云南镍矿地质特征及找镍方向   总被引：1，自引：0，他引：1  

薛步高 《云南地质》2008,27(1):1-11

云南硫化镍矿以与铂钯矿的伴生镍为主（11．76万t）,其中：大理-弥渡（6．85万t）、金平（6．38万t）、元谋-永仁-牟定（5．12万t）。硅酸镍主要在墨江-元江（64．41万t）;蛇绿混杂岩型硫砷化物镍矿（1．73万t）,是云南-大特色。与成矿有关的岩体主要是华力西期,次为加里东期,产出与深大断裂有关。找矿方向应以富宁、金平及景东东山-红河底玛为主攻目标。  相似文献   

Evaluation of undrained failure envelopes of caisson foundations under combined loading     

《Applied Ocean Research》2016

In this paper, results of a three-dimensional finite element study addressing the effect of embedment ratio (L/D) of caisson foundations on the undrained bearing capacity under uniaxial and combined loadings are discussed. The undrained response of caisson foundations under uniaxial vertical (V), horizontal (H) and moment (M) loading are investigated. A series of equations are proposed to predict the ultimate vertical, moment and maximum horizontal bearing capacity factors. The undrained response of caisson foundations under combined V-H and V-M load space is studied and presented using failure envelopes generated with side-swipe method. The kinematic mechanism accompanying failure under uniaxial loading is addressed and presented for different embedment ratios. Predictions of the uniaxial bearing capacities are compared with other models and it is confirmed that the proposed equations appropriately describe the capacity of caisson foundations under uniaxial vertical, horizontal and moment loading in homogenous undrained soils. The results of this paper can be used as a basis for standard design codes of off-shore skirted shallow foundations which will be the first of its kind.  相似文献   

Rotation–translation mechanisms for upper-bound solution of bearing capacity problems     

Orang Farzaneh  Navid Ganjian  Faradjollah Askari 《Computers and Geotechnics》2010

To obtain rigorous upper-bound solutions for the bearing capacity of strip footings subjected to combined loadings, a new collapse mechanism consisting of three rigid blocks undergoing impending rotational or translational movements is proposed. The proposed mechanism improves the efficiency of the previously-developed rigid block mechanisms to account for eccentric loading condition in restricted bearing capacity problems. The comparisons show a good agreement between the results obtained using the present method and those of the known solutions. The effectiveness of the proposed mechanism was examined through investigating the bearing capacity of eccentrically loaded strip footings over thin layer foundation soils.  相似文献   

Bearing capacity of interfering multiple strip footings by using lower bound finite elements limit analysis     

Jyant Kumar  Paramita Bhattacharya 《Computers and Geotechnics》2010

The ultimate bearing capacity of a number of multiple strip footings, identically spaced and equally loaded to failure at the same time, is computed by using the lower bound limit analysis in combination with finite elements. The efficiency factor (ξ_γ), due to the component of soil unit weight, is computed with respect to changes in the clear spacing (S) between the footings. It is noted that the failure load for a footing in the group becomes always greater than that of a single isolated footing. The values of ξ_γ for the smooth footings are found to be always lower than the rough footings. The values of ξ_γ are found to increase continuously with a decrease in the spacing between footings. As compared to the available theoretical and experimental results reported in literature, the present analysis provides generally a little lower values of ξ_γ.  相似文献   

Laboratory and field test study on the improvement of marine clay slurry by in-situ solidification     

Yonghui Chen  Long Chen  Geng Chen  Jianrong Chen 《Marine Georesources & Geotechnology》2013,31(6):695-703

Abstract

Soil solidification technology can create an artificial hard shell on a soft soil surface but the type and proportion of the curing agent, the construction technology, and the strengthening depth have large influences on the strengthening effect and engineering cost. This study introduces a new technology of soil solidification whereby an artificial hard shell layer is used as a new method to improve the soft ground. For the in-situ solidification technology, the soil and curing agent are mixed well by using a strong stirring machine so that the soil is strengthened rapidly and forms a hard crust. We introduce the key technology of the in-situ soil solidification method and determine the in-situ crust carrying capacity. The indoor experiment on the curing agent proportions is validated with field tests and a vane shear test, static penetration test, and plate loading test are used to evaluate the reinforcement effect. The experimental results show that the in-situ curing technology of dredged fill processing markedly reduced the reinforcement depth range of the soil water content, improved the physical and mechanical indices, and increased the bearing capacity and strength of the artificial hard shell layer, thereby fully meeting the requirements for the bearing capacity of construction machinery.  相似文献   

Assessment of direct CPT and CPTU methods for predicting the ultimate bearing capacity of single piles   总被引：1，自引：0，他引：1  

Guojun Cai  Songyu Liu  Liyuan Tong  Guangyin Du 《Engineering Geology》2009,104(3-4):211-222

Twelve methods to determine axial pile capacity directly based on cone penetration test (CPT) and piezocone penetration test (CPTU) data are presented, compared and evaluated. Analyses and evaluation were conducted on three types of piles of different size and length. All the tested piles have failed at the end of static load test. Both the CPT methods and the CPTU methods were used to estimate the load bearing capacities of the investigated piles (Q_p). The static load test was performed to determine the measured load bearing capacities (Q_m). The pile capacities determined through different methods were compared with the measured values obtained from the static load tests. Two criteria were selected as bases of evaluation: the best fit line for Q_p versus Q_m and the arithmetic mean and standard deviation for the ratio Q_p/Q_m. Results of the analyses showed that the best methods for determining pile capacity are the two CPTU methods. Furthermore, the CPTU method is simple, easy to apply, and not influenced by the subjective judgements of operating staff. Therefore, it is quite suitable for the application in pile engineering practice.  相似文献   

Local community training and education in southern Tanzania—a case study     

Vicki Howe   《Marine Policy》2001,25(6)

Local coastal communities are highly dependent upon the marine environment not only for protein but also as a primary source of income. In addition, there are growing economic opportunities offered within the coastal zone. As populations increase in these areas there is an increasing demand on coastal resources. This in turn requires effective management initiatives at regional, national and local levels.The Marine Education and Training Programme in Mtwara, southern Tanzania was a small scale capacity building project that incorporated two elements; a primary schools field day education programme and a marine coastal resources course for fishermen and women from the Mtwara District. The programme ran for a period of 1 year and during that time 14 schools, 198 children, 34 fishermen, 2 women and 14 villages participated. Results from preliminary evaluation indicated that such education is not only welcome by the local government offices, teachers, village chairmen and fishermen as an expansion of the knowledge base, but is also an important and valuable stepping stone for the local communities to become active in issues regarding the management of coastal resources.  相似文献   

中国西南岩溶石山贫困地区的生态重建   总被引：80，自引：3，他引：80  

蔡运龙 《地球科学进展》1996,11(6):602-606

我国西南岩溶石山地区的贫困－环境退化问题非常突出，这里的生态重建研究，对当地的消除贫困和持续发展至关重要，也是我国扶贫攻坚的重点和难点。生态重建研究还有助于促进岩溶学的综合化、人文化、模型化和实用化。  相似文献   

Bearing capacity of a strip foundation on a sand layer overlying a smooth rigid stratum     

K. Z. Andrawes  R. R. Al-Omari  W. M. Kirkpatrick 《Geotechnical and Geological Engineering》1996,14(3):227-236

The effect of a smooth rigid stratum, located beneath a dense sand layer, on the bearing capacity and settlement of surface and shallow strip footings is investigated using an advanced experimental model. A theoretical analysis is presented for the bearing capacity of surface footings. The results indicate that the bearing capacity reaches a minimum value at a specific sand-layer thickness. Any increase in the layer thickness above this value causes an increase in the bearing capacity up to that corresponding to a continuous media.Notation H= thickness of the sand layer - B= foundation width - N _q and N = bearing capacity factors for a semi-infinite layer - N _qs and N _s= bearing capacity factors for a finite layer - H _o /B= limiting depth - D _r= relative density - = angle of soil internal friction - M= model width - D= depth of surcharge - q= bearing stress, pressure applied on the footing - q _u= bearing capacity - = unit weight of sand  相似文献   

Fluctuant bearing capacity of shallow foundations during earthquakes   总被引：2，自引：0，他引：2  

J. Merlos  M.P. Romo   《Soil Dynamics and Earthquake Engineering》2006,26(2-4):103-114

A limit equilibrium method to compute both dynamic bearing capacity and earthquake-induced settlements of foundations on soils using a log spiral potential failure surface is presented in this paper. The method is limited to soil materials that conform to the Mohr–Coulomb criterion. Time-varying inertia forces can be applied directly to the building. The procedure is capable of estimating vertical displacements and foundation tilting by integrating the differential equation developed from equilibrium of acting and resisting moments. The reliability of the method is assessed by comparing calculated and observed permanent movements of foundations for the September 1985 Earthquake in the soft ground area of Mexico City. The position of the failure surface is obtained by a minimization process at every time increment during the shaking. Results show that when an earthquake occurs the potential failure surface, obtained from static load, moves upwards and its length shortens as the seismic accelerations increase, reducing the bearing capacity and thus increasing its seismic risk. In this paper, the influence of earthquake acceleration on the time-varying positions of the potential failure is shown graphically.  相似文献