Underground Wall Research Articles

ASSESSMENT ON EVALUATION OF OUT-OF-PLANE SHEAR STRENGTH OF REINFORCED CONCRETE PLATE SEISMIC-RETROFITTED WITH POST-INSTALLED SHEAR REINFORCEMENT

A post-installed shear reinforcement (PSR) method that is applied to flat plates such as foundation slabs and underground outer walls from inside the building was developed. In this study, the out-of-plane shear strength evaluation formula was proposed using the past test results. In addition, since these flat plates are subjected to seismic force while receiving earth pressure, it is expected that they will be in a complicated stress state during an earthquake. In such a case, finite element analysis is useful, so the experimental results were simulated to verify the finite element analysis method for the flat plate with PSR.

Stress–Strain Investigation of the Rock Mass Based on Overcoring with CSIRO HI Cell Test and Numerical Modeling: A Case Study from an Italian Underground Marble Quarry

The present research illustrates the application of a methodological approach to studying the stress–strain distribution in a marble quarry of the Apuan Alps mining area (Italy). This study has been carried out in the framework of a project involving the University of Siena and the UOC Ingegneria Mineraria—USL Toscana Nord-Ovest, Tuscany Region. This stress–strain analysis aims foremost to monitor the slope stability conditions to guarantee a safe workplace for the personnel involved in mining activities, and to enable more sustainable long-term planning for excavation and production. The involved survey activities are as follows: (i) terrestrial laser scanning; (ii) engineering–geological data mapping; and (iii) in situ marble stress measuring through four CSIRO-type cell tests executed in different locations and at various depths within the underground excavation walls. The gathered data converged into numerical models of the quarry, both in 2D (DEM) and 3D (FEM), calibrated by in situ stress results through a rigorous back analysis assessment using least squares procedures. The created models represent a valuable tool for the identification and securing of risk areas and for future excavation planning in respect of the site efficiency and safety.

Method for evaluating the soundness of underground walls

AbstractThe elastic wave caused by the input at the wallhead spreads throughout the plane of the wall, and thus, inspecting the soundness of underground walls using a pile integrity test (PIT) is a challenging task. This paper presents a feasible method for evaluating the soundness of underground walls via a PIT. In particular, by applying a low‐pass filter to the reflected wave recorded at the wall head, the wave components reflected from the wall ends and cracks are effectively separated from the components reflected from the wall sides. Hence, through the proposed strategy, the wave can be clearly identified for soundness evaluation.

Lateral Pressure of Poured Concrete: Arguments from Ultra-Deep Diaphragm Wall (120 m) Construction

Formwork lateral pressures are critical with respect to engineering safety, and laboratory tests are often limited by time, height, etc. Formwork lateral pressures are related to early concrete fluid behavior (e.g., thixotropy). In this paper, we propose the use of ultra-deep underground diaphragm walls instead of formwork for conventional lateral pressure testing. During the construction process, three measurement points were set up in an ultra-deep diaphragm wall at −40 m, −80 m and −100 m. The concrete was divided into 22 casts, and the development of lateral pressure and the effect of time on lateral pressure were observed under each of the casts. We found that the characteristic height of all three measurement points was approximately 21 m. The average casting speed for this test was 16.846 m/h, with the fastest speed of 32.148 m/h. A time-dependent phenomenon of rapid rise and fall in lateral pressure with each casting was observed. This method provides a new way to conceptualize formwork lateral pressure, with the advantages of long testing time, high casting height and multiple tests, not only for formwork lateral pressure but also for early age thixotropy measurement of concrete.

Research on Construction Technology of Combined Omni-directional High-pressure Jet Pile

With the vertical and horizontal expansion of urban underground space, there is an urgent need for the construction technology of underground building structures, and the application of underground diaphragm walls as basement support design is becoming more and more common. The application theory of the high-pressure rotary jetting pile as a water stop for the ground connection wall joint has great application potential in practical engineering. This paper analyzes the process principle, characteristics, process, operation points and economic and social benefits of the combined all-round high-pressure jetting pile construction technology, and demonstrates the advantages of this method in specific applications from multiple perspectives. The method adopts a three-axis mixing pile driver and a conventional omnidirectional high-pressure rotary jet pile equipment to form a new type of construction machine. It is a kind of micro-perturbation grouting construction technology, which can quickly penetrate the complex underground geology and avoid the impact of hole collapse on drilling. Strong controllability, can effectively protect the safety of surrounding buildings and municipal facilities.

Characterisation of andersonite by Raman, luminescence and laser-induced breakdown spectroscopy

Andersonite (Na2Ca[UO2(CO3)3]·(5+x)(H2O) where x ≤ 1) has been reported from oxidised, hydrothermal uranium ores, typically as efflorescent coatings on the underground walls of mine workings. It may also occur in underground repositories for spent nuclear fuels owing to the preponderance of cementitious materials used as grouts, backfill and for structural stability. Should this be the case, its high solubility would be expected to lead to enhanced uranium mobility. This study reports on the use of Raman, time-resolved luminescence and laser-induced breakdown spectroscopy to characterise andersonite; the first attempt to use all three laser-based techniques in tandem for this mineral. Well defined Raman features were observed with the resolved peaks corresponding well with previous studies, although differences were found in the number of resolvable peaks due to the low Raman signal emitted in some of the wavenumber regions selected. Seven emission and eight excitation luminescence peaks were resolved for the phase and a lifetime value of 96.8 ± 6.7 μs was extracted from luminescence decay measurements. Compositional LIBS analysis was successful in identifying minor K-bearing inclusions in the specimen, confirmed by optical and scanning electron microscopy, that were not detectable by the other methods employed. The findings indicate that multiple laser-based techniques offer the potential for real-time characterisation of uranyl phases formed in environments where intrusive sampling and ‘off-site’ laboratory analysis is impracticable.

Effects of natural zeolite and sulfate environment on mechanical properties and permeability of cement–bentonite cutoff wall

Cement–bentonite (CB) slurry cutoff walls are extensively utilized to restrict the horizontal flow of fluids. In this study, cement was replaced by four various contents of 0%, 10%, 20%, and 30% by natural zeolite to evaluate its effects on the unconfined compressive strength, flexural strength, tensile strength, and the coefficient of permeability of cement–bentonite–zeolite (CBZ) specimens. Since underground cutoff walls are always in danger of sulfate attack, the CBZ specimens were immersed in three different containers with three different pH values of 2, 5, and 8 to study the sulfate resistance of this material. Results have indicated that the strength of specimens decreases with an increase in zeolite content at early ages; however, increasing the amount of zeolite up to 20% improves the mechanical properties and permeability of cutoff wall materials at late ages. The bentonite/cement (B/C) ratio equal to 0.2 shows a relatively better response than B/C ratios equal to 0.14 and 0.3. Curing specimens in the sulfate environment increased the mechanical strength of specimens and decreased the coefficient of permeability at first ages. At the late ages, curing in sulfate solutions manifested disadvantageous effects on specimens; however, specimens containing zeolite indicated higher sulfate resistance than specimens without zeolite.

Horizontal Pressure Reduction on the Underground Contour of the Structure by Means of a Cut-Off Wall

The article deals with the issue of reducing the horizontal pressure of the ground on the underground walls. The relevance of this issue is stipulated by the need to ensure the strength and operational reliability of the underground part of buildings and structures having a large burial in the foundation. It is important to solve this problem and to ensure the strength of the shallow subway vertical walls. One of the ways to reduce the horizontal ground pressure on the retaining structures is the construction of the cut-off walls. These walls should be located in the zone of expected soil collapse. The simplest way of theoretical solution of this problem is the finite element method (FEM), which cannot be regarded as absolutely reliable because in this situation, we deal with limit equilibrium of soil mass, i.e. with the class of problems for which FEM does not always give guaranteed reliable results even in qualitative terms. Therefore, an additional control in the form of some approved schemes based on obvious, easily verifiable provisions is required. The paper presents a technique for determining the size and position of cut-off walls on the basis of known solutions of the theory of limiting equilibrium of soils. The calculation algorithm is exemplified by an illustrative calculation model.

Research on Deformation Law of Deep Foundation Pit of Station in Core Region of Saturated Soft Loess Based on Monitoring

Saturated soft loess has a large pore structure, high compressibility, low strength, fluid plastic state, and poor engineering properties. It is still one of the key problems that engineering needs to solve. In order to study the influence of deep foundation pit excavation in the saturated soft loess area on the deformation of foundation pits, the deformation laws of ground settlement, enclosure structure, and supporting axial force were clarified based on the field tests on the deformation characteristics of deep foundation pits in areas with the high‐water level in saturated soft loess, combined with geological conditions and on‐site construction procedures. The results indicate the following: water supply and construction process were found to be the main factor in changing the surface settlement curve of deep foundation pits in saturated soft loess; increasing the construction speed of the pit bottom floor, inverted braces, floor frame beams, and sidewall frame beams to close the structure, which is conducive to restraining the deformation of the continuous underground wall and foundation pits in similar areas. In the initial stage of support layout, the axial force of steel support tends to increase too fast or even exceed the standard control value. Therefore, a reasonable preadding axial force is an effective means to control the deformation of the continuous underground wall and the axial force of the steel support. The current research results may provide a reference for constructing deep foundation pits in similar areas.

Analisis Kapasitas Struktur Dinding Squat Wall (Studi Kasus Underpass Pompa Sentiong Jakarta)

There is a potential overflow of a river during rain, resulting in water levels raised beyond normal water levels in the Sentiong Underpass Area, Jakarta in which is one of the strategic locations in Central Jakarta. To guarantee and maximize water flow in the Sentiong Underpass area, a water discharge regulatory system was created to be the form of underground wall structures equipped with pump houses. This wall structure is made of reinforced concrete structures underground at ± 3 m depth. This research aims to evaluate and analyze the underground wall capacity with reference to principles designed by SNI 2847-2013 and SNI 1727-2013. Analysis of data used based on field data including soil test parameters and vehicle traffic. Structural analysis which used is Computer Program (STAADPro), then based on the data obtained from the results of analysis and evaluation can be determined magnitude of displacement and dimensions of the reinforcement. The wall structure in Sentiong Area, Jakarta was planned to use K-300 concrete as high as 3m underground, 40 cm of wall thickness, bottom floor thickness 40 cm, and upper floor thickness 20 cm. The total length of this underground wall structure was planned 32 m. Based on the results of the analysis, it was found that displacement and capacity structure qualified safely with design steel reinforcement diameters of D13 mm and D16 mm.

Assessment of a Rock Pillar Failure by Using Change Detection Analysis and FEM Modelling

In this paper, various methods have been used to control and evaluate engineering difficulties in mining accurately. Different unstable scenarios occurring at the surfaces of underground mine walls, have been identified by comparing 3D terrestrial laser scanning surveys and subsequent point cloud 3D analysis. These techniques, combined with a change detection analysis approach and the integration of rock mechanics’ modelling, represent an asset for the assessment and management of the risk in mining. The change detection analysis can be used as control of mining and industrial processes as well as to identify valid model scenarios for establishing possible failure causes. A pillar spalling failure has been identified in an Italian underground marble quarry and this topic represents the basis of the present paper. A Finite-Element Method was used to verify the occurrence of relatively high-stress concentrations in the pillar. The FEM modelling revealed that stresses in the proximity of the pillar may have sufficient magnitude to induce cracks growth and spalling failure.

Numerical Simulation of Soil Displacement and Settlement in Deep Foundation Pit Excavations Near Water

Advancing urbanization in China requires large-scale high-rise construction and underground transportation projects. Consequently, there is an increasing number of deep foundation pits adjacent to water bodies, and accidents occur frequently. This study uses a numerical simulation method to study the stability of the deep foundation pit near water based on the Biot three-dimensional seepage-stress coupling model, with the open-cut section on the south bank of the Jinan Yellow River Tunnel Project as the engineering field test. This indicates the following: (1) the maximum horizontal displacement of the diaphragm wall occurred in the fifth excavation stage, and a horizontal brace effectively controlled the inward horizontal displacement of the foundation pit; (2) considering the effect of seepage in the soft soil foundation, the maximum vertical displacement of the ground surface at each excavation stage occurred adjacent to the underground continuous wall. As the depth of the foundation pit increased, the vertical surface settlement decreases gradually in the direction away from the excavation face; (3) considering the seepage conditions, within each interval of excavation of the foundation pit, the horizontal displacement of the continuous underground wall and ground settlement declined; and (4) the numerical simulation and field monitoring data were in good agreement. Under the conditions of accurate model simplification and parameter selection, numerical simulations can adequately forecast conditions of the actual project.

The fusion of physical mechanism and artificial intelligence – A case study of water-tightness estimation for geometrically imperfect cut-off walls

Underground cut-off walls are widely used in various applications to hinder groundwater flow and contaminant transportation. Although the cut-off walls are installed with due discretion, occasional construction errors were found to be inevitable, causing significant leakage or even failures. An on-site risk assessment tool is needed, to map the input construction error and water-tightness performance of the cut-off walls quickly and accurately. Although a highly efficient physical-based algorithm (three-dimensional discretized algorithm, TDA) is developed, its calculation speed may not suffice to serve as an instant on-site evaluation tool. In this regard, a direct relationship between the random seeds of positioning errors and seepage flow rate is expected to be explored, and based on this, a surrogate model using the AI approach is established. A novel physical-based Neural Network (NN) model is proposed to train NN from a more physical and interpretative perspective. The proposed physical-based NN is reasonably accurate but much more efficient than the benchmark physical-based method (TDA), and the prediction accuracy and result interpretability is also superior than the traditional NN.

Nonsteady Heat Loses to the Ground from a Building with Heated Underground Floor or Slab on Ground

Numerical model and research results of nonsteady heat transfer between building and ground basement are in the article. Two most common cases of heat contact between building and ground basement are compared: building with heated underground floor and building on the slab on ground. Nonsteady heat loses over period about several years of building exploitation are analyzed that made possible to establish a patterns of heat transfer between building and ground with taking into account of ground around of building inertness. Heat loses from building represented using mean values at the one unit of length of building perimeter. In case of building with underground floor calculated nonsteady heat loses of floor and underground wall are shown. Also shown results of nonsteady heat transfer to ground from outdoor air and groundwater. Numerical methodic used in research based on explicit finite-difference method applicated to boundary value problem of nonsteady heat transfer in ground. The problem taking into account existence of moveable groundwater without heat transfer calculation in the volume of groundwater.

The new approach to creating progressive and low-waste mining technology for thin coal seams

The problem of mining low-thickness coal seams in the Western Donbas is described in the article. Technological, economic and environmental reasons reducing the effectiveness of traditional technologies for their development are analyzed in detail and the new progressive approach is proposed to solve it. Attention is paid to the importance of hard coal for Ukraine energy independence and thin coal seams, which is the lowest indicator among coal deposits exploited in the developed countries worldwide. The key role of the Western Donbas mines in the Ukraine coal mining industry development is shown, where coal seams with a geological thickness in a range of 0.55 – 0.80 m take more than 50% of coal reserves. It leads to coal clogging and rising of the further enrichment costs. The interrelation of mining, geological seam thickness, and wall rock undercut is established, as well as decade-long tendency out of seam size increase is evaluated. It appropriately correlates with the general tendency of a geological thickness decrease and it leads to an increase of total ash content. The sources are defined and the volumes of waste rock run from coal mine to the surface are quantified, where 80 – 90% are underground mine working development and wall rock undercut while longwall mining operations. The negative influence of the applied mining technologies for low-thickness seams is shown. Whereby existing waste rock dumps are additionally replenished annually by 3.0 – 3.5 million of large-sized coal enrichment wastes and transported back onto waste rock dumps for very high expenses. It is determined that three waste dumps are located near urban settlements, which increases the environmental fee for their placement in three times. The new approach for selective mining of low-thickness seams with rock undercut placement in the gob area is proposed and it is characterized by the addition to the mechanized support of horizontally-closed scraper backfilling conveyor with a tamping device for rock compaction, which reduces the mine rock output by 25 – 30%. The preliminary calculations of parameters and prospective economic efficiency of the proposed mining technology for low-thickness coal seams are carried out in case of one typical longwall face taking into account the mined rock transportation cost to coal-preparation plant and its enrichment, reducing the cost of mine working supports. Its technology is by 17% more cost effective, than traditional mining technology while rough coal ash content does not exceed 21%.

Pore Structure, Morphology, and Strength of Self-Compacting Foam Material Backfilled Behind the Underground Pipe-Wall of Yellow River.

The backfill material for the underground pipe wall of Yellow River embankment was developed to avoid the high settlement and environmental damage caused by high filling and excavation. The interrelation between microstructure and compressive strength of the self-compacting foam backfill material with different water–binder ratios and density grades was investigated. The results indicated that the average pores size of the foam backfill material increased with increasing the water–binder ratio. Moreover, the compressive strength of the foam backfill material first increased and then decreased with continuously increasing the water–binder ratio. Based on the observation and the analysis of the computed tomography (CT) image, it can be found that the pore size of the foam backfill material decreased with the increment of the density grade. The overall findings demonstrated that the pore size and volume played an important role in affecting the performance of the foam backfill material used for the construction of the underground pipe wall of Yellow River embankment.

Utilization of Underground Walls in Urban Areas

The paper deals with the solution of the problem of the buildings foundation in confined spaces of urban development. The most commonly used solutions are the underground walls, which provide space for the construction pit during the construction of underground parts of buildings. They must meet certain conditions in the urban development. The paper focuses on the analysis of the interaction of wall systems (mainly sheeting structures of building pits) and the surrounding earth massif. The distribution of the contact stress influences decisively the dimensioning of the foundation structure and the assessment of the foundation soil in terms of limit states. Similarly, other load-bearing structures ensuring the stability and usability of a building have been affected by an increase in the deformation load, which may cause a noticeable increase in internal forces and bending moments, which are not normally considered or assumed in static calculations of external loads, or their determination is based on false assumptions. If the magnitude of the deformation effects is incorrectly determined, the serviceability or loss of stability of the building structure may be limited. For this reason, to ensure a reliable and economical design, it is necessary to describe as closely as possible the interaction of the foundation structure with the subsoil. A prerequisite for a correct and economical solution to the problem is to capture the physical nature of the task at all stages of the solution. The use of the possibilities provided by the mathematical apparatus of the most versatile numerical method - finite element method (FEM) also contributes significantly to a more complex analysis of the problem. The practical lining wall model of the Eurovea shopping and entertainment center in Bratislava, Slovakia has been chosen as a practical example of the calculation. The main reason was the availability of the results of available inclinometric measurements. These have been compared with the results of the structural design model. The task was to create a model of the underground (lining) wall and compare the obtained results with the inclinometric measurements on realized objects. The obtained results have been presented in graphical form.

Product Resource and Climate Footprint Analysis during Architectural Design in BIM

Significant global economic growth in the building sector is recently being noticed according to cities developments. Buildings and construction materials dominate the increasing demand for natural resources, greenhouse gas emissions, and landfill space. This article assesses the application of the product footprints for material, energy, and water as well as the product climate footprint for different design alternatives of building elements. The alternatives include different designs of foundations, exterior walls, and ceilings using recycled aggregates for concrete production. The approach is assessed cradle-to-gate within the life cycle assessment (LCA) boundaries for building elements and construction materials using a product resource and climate footprint analysis. The material footprint is determined by the indicators Raw Material Input (RMI) and Total Material Requirement (TMR), and the energy footprint by the Cumulated Energy Demand (CED). The water footprint is defined using the Available Water Remaining (AWARE) method. The climate footprint is quantified by the indicator Global Warming Impact (GWI) using Global Warming Potential (GWP) values from the Fifth Assessment Report of the IPCC. The LCA calculation is integrated into a building information modeling (BIM) tool to make changes in footprint results visible to planners, architects, and civil engineers. Results show that material footprint could be significantly decreased when the recycled aggregates are considered to produce waterproof concrete of foundation and underground exterior walls.

DYNAMIC CONSTRUCTION CONTROL METHOD FOR A DEEP FOUNDATION PIT WITH SAND-PEBBLE GEOLOGY

Taking the water-rich sand and pebble geology deep foundation pit of Jinfu Station of Chengdu Metro Line 6 as the research object, combined with the ladder excavation method of slotting, utilizing finite difference software FLAC 3D as well as on-site monitoring result, the deformation law of the diaphragm wall during the dynamic excavation of the foundation pit is analysed, and the influence of the relative stiffness between the vertical and horizontal walls of the foundation pit on the lateral deformation of the retaining structure is discussed. The results show that while using the ladder excavation method of slotting, the maximum lateral displacement of the underground diaphragm walls decreases gradually with the excavation depth of the foundation pit, which occurs at the intersection of the middle point of the oblique excavation line and the step distance section of the transverse excavation. Additionally, the lateral displacement increases closer to the excavation section. The lateral displacement of the envelope enclosure mainly depends on the relative constraint stiffness of the vertical and horizontal underground diaphragm wall of the foundation pit. The use of the ladder layered excavation method of slotting can effectively reduce the lateral displacement of the underground diaphragm wall. The simulated result and on-site monitoring result are nearly the same. These results can provide a corresponding theory and engineering basis for the selection of excavation methods for the same type of sand and pebble stratum foundation pit.

Use of multiple isotopes to evaluate nitrate dynamics in groundwater under the barrier effect of underground cutoff walls.

Underground cutoff walls are useful in conserving groundwater and preventing seawater intrusion in coastal regions. However, the environmental effects of human activities on groundwater quality in the upstream area of the underground cutoff wall over the long term are not clear. In this study, combined analysis of multiple isotopes (δ15N-NO3-, δ18O-NO3-, δ2H, and δ18O-H2O) and nitrate concentrations was used to assess the effect of underground cutoff walls on nitrogen dynamics in groundwater in an agricultural area in China. We sampled groundwater wells in the upstream and downstream areas of the underground walls in April, July, and September. The results indicated that the underground cutoff walls hampered the horizontal groundwater flow, making the upstream groundwater a closed system, which led to an increase in the nitrate concentration and accelerated nitrification processes. Manure was the main nitrate source in the upstream groundwater, and its levels in the groundwater were similar during the three seasons, indicating that there was no difference in the nitrate sources in the upstream groundwater among the three seasons. Hence, further management measures for manure application may be critical for groundwater protection in the upstream area of underground cutoff walls.