A decision support system for geotechnical applications

A knowledge-based system shell called ‘Confound’ has been developed for the production of decision support systems. It was initially used for developing a system for conceptual foundation design but has subsequently been used for retaining wall, expansive soil and ground investigation applications. It uses a hierarchical object-oriented knowledge base where each object represents a decision in the decision making process. A simple rule-based approach is used to provide advice on the suitability of each potential choice, based on project specific information that is provided by the user. Confound has the ability to work with incomplete information and uses a system of confidence levels so that the user is aware of the confidence with which each piece of advice is given. Conflicting information in areas where knowledge is poorly defined can also be handled. Confound is designed to leave the user in full control. It simply provides comments on suitability (with an indication of confidence) and leaves the final decision to the user.     

A novel approach to the analytical modelling of an auger conveyor system for lunar regolith transportation

Acta Geotechnica - Auger-based transportation systems are a promising method to transport lunar regolith for in situ resource utilisation. An analytical model based on terrestrial auger conveyor...     

A design methodology for rock slopes susceptible to wedge failure using fracture system modelling

This paper demonstrates how the use of fracture system modelling can be linked to limit equilibrium analysis of rock slopes susceptible to wedge failure. The use of fracture systems highlights some of the limitations inherent in traditional structural data analysis and representation. Consequently it allows for more comprehensive input data that can be used for stability analysis of rock slopes. In particular the developed methodology addresses important issues such as spatial variability and wedge size distributions. The paper introduces a series of guidelines for interpretation of the results of rock slopes. The proposed techniques arguably result in an improved level of confidence in the design of rock slopes susceptible to wedge failure.     

A kinematic model for the structure of lee-side deposits

A kinematic model for the structure of the lee-side deposit of a dune-like bedform, Gilbert-type delta, or similar step is developed, based on the assumptions that initial deposition is entirely by grainfall, that the rate of deposition decreases as a power function of distance downflow from the brink of the slipface, and that the resulting steepening of the slipface is periodically interrupted by avalanching. The parameters used in the model are: (1) the deposition rate at a given distance from the brink, (2) the exponent in the equation relating the deposition rate to distance from the brink, (3) the bedform migration rate, (4) the bedform height, (5) the avalanche speed, (6) the angle of initial yield, and (7) the residual angle after avalanching. From these parameters can be calculated structural characteristics such as the proportions of bottomset and foreset deposits, the proportions of avalanche and grainfall deposits in the foreset deposit, and the spacing of avalanche-grainfall couplets. The model correctly predicts the trends of changing avalanche activity and changing structural character with changes in flow character, grain size, and bedform height in both air and water. Moreover, the model correctly predicts certain consistent structural differences between aeolian and subaqueous lee-side deposits. Quantitative evaluation of the model requires more accurate data on the values of the input parameters than are presently available.     

全球洋中脊系统的构造特征及其运动学意义

本文将全球洋中脊系统作为研究整体,根据洋中脊的全球分布、运动学特征及其初始形成时与泛大陆的构造几何关系,将全球现今的洋中脊系统划分为内、外支洋中脊。外支洋中脊为探索者洋中脊-太平洋洋隆-东南印度洋中脊-西北印度洋中脊,起源于泛大洋及冈瓦纳大陆内部;内支洋中脊为西南印度洋中脊-大西洋中脊-北冰洋加科尔洋中脊,起源于泛大陆内部。两者之间通过俯冲带、转换断层以及弥散性板块边界实现全球板块构造在运动上的平衡,并保持地球的球形几何形态恒定。外支洋中脊在全球板块构造上造成泛大洋缩减,并持续被太平洋取代,直接推动了环太平洋俯冲带的形成;内支洋中脊造成大西洋盆、印度洋盆中生代以来持续扩张。中生代以来,外支洋中脊和内支洋中脊共同作用引起非洲板块、印度澳大利亚板块向北运动,新特提斯洋盆关闭,形成特提斯(阿尔卑斯山-喀尔巴阡山-扎格罗斯山-喜马拉雅山)碰撞造山带,并通过洋中脊扩张平衡了相关的岩石圈缩短。     

A unified kinematic model for the evolution of detachment folds

Detachment folds represent a major structural element in a number of fold belts. They are common in the Jura Mountains, the Zagros fold belt, the Central Appalachian fold belt, the Wyoming fold-belt, the Brooks Range, the Parry Islands fold belt, and parts of the SubAndean belt. These structures form in stratigraphic packages with high competency contrasts among units. The competent upper units exhibit parallel fold geometries, whereas the weak lower unit displays disharmonic folding and significant penetrative deformation. Two distinct geometric types, disharmonic detachment folds, and lift-off folds have been recognized. However, these structures commonly represent different stages in the progressive evolution of detachment folds. The structures first form by symmetric or asymmetric folding, with the fold wavelength controlled by the thickness of the dominant units. Volumetric constraints require sinking of units in the synclines, and movement of the ductile unit from the synclines to the anticlines. Continuing deformation results in increasing fold amplitudes and tighter geometries resulting from both limb segment rotation and hinge migration. Initially, limb rotation occurs primarily by flexural slip folding, but in the late stages of deformation, the rotation may involve significant internal deformation of units between locked hinges. The folds eventually assume tight isoclinal geometries resembling lift-off folds. Variations in the geometry of detachment fold geometry, such as fold asymmetry, significant faulting, and fold associated with multiple detachments, are related to variations in the mechanical stratigraphy and pre-existing structure.     

Understanding the triggering mechanism and possible kinematic evolution of a reactivated landslide in the Three Gorges Reservoir

More than 5000 landslides or potential landslides have been induced in the Three Gorges Reservoir (TGR) region since the impoundment in 2003, which have caused great damage and remain a huge threat to the dam and people living in the reservoir area. Understanding the deformation characteristics and failure mechanism of the landslides can be helpful in stability evaluation and landslide prediction. The primary aim of this study is to research the characteristics of the landslide motion and its relationships with environmental triggers, taking the Quchi landslide, a large, slow-moving, reactivated landslide in the TGR region, as an example. The instability clearly showed visible signs of movements since 2002, and after that, the slope has been experiencing persistent deformation. By combining 4 years of meteorological, hydrological data with displacement measurements from open fractures, deep boreholes, and surface points, as well as in situ observations, this paper reports the geological and geotechnical investigations performed to define the movement. The deformation is believed to be governed by reservoir water levels, while the precipitation has a minor effect. Seasonally, the slope movement has a very distinctive pattern with large deformation starting abruptly right after reservoir drawdown in June and lasting into late summer (September). Then there is a rapid transition to constant deformation (almost no displacement) as the reservoir level rises. The slope displacements appear to gradually increase every year, which suggests very high possibility of the large and overall failure of the slide. Both monitoring results and geomorphological observations have highlighted that the two active slide masses Q1 and Q2 would probably collapse in different kinematic evolution modes, i.e., the multistage failure and whole sliding motion.     

A kinematic hardening constitutive model for sands: the multiaxial formulation

This paper explores the possibility of using well-accepted concepts—Mohr-Coulomb-like strength criterion, critical state, existence of a small strain elastic region, hyperbolic relationship for representing global plastic stress–strain behaviour, dependence of strength on state parameter and flow rules derived from the Cam-Clay Model—to represent the general multiaxial stress–strain behaviour of granular materials over the full range of void ratios and stress level (neglecting grain crushing). The result is a simple model based on bounding surface and kinematic hardening plasticity, which is based on a single set of constitutive parameters, namely two for the elastic behaviour plus eight for the plastic behaviour, which all have a clear and easily understandable physical meaning. In order to assist the convenience of the numerical implementation, the model is defined in a ‘normalized’ stress space in which the stress–strain behaviour does not undergo any strain softening and so certain potential numerical difficulties are avoided. In the first part the multiaxial formulation of the model is described in detail, using appropriate mixed invariants, which rationally combine stress history and stress. The model simulations are compared with some experimental results for tests on granular soils along stress paths lying outside the triaxial plane over a wide range of densities and mean stresses, using constitutive parameters calibrated using triaxial tests. Furthermore, the study is extended to the analysis of the effects induced by the different shapes of the yield and bounding surfaces, revealing the different role played by the size and the curvature of the bounding surface on the simulated behaviour of completely stress- and partly strain-driven tests. Copyright © 1999 John Wiley & Sons, Ltd.     

A kinematic evolutionary model for the Penninic sector of the central Ligurian Alps

The nappe pile presently cropping out in the central sector of the Ligurian Alps, is represented by some principal groups of tectonic units. Starting from the foreland, the outer and lower, weakly metamorphic (up to 0.3 GPa) Briançonnais units support the high-pressure (up to 1.3 GPa) ensemble of inner Briançonnais nappes, in turn overridden by the Prepiedmont units, sourced from the European continental margin. Prepiedmont units form two superposed groups. The lower is composed only of a pre-Namurian basement (Alpine metamorphism up to 0.6 GPa); and the upper is mainly composed of a slightly metamorphic (greenschist facies) post-Namurian cover. At the top lie the high-pressure metamorphosed (up to 0.8 GPa in the sector here considered) ophiolitic units. The group of the non-metamorphic Helminthoid Flysch nappes (original stratigraphic cover of the ophiolitic units) has travelled the greatest distance and is presently mainly set onto the outer part of the chain. Only events up to the stacking of the nappe pile are discussed, disregarding late-stage deformation. As the examined sector is located at a considerable distance from the collisional zone, late processes did not change the overall order of superposition formerly acquired. The model proposes the development of two major, subhorizontal detachment surfaces. The first, shallower one confines at the base a very thin-skinned set of nappes, nearly totally made up of Prepiedmont sedimentary covers that are bounded at their top by the Helminthoid Flysch units. Both these groups underwent a mainly horizontal outwards transport. In contrast, the underlying Prepiedmont crust and the adjoining Briançonnais inner sector (separated by the second, deeper major detachment surface) were progressively dragged into the subduction zone under the ophiolitic units and duplexes were generated. Exhumation of the metamorphic units occurred along the subduction channel, as did stacking of the nappe pile.     

A proposal for a new position for the Aptian/Albian boundary

The Aptian/Albian boundary, as currently placed, presents problems which have not yet been solved and possibly never will be. No detailed definition of recent years can be applied on a world-wide scale, which will be needed for any definition acceptable to the Subcommission on Cretaceous Stratigraphy. The only satisfactory and workable solution is to choose a completely new position. It is suggested that this should be at the base of the Zone of Lyelliceras lyelli. This would change the start of the Albian from appproximately 112 Ma to 109 Ma but it would be a standard which should be recognizable on all five continents.     

A proposal for an extended typology of groundwater habitats

Many governments now require the ecological condition of groundwater ecosystems to be considered when making policy decisions. However, groundwater habitats and communities occur at different spatial scales to those at which aquifers are managed, making their inclusion in policy decisions difficult. A system of classifying groundwater ecosystems is needed to aid this, yet such a typology is currently not available. Here, a hierarchical model for a typology of groundwater habitats is suggested, which considers three spatial scales: macro, meso, and local. On a macroscale, communities are influenced by biogeographic characteristics; at a mesoscale they are influenced by the hydrogeological type of the aquifer; and on local scale by the hydrological exchange with surface water and hence the oxygen and nutrient supply. Consequently, groundwater habitats are assumed to be defined by biogeographic particularities, the hydrogeological aquifer type and by localized hydrological exchange with surface water. By adopting a ‘groundwater habitat typology’, groundwater biologists may be able to work with hydrogeologists to assist in the sustainable management of groundwater by predicting groundwater biodiversity and the distribution of important or endangered species. The typology proposed here is a first step towards achieving this goal.     

Test of the vibrational modelling for the λ-type transitions: Application to the α-β quartz transition

Vibrational modelling is at the present time the only known way to predict the heat capacities of the Earth's mantle minerals at high-pressure and high-temperature. To test the validity of this method for λ-type transitions, we have applied it to the α-β quartz transition (T ₀=846±1 K). Raman spectra of quartz were recorded up to 900 K. Measured frequency shifts of the α-quartz Raman modes were then used in conjunction with available high-pressure Raman data to calculate intrinsic mode anharmonicity, through the parameter a _i=(?Lnv_i/?T)_v. Vibrational modelling of the heat capacity at constant volume, Cv, and at constant pressure, Cp, including anharmonic corrections deduced from the a _i parameters, are compared to experimental data. Taking into account the soft-mode associated to the α-β quartz transition, the model reproduces the excess of Cp related to the transition. Then, this study confirms that detecting a soft-mode from vibrational data allows one to predict λ-type transitions. However, when modelling the thermodynamic properties, the contribution of a soft-mode cannot be established from spectroscopic data. Therefore, one needs first to determine this contribution in order to predict the heat capacities of Earth's mantle minerals displaying λ-type transitions. In α-quartz, this contribution has been determined as 0.007% of the total number of the optic modes in the model of the density of states.     

A possible explanation for the Arp-Burbidge paradox

The Arp-Burbidge paradox (the enhanced density of distant quasars in the vicinity of some nearby galaxies) can potentially be explained as an effect of gravitational lensing within the existing cosmological paradigm. Distant, rich X-ray clusters, or even superclusters, of galaxies are observed along the lines of sight toward many of the objects on which this “paradox” is based. Such clusters can act as complex, transparent gravitational lenses, which can change the observed surface density of background objects due to the gravitational fields of both the cluster as a whole and of massive member galaxies, as well as of possible intergalactic globular clusters that may contain an appreciable fraction (～10%) of the dark matter in galaxy clusters. We have verified the statistical basis for the supposedly “paradoxical” observational facts using data from the SDSS catalog, and used the minimal spanning tree method to search for inhomogeneities in the surface distributions of 32 800 quasars in one region of the celestial sphere (α = 120°–260°, δ = 20°–70°).     

A new proposal for the late Cenozoic geodynamic evolution of the western Mediterranean

A simple mechanism of arcuate fold belt and back-arc basin formation is presented based on the opening of mega-continental tension gashes along pre-existing, deep, parallel and steep faults that separate lithospheric units with different properties. If plate convergence is parallel to these faults, the fault-bounded units open at right angles to the convergence vector, adopting an arcuate shape with thrusting in front of the bowed-out units and extensional basin opening between the separated units. This model is applied to the Cenozoic geodynamic evolution of the western Mediterranean. After the Iberian collision 35–30 Ma, several ellipsoidal basins (Valencia, Alboran, North Algerian and Liguro–Provençal) developed by 10 Ma along the eastern margin of the Iberian plate. The formation of these basins is attributed to an increase in NE–SW horizontal tectonic palaeostress during early–middle Miocene times resulting from the post-subduction collision of the Tethyan oceanic lithosphere.     

A waveguide-based flexible CO2-laser heating system for diamond-anvil cell applications

Fiber-based laser heating systems offer high flexibility and are increasingly used in high-pressure/high-temperature research. Previous fiber-based laser heating systems were based on lasers delivering radiation with 1-μm wavelength that show unfavorable heating characteristics for many sample materials. We report on the development and first experiments of a waveguide (fiber)-based CO₂-laser heating system that can be used in a flexible manner for high-temperature research and for high-pressure/temperature experiments when combined with diamond-anvil cells. The waveguide-based CO₂-laser heating system allows convenient heating of optically transparent samples without the need for adding an additional laser absorber. In a pilot experiment, the flexible heating system has been installed on a Brillouin scattering system to measure high-temperature sound-wave velocities in single-crystal MgO. The waveguide-based CO₂-laser heating system offers perspectives for a variety of scientific applications, most importantly those that require the use of synchrotron facilities where space is limited and flexible solutions are required.     

A proposal for an approach to mapping susceptibility to landslides using natural language processing and machine learning

Landslides - Compiling an inventory is a fundamental step for carrying out assessments of landslide hazards. However, data in sufficient quantity and quality are not always available. Thus, this...     

A fundamental problem with the kinematic interpretation of geological structures

Non-steady flows are ubiquitous in nature. Not only do imposed boundary conditions vary with time and rock rheology change during the course of deformation but also deformation is generally heterogeneous and all of these conditions lead to non-steady flow histories.In modern kinematic analysis, flow apophyses, the instantaneous stretching axes and the vorticity vector, collectively referred to as the `eigen directions' of deformation, are used in place of Bruno Sander's kinematic axes. For deformation with a steady flow history, this practice is well justified and has led to great advances in structural geology. But for non-steady flow histories, the geometrical relationships among eigen directions (flow pattern) vary with time. This makes it inappropriate to correlate an association of structures and fabrics with certain `time-invariant' flow patterns and hence raises the question: How should we interpret geological structures and fabrics kinematically, without the assumption of homogeneous and steady deformation? We suggest that the answer lies primarily in forward-modeling of deformation, based on a knowledge of rock properties.