing strata are found under ridge and valley only beneath the water table. Furthermore, pyrite and carbonate react quickly and many deep reaction fronts for these minerals are described in the literature. We propose that deep transport of O₂ initiates weathering at SSHO and many other localities because pyrite commonly oxidizes autocatalytically to acidify porewaters and open porosity. According to this hypothesis, the mineral distributions at SSHO are nested reaction fronts that overprint protolith stratigraphy. The fronts are hypothesized to lie subparallel to the land surface because O₂ diffuses to the water table and causes oxidative dissolution of pyrite. Pyrite‐derived sulfuric acid (H₂SO₄) plus CO₂ also dissolve carbonates above the water table. To understand how reaction fronts record long‐term coupling between erosion and weathering will require intensive mapping of the subsurface. Copyright © 2013 John Wiley & Sons, Ltd.     

考虑渐近状态特性的超固结土本构模型

基于超固结土的UH模型,结合渐近状态概念,将适用于饱和砂土的渐近状态本构模型推广为考虑渐近状态特性的超固结土本构模型,用于描述土的超固结性和渐近状态特性。通过采用变换应力方法实现了模型的三维化。新提出的本构模型简单、参数较少,与剑桥模型相比,仅增加了一个材料参数,即伏斯列夫面斜率。该模型能够合理反映超固结土的硬化、软化、临界状态、剪缩、剪胀、应力路径依赖性、渐近状态等特性。     

动荷载作用下结构性软土微结构变化的分形研究

为探讨天津滨海新区典型结构性软土的动力特性,采用动三轴试验和压汞试验,对交通荷载作用下结构性软土微观结构变化进行了研究。取原状土和动荷载作用后的土样进行压汞测试,用分形理论对压汞测试数据进行分析,探讨孔隙分布特征,提出孔径划分的方法,给出了卓越频率与土体孔隙变化的规律。研究结果表明：在动荷载作用后,天津滨海新区典型软土的孔隙分布发生改变,可分为3种类型;利用Menger海绵模型研究交通荷载作用下结构性软土的孔隙分布特性是可行的;用孔隙分维数可实现对卓越频率的预测以及路基土体变形行为的机制分析。     

Assessment of Compressibility Behavior of Naturally Cemented Soft Clays

It Naturally cemented soft clays have components of strength and stiffness, which cannot be accounted for by classical soil mechanics (Leroueil and Vaughan 1990). This stems from the influence of structure caused by cementation due to environmental factors. It is necessary to evaluate the cementation bond strength at preyield and postyield stress levels of loading, to understand comprehensively the observed response from micromechanic considerations. This helps to better understand and evolve approaches to model the constitutive behavior in a consistent manner, according to the physical phenomenon of formation of cementation as an additional component to what is otherwise normally regarded as frictional behavior arising only from particulate nature of clays. Comparing the behavior of deep deposits of Pusan soft clays under stress with corresponding response of the same clay in its remolded state, it has been possible to take into account particulate and nonparticulate responses. The evolution of cementation bonding is modeled for different Pusan clays with the yield stress in oedometer compression as a normalizing parameter for obtaining the generalized relationship of cementation bonding with increase in stress. The already established model for determining the remolded behavior is appropriately modified to assess the behavior influenced by cementation. The model proposed consists of parameters, which are determined in routine investigations.     

Gravitational Sedimentation Behavior of Sensitive Marine Ariake Clays

It has been well documented that natural marine Ariake clays are sensitive clays. In this study, extensive data of marine Ariake clays are obtained to investigate the gravitational compression behavior for sensitive clays. Analysis results indicate that the compression behavior of remolded Ariake clays is not different from that of other remolded/reconstituted soils. But natural Ariake clays do not follow the gravitational compression pattern reported by Skempton (1970) Skempton, A. W. 1970. “The consolidation of clays by gravitational compaction”. In Q. J. Geol. Soc 373–411.  [Google Scholar] for natural sedimentary soils. At a given value of effective overburden pressure, the void ratios of natural Ariake clays are almost independent of liquid limits. Most natural Ariake clays lie above the sedimentation compression line proposed by Burland (1990) Burland, J. B. 1990. On the compressibility and shear strength of natural clays. Gèotechnique, 40: 329–378. [Crossref], [Web of Science ®] , [Google Scholar]. When the liquid limit is larger than 90% and the ratio of natural water content over liquid limit ranges 0.8–1.1, the natural Ariake clays lie around the sedimentation compression line. In addition, the natural Ariake clay with higher value of the ratio of natural water content over liquid limit lies above the natural Ariake clay with lower value of the ratio of natural water content over liquid limit. Salt removal is the most probable cause for such a phenomenon.     

Performance of geosynthetic-reinforced granular piles in soft clays: Model tests and numerical analysis

The laboratory model tests and numerical analyses have been performed on reinforced granular piles installed in very soft clay. The granular piles were reinforced with geosynthetic in the form of vertical encasement, horizontal strips and combined vertical-horizontal reinforcement. The short term-displacement control model tests were carried out either only a granular pile loaded or with an entire area loaded. The laboratory results in the form of vertical load intensity-settlement behaviour were compared with that obtained from FEM software, PLAXIS 3D. The results indicated significant improvement in ultimate load intensity and stiffness of treated ground due to inclusion of geosynthetic.     

Rate-Dependent and Long-Term Yield Stress and Strength of Soft Wenzhou Marine Clay: Experiments and Modeling

This paper focuses on the rate-dependent yield stress, undrained strength, and long-term undrained strength of clay. Various oedometer and triaxial tests were performed on Wenzhou marine clay. The uniqueness of rate-dependent and long-term yield stress and strength is discussed. A new anisotropic elastic viscoplastic model is proposed by adopting the concept of anisotropy and isotropy processes. The determination of model parameters is discussed, demonstrating how all model parameters can be determined in a straightforward way requiring the same basic tests as for the Modified Cam Clay model. Experimental verifications are carried out using the constant strain-rate and creep tests on the Wenzhou marine clay.     

软黏土中吸力锚循环失稳过程的模型试验

开展了张紧式吸力锚在侧壁最优系泊点处遭受平均荷载和循环荷载共同作用下的模型试验,着重研究了软黏土中吸力锚在等幅及变幅循环荷载下的变形失稳过程。研究发现,循环累积位移过大是锚发生破坏的主要原因。对于等幅循环加载试验,由于竖向附加荷重的施加,锚在水平向的循环累积位移要明显大于竖向,表现为明显的水平破坏模式。在特定的平均荷载水平下,循环荷载水平越高,锚的累积位移发展得越快,达到破坏所需的循环次数就越少。循环位移随循环次数的增长变化不明显,但随循环荷载水平的增大而增大。对于变幅循环加载试验,系泊点各方向的循环累积位移与循环位移均与循环荷载水平成正比。不同的循环加载时程下,锚的竖向累积位移均比水平累积位移大,表现为偏向于竖向破坏的中间破坏模式。锚前期的循环加载历史对后续加载产生的累积变形有明显影响。与静力加载相比,循环加载时锚的运动方向角有所增大,这可能是由于锚底孔压的累积要大于锚侧孔压的累积,从有效应力的角度分析,锚底有效应力的减少相对锚侧明显,进而使得锚竖向承载力减小得更多,导致锚的竖向运动更明显。