三峡高重力坝技术实践综述     

钮新强 《水科学进展》2013,24(3):442-448

三峡工程重力坝最大高度181 m,目前已蓄水至设计水位。大坝设计和施工过程中,通过特殊地质勘探、多种稳定计算方法对比分析、综合工程措施解决左岸坝段深层抗滑稳定问题;布置多层大孔口解决大流量、多任务的泄洪要求,运用钢筋混凝土有限元方法计算孔口配筋;运用二次风冷骨料、个性化动态通水、表面保温等技术进行温控防裂;采用富浆混凝土防渗、预埋冷却水管等技术进行碾压混凝土施工;采用封闭抽排方案、无盖重固结灌浆技术进行坝基处理。分析了大坝运行过程中纵缝开度变化、水位影响下坝踵应力变化的规律,提出了高重力坝在纵缝结构整体性、坝踵应力与应力控制标准、强震作用下大坝破坏机理及抗震措施等方面有待进一步研究的问题。  相似文献   

南京滁河漫滩软土性状研究     

周超 《岩土工程技术》2013,(6):284-287

近年来,随着经济水平的不断发展,建筑物规模不断扩大,地下空间的开发利用逐渐引起重视.滁河漫滩区软土深厚,随着基坑规模的扩大,合理提供软土的物理力学参数将会在安全可靠的前提下节省大量的基坑围护费用,不仅能够产生经济上的效益,还能为建立完整的区域软土评价体系提供支持.对滁河漫滩区软弱土层性状进行多种手段对比分析,对原位测试经验公式进行修正,提供根据原位测试计算滁河漫滩区软土层承载力的方法,并对滁河漫滩区软土层在工程建设中的不利影响进行分析.  相似文献   

Coupled consolidation model for negative skin friction on piles in clay layers     

《Geomechanics and Geoengineering》2013,8(2):141-149

Expansive soils swell on absorbing water and shrink on evaporation thereof. Because of this alternate swelling and shrinkage, civil engineering structures founded in them are severely damaged. For counteracting the problems of expansive soils, different innovative techniques were suggested. Stabilization of expansive clays with various additives has also met with considerable success. This paper presents, by comparison, the effect of lime and fly ash on free swell index (FSI), swell potential, swelling pressure, coefficient of consolidation, compression index, secondary consolidation characteristics and shear strength. Lime content was varied as 0%, 2%, 4%?and 6%?and fly ash content as 0%, 10%?and 20%. A fly ash content of 20%?showed significant reduction in swell potential, swelling pressure, compression index and secondary consolidation characteristics and resulted in increase in maximum dry density and shear strength. Swell potential and swelling pressure decreased with increase in lime content also. Further, consolidation characteristics improved. Compaction characteristics and unconfined compression strength improved at 4%?lime and reduced at 6%?lime.  相似文献   

Effect of lime and fly ash on swell,consolidation and shear strength characteristics of expansive clays: a comparative study     

《Geomechanics and Geoengineering》2013,8(2):175-181

Expansive soils swell on absorbing water and shrink on evaporation thereof. Because of this alternate swelling and shrinkage, civil engineering structures founded in them are severely damaged. For counteracting the problems of expansive soils, different innovative techniques were suggested. Stabilization of expansive clays with various additives has also met with considerable success. This paper presents, by comparison, the effect of lime and fly ash on free swell index (FSI), swell potential, swelling pressure, coefficient of consolidation, compression index, secondary consolidation characteristics and shear strength. Lime content (weight of lime/weight of dry soil) was varied as 0%, 2%, 4%?and 6%?and fly ash content (weight of fly ash/weight of dry soil) as 0%, 10%?and 20%. A fly ash content of 20%?showed significant reduction in swell potential, swelling pressure, compression index and secondary consolidation characteristics and resulted in increase in maximum dry density and shear strength. Swell potential and swelling pressure decreased with increase in lime content also. Further, consolidation characteristics improved. Compaction characteristics and unconfined compression strength improved at 4%?lime and reduced at 6%?lime.  相似文献   

An evaluation of the osmotic method of controlling suction∗     

《Geomechanics and Geoengineering》2013,8(1):1-11

Experimental techniques of testing the mechanical properties of unsaturated soils are complex and difficult to conduct. As a consequence, complete sets of parameters that characterise the behaviour of unsaturated soils remain scarce and necessary. In this context, it has been found useful to gather the information obtained after some years of practice of the osmotic technique of controlling suction. As compared to the more documented axis-translation technique, the osmotic technique has its own advantages and drawbacks that are discussed in this paper, together with some potential future developments.

The osmotic method has been developed by soil scientists in the 1960s and adapted to geotechnical testing in the early 1970s. This paper presents the osmotic technique and comments on its advantages (including suction condition close to reality and higher suctions easily attained) and drawbacks (including some concern with the membrane resistance and some membrane effects in the suction/concentration calibration). Various applications to geotechnical testing are presented such as the determination of the water retention curve, oedometer and triaxial testing procedures and the determination of the permeability of unsaturated soils. Recent developments, that include the extension of the method up to high suctions (10 MPa) are also described, together with some recent and novel applications such as data from high controlled suction oedometer compression test and the determination of the oil/water retention properties of oil reservoir chalks.  相似文献   

A novel technique for studying diffusion of contaminants in fine-grained soils     

《Geomechanics and Geoengineering》2013,8(3):199-209

Diffusion is one of the predominant contaminant transport mechanisms in fine-grained soils. Usually, conventional methods such as half-cell and column tests are adopted for establishing diffusion characteristics of such soils. However, these techniques are destructive in nature, quite time-consuming, and require cumbersome chemical analysis of the soil and its pore-solution. Hence, development of a technique that would overcome these limitations and would yield precise results, in extremely short duration, becomes essential. With this in view, a modified Perspex diffusion cell with provision for inserting a series of stainless steel electrodes has been fabricated to monitor the diffusive contaminant transport, indirectly, based on the variation of electrical impedance of the soil. An LCR meter is employed to measure the electrical impedance of the soil across each electrode over a period. Further, the electrical impedance variation is indirectly correlated to the diffusion of contaminants that occurs in the soil. Details of the study and the test setup developed for this purpose are presented in this paper. It has been demonstrated that the technique based on electrical impedance measurement is quite useful and efficient for establishing diffusion characteristics of the fine-grained soil.  相似文献   

Modelling of the effect of scale on the compressibility parameters of fine-grained soils     

《Geomechanics and Geoengineering》2013,8(4):262-270

ABSTRACT

The effect of sample scale represents a challenge when obtaining engineering parameters in the laboratory compared to those obtained in the field. This study aimed at contributing to existing knowledge numerically using the finite element software PLAXIS 2D. The investigations were analysed in terms of height scale (HS) and diameter scale (DS) through a series of laboratory tests. Its effect on compressibility parameters such as coefficient of consolidation (c_v) was noted experimentally and showed that the sample scale greatly influences soil parameters most particularly at DS. The soil behaviour was found to be dependent on both DS and HS with a correlation factor of 0.650 and 0.062, respectively. The experimental data were validated in PLAXIS and a new proposed model was developed in PLAXIS 2D under the DS. The new proposed model developed was found to show no significant difference with the laboratory data.  相似文献   

BEFOLKMNGS- OG ERHVERVSUDVIKLINGEN PÅ RØMØ 1950–70     

BODIL ENGELL M.Sc. 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):63-67

Engell. Bodil, 1977: Befolknings- og erhvervsudviklingen på Rømø 1950–70. Geografisk Tidsskrift 76: 63–67. København juni 1, 1977.

The general trend of unequal development between rural and urban intensifies on small islands. The development on the island of Rømø has further a special trend because of its intermediate position caused by the construction of the road-dam to Rømø, opened 1949. Furthermore, the recreational potential of the island and the special location close to the Danish-German border is of importance.  相似文献   

Elastoplastic multiphase model for simulating the response of piled raft foundations subject to combined loadings     

G. Hassen  P. de Buhan 《国际地质力学数值与分析法杂志》2006,30(9):843-864

A multiphase model and corresponding computational time‐saving finite element code is proposed in this paper for predicting the settlements experienced by a piled raft foundation when subject to the combined action of vertical and lateral loadings. This model, which is formulated in the framework of an elastoplastic behaviour for the soil and the reinforcing piles as well, explicitly accounts for the shear and flexural behaviour of the latter. Starting from a simple analytical example where all the concepts attached to this model are clearly illustrated, the main stages leading to its finite element implementation are then presented. The numerical tool thus elaborated, is applied to the simulation of a pile‐reinforced strip foundation submitted to a horizontally applied seismic load in addition to a permanent vertical load. One of the key results of such a simulation in terms of design recommendation, lies in the conclusion that, while the shear and flexural contributions of the reinforcement play quite a negligible role in the case of a vertical load (as compared with their axial resistance), they remain absolutely essential for withstanding the seismic lateral loading. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Correction to the gas phase pressure term in the continuum model for partially saturated granular media presented by Pietruszczak and co‐workers     

Simon M. Iveson 《国际地质力学数值与分析法杂志》2003,27(7):627-632

Pietruszczak and coworkers (Internat. J. Numer. Anal. Methods Geomech. 1994; 18 (2):93–105; Comput. Geotech. 1991; 12 ( ):55–71) have presented a continuum‐based model for predicting the dynamic mechanical response of partially saturated granular media with viscous interstitial liquids. In their model they assume that the gas phase is distributed uniformly throughout the medium as discrete spherical air bubbles occupying the voids between the particles. However, their derivation of the air pressure inside these gas bubbles is inconsistent with their stated assumptions. In addition the resultant dependence of gas pressure on liquid saturation lies outside of the plausible range of possible values for discrete air bubbles. This results in an over‐prediction of the average bulk modulus of the void phase. Corrected equations are presented. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献