红层的工程地质特性及其边坡破坏形式

红层在我国分布广泛,其岩性呈现多样性和不均匀性,粘土矿物含量高,化学成分以次生S iO2及倍半氧化物为主。红层具有膨胀崩解的特性,软化系数较低。在红层边坡中易产生崩塌落石、风化剥落及滑坡等地质灾害,并提出相应的防治措施。     

Engineering geological environment of Athens, Greece

 Engineering geological information including geotechnical and geological data from exploratory boreholes and trial pits located in the wider area of Athens were stored in a database system. Based on the data processing and field mapping, the geological formations encountered in the foundation materials of the city were divided into individual geotechnical units according to uniformity in lithological character and relevant age. Engineering geological zonation maps of the studied area for urban planning purposes were compiled at an original scale of 1 : 25,000. Received: 4 October 1999 · Accepted: 3 April 2000     

Engineering geological appraisal of the Sulakyurt dam site,Turkey

This paper discusses the engineering geological investigations, diversion tunnel support design and slope stability assessment studies carried out at the Sulakyurt dam site, northeast of Ankara, Turkey. The Sulakyurt dam will be used for flood flow control and water storage for irrigation. Engineering geological mapping, discontinuity surveys, core drilling, water absorption and laboratory tests were undertaken. The RMR, Q and GSI approaches were used to estimate the rock mass quality, site characteristics, rock mass parameters and appropriate tunnel support elements. The results of kinematic and limit equilibrium analyses for the slopes on the right and left banks are reported.      

Geotechnical properties of an unsaturated pyroclastic soil from Roma

The paper presents the results of an experimental investigation on the mechanical behaviour of an unsaturated pyroclastic soil typical of the subsoil of Roma (Italy). In its natural state, the material is a bonded coarse-grained weak rock. The deposits of pozzolana are unsaturated in situ; this has an important practical relevance in the evaluation of the stability conditions of natural slopes and cuts. The experimental investigation consisted mainly of pressure plate tests, oedometer tests and special isotropic and triaxial compression tests at increasing values of mean net pressures in the range 50–400 kPa and at different constant levels of suction (20–75 kPa). The compressibility and shear strength properties of the material are presented in some detail. Special attention is given to defining the failure envelope at relatively low confining stresses and assessing the influence of the degree of saturation on the failure conditions.

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Engineering geological properties of altered rocks and implications for railway construction in the Sanjiang orogenic belt,Southwest China

The Yunnan-Tibet Railway, currently under construction, crosses five altered rock zones in the Sanjiang orogenic belt, southwestern China. They are mainly montmorillonitized rock zones formed by hydrothermal alteration. Based on field investigation and laboratory tests, this paper presents the geological characteristics and engineering properties of the altered rocks encountered during the construction of the railway. Being characterized by a high montmorillonite content, high degree of alteration, high physico-chemical activity and high swelling potential, these rocks always lead to engineering geological problems. The concept of “alteration coefficient” is put forward; the greater the alteration coefficient, the higher the alteration degree and swelling potential. Countermeasures are proposed to tackle the engineering problems during tunnel construction caused by the altered rock.     

Engineering geological zoning of India

Engineering geological types of territory in India have been delineated which provide almost similar engineering geological conditions for assisting in unified method of engineering geological study, construction standards and working out other instructions for project planning.     

Engineering geological mapping of gypsiferous formations,Sivas, Central Eastern Turkey

Preliminary engineering geological investigation has been carried out for a proposed railway route in Central Eastern Turkey. The area is dominantly composed of Pliocene clastic deposits and Oligo-Miocene evaporitic formations overlying older rocks of flysch and limestones. Problems caused by the engineering characteristics of gypsum, anhydrite and halite, which should be taken into consideration in any kind of engineering work, are discussed. Engineering geological mapping of the gypsiferous formations is complicated due to the complex distribution of different lithologies resulting from variable mode of occurrence of gypsum/anhydrite, widespread karstic solution phenomena, tectonic deformation and the deformation caused by anhydrite to gypsum transition.     

Engineering geological characteristics of the pliocene clays of Bulgaria

The wide distribution of the Pliocene clays over the territory of Bulgaria and the landslides which appear in them draw the attention of a great number of specialists. Three types of clays may be distinguished: sandy and silty clays, heavy clays with silty seams, and fat clays overlying coal layers. They are water-saturated and show a plastic consistence. With increasing depth, the density decreases and the moisture increases. Sandy and silty clays show the upper-most degree of lithification. Fat clays are at the first stage of physical ageing. The processes of lithification are the cause or a dense system of fissures, some showing a constant dip, about 45°, which reduces the strength of the clays. The internal friction angle and the cohesion are independently determined in laboratory conditions. The possibility of determining, with the help of different-size samples, how the fissuration affects the shear strength is examined. The authors propose to use the residual resistivity of fissured clays for calculating the long-term stability of slopes.

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Résumé L’étendue considérable des argiles pliocènes sur le territoire de la Bulgarie et les glissements de terrains qui s’y développent attirent l’attention d’un grand nombre de spécialistes. On distingue des argiles sableuses et silteuses, des argiles lourdes à passées silteuses et des argiles grasses reposant sur des couches de charbon. Elles sont saturées en eau et ont une consistance plastique. En profondeur, la densité diminue et l’humidité augmente. Les argiles sableuses et silteuses ont le plus haut degré de lithircation. Les argiles grasses sont au premier stade d’un vieillissement physique. Les processus de lithification sont cause de la formation d’un système dense de fissures dont certaines ont un pendage constant, environ 45°, ce qui diminue la résistance des argiles. On propose de déterminer indépendamment, dans les conditions de laboratoire, l’angle du frottement interne et la cohésion. On étudie la possibilité de déterminer, à l’aide d’échantillons de dimensions différentes, le degré d’influence de la fissuration sur la résistance au cisaillement. Les auteurs proposent d’utiliser la résistivité résiduelle des argiles fissurées pour calculer la stabilité des pentes à long terme.

     

Engineering geological and geophysical investigation of the reclaimed Lekki Peninsula, Lagos, South West Nigeria

 It was hoped to develop an area of reclaimed land on the Lekki Peninsula of Lagos State. An investigation was therefore carried out in order to establish the subsurface geological/geo-electrical sequence; to identify the sand columns and determine their thickness and prepare a map of the geomorphological features of the original, pre-fill terrain. Vertical electrical resistivity soundings (VES) and penetrometer tests were carried out in a sand filled segment of the Lekki Peninsula. The information obtained showed a good correlation between the geomorphological features as interpreted from the aerial photographs and those identified from maps derived from the VES/penetrometer results. Received: 28 August 1998 · Accepted: 18 January 1999