井场边坡稳定性评价及工程处治方案

乐山市境内某井场平整形成填方边坡.边坡坡脚井场污水池开挖中,临空面和边坡支挡工程均出现变形破坏.根据变形破坏的分布规律,从场地地形、建筑物分布、边坡特征和原始坡体物质结构方面,分析该边坡变形机理,评价其稳定性影响因素.并采用极限平衡法对边坡的稳定性及下滑推力进行计算.在此基础上,针对性地提出该边坡的工程处治方案,保证后期井场及污水池的作业安全.     

新型快速锚固锚索的研发及应用

介绍了直立高填方区边坡治理工程中应用的一种新型的快速锚固技术———预应力混凝土管水平向快速锚固锚索的研发过程,阐述了其力学原理及其构造、特性,并结合工程实例,介绍了新型快速锚固锚索的实施过程及技术要点。     

化学方法改良吹填土固结沉降性质研究

大连市大窑湾港区的吹填土为高分散性低液限粉质黏土,其特点是亲水性高,含水量大,排水率低,这造成了吹填土承载力低,在荷载作用下变形量大,在很长一段时间内无法作为正常建筑地基使用.通过在盐水环境下添加不同剂量的浓度为0.1%的絮凝剂Praestol-2515或Praestol-650溶液,可以观察到土颗粒迅速聚合,土粒粒径明显增大,粒间胶结更加均匀和紧密,形成絮状物,从而促进了土颗粒与自由水分的分离,导致过饱和吹填土（悬浊液）沉降速度大大提高,极大地缩短了吹填土的排水固结时间,在短期内达到建筑地基所需要的变形量和承载能力.研究结果对于沿海地区过饱和吹填土的造陆工程,以及类似的高含水率黏性土的地基处理具有重要的启示意义.     

GEOMORPHIC AND STRATIGRAPHIC COMPLEXITY: HOLOCENE ALLUVIAL HISTORY OF UPPER WOLLOMBI BROOK, AUSTRALIA

Holocene and post‐European settlement alluvial histories of three nested drainage basins were reconstructed from detailed litho‐ and chronostratigraphy of cut and fill terraces and flood‐plains in the upper Wollombi Brook catchment. Fernances Creek (13.8 km²) valley fill consisted of intercalated thin mud sheets deposited in ephemeral swamps and thick sand sheets deposited by discontinuous channels. Dairy Arm (39.8 km²) valley fill was more complex, with inset alluvial fills in the upper basin and overlapping vertically stacked fills in the lower basin. However, correlative lithostrati‐graphic units were not found on all tributaries. Furthermore, basal radiocarbon dates on the last inset fill of four tributaries did not overlap, allowing for plus or minus twice the standard deviation of the reported ages. Wollombi Brook (341 km²) valley fill was also complex, with longitudinally discontinuous units, most of which were not found in the two tributaries. Upstream late Holocene channel incision was coeval with downstream chain of ponds because sediment generated by incision was stored in the intervening valley. Historical channel incision occurred between 1838 and 1867 on Fernances Creek at a locally steeper section of valley floor during the period of peak population and frequent floods immediately after a road crossing was constructed, but coincided with a catastrophic flood on Dairy Arm (June 1949) and on Wollombi Brook (1927). Lack of correlative litho‐ and chronostrati‐graphic units plus out‐of‐phase post‐European incision indicate that stratigraphic complexity is a function of geomorphic complexity due to the operation of geomorphic thresholds and complex response.     

Biogrouting of hydraulic fill fine sands for reclamation projects

ABSTRACT

Biogrouting, which is a new method for soil improvement, was used in an attempt to cement a type of hydraulic fill fine sands (called black sands) in reclamation projects in Tianjin, China, to form a working layer for mechanical equipment. Several factors influencing biogrouting with regard to cementing solution, including injection frequency, reaction time, concentration, and flow rate, were controlled to prepare black sand columns. This paper reports on an investigation of bacterial fixation, calcium ion utilization, and calcium carbonate distributions of biogrouted sand specimens. At the end of the tests, the geotechnical performances of the sand specimens were determined. The results showed that the biogrouting method effectively solidified black sands, by increasing the unconfined compressive strength of a sand column to 1.91?MPa and reducing the permeability coefficient by three orders of magnitude. A relationship between the unconfined compressive strengths and calcium carbonate contents was put forward, in addition to a relationship between the permeability coefficients and the calcium carbonate contents. According to the experimental results, some reasonable suggestions regarding the application of biogrouting to the consolidation of hydraulic fill fine sands in reclamation projects were proposed.     

Mechanism test on inhomogeneity of dredged fill during vacuum preloading consolidation

Abstract

First, this article presents a simulation experiment of hydraulic reclamation, and then a vacuum preloading (VP) test using the sedimentary soil obtained by the first experiment. In the VP test, the distribution and variation of different physico-mechanical parameters before and after the treatment were tested. According to the test results, the concept “non-Terzaghi soil” is proposed to explain the inhomogeneity and its mechanism rendered by “seepage separation.” And then a staged VP (SVP) drainage consolidation method has been introduced to improve the inhomogeneity and seepage curtain phenomena around prefabricated vertical drains (PVDs) during the consolidation. The test results demonstrate that the clogging problem around PVDs has been prevented and the consolidation efficiency has been promoted after the SVP test. It has been noticed that the cumulative drainage volume and the settlement displacement of SVP test were 27% and 24%, respectively, greater than that of VP test, and the soil tends to be more homogeneous. Moreover, it has been shown that the inhomogeneity degree of the permeability coefficient, unit weight, void ratio, water content, cohesion, internal friction angle, compression modulus, and the soil surface settlement in slurry after the SVP test were 3.10, 1.02, 1.03, 1.09, 2.30, 1.92, 1.19, and 1.02, whereas that after VP test was 397.27, 1.07, 1.40, 1.40, 4.74, 3.00, 1.76, and 1.22. Finally, the mechanism of SVP method has been discussed.     

高温冻土区填土路基融化固结变形分析

基于修正拉格朗日（U.L）描述下的大变形固结理论和考虑相变作用的温度场得到大变形融化固结理论,对不同路堤高度下填土路基温度场和融沉变形进行研究. 结果表明：高温冻土区合理高度的路堤在5~10 a内使冻土上限略微抬升,但冻土有明显升温. 冻土上限在未来的5~10 a后会急剧下降,且路堤高度越小,下降量越大. 与小变形融化固结理论相比,大变形融化固结理论预测高含量冻土融沉变形的精度更高. 融沉量与路堤高度成正比,且随着时间的增长,融沉变形呈阶梯型发展,路堤越高,阶梯现象越显著. 定义融沉量与路堤高度之比为沉降比,研究发现路堤越低,其沉降比越大,且随时间线性增长. 沉降比是冻土融深增量的单值函数,与路堤高度无关,通过沉降比函数可以快速而实用的求出融沉变形量.     

一种快速确定二维地震勘探最佳施工因素的方法

在二维地震勘探中,当地表遇到不能钻井放炮的障碍物时,如果要满足设计叠加次数,就必须采取变观激发的办法。变观激发时如何合理选择最大炮检距,保证区内浅、中、深目的层达到最大叠加次数,且在地层倾向未知的情况下,可通过变观激发试验,从监视记录上直接确定其下倾方向激发上倾接收的施工方法。     

Engineering geological parameters affecting the response of Τhessaloniki's urban fill to a major seismic event

In urban areas where there has been continuous occupation of the land for centuries, there are likely to be large areas of filled ground. Fills may have arisen inadvertently from the rubble of demolished buildings and the slow accumulation of refuse. Old urban fills of this type may contain soil, rubble, refuse and even whole parts of past constructions. Despite the fact that areas covered with such deposits are generally prone to severe problems, especially under conditions of dynamic loading, still their influence, as a foundation material on the seismic behaviour of modern buildings is practically unpredictable.Thessaloniki is an old historical city of Macedonia, Greece with no less than 2300 years of continuous urban evolution. A thick and heterogeneous layer of artificial deposits covers the biggest part of the historical centre of the city, as is the case for many old historical cities. The presence of this extensive formation influences the urban development, as it constitutes the foundation of the majority of the buildings of the historical centre, and its investigation is essential for most of the major constructions proposed. The complexity and heterogeneity of Thessaloniki's fill makes the assessment of its engineering behaviour a rather complicated task. This is due to the big range of values of accumulated geotechnical data but also to the fact that these data have been produced by unrelated methods and applied tests.The aim of this paper is to assess the engineering performance of Thessaloniki's fill based on its behaviour as foundation material to a major seismic event. This is carried out by the evaluation of the influence of engineering geological parameters to the damage distribution of the 1978 earthquake, based on the official database which recorded the condition of all the buildings of the historical centre. The statistical elaboration of the damage distribution was carried out following a classification scheme for the fill, based on the fill's classes produced by this scheme, the fill's thickness and the combination of both.The results are given in terms of damage ratios i.e. the ratios of the number of buildings in each damage status per total number of buildings inspected. The correlation of the engineering response with the thickness of the fill showed that there is a significant increase of the percentage of damaged buildings with increasing thickness. However, further analysis of these results showed that the above increase does not apply to all classes equally, which actually suggests that different parts of the fill behave differently in respect to the fill thickness. These results clearly show that a classification scheme and the determination of the boundary conditions should be used as a combined tool from an engineering geological point of view, in order to form a basis for the better understanding of the engineering behaviour of such deposits, the interpretation of geotechnical data and the design of more sophisticated investigations.     

某机场高填筑体下伏地基土变形评价

某机场工程土石方总量超过4×107m3,填方边坡最大高度102m。填方地基为砂层、卵石层、粉质粘土、砾岩及泥岩等组成的第四系河流沉积,结构复杂,物理力学特性变化大,场地附近有3条大的活动断裂,地震烈度为 度。本文在研究了区域地质背景、填筑材料和施工方法的基础上,对九黄机场高填筑体下伏地基土的变形进行了分析评价。