In situ TBM penetration tests and rock mass boreability analysis in hard rock tunnels

Boreability is popularly adopted to express the ease or difficulty with which a rock mass can be penetrated by a tunnel boring machine. Because the boreability is related to the rock mass properties, TBM specifications and TBM operation parameters, an accurately definable quantity has not been obtained so far. In order to analyze and compare rock mass boreability, a series of TBM shield friction tests were conducted in a TBM tunneling site. Two sets of TBM penetration tests were performed in different rock mass conditions during tunneling in rock. In each step of the penetration test, the rock muck was collected to perform the muck sieve analyses and the shape of large chips was surveyed in order to analyze the TBM chipping efficiency under different cutter thrusts. The results showed that a critical point exists in the penetration curves. The penetration per revolution increases rapidly with increasing thrust per cutter when it is higher than the critical value. The muck sieve analysis results verified that with increasing thrust force, the muck size increases and the rock breakage efficiency also increases. When the thrust is greater than the critical value, the muck becomes well-graded. The muck shape analysis results also showed with the increase of the thrust, the chip shape changes from flat to elongated and flat. The boreability index at the critical point of penetration of 1 mm/rev. defined as the specific rock mass boreability index is proposed to evaluate rock mass boreability.     

Development of mucks from the weathering of peats: its importance as an isolation barrier

A decrease in water level in areas of marsh accumulation initiates the process of peat weathering, known as the process of muck formation. This process is strictly connected with the disintegration of peats and results in the formation of sediment characterised by different physical, chemical and mechanical properties. Compared with the peats from which they originate, mucks are characterised by lower hydrophilous properties, higher sorption capacity, lower porosity, lower plasticity and lower shrinkage and compressibility. Due to these properties, a muck horizon can act as an isolation barrier against industrial and agricultural waste and hence is advantageous for environment protection. In addition, mucks have much more favourable physical and mechanical parameters than the peats from which they were formed.     

砂卵石地层高水压条件下盾构掘进喷涌控制研究

以兰州地铁1号线一期工程世纪大道站—中间风井区段为背景,综合运用现场调查与过程监测、实验室模拟试验、三维数值模拟等方法与手段,对砂卵石地层高水压条件下土压平衡盾构掘进基于渣土改良的喷涌控制的可靠性进行了研究。主要取得以下成果:(1)建立了砂卵石地层高水压条件下盾构掘进改良渣土抗渗性(喷涌控制)的定量试验模拟与测试方法;(2)确定了单掺钠基膨润土浆液改良渣土的膨润土浆液最优浓度和掺加膨润土浆液的最优体积比,并证明了其改良后的渣土的抗渗性能具有较高的喷涌控制可靠性;(3)同时掺加钠基膨润土浆液和泡沫改良渣土,泡沫的掺入体积比应小于1∶5。研究结果有力地支撑了世纪大道站—中间风井区段高水压条件下,盾构以-28‰的超大纵坡下坡掘进过程的喷涌控制,规避了盾构设备受淹风险。     

Evaluation of the laboratory prediction of surface properties of bituminous mixtures

An experimental and analytical investigation was carried out both in laboratory and in situ on wearing courses. The approach presented in this paper aims to predict the in situ density and surface properties of bituminous layers, during the phase of mix design in laboratory. Therefore, the main attempt of this study is to identify, amongst the commonly available laboratory equipments, the most adequate for producing specimens that, used for carrying out simple and reliable laboratory test, allow the prediction of the surface characteristics of the mixture as laid on site.This is done by comparing the data collected from an experimental site with those calculated from laboratory specimens compacted with the superpave gyratory compactor (SGC).Typical laboratory tests (such as the sand patch method and the skid test) as well as the surface data obtained with a laser profilometer have been considered for characterizing the properties of a standard Italian wearing course, laid in two different final thicknesses and produced with the most common raw materials, according to the currently used techniques for mixtures production and laying process for maintenance work. An evaluation of the SGC ability to represent the density and surface properties of the mixture once on site is then discussed.     

A preliminary design approach for guledar irrigation dam project

This paper describes the results of engineering geological and rock mechanics studies carried out at the Güledar irrigation dam project. Project is designed to regulate the drainage and to irrigate the agricultural areas. The dam site is located within Güledar Sirkeli formations composed of sandstone, limestone and diabase. Studies maintained both at field and laboratory. Field studies included geological mapping, core drilling, sampling for laboratory testing, pressurized water tests, and intensive discontinuity surveying. Some physical and mechanical properties were determined at laboratory. The rock mass qualities of rock units were determined, and described as poor to fair quality. The corresponding Hoek and Brown failure envelopes have been drawn and failure equations have been suggested for stability analysis of dam foundation, slope stability and diversion tunnels for each rock unit.     

An evaluation of the procedure and results of laboratory crushing in quality assessment of rock aggregate raw materials

Quality estimation of rock aggregate raw materials is often performed with mechanical tests on aggregates crushed with laboratory crushers. However, standardised mechanical tests are intended for testing products, not raw materials. Different laboratory crushers produce aggregates with varying shape properties [flakiness index (FI), shape index and surface roughness], and this has a distinctive impact on the results from mechanical tests. Setting of crushers also plays an important role in laboratory crushing of aggregates and it should be adjusted according to required particle size. Four laboratory crushers and three apparati to measure resistance to wear by abrasion from a studded tyres test (A_N test) from three laboratories were compared and studied. The A_N test was carried out according to the EN standard and on bar-sieved samples in order to find how FI or surface roughness affects the A_N value.     

基于TBM掘进参数和渣料特征的岩体质量指标辨识

在工程实践和前人研究成果的基础上,综合分析了TBM法隧洞的围岩地质条件对TBM掘进过程的影响,提出了一种基于TBM掘进参数和渣料特征的围岩质量指标(RMR)辨识方法。该方法一方面可将TBM的实时工作参数输入到回归公式或神经网络模型中,实现岩体质量指标的辨识;另一方面可通过分析TBM渣料特征得到岩体的镶嵌结构、不连续面状态以及地下水等地质信息,进而对岩体的地质力学强度(GSITBM)和质量指标(RMRTBM)进行估计。鉴于这两种方式的显著特征,建议在地质条件较好时优先采用基于掘进参数的辨识方法,地质条件较差时采用基于渣料特征的评价方法。在对TBM法隧洞围岩质量指标辨识研究的基础上,对岩体基本力学参数的估计方法进行了研究。     

New approach to junction efficiency analysis of hexagonal geogrid using digital image correlation method

Geosynthetics are commonly used in many civil engineering applications. At the same time, intensive development of these materials is being carried out. Therefore, it becomes more and more important to correctly determine the mechanical parameters of geosynthetics in laboratory tests. This is especially important for more complicated hexagonal geogrids. This article presents the results of the laboratory research carried out to evaluate the junction efficiency of hexagonal geogrid under static load by analyzing deformations of geogrid junctions and ribs. A new approach to determination the efficiency is given by the newly defined strain junction efficiency coefficient based on the true principal strains. In the laboratory tests the digital image correlation (DIC) method was used. This method allowed for the determination of displacements and strains of geogrid specimens in any direction and at any point. The results of the conducted research and analysis indicate that the proposed innovative junction effectiveness assessment method enables a better presentation of the geogrid performance at different levels of tensile load. In addition to the parameters given in the technical approval for this material, the proposed new strain junction efficiency coefficient can be an effective parameter for evaluating hexagonal geogrid performance at different strain levels.     

碱激发工业渣体混凝土的研究

碱激发渣体作为胶结材配制环境降负混凝土是一种有效利用各类渣体的好途径。该文试验就几种渣体进行了碱激发的研究。在溶渣比为0．46，胶凝材料（各种渣体的复合）为400kg／m^3，且不采取任何特殊措施的情况下。配制出28d抗压强度大干70MPa的碱激发渣体混凝土。并对此混凝土的耐酸性能进行了研究，结果表明，锂渣能提高碱激发矿渣-粉煤灰混凝土的耐酸性能。     

Earth pressure balance tunnelling in rock masses: Laboratory feasibility study of the conditioning process

Earth pressure balance (EPB) shield tunnelling is considered to be an effective tunnelling method when surface settlements must be avoided by controlling face stability and underground water inflow. EPB technology is applied increasingly to the conditioning of rock masses in which the presence of polluting material is foreseen and must be controlled, or when explosive gases from the rock mass must be prevented from entering in the machine. The use of an EPB machine in ‘closed mode’ can prevent the dispersion of dangerous materials in the underground environment. This study was performed to evaluate the feasibility of using EPB technology in rock masses and the effectiveness of this tunnelling process in terms of soil conditioning, conditioned soil permeability, pressure transmission on the tunnel face, and the ability to extract the material with a screw conveyor. The research was developed with a set of laboratory tests carried out on three different types of rock masses where tunnelling with EPB machines are planned to be constructed in Italy but the results can be easily applied to similar rock mass types. The tests have been carried out both with slump tests and with a specially constructed screw conveyor extraction device. In the paper the most important results are presented and discussed.     

The influences of geological and land use settings on shallow landslides triggered by an intense rainfall event in a coastal terraced environment

Several factors (including slope morphology, geological and structural settings, the mechanical properties of soils, weathering, hydrological and hydrogeological conditions and land use changes) can affect the origin and development of shallow landslides induced by rainfall. On 25 October 2011, an intense rainfall occurred in a wide area of Italy between eastern Liguria and northern Tuscany, triggering thousands of shallow landslides and causing widespread flooding. Floods and landslides caused severe damage to villages and infrastructure and caused 13 fatalities. This study was conducted to investigate the shallow landslides triggered by the rainfall in the Vernazza basin (Cinque Terre in eastern Liguria), where landslides and debris floods caused 3 fatalities and damage of approximately €130 million. The Vernazza basin, which is characterised by steep slopes, geological heterogeneity and unusual land use settings (approximately 50 % of the slopes have been terraced for centuries), was chosen as the focus of this study, conducted to assess the influences of several factors on landslide occurrence. Field surveys and engineering geological investigations, including laboratory and in situ tests, were carried out at various sites to assess the stratigraphic and geotechnical features of the soil slope covers. A basic engineering geological zoning was carried out, taking into account the bedrock lithology, the geotechnical properties of the soils and the land use settings. On the basis of a detailed inventory of the shallow landslides that occurred, the distribution of the landslides was analysed with respect to the slopes, the bedrock lithology, the land uses and the engineering geological setting. Terraced areas on impermeable bedrock were identified as the main landslide-prone areas. The results of the study also showed that the time since abandonment of terraces plays an important role in the occurrence of shallow landslides induced by rainfall.     

Concept development of an underground research tunnel for validating the Korean reference HLW disposal system

In order to dispose of high-level radioactive waste (HLW) safely in geological formations, it is necessary to assess the feasibility, safety, appropriateness, and stability of the disposal concept at an underground research laboratory (URL) constructed in the same geological formation as the host rock. In this study, minimum requirements and the conceptual design for an efficient construction of a small scale URL were derived based on a literature review. To confirm the validity of the conceptual design for construction at KAERI, a geological survey including a seismic refraction survey, electronic resistivity survey, borehole drilling, and in situ and laboratory tests were carried out. The mechanical stability of the URL was investigated with a consideration of the surface topography, tunnel geometry, tunnel slope, sequential excavation, in situ stress ratio, erosion effect, and rock property variation along the tunnel using the three-dimensional code, FLAC3D. From the study, it was possible to conclude that the small scale URL will be effectively constructed in a granite mass at KAERI and will satisfy the minimum requirements.     

A simple approach to 3D geological modelling and visualization

3D geological modeling has become one of the most reliable and effective means of displaying geological structures, but most commercial software products for 3D geological modeling need special techniques and much pre-processing work as well as being expensive and complicated to operate. In this paper, a simple approach to building a 3D geological model is proposed, integrating such popular software packages as 3D Studio Max (3DSMax), ArcGIS, and Virtual Reality Modeling Language (VRML). The approach can be used to build accurate 3D geological structures and to model stratigraphy at almost any level of complexity. Moreover, the resulting model can be operated interactively, including zooming in or out, rotating and moving. The paper demonstrates how this new approach can be a very effective method for 3D geological modeling.     

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.     

局部屈曲或局部和畸变屈曲综合作用下冷弯型钢梁的有限元模拟

有限元法可以解决冷弯钢梁复杂的相关联屈曲问题,其中包括很多重要的关键因素:几何缺陷、材料非线性和后屈曲等。也是该方法与其他分析方法的不同之处。根据特定的冷弯Z型钢梁的材料和几何非线性建立了两类研究屈曲性能的有限元模型。其中,一个模型用于分析局部和畸变屈曲综合作用,而另一个仅用于分析局部屈曲。通过先前的四点弯曲试验证实了有限元模型的有效性。利用ABAQUS软件,模拟了一个简化的试验装置。在局部屈曲有限元模型中,通过在梁翼缘角部设置弹簧以防止畸变屈曲。由于更多的模型与试验结果相吻合,证实了对承载力和变形的预测。未来的研究将优化有限元模型,以得到侧向受约束的冷弯型钢梁不同的屈曲形式,如:局部,畸变或局部与畸变综合作用。     

Finite element modelling of cold-formed steel beams under local buckling or combined local/distortional buckling

The finite element (FE) method is capable of solving the complex interactive buckling of cold-formed steel beams allowing for all important governing features such as geometrical imperfections, material nonlinearity, postbuckling, etc.; this is unlikely to be achieved by analytical methods. In this paper, two series of finite element models for buckling behaviour of laterally-restrained cold-formed steel Z-section beams have been developed with special reference to material and geometrical nonlinearities: one to allow for the possibility of combined local/distortional buckling and the other to allow for local buckling only. Four-point bending tests carried out by previous researchers have been used to verify the FE models. A simplified configuration of the test setup has been modelled in ABAQUS. In the local buckling FE models, distortional buckling has been restricted in the member using translational springs applied to the lip/flange corner of the beam. Predictions of load carrying capacity and deformed shapes exhibit excellent agreement with both the results from the more extensive models and laboratory tests. Further papers will exploit the developed FE models to investigate the different forms of buckling that occur in laterally-restrained cold-formed steel beams i.e. local, distortional and combined local/distortional.     

Pumpspeicherbecken im Karstgrundwasserleiter des Weißen Jura der Schwäbischen Alb

Extensive geological and hydrogeological investigations have been undertaken for the planned pumped-storage hydroelectric power plant in “Blautal” (Swabian Alb, Germany) in order to characterise the Jurassic karst aquifer in which the lower reservoir will be constructed. The preferred option for the plant setup is to integrate the lower reservoir into the groundwater without sealing. Therefore, in order to reliably predict the impact of the pumped storage plant operations on the surrounding drinking water wells and groundwater dependent ecosystems, a comprehensive database has been developed to assess the hydraulic conditions of the karst aquifer. A large scale geological site investigation was carried out to characterise the rock mass and extensive hydraulic tests were performed in many boreholes. The results of the hydraulic characterisation were then implemented in a three dimensional flow model. In this paper, the first results of the geological and hydrogeological investigations are presented and discussed.     

Une méthodologie d'analyse et de cartographie de l'aléa "initiation de laves torrentielles" – application au torrent du Bragousse (France)

Debris flows may result in personal injury or loss of life as well as damage to constructions. The economic consequences of such events are important, and likely to become more so with increasing urbanisation. In this paper, "debris flow" is defined as a viscous flow of saturated materials at high velocities of up to 20?m/s in channels. These materials have a high concentration of solids such that their dynamics may be considered at the interface between mechanical and hydraulic flow. The occurrence of a debris flow results from a number of interrelated factors including topography, geology, geomorphology and hydrogeology. The triggering factor is most often water, frequently a violent rainstorm. In order to identify the initiation mechanisms, it is necessary to have a knowledge of the environmental situation in the particular catchment area. Clearly, this will involve an understanding of: (1) the catchment area and its geological conditions; (2) the climatic characteristics of the locality and the nature of the materials in the source area; (3) the pattern of such events in the past. In order to obtain such an understanding, a dual approach of field and laboratory work was considered appropriate. Twelve catchment areas in the northern and southern French Alps were studied to assess the significance of the three aspects mentioned above. The study of numerous debris flow deposits sampled in these catchment areas suggested two types of debris flows: those with a cohesive matrix and those with a granular matrix. In the field, they were categorised on the basis of a morphological consideration of the area as well as according to the texture and grain size of the material in the flow. In the laboratory, granulometric tests were used. In addition, the granulometric and geotechnical characteristics of the source areas were compared with those of the debris flow materials. The grain size distribution appears to be an important factor in determining the likelihood that the source area materials would be moved by violent storms and from a debris flow. From tests undertaken on the <20?mm fraction, superficial deposits with between 16 and 40% of the particles of <50?μm seemed to be most likely to result in debris flows. This paper discusses the fieldwork undertaken from the upper catchment area down to the channel of a debris flow. Each mechanism is described with an analysis of the geological and topographical contexts, the extent of the movement and the hydrological processes that lead to the initiation of a debris flow. On the basis of this, maps have been produced to show the potential for the initiation of a debris flow. Five criteria were chosen to define the debris-flow hazard: (1) slope angle; (2) nature of the geological formation and hydrogeological characteristics; (3) slope erodability and instability; (4) grain size; (5) available volumes of superficial deposits present in the source area. These five indices form the global index. The maps show the spatial distribution of the hazard and can be useful in determining the most appropriate remedial/protective works to be undertaken in zones of the greatest risk.     

Performance-Based Analysis of Earth Dams: Procedures and Application to a Sample Case

The paper illustrates theoretical and experimental procedures adopted to characterize the seismic response of earth dams by performance-based criteria. The study refers to a real case, the Camastra Dam, a zoned earth dam with vertical clay core, placed in a highly seismic zone of Southern Italy. At first, the analysis objectives have been identified along with the physical quantities needed to achieve them for characterizing dam seismic performance. A theoretical approach, consistent with the identified analysis objectives, has been later selected. The adopted approach is based on continuum mechanics and accounts for coupling between soil skeleton and pore water phase. It is also able to describe the main features of soil response under cyclic loading conditions since it implements an advanced constitutive law for the soil skeleton. Big effort has been paid to the mechanical characterization of the dam materials. In addition to data coming from the interpretation of the laboratory tests performed at the time of dam construction, in situ tests (SASW, Down Hole, DMT) have been recently carried out on the embankment and foundation soils and interpreted consistently with the requirements of the selected theoretical model. Preliminarily, the static stages of the dam lifetime have been numerically simulated to reproduce the behaviour observed in terms of cross-arm settlements and pore water pressures, in order to obtain or verify some soil parameters and initialize the state variables for the simulation of the seismic stages. A seismological study of the dam site provided the expected seismic scenarios in terms of time histories of acceleration, needed as input for the dynamic analyses. The seismic response of the Camastra Dam was finally investigated and discussed in the light of performance-based criteria.