Complex Geotechnical Conditions Research Articles

Optimization of rational parameters for fastening and protection systems of mine workings in conditions of occurrence of unpredictable rock pressure manifestations

Purpose. To develop and substantiate rational parameters of a support and protective system for maintaining mine workings under conditions of potential unpredictable manifestations of rock pressure, ensuring the stability of the workings for their subsequent reuse after longwall face retreat. Methods. The study is based on geomechanical modeling within an elastic-plastic framework using a bilinear “stress-strain” diagram for each lithological unit and support element. Calculations were performed considering the actual physical and mechanical properties of the surrounding rock. The modeling included standard and combined support schemes involving cable bolts (6.0 m length) and steel-polymer bolts (2.8 m length), with the inclusion of additional support elements in the zone of potential secondary caving. Findings. The proposed combined support system comprising cable and steel-polymer bolts enabled the formation of a high-load-bearing reinforced rock plate. Comparative analysis of the stress-strain state (SSS) demonstrated a reduction in hazardous stress concentrations by 10-40%, and the affected areas decreased by a factor of 4.2-4.6. The recommended system effectively counteracts rock pressure even under unpredictable geotechnical conditions. Originality. For the first time, the correlation between the structural configuration of the combined bolting system and the spatial stress distribution in the rock mass has been substantiated, ensuring the transition from a frame-bearing to a rock-reinforced bearing structure. A methodology for selecting support parameters is proposed, considering the integrated influence of jointing, water saturation, and rock rheology. Practical implications. The obtained results allow for a significant improvement in the reliability and safety of mine workings in complex geotechnical conditions and facilitate their reuse with minimal repair costs.

Application of Digital Twins for Deep Pit Construction during the Transformation of Cultural Heritage Objects

The behavior of excavation support structures in complex geotechnical conditions and dense urban development was investigated. A rational structural scheme was established using the example of restoration with adaptation – transformation – of a cultural heritage site. For this purpose, during the scientific and technical support, a digital model (digital twin) of the deep excavation was created, and the stress-strain state (SSS) of the structure was determined in accordance with the design solutions, and recommendations for their optimization were developed. At the excavation stage, based on the analysis of observations of the support deformations and surrounding buildings, the digital model was adjusted, and design solutions for the strutting system were developed. Deep excavations in complex soil conditions are an integral part of modern urban construction. In densely built-up areas and complex soil conditions, a number of tasks arise related to ensuring the stability of the excavation and the safety of adjacent buildings. The article discusses issues related to modeling the interaction of the "soil - excavation structure - adjacent buildings" system during excavation. The study is conducted using numerical modeling with nonlinear soil deformation laws. The influence of various excavation support parameters (type, depth, location) on the stress-strain state of the soil mass and adjacent buildings is studied. Based on the results obtained, recommendations are proposed for selecting the optimal excavation support parameters to ensure its stability and minimize the impact on adjacent buildings. A promising direction in the design of excavation structures is to increase the economic efficiency and reliability of design solutions by using rational structural schemes that take into account the site's characteristics. In complex configuration excavations, the SSS must be modeled using spatial models. Taking into account the spatial effects of the structural scheme make it possible to solve two main tasks: 1) maximum utilization of the structure's bearing capacity potential, reducing margins to acceptable values; 2) elimination of design errors caused by the discrepancy between the stress-strain state of structures, determined based on 2D model calculations, and their actual state.

Features of silo operation in difficult ge-otechnical conditions

The performance of corrugated-wall steel silos for grain storage under complex geotechnical conditions depends significantly on the silo diameter and the height-to-diameter ratio. A key factor influencing foundation design is the vertical pressure exerted by the grain on the silo bottom, which increases with diameter. Based on pressure levels, all factory-made silos are divided into three groups: small (d = 11–16 m, 80–120 kPa), medium (d = 16–22 m, 120–160 kPa), and large (d = 22–28 m, 160–200 kPa). Each group demonstrates different performance characteristics under weak or collapsible soils. For the first group, natural subsoil or compacted soil cushions may be sufficient even under poor conditions. It has been established that for silos of the second group it is advisable to reinforce weak and subsiding soils or cut through them with pile foundations, especially for the bottom base, or to apply correctly substantiated calculation models of the joint operation of the components of the system “subsidence (weak) soil base – ring foundation – silo gallery – compacted base – bottom plate”. For the third group, construction on a unified foundation slab that supports the silo walls, bottom, and under-silo gallery is recommended. This solution ensures more uniform deformation and reduces the risk of operational problems. The results of surveys and numerical modeling confirm that the second group of silos is most prone to operational complications, especially if geotechnical control is not observed when compacting the backfill under the bottom. A set of recommendations is proposed that take into account the influence of the h/d ratio, the level of loads, and the type of soil base when choosing the type of foundations, which increases the reliability and durability of structures.

Study on the deformation characteristics of diaphragm walls in deep excavations within the Ningbo soft soil region

In soft soil environments, deep foundation pit excavation often leads to significant surface settlement, lateral displacement of support structures, and uneven settlement of surrounding buildings due to the complex geotechnical conditions and the inherent characteristics of soft soil, such as high compressibility and low shear strength. This study systematically analyzes 23 deep foundation pit excavation cases from Ningbo city, located in a silty clay region, to examine the deformation behavior during excavation. The research focuses on the impact of key factors such as excavation depth, pit dimensions, support structure parameters, and soil characteristics on the deformation of diaphragm walls. The results show that the maximum lateral displacement of diaphragm walls ranges from 0.09 to 0.84% of the excavation depth, with an average value of 0.36%. Deeper excavations lead to greater lateral deformation due to increased soil pressure and pore water pressure, with the maximum displacement typically occurring at 1.0–1.3 times the excavation depth. Soft soil thickness significantly amplifies wall deformation, with the displacement ratio increasing linearly with the ratio of soft soil thickness to wall depth. Increased wall stiffness, embedment depth, and support system stiffness effectively reduce lateral displacement. These findings provide a quantitative basis for optimizing diaphragm wall design and support systems to mitigate deformation risks, offering valuable guidance for deep foundation pits in similar soft soil environments.

Application of generative AI to automate numerical analysis and synthetic data generation in geotechnical engineering

Purpose This study explores the integration of generative artificial intelligence (AI) into numerical analysis workflows in geotechnical engineering to address the challenges of generating synthetic datasets. This study aims to create a framework that allows practitioners with limited programming skills to automate complex simulations, enabling the development of extensive data sets for AI and machine learning applications. Design/methodology/approach The study proposes a seven-step methodology using the finite element method and Python programming to auotmate numerical modelling. Generative AI, specifically ChatGPT, is used as a virtual assistant to guide practitioners through automation. The methodology is validated through a pilot study predicting excavation-induced ground displacement in Sydney’s Hawkesbury Sandstone. Findings Integrating generative AI into numerical analysis workflows accelerates data generation and improves the quality of synthetic datasets. The pilot study indicates that the generated datasets closely align with real-world measurements, confirming the robustness and reliability of the proposed framework. Research limitations/implications The study’s accuracy may be affected by assumptions in numerical analysis and input parameter quality. Future research should explore more complex geotechnical conditions, such as 3D effects, to further validate and enhance the methodology. Practical implications This framework provides an efficient solution for geotechnical practitioners to generate extensive datassets for AI training, reducing reliance on experienced programmers. It streamlines workflows and enhances data-driven decision-making in geotechnical engineering. Originality/value The paper introduces a novel integration of generative AI into numerical analysis workflows, offering an innovative approach to automate synthetic data generation. It serves as a valuable tool for advancing AI applications in geotechnical engineering, particularly for those with limited programming experience.

Deep foundation for high rise in tricky soil conditions and surroundings in Scandinavia – Walkthrough of various high‐rise projects from initial geology to final execution and everything in between

Abstract This report explores the challenges and innovative solutions associated with constructing deep foundations for high‐rise buildings in Scandinavia. The focus is on three projects: Lighthouse and Mindet 6 in Aarhus, Denmark and Karlatornet in Gothenburg, Sweden. Each project faces complex geotechnical conditions, requiring advanced engineering techniques. The report highlights the importance of early involvement in project planning, allowing for tailored solutions to geotechnical challenges. Per Aarsleff A/S employed value engineering techniques to optimize designs, ensuring both cost‐effectiveness and structural integrity. Test piles were crucial in validating foundation designs, offering real‐time data for precise calibration. The report emphasizes the important collaborative approach between engineers, clients, and other stakeholders, leading to innovative design solutions and successful project execution. The strategic use of advanced machinery, such as Aarsleff's Bauer BG55 drilling rig, underscores the technical prowess required for these projects. The report showcases how complex soil conditions and engineering hurdles were overcome through meticulous planning, technology, and continuous collaboration, setting a standard for high‐rise construction in challenging environments in Scandinavia.

Assessment of the Influence of Formation Conditions of Embankments and Spoil Heaps on Their Stability When Dumped on Clay-Salt Slurries

The formation of geotechnical structures on foundations composed of low-strength soils is associated with a number of risks and difficulties. Soils such as clay-salt slurries are characterized by low bearing capacity and a tendency to deform under load. In this study, a numerical simulation of the stability analysis of an embankment constructed on low-strength soils consisting of clay-salt slurries is carried out, and the study of the dependence of the stability and behavior of the embankment on the configuration of this foundation, without taking into account the embedment of rocks and with introduction of rocks into the geotechnical system, is considered. The results prove that the sloping configuration of low-strength soils greatly complicates the stability of the embankment. It is noted that the stability factor is significantly reduced under the influence of loads on low-strength soil, particularly when the geotechnical system has a configuration with slope angles of 5° and 10°, and, in addition, when rocks are embedded in low-strength soil if the underlying soil layer is a weak foundation. In view of this, the assessment of embankment stability on clay-salt slurries requires careful analysis due to a number of specific characteristics of these soils that create complex geotechnical conditions.

Investigation of individual problems of calculation of drainage pipes in complex geotechnical conditions

The article notes that changes in the loads acting on the drainage pipe (pipeline) in accordance with the relative ability of the drainage pipe and the ground filling to deform are essential. To determine the magnitude of the loads on the drainage pipeline laid in the trench, the formula proposed by A. Marston most accurately corresponds to the results of experiments and is convenient for engineering practice. The perforation of the walls of the drainage pipe affects their strength not only when the pipes are crushed, but also for the conditions of transportation and installation of pipes. The contact interaction of the cross-section of the drainage pipe with the soil base is investigated, in this case, the interaction of cylindrical (having a semicircular contact) or reloid (having a contact of the circle sector) shells lying on an elastic soil base is considered. A differential equation is considered to describe the deformation of an elastic shell, which includes the stiffness parameter, linear differential operators, components of displacement of the neutral axis of the drainage pipe, external load and dimensionless coordinates. For the elastic base models of E.Winkler and V.Z.Vlasov, a general solution of the differential equation describing the deformation of the drainage pipe is proposed. The solution of this equation and the external load is presented in the form of double or single trigonometric series, depending on the task (two-dimensional or one-dimensional). A horizontally lying cylindrical (or reloid) shell (drainage pipe) supported on a ground base is considered. The contact pressure is determined by summing the Fourier coefficients. This solution additionally takes into account the distribution capacity of the ground base of the drainage pipe.

Ways to address the construction of new buildings in old urban areas

This paper deals with the problem of constructing new buildings in old urban areas, with emphasis on determining the actual dimensions of the active footprint of existing foundations. The study focuses on the problems associated with limited space for construction, geotechnical conditions, soil characteristics, as well as the features of near-surface foundations and methods for calculating their settlement. The paper proposes a methodology that, when applied, provides a more accurate and reliable determination of non-uniformity of base deformations of neighboring foundations. This is achieved by taking into account a number of factors, such as the sequence of erection, soil compaction, the size of the footings and the magnitude of loads. The proposed approach also substantiates the optimal spacing of the designed neighboring foundations, helping to reduce the negative impact on existing structures and ensuring the stability and durability of both new and existing structures. The results of this study represent a significant contribution to the development of effective construction solutions in limited urban spaces, and can be used by designers and builders to optimize construction processes and ensure the stability of buildings in complex geotechnical conditions.

The Data-Driven Homogenization of Mohr–Coulomb Parameters Based on a Bayesian Optimized Back Propagation Artificial Neural Network (BP-ANN)

Homogenization methods can characterize the mechanical properties of these materials based on appropriate constitutive models and data. They are also applied to the characterization of mechanical parameters under complex geotechnical conditions in geotechnical engineering because of the complexity and heterogeneous nature of geotechnical materials. Unfortunately, existing homogenization methods for geotechnical mechanical parameters often incur immense computational costs. Hence, a framework that utilizes finite element analysis for generating a dataset which is then trained using a Bayesian Optimized Back Propagation Artificial Neural Network (BP-ANN) to obtain the homogenized Mohr–Coulomb parameters of the soils is proposed. This is the first time that Bayesian optimization and a BP-ANN have been used in conjunction to predict the homogenized mechanical parameters of soils. The dataset used for training the data is generated using the commercial FEM software ABAQUS (6.10). The maximum difference between the top and bottom part of the tunnel of the heterogeneous model and homogeneous model of our test cases only varies by 5.3%, thereby verifying the excellence of the Bayesian Optimized BP-ANN.

RELIABILITY OF RMR CLASSIFICATION DURING THE CONSTRUCTION OF ZENICA TUNNEL

Construction of underground tunnels in the rock mass is a very complex task from the aspect of stability of the rock mass in the secondary state of stress and defining the method of support. The method of excavation and the construction of the primary support are adapted to the state of the rock mass, which is why an adequate analysis of the rock mass as a work environment is of great importance. In order to define as precisely as possible, the quality of the rock mass as a work environment, classifications of the rock mass have been developed in recent times. The classifications are based on which the condition is assessed and its characteristics important for design are defined. In tunnel construction in Bosnia and Herzegovina, the RMR classification is most often used, the reliability of which varies depending on the characteristics of the rock mass in which the room is made. The paper analyzed the reliability of the RMR classification for the construction of the "Zenica" road tunnel, which was built in complex geotechnical conditions. Key words: rock mass, uniaxial compressive strength, reliability, RMR classification

Construction practice of water conveyance tunnel among complex geotechnical conditions: a case study

The construction practice of water conveyance tunnels often encounters various complex geotechnical engineering conditions, which bring huge challenges to the design and construction of water conveyance tunnels. Based on the theory of rock elastic–plastic mechanics and finite element analysis technology, this article carried out investigations of engineering geological features, geological formations and hydrological conditions establishes a calculation model for the 3# water conveyance tunnel of the Fenhe River Diversion Project, and analyzes the variation law of surrounding rock stress and displacement during TBM excavation of the tunnel. The results indicate that the dominant direction of the rock mass principal stress measured by the hydraulic fracturing method is NE84°, and the maximum horizontal principal stress, minimum horizontal principal stress, and vertical stress decrease sequentially, analyzing the characteristics of shield TBM construction technology, it is applied to the construction of water transfer tunnels. The numerical simulation of TBM construction using FLAC3D software shows that as the excavation surface advances, the subsidence value of the tunnel roof first slowly increases, then rapidly increases, and then tends to stabilize. The horizontal displacement of the surrounding rock is increasing. The maximum principal stress of the surrounding rock gradually increases. The final surrounding rock stress is 35 MPa. The TBM shield machine with mud water balance driven by indirectly controlled frequency conversion motor is selected for TBM construction of the tunnel. The study offers statistical information to support tunneling technology for water conveyance in the geotechnical engineering practice.

Effectiveness of compensatory injection as a means of regulating the stresses in complex geotechnical conditions

Deep excavations in dense urban areas often result in additional settlement of buildings that fall within the influence area of new construction. The most sensitive to such settlements, according to the normative literature, are historic buildings. One of the ways to regulate additional building settlement in the influence area of deep excavations is compensatory injection. The hydraulic fracture network created in the foundation creates additional lateral compression of the soil and changes its physical and mechanical properties. The article deals with a real example of an emergency situation at one of the objects in Tyumen, where during excavation of a pit with the designed depth of 7 meters for the construction of a five-storey building with an extended two-level underground space significant excessive settlement of the adjacent historic building and damage to its bearing structures were revealed as a consequence of the additional settlement development. The purpose of the present study is to evaluate the effectiveness of compensatory injection using collar technology to reduce excessive additional settlement of buildings in the zone of influence of deep excavations. A comprehensive analysis of the impact of new construction on the surrounding environment has been carried out by the authors of the article by means of numerical simulation. Analyzing the results of numerical modelling, the authors of the article developed measures to eliminate the emergency situation and stabilise the foundation. Based on the results of geodetic monitoring, it was found that the installation of a geotechnical barrier by injecting soil using the collar technique not only stabilised the foundation but also brought the building into position to meet regulatory requirements.

The Governor Mario M. Cuomo Bridge, NY, USA: solutions to complex geotechnical conditions

Deriving its name from a local Native American tribe and the Dutch word for sea, the Tappan Zee (NY, USA) is perhaps the most difficult section along the Hudson River for building a bridge. Swells of 1 m, swift tides, winter storms and ice flows aside, the 5 km crossing faces daunting circumstances beneath the surface in the form of poor and varied geotechnical conditions. Innovative design and construction first found a solution to these challenges in the 1950s with the completion of the Tappan Zee Bridge. However, with traffic volumes exceeding its design basis, exponentially increasing maintenance costs and functionally obsolete features, ‘the Tapp’ was nearing the end of its serviceable life. Its twin-span replacement, the Governor Mario M. Cuomo Bridge, took a diametrically different approach to the river and its complex soil strata. This paper looks back briefly at the unique floating bridge strategy used in the 1950s before examining the deep-foundation approach of the 2010s. The US$4 billion Cuomo Bridge took advantage of new resources such as driven pipe piles more than 115 m in length, large-displacement isolation bearings and modular joints and the use of prefabricated components and several massive barge-mounted cranes.

Forecasting and controlling two main failure mechanisms in the Middle East’s longest highway tunnel

Forecasting and controlling two main failure mechanisms in the Middle East’s longest highway tunnel

Côte D’Or National Sports Complex, Mauritius: engineering a new African sporting hub

The Côte D’Or National Sports Complex provided the African island nation of Mauritius with world-class sporting venues for the 2019 Indian Ocean Island Games. The new high-performance facilities were designed and built in just 2 years against a backdrop of complex geotechnical conditions, rigorous settlement criteria and the challenges of operating in a tropical environment prone to seasonal cyclone activity. Additional considerations included the limited local procurement capacity and material availability. The lessons learned and standards applied provide a useful resource for similar works in the Indian Ocean region.

Cut-off grade determination at Shiraldzhin gold deposit by the analogy method of geotechnical engineering

Shiraldzhin deposit is a genetic and commercial analog of actual Dzhamgyr mining project. Exploration and operation in both cases are implemented within the unified engineering and management package. The largest and best explored ore occurrence at Shiraldzhin is Sterzhnevoe ore body traceable to 1200 and 350 m along the strike and dip, respectively. The ore body is 0.2 to 13 m thick (average thickness 2.89 m), has the western dip and occurs at the angle of 30–70°. Down to the Level of +2650 m, the proven reserves are appraised as 1795.7 kt of ore and 5985.5 kg of gold at gold content of 3 g/t. For the preliminary risk assessment of Shiraldzhin gold mining in Kyrgyzstan, the analogy method is used, including geotechnical stability parameters of enclosing rock mass and ore body, and correlation of expenses connected with preparatory works, stone drivage and stoping. The correlation factor is determined from the difference of geotechnical parameters of rock masses and ore bodies at the deposits. Considering the global market price of gold and with regard to the operating costs, the cut-off grade is determined for gold-bearing blocks. It is mentioned that the main investment risk of Dzhamgyr and Shiraldzhin gold projects is conditioned by complex geotechnical conditions of mining at intolerable loss and dilution in case of shrinkage stoping. It is required to undertake a test survey to estimate feasibility of more effective accessing and extraction flow charts, in particular, completely mechanized breast stoping and open pit mining.

Порівняння методів розрахунку плитних фундаментів з урахуванням результатів інженерно-геологічних вишукувань та геодезичних спостережень за процесом просідання

Increasing the height of buildings and structures in combination with the development of areas with unfavorable geotechnical conditions cause the use of foundations in the form of solid reinforced concrete slabs. In complex geotechnical conditions and under high loads, the soils can work beyond linear deformation. This necessitates the calculation of the system "building-foundation-soil" based on the assumptions of nonlinear soil mechanics. The issue of designing foundations for cylindrical structures of the agro-industrial complex, in particular granaries, is especially relevant. The task of this study is a comparative analysis of different methods for calculating the subsidence of slab foundations to select a rational model of deformation of the soil. The comparison of calculation methods is carried out on the example of the foundation under the granary with a volume of 8841 m3. The foundation is made in the form of a round reinforced concrete slab with a diameter of 20.4 m. The characteristics of the soil are established by the results of geotechnical surveys. The calculation according to the Winkler model (elastic base plate with one coefficient of subgrade reaction) was performed in the "Cross" module of the SCAD Office software package. With a total load on the foundation of 2741 tf, its average subsidence is 2.15 cm. The calculation according to the model of three-dimensional finite elements of cubic shape was performed in the environment of the SCAD Office software package. The average subsidence of the foundation is 2.4 cm. The calculation by the method of layer-by-layer summation according to the instructions of DBN B.2.1-10: 2018 gave the subsidence of the foundation slab equal to 13.7 cm. The actual average subsidence of the foundation during the observation period in different areas of the foundation was 1.1… 2.4 cm and averaged 1.75 cm. The comparison of the analyzed methods for determining the subsidence of the foundation indicates the closeness of the results of calculations on the model of the slab on an elastic basis and the model of three-dimensional finite elements to the actual value of subsidence and the greatly higher result of the calculation by layer summation. The use of the latter method leads to excessive reliability in the design of foundations.

Einsatz kombinierter Bohrverfahren zur Vorauserkundung mit digitalem Bohrdatenmanagement

Abstract The purpose of exploration drillings in tunnelling operations is to investigate rock structure, geological composition of the rock, especially with regard to fault zones, and the identification and characterisation of water‐bearing zones. When determining the quality of exploration, the economic parameters must be taken into account. The application of combined exploration drilling methods allows the successful drilling of exploration drillings even in complex geotechnical and hydrogeological rock conditions. The concept provides the flexibility to switch between drilling systems and to realise probe measures tailored to the specific geology quickly and according to economic requirements. For successful exploration projects, documents and findings from past projects are used in the planning phase. The use of digital drilling data management offers enormous potential for optimising data evaluation. The determination of machine, equipment and the preparation of a drilling plan can thus be prepared much more specifically for the upcoming exploration. During execution, direct conclusions can be reached regarding e.g. drillability or drilling tool condition on the basis of the process‐oriented process analysis.

Evaluation of Anthropogenic Substrate Variability Based on Non-Destructive Testing of Ground Anchors

The purpose of this paper is to describe the variability of soil rheological properties based on research carried out using load tests of ground anchors under complex geotechnical conditions. The heterogeneity of soil should always be considered when designing geotechnical constructions. In the present case, the earthwork created at the Warsaw Slope revealed an embankment of anthropogenic origin, located in a geologically and geomorphologically complex area of the Vistula valley slope. Excavation protection was anchored mainly in soils of anthropogenic origin. When the acceptance tests of the ground anchor were completed, the subsoil randomness was confirmed using nondirect, geostatistical methods. A standard solid rheological model with nonlinear fitting to the data was used. This model was established to describe the creeping activity of the ground anchor more accurately. The characteristics of man-made embankments were described using the parameters obtained with the rheological model of the subsoil.