Engineering Geological Model Research Articles

Unconventional pseudostatic stability analysis of the Diezma landslide (Granada, Spain) based on a high-resolution engineering-geological model

A novel unconventional pseudostatic analysis is proposed here to infer on the sensitivity of a landslide to earthquakes characterized by different physical properties. Several sine waves with different amplitudes, frequencies and phases were applied to the landslide mass assuming limit equilibrium conditions. The unconventional approach was used for the Diezma landslide case study. The landslide is located 25km from the city of Granada (Spain). Although the slope had repeatedly suffered small-scale stability problems since the construction of the A-92 highway, a larger failure occurred on 18 March 2001 and damaged the highway between kilometers 272.6 and 272.8. The landslide had an estimated volume of 1.2Mm3 and involved a disordered deposit of silt and clay with heterometric blocks within the Numidoide Formation, which outcrops along the contact between the Maláguide and Dorsal domains of the Betic Cordillera mountain range. Despite the 18 million Euros spent since 1999 on geotechnical investigations and stabilization solutions, the numerous reactivations that occurred through 2010 and 2013 demonstrate the persistent activity of the landslide.The geometry of the large slope failure corresponding to the first activation of the Diezma landslide was used to back-analyze the stability of the slope based on a high-resolution engineering-geological model. The model was developed from the analysis of numerous borehole logs as well as from geophysical investigations consisting of seismic noise measurements.The results demonstrate that the safety factor (SF) of the Diezma landslide varies significantly for frequencies less than 1Hz; moreover, unstable conditions are reached at frequency values between 0.5 and 1Hz for water pressure distributions corresponding to Bishop factors (ru) between 0 and 0.36. To estimate the co-seismic displacements, the geometrical and mechanical properties of the landslide mass were used to derive its characteristic periods for thickness (Ts) and length (Tl), which were compared with the characteristic period of the earthquake (Tm). The results indicate that the maximum expected co-seismic displacements are up to 2m for an earthquake with a Tm value close to 1s and an Arias Intensity on the order of 1m/s.

The characteristics of deformation and failure of coal seam floor due to mining in Xinmi coal field in China

Deformation and failure of a “three-weak” (weak roof, thick weak coal, and weak floor) coal seam floor subject to mining are studied in this paper. Firstly, by using a group of strain sensors buried at different floor depths, we measured the relationships of the axial strain to the distance from the advancing face field. The floor depths and stratum positions, and as well as the peak width, which is the distance of the first maximum strain increment to the working face, were drawn. The axial stress and its zone of influence, which is the distance from the face to the borehole along the roadway, and at which there is obvious strain increment difference, were also drawn. Secondly, we established an analytical mechanical model and found the analytical solution of the floor’s supporting pressure distribution ahead of the face. And thirdly, we set up a numerical simulation engineering geological model and simulated stress distribution and deformation characteristics of the floor with complex multi-stratum (11 strata) structure. The results from the three approaches showed that: (1) the failure depth (<10.0 m) and zone of influence (up to 36.0 m) induced by mining ahead of the three-weak seam face were much smaller than those common seam faces; (2) the axial strain fluctuated greater than the radial one, with its max peak keeping at about 8.0 m ahead of the advancing face, and its zone of influence spreading to 36.0 m; (3) the peak width of axial strain and its zone of influence in the haulage roadway were stronger than those in the ventilation roadway; and (4) the three weak coal seam played a strong buffering action against deformation and failure due to mining. This research may be of interest to assist with improving strata control and health and safety in operating coal mines.

Erratum to: Engineering geological models: an introduction: IAEG commission 25

The authors would like to correct errors in the original publication as detailed below. The fifth author’s second initial was incorrectly typed as ‘‘F’’ instead of ‘‘R’’. The fifth author’s name should read as ‘‘J. R. Keaton’’. In the original published article, the word ‘‘model’’ in the sub-headings of the Conclusion section was changed to ‘‘mode’’ during copyediting. The Conclusion’s sub-headings should read as ‘‘conceptual engineering geological model’’, ‘‘observational engineering geological model’’ and ‘‘analytical model’’.

Engineering geological models: an introduction: IAEG commission 25

The generation and use of engineering geological models should be a fundamental activity for any geotechnical project. Such models are an essential tool for engineering quality control and provide a transparent way of identifying project-specific critical engineering geological issues and parameters. Models should also form the basis for designing the scope, the method and assessing the effectiveness of site investigations. However, whilst the idea of models in engineering geology has existed for several decades, there has been little published that systematically distinguishes the different model types and how and when they might be used. This paper presents the views of the International Association for Engineering Geology and the Environment Commission C25 on the ‘Use of Engineering Geological Models’.

Specific aspects of engineering-geological models in Croatian karst terrain

The experiences of developing engineering geological models in karst areas for designing and construction purposes prove the necessity of considering at least three basic submodels: sedimentological, structural-tectonic and the weathering one. The research presented here deals with very important and frequently neglected segments in each of the submodels. Therefore, particular attention should be directed to: better understanding of carbonate sediment deposition,determination of environment and diagenetic processes, study of the 3D anisotropy of discontinuity frequency, and differentiation of weathering zones. The given data and examples elaborate and justify such an approach, which enables a more realistic detailed engineering model, more reliable evaluations of the engineering geological/geotechnical parameters and real site conditions.

Engineering geological investigations of mechanized tunneling in soft ground: A case study, East–West lot of line 7, Tehran Metro, Iran

The essential requirements of a successful TBM tunneling operation are the complete characterization of the ground and the thorough identification of geological and geotechnical risks. These besides other information are needed for selecting the right TBM and determining its technical specifications for proper soil conditioning and for achieving the optimum TBM performance. This paper concentrates on a methodology for engineering geological investigations and geotechnical ground characterization, which is important for successful application of mechanized tunneling methods in soft alluvial sediments along the East–West section of line 7 of the Tehran Metro. Geotechnical considerations related to tunneling with a soft ground TBM are described in detail, including the site investigation program, project-specific soil grouping system, distribution of soil types, geological–geotechnical risks (oversize grains, clogging, soil abrasiveness, fine grain content, permeability and groundwater fluctuation) and the engineering geological subsurface model. The encountered soil materials have been divided into four categories according to physical characteristics and engineering properties. In this study, the characteristics of the ground and the hydrogeological regime indicate that an EPB-TBM is rather a slurry-TBM. Although the engineering geological conditions of the ground along the tunnel are favorable for EPB-TBM, stickiness of fine-grained soils, abrasiveness of soils, existence of coarse-grained soils with low fine content and groundwater fluctuations are the most important risks for applying mechanized tunneling method in this specific project.

Kinematics and geological constraints of the slow-moving Pisciotta rock slide (southern Italy)

The Pisciotta landslide is a slow-moving deep-seated rock slide in the Campania region of southern Italy, which has damaged a provincial road several times in the last decades and currently poses a hazard to the national railway that intersects the toe of the landslide. The landslide involves an Oligocene turbidite series, which is composed of intercalated calcarenites, marls and mudrocks.The principal objectives of this study were to investigate the morphological evolution of the unstable slope, quantitatively analyse ground deformations and construct an engineering-geological model that is consistent with the spatial features of the landslide. The long-term evolution of the unstable slope was assessed through the examination of available aerial photos from 1943 to 2006. Kinematic analyses of the ground deformations were conducted based on observed progressive displacement of the road, as evident from the topographic maps and orthophotos (1955–2006), and the bi-weekly displacement survey of 50 targets distributed across the landslide area (September 2006–March 2009). The engineering-geological model of the landslide was reconstructed from the stratigraphic data obtained from the study of borehole data and monitoring of inclinometers as well as from geological, structural and geophysical surveys. The analysis of the aerial photographs revealed an early stage of deformation in 1943, which has been gradually widening since then. In addition to the main scarp and the landslide flanks, other significant landslide structures such as the longitudinal and transverse cracks as well as the positive or negative morphologies were monitored and mapped in the subsequent years. These studies indicated a progressive erosion of the upper part of the slope and a bulging of the foot. Long-term kinematic analysis based on the progressive displacements of the road allowed the measurement of the ground deformations from 1955 to 2009, which revealed a cumulative horizontal displacement of up to 53m and an average velocity of 0.98myear−1, which has increased in the recent decades. In addition, the recent monitoring of the ground deformations demonstrated a continuous activity with an approximately constant rate of displacement and a composite kinematic history of the landslide body through differential displacements and associated velocities. The engineering-geological model of the landslide was found to be controlled by specific stratigraphic and structural constraints. The landslide involves a stratigraphic interval of the Saraceno Formation (Nord-Calabrese tectonic unit) with a largely marly–argillaceous composition whose structural setting displays complex folding (at the mesoscale) and faulting with an approximately monocline attitude of bedding and a downslope dip direction at the macroscale. The left flank of the landslide rests on a normal fault.

Engineering geological conditions of the Holocene sediments of Anzali area, South Caspian Coast, North Iran

A broad assessment of the geological, sedimentological, and geotechnical characteristics of the coastal Holocene sediments of Anzali Area (North Iran) was made to provide a useful guide for development, planning, and construction. Based on the sedimentological and geotechnical properties of the sediments, three engineering geological units as Upper Sandy Zone (USZ), Middle Clayey Zone (MCZ), and Lower Sandy Zone (LSZ) were identified and introduced in the form of an engineering geological model. Then the engineering geological characteristics of the units of the model were analyzed and the main engineering geological problems associated with the deposits of each unit were identified. The results showed that USZ has high liquefaction potential, low bearing capacity, settlement susceptibility, and excavation problem; MCZ has low-bearing capacity as well as high settlement susceptibility and excavation problem; and LSZ has good geotechnical properties, then it poses few problems.

Dynamic properties of low velocity alluvial deposits influencing seismically-induced shear strains: the Grottaperfetta valley test-site (Rome, Italy)

The presence of peats and high compressibility inorganic clays within alluvial fills on the left-side tributaries of the Tiber River, close to Rome’s historic center in Italy, is well documented in literature. Nevertheless, few literature data exist until now on the dynamic properties of these deposits by undisturbed bore-hole samples. The Galba test-site was set up to characterise dynamic properties of the alluvial deposits by using lab-tests as well as to derive velocity profiles by seismic noise measurements. These were performed in the Giustiniano Imperatore area located in the Grottaperfetta valley, about 2 km south of Rome’s historic centre. The alluvial deposits filled a paleovalley excavated in the bedrock during the Wurm glacial (18–20 ky). The stratigraphic setting of the alluvial body was reconstructed along three geological cross-sections by means of the available logs; seven lithotecnical horizons can be distinguished within the alluvial body, some tens of meters thick, based on both log-stratigraphic data and in-site geotechnical tests. These horizons include peaty layers (T) and high compressibility inorganic clays (AGI), which characterise the alluvial deposits in the Grottaperfetta valley. They do not have direct correlation with the alluvial horizons which constitute the alluvial body of the main Tiber valley in Rome’s historical centre. These alluvial horizons which are distinguished and characterised at the Galba test-site can be regarded as typical of other lateral valleys of the Tiber River in Southern Rome. They are characterised by the presence of similar high compressibility clayey deposits as well as peaty layers up to some meters thick. Undisturbed samples were also obtained at the Galba test-site for dynamic testing via resonant column and cyclic torsional shear tests. In order to attribute dynamic properties to the alluvial body at the Grottaperfetta valley, an extrapolation process was performed based on a detailed engineering-geology model of the alluvial body which was reconstructed along three transversal geological sections of the valley using bore-hole data. Three subsoil profiles, considered representative of the geological setting along the three reconstructed transversal cross sections, were analysed by seismic noise measurements performed specifically to derive S-waves velocity profiles. The results obtained show a very low velocity (<180 m/s) for the layers T and AGI. 1D modelling of seismic shaking was performed by the code Shake91, in order to evaluate the influence of the low-velocity strata on maximum shear strains induced within the alluvial deposits under the maximum expected seismic action. The results of the numerical modelling indicate that the AGI and the T layers play a key role in: (i) concentrating the maximum shear strain along the subsoil profiles, even though the volumetric threshold is never exceeded; (ii) increasing the maximum shear strain along the subsoil profiles; (iii) causing the resonance frequency of the alluvial fill to assume an almost constant value (about 1Hz) which is quite similar to that measured in the main Tiber River valley, despite a significant change in thickness of the alluvial body along the Grottaperfetta valley.

Back analysis of a rock landslide to infer rheological parameters

On 30 January 2009, a rock slide involving approximately 0.23Mm3 of highly jointed gneiss from the local Ercinic substratum was recorded in southern Italy. The landslide occurred after exceptional autumnal rainfalls and involved a quarry whose activity has been documented over the past 10years by aerial images.An engineering-geology model of the slope involved in the landslide was developed based on the geomechanical classification of the outcropping rock masses, the ISRM (2007) indexes Ib (the block size index) and Jv (the volumetric joint count), and the observed geological setting of the slope. An equivalent continuum approach was adopted to attribute strength and stiffness parameter values to the different classes of jointed rock masses.A simplified evolutionary model of the slope was developed, starting from 300ka (i.e., from the erosional phase following the deposition of the 300-m-a.s.l. marine terrace deposits overlaying the gneiss substratum) to 30 January 2009. The model took into account the main depositional phases as indicated by the Pleistocene marine terrace deposits and the documented stages of quarry activity.Time-dependent stress–strain numerical modelling was performed by the FDM software FLAC 6.0. A visco-plastic Burger model was used to back-analyse the landslide event and to define the values of the rheological parameters for the jointed gneiss.The results, which were strongly constrained by the geomorphological evidences and by the displacement field observed before and after the landslide, demonstrated a combination of i) time-dependent gravitational slope deformation and ii) anthropogenic release due to quarry activity, which induced a progressive failure process and an increase in the jointing within the gneissic rock mass located behind the cut-wall of the quarry. Failure was ultimately triggered by intense rainfalls that occurred in the 3months before the landslide.The stress–strain numerical modelling demonstrated the reliability of visco-plastic rheology for simulating the rock mass creep in this case history: viscosity values in the range of 1019–1023Pa·s were derived.

3D Modeling of Tunnel Engineering based on Geological Body

3D geological modeling has involved the complexity of two aspects: data and models. 3D geological modeling of the tunnel project real environment needs to fully abstract data, the entity model needs to be decomposed into the geometric model, property model, and the relationship of geological structure between tunnel engineering geological body and the surrounding geological body needs to know. The paper has researched and analyzed the process and method of the tunnel engineering geological body modeling, and the conclusion has shown that the 3D modeling based on the overall tunnel engineering geological body is more suitable for the real environment; its effect of modeling is obviously superior to the simple superposition of the general geometric modeling and property modeling.

Based on the profile of complex three dimensional stratum modeling

With the development of computer technology and geological modeling study of the gradual maturity, 3D for the engineering geological modeling and information visualization analysis system of opportunities and challenges brought about. Have carried on the detailed introduction to the three dimensional geological modeling tool and the method. Summarized the three dimensional geological modeling basic step. Surface topography information deduce the initial construction of the geological model project . Carry out the calculation of occurrence. How to use the discrete value of the occurrence of information, production level surface equation method , And study of the surface intersection, Initial generation of 3D geological model .This paper discusses the adoption of the new access to the geological information on how to modify the initial model editor .Application algorithm for the generation of surface fitting interpolation. Display system for the section of geological strata, faultage and three-dimensional geological model of the effect drawings of block geological. At the same time, it provides a reliable scientific authority for the decision-making of the underground construction projects.

Overburden failure and the prevention of water and sand inrush during coal mining under thin bedrock

Coal mining under thin bedrock or thick unconsolidated soil layers brings mining problems related to these special geological conditions. The meaning of the term “thin bedrock” is defined through the thickness statistics of the coal seam and the bedrock layer. The coal-bearing strata having thick, unconsolidated aquifers and thin bedrock located at the Taiping Coal Mine in Shandong province were taken as a geological prototype for subsequent study. The geological, hydro-geological and engineering characteristics of the thin bedrock were analyzed. An engineering geological model was than established. Overburden failure and the development of “Three Zones” were studied by physical model tests. The rupture pattern and rock failure were analyzed for mining conditions under thin bedrock. The height of the caving zone and the freely flowing water fractured zone of different mining thicknesses were separately calculated. The results show that a mining thickness greater than 3.5 m causes the height of the freely flowing water fractured zone to be sufficient to touch the weathered zone and the bottom of the Quaternary system aquifer, to various degrees. This, then, would lead to water and sand inrush into the working face. Measures to prevent water and sand flow inrush disasters by eliminating the power source are put foreword. A field dewatering scheme was designed and observational data were obtained. The dewatering project had an obvious effect and the water level at working face number 8309 dropped to a safe level. The average draw down of the groundwater was observed to be 7.86 m. This showed that the dewatering project played a role in decreasing the hydraulic pressure and ensuring safety mining.

Study on Geology Model of Ge-He-Yan's Back Rock Mass Slope

According to the research of geology condition in Ge-he-yan's back rock mass slope,set up the homologous engineering geology model, carried on parts of qualitative analysises, combined with numerical analysis method based on the unloading rock mass theory, gave the quantitative analysis of the engineering geology model, then got the special deformation mechanism of this slope.

Analysis of Accumulated Damage Effects on the Roof of Mined-Out Areas under Blasting Vibration

Under the repeated blasting vibrations, the roof of the mined-out areas will suddenly collapse and fall because of its accumulated damage, which is a hidden danger for the miners and equipment on the surface. Based on the mined-out areas in Antaibao Surface Mine, the three-dimension engineering geological model and computational model were built using FLAC3Dtechnique. According to the effect of the load of the mechanical construction equipment, and the blasting vibration velocity recorded by field monitoring, the equal-time-interval blasting vibration as normal incidence was exerted on the surface of the mined-out areas three times. Consequently the accumulated damage effect of the roof and surrounding rocks of mined-out areas were analyzed, the stress concentration extent and the range of principal stress were discussed as well. The dynamic response characteristics of deformation and the accumulated progressive displacement were revealed via the monitoring displacement curves. The above mentioned results can provide theoretical and technical basis for similar projects on reducing the hidden danger and ensuring safe mining.

Summarizing the opportunities of engineering geological models and modelling

A cikk celja, hogy a melyepitesi mernokgeologiaban, elsősorban az alagutepitesnel hasznalatos numerikus modellezeseket bemutassa, azok előnyeit es hatranyait elemezze es ismertesse a geotechnikai modellalkotas lepeseit es kapcsolatat a mernokgeologiai modellel. A cikk kiter a kőzetmechanikai modellezesben kulcsszerepet jatszo izotropia, homogenitas, illetve kontinuitas kerdesere is. Elsősorban kőzetmechanikai szempontbol elemzi a numerikus modellalkotasok lehetősegeit, de a bemutatott elmeletek ertelemszerűen kiterjeszthetőek a talajmechanikai viszonyokra is.

Earthquake triggering of landslides in highly jointed rock masses: Reconstruction of the 1783 Scilla rock avalanche (Italy)

The Scilla rock avalanche occurred on 6 February 1783 along the coast of the Calabria region (southern Italy), close to the Messina Strait. It was triggered by a mainshock of the “Terremoto delle Calabrie” seismic sequence, and it induced a tsunami wave responsible for more than 1500 casualties along the neighbouring Marina Grande beach. Based on subaerial and submarine surveys, a 5×106m3 subaerial landslide was identified together with a 3×106m3 submarine scar area, whereas block deposits are present in both the subaerial and submerged regions. A detailed geological reconstruction of the slope was obtained and a geomechanical characterisation of the metamorphic rocks involved in the landslide was performed. Based on this reconstruction, intense jointing conditions of the rock mass can be related to main fault zones parallel and normally oriented to the actual coastline. An engineering geology model of the landslide was devised according to an equivalent continuum approach to evaluate both stiffness and strength of the rock mass within the slope. A finite difference stress–strain numerical modelling of the Scilla landslide was performed under dynamic conditions to back-analyse the landslide trigger as well as local seismic amplifications.This modelling gave new insights into the physical interactions between seismic inputs and slopes, as it demonstrated the fundamental role played by i) the interaction between the seismic input and geological setting of unsheared rock slopes (i.e., without preexisting landslide masses), ii) cumulated strain effects due to seismic sequences, and iii) jointing conditions of the involved rock masses responsible for the seismic amplification of the landslide-prone volume, driving it toward failure conditions.

GSIS: A 3D geological multi-body modeling system from netty cross-sections with topology

True 3D geological models are instrumental in addressing practical geology problems. A 3D geological modeling method is a vital module which converts raw data in lower dimensions into 3D bodies. To be geologically practical, the method must take cross-sections as the main data source and must be capable of modeling areas with complex faults, maintaining data consistency as well as carrying out multi-body modeling. To realize such a practical geological modeling system, GSIS (Geological Spatial Information System) is developed based on the core method of 3D geological multi-body modeling from netty cross-sections with topology. According to the intersecting netty cross-section approach, the presented method divides the modeling area into several cross-section grids. Thus, the modeling is simplified into the independent modeling of each cross-section grid and their merger into an integrated model. Different approaches are employed when constructing models in a specific cross-section grid, depending on whether a fault is present in the grid in question. In the absence of a fault, the basic approach is employed; otherwise, the basic approach is extended to add fault-related treatments. In both approaches, arcs are classified into subsets by their connections, attributes, and topological relationships. Arcs in the same subset of the lowest level are triangulated and interpolated to generate stratum interfaces. In this work, the application of GSIS in the Beijing multi-parameter stereo geological survey project is presented. Among seven successfully constructed models, the engineering geological model of the new city zone in Shunyi district and the bedrock geological model of the central city zone are cited as examples. These demonstrate GSIS’s capacity in modeling large areas with complex geology.

Geological, geomechanical and geostatistical assessment of rockfall hazard in San Quirico Village (Abruzzo, Italy)

This paper describes the results of a rockfall hazard assessment for the village of San Quirico (Abruzzo region, Italy) based on an engineering-geological model. After the collection of geological, geomechanical, and geomorphological data, the rockfall hazard assessment was performed based on two separate approaches: i) simulation of detachment of rock blocks and their downhill movement using a GIS; and ii) application of geostatistical techniques to the analysis of georeferenced observations of previously fallen blocks, in order to assess the probability of arrival of blocks due to potential future collapses. The results show that the trajectographic analysis is significantly influenced by the input parameters, with particular reference to the coefficients of restitution values. In order to solve this problem, the model was calibrated based on repeated field observations. The geostatistical approach is useful because it gives the best estimation of point-source phenomena such as rockfalls; however, the sensitivity of results to basic assumptions, e.g. assessment of variograms and choice of a threshold value, may be problematic. Consequently, interpolations derived from different variograms have been used and compared among them; hence, those showing the lowest errors were adopted. The data sets which were statistically analysed are relevant to both kinetic energy and surveyed rock blocks in the accumulation area. The obtained maps highlight areas susceptible to rock block arrivals, and show that the area accommodating the new settlement of S. Quirico Village has the highest level of hazard according to both probabilistic and deterministic methods.

Wire frame: A reliable approach to build sealed engineering geological models

The technique of 3D geological modeling (3DGM) is an effective tool for representing complex geological objects. In order to improve the accuracy of geological models applied in numerical simulation methods such as finite elements and finite differences, we can use 3DGM as a modeling tool. To do this, however, 3DGM must provide the ability to model geological and artificial objects in a unified way, and its geological model must be seamless for mesh generation. We present the concept of a sealed engineering geological model (SEGM), and describe its topological representation. Three kinds of conditions: geometric continuity, topological consistency and geological consistency, which must be satisfied by SEGM, are discussed in detail. A new method for constructing an SEGM based on a wire frame is proposed. It includes three main components: wire frame construction, interface modification and reconstruction, and block tracing. Building a unitary wire frame, which is composed of many simple arcs and connects all interfaces seamlessly, is the key of this method. An algorithm, involving two intersections computations and partition of simple arcs, is proposed for building a wire frame. Additionally, we also propose a local iterative algorithm for computing fault traces. As an example, we build an SEGM for the dam area of a hydraulic engineering project in the HuNan province of China.