Unconsolidated Research Articles

Effect of Preloading with Consolidation on the Undrained Bearing Capacity of Ring Foundations

The undrained bearing capacity of ring foundations has received significant attention from researchers, but most of the reported studies do not reflect the effect of consolidation due to preloading. In this work, we investigated the postconsolidation undrained vertical capacity of ring foundations resting on nonhomogeneous clays using finite differential analyses and the modified Cam-clay constitutive model. The results are presented in nondimensional form and were compared with data available in the literature. The coupling influences of the internal opening of the foundation, the magnitude of the preloading, the duration of the consolidation, and the initial overconsolidation ratio of the clay were all considered. A methodology based on approximating expressions that captured the numerical results well is proposed as a way of predicting the undrained capacity gain of ring foundations for any degree of preloading and consolidation.

The PVD-Accelerated Soil Deposit Consolidation Based on Elliptic Cylindrical Model

One method to deal with the problem of soft soil is to accelerate consolidation by preloading and prefabricating a vertical drain (PVD). Consolidation analysis was based on a one-dimensional theory that required PVD as an equivalent circular well. Further studies on a simple approximate for consolidated soil were represented by equivalent permeability coefficients, kve. The equivalent conductivity coefficient is influenced by the soil and PVD permeability coefficients. The formulation of kve based on the influence area in cylindrical has been applied to a lot of construction projects. According to the comparative analysis of the classical consolidation theory, it is considered that the diameter of the circle is less representative. This study proposed a simple formulation of kve based on the elliptical assumption of influence area. The kvewas derived based on an equal average degree of consolidation in one dimension, which applied the elliptical coordinate for degree of consolidation in the radial direction. The formulation is based on an elliptical cross-section and a cylindrical coordinate formulation. The validation of this formula is conducted with numerical calculations using 2D FEM. The results show that the consolidation time in the elliptical discharge area is shorter than that in the circular discharge area. Doi: 10.28991/CEJ-2023-09-07-08 Full Text: PDF

Analytical model for consolidation and bearing capacity of soft soil stabilized by combined PVD-deep cement mixing columns

Analytical model for consolidation and bearing capacity of soft soil stabilized by combined PVD-deep cement mixing columns

Packed Piles in Rolled Wells on the Loess of Southern Kazakhstan

The features of the structure of loess soils, widespread on the territory of southern Kazakhstan, are considered, which must be taken into account when preparing foundations and laying foundations in this region. The assessment of the possibility of using promising foundations from piles in rolled wells in local conditions based on the algorithm of their implementation in other regions is given. The experience of the device of these structures in Shymkent and the factors constraining their widespread implementation are given. In the south of Kazakhstan, in particular, in Shymkent, the problem of building reliable foundations is very acute. This is due to complex geological conditions, namely, the spread of loess subsidence soils. Loess rocks are found on all continents, but they are most widely distributed in Europe, Asia and America. According to experts, with an average loess capacity of 10 m, the total area occupied by loess rocks on the globe is 19 million km2 [1]. Loess soils, from the point of view of builders, have an insidious property – to change their condition when they are soaked. Therefore, a review of the origin of loess bases can clarify the essence of the physical phenomena occurring in its thickness during the construction and operation of buildings and structures

The role of free‐strain assumption in axisymmetric electro‐osmosis‐enhanced preloading consolidation of unsaturated soil

AbstractThe axisymmetric, equal‐strain consolidation theory of soil is widely employed in engineering due to the user‐friendliness of its solution. However, the radially averaged excess pore pressure (EPP) is unable to reveal the coupling effect of the radial electric field when the soil is consolidated by electro‐osmotic and surcharge preloading. In this paper, the axisymmetric consolidation analytical models with free strain and equal strain assumptions are developed to investigate the importance of the free strain assumption in the consolidation of unsaturated soil by electro‐osmosis‐aided preloading. The finite Hankel transform, decoupling technique, and Laplace transform are then utilised to derive the semi‐analytical solutions. Finally, the comparison of EPP, surface settlement, and average degree of consolidation under the two assumptions reveals that the free‐strain solution accurately shows the distribution of EPP at any point in the soils and the development of surface settlement at different radii, thus helping to analyse the electro‐osmotic consolidation characteristics. Moreover, it was discovered that electro‐osmosis combined with preloading allows for a more uniform consolidation of unsaturated soil. The difference in the average degree of consolidation under both assumptions is insignificant, while the installation distance of the cathode and anode vertical wells has a significant effect.

A State-of-the-Art Review of Organic Polymer Modifiers for Slope Eco-Engineering.

In slope ecological restoration projects, reinforcing soil and promoting vegetation growth are essential measures. Guest soil spraying technology can be used to backfill modified soil and vegetation seeds onto the slope surface, resulting in successful ecological restoration. The use of organic polymer modifiers to reinforce soil has several benefits, such as high strength, effective results, and low pollution levels. Organic polymer soil modifiers can be divided into two categories: synthetic polymer modifiers and biopolymer modifiers. This paper provides a thorough review of the properties and interaction mechanisms of two types of polymer modifiers in soil consolidation. The properties of organic polymer modifiers make them applicable in soil and vegetation engineering on slopes. These modifiers can enhance soil mechanics, infiltration, and erosion resistance and promote vegetation growth. Therefore, the suitability of organic polymer modifiers for soil and vegetation engineering on slopes is demonstrated by their properties and potential for improvement in key areas. Furthermore, challenges and future prospects for slope protection technology using organic polymer modifiers are suggested.

Analysis of Land Subsidence in Peatlands in the Awareness Area of Pekanbaru, Riau, Indonesia

This study area is administratively located in Parit Indah District, Bukit Raya District, Pekanbaru City, Riau Province. Geographically, the research area is located at coordinates 0° 28' 30.92" N 101° 28' 9.45" E N 0° 27' 25.63" - 101° 29' 47.30" E. The aim of this study was to find out the effect of peat soil types on subsidence. The data collection method in this study was carried out using sieve analysis, water content analysis, specific gravity, subsidence analysis, and soil testing in the laboratory. The effect of peat soil on subsidence has a significant effect between the type of peat and subsidence, the higher the maturity level of the peat, the lower the level of subsidence on peat soil. Based on the results of the study, the soil consolidation test with a depth of 75cm-3m had a soil settlement value of 0.467. It is recommended to do this to reduce the impact of subsidence in the land area such as the research area so that it does not have too much impact on the construction which is carried out by hardening the location using the vertical wick drain method, as well as for building foundations it can be done using chicken claw foundation.

Evaluation of ground surface deformation in discontinuous permafrost regions along the China-Russia Crude Oil Pipelines in Northeast China using InSAR and ground surveys

Adequately and timely measuring and evaluating the ground surface deformation (GSD) are keys to the prudent mitigation of frost hazards of foundation soils and thus to the safe and cost-effective operation of oil pipelines in permafrost regions. Thus, it is crucial to accurately evaluate the GSD along the route of China-Russia Crude Oil Pipelines (CRCOPs) for a better understanding of frequent and substantial (differential) frost heave and thaw settlement of pipeline foundation soils in permafrost regions. In this study, GSDs along the CRCOPs from Xiufeng town to Jinsong town, northern Heilongjiang Province were monitored in discontinuous permafrost regions in the northern Da Xing'anling Mountains, Northeast China. The Sentinel-1B images from 2017 to 2021 and the Small Baseline Subset Interferometric Synthetic Aperture Radar (SBAS-InSAR) technology were used in combination with the Geographical Detector (GeoDetector) for identifying the drivers for GSDs and with ground survey data for validation analysis of GSD at chosen sites (e.g., MDX304 and others). InSAR results show that most of the annual GSD rates along the CRCOPs range from −10 to 0 mm/a, with larger deformation rates in Ta’he, Cuigang, and Jinsong. GeoDetector analysis shows that latitude and soil types are the most important contributors to GSDs along the CRCOPs, and; GSDs are closely related to elevation, ground temperature at the depth of 1 m (GT1m), normalized difference vegetation index (NDVI), annual precipitation (AP), and slope aspects. Analyses of ground and oil-flow temperatures and survey results of electrical resistivity tomography (ERT) show that permafrost along CRCOPs has been degrading and thawing, resulting in thaw settlement, consolidation, and deformation of pipeline foundation soils and underlying/lateral permafrost layers and subsequently, the ground surface subsidence. This study provides key deformation data for the assessment and mitigation of frost hazards along the CRCOPs.

Rebound Calculation for Deep Excavation in Soft Soil Based on Rebound-Recompression Method

The excavation-induced stress relief and inward movement of the retaining wall will result in soil rebound deformation at the bottom of the excavation, adversely affecting nearby existing tunnels and foundation piles. Various existing methods for calculating the excavation rebound rely on rebound parameters and void ratio obtained from laboratory tests, with considering the effects of sampling, specimen preparation and laboratory procedures on the rebound parameters. As a result, a novel method is proposed in this article for calculating excavation rebound based on rebound-recompression method (RRM). This method first modifies initial void ratio (e0) and laboratory recompression index (CLR) used in traditional methods (TM) for calculation, based on field rebound and recompression curve proposed by the RRM, to in situ void ratio (ev0) and field recompression index (CFR). Then, the final rebound at the bottom of the excavation is calculated using a layered summation method. In addition, through two engineering examples, the proposed method is compared with existing calculation methods and measurements, demonstrating that this method is easy of calculate, yields reliable results, and can accurately predict the final soil rebound at the bottom of the excavation.

Study on Soil Corrosion Resistance Reinforced with Reactive Powder Concrete in Chloride Environment

The accumulation of residue soil (generally composed of soil, residue, or mud consolidation) is one of the important causes of damage to the environment limiting urban development. At present, the recycling rate of residue soil in developed countries is as high as 90%, while in China it is less than 5%. In marine construction, reinforced concrete often suffers from corrosion, which leads to a decrease in the service life and durability of the structure. Reactive powder concrete (RPC) with high strength and good corrosion resistance can solve these problems. In order to efficiently dispose of residue soil, protect the environment, and promote urbanization development, this study uses residue soil as a raw material to replace some cement in RPC, and studies the corrosion resistance of it (under dry–wet alternations and freeze–thaw cycles). In this study, five types of reinforced RPC with different residue soil contents (0%, 2.5%, 5%, 7.5%, and 10%) are prepared. Firstly, the working performance of blank freshly mixed residue soil RPC slurry is analyzed. Then, the corrosion resistance of residue-soil-reinforced RPC under the dry–wet alternations with 3% NaCl and freeze–thaw cycles is analyzed through parameters such as mass loss rate, electrical resistivity, ultrasonic velocity, AC impedance spectroscopy, and Tafel. The results show that under the dry–wet alternations, when the residue soil content is 10%, the corrosion rate and corrosion depth of the residue-soil-reinforced RPC are the minimum, at 43,744.84 g/m2h and 640.22 mm/year, respectively. Under the freeze–thaw cycles, the corrosion rate and corrosion depth of the 10% residue soil content group are higher than that of the 5%, being 52,592.87 g/m2h and 769.71 mm/year, respectivley. Compared to the other groups, the reinforced RPC with 10% residue soil content shows good corrosion resistance in both dry–wet alternations and freeze–thaw cycles. Replacing some of the cement in RPC with residual soil to control the amount of residual soil at 10% of the total mass of RPC can effectively improve the corrosion resistance of residue-soil-reinforced RPC and maximize the consumption of residue soil. This plan provides a feasible method for residue soil treatment in the construction industry, while also providing inspiration for research on the corrosion resistance of concrete in marine buildings.

The potential role of a narrow foramen rotundum and foramen ovale in the development of concomitant continuous pain in trigeminal neuralgia

The most characteristic symptom of trigeminal neuralgia (TN) is paroxysmal and lancinating pain along the sensory distribution of the trigeminal nerve. Notably, a proportion of TN patients also experience persistent throbbing or burning in the same territory as their paroxysmal pain, termed concomitant continuous pain (CCP). The neurovascular compression (NVC) theory has been regarded as the primary cause of paroxysmal pain in TN. In contrast, the mechanisms underlying CCP can hardly be explained by NVC and have yet to be clearly elucidated. Both the foramen rotundum (FR) and foramen ovale (FO) are substantial bony apertures in the middle cranial fossa, through which the second (V2) and third divisions (V3) of the trigeminal nerve pass, respectively. Prior studies have proposed that a narrow FR and FO on the right side may result in a greater incidence of right-sided symptoms and be involved in the development of TN. However, given the nature of CCP and certain anatomical findings, we postulate that secondary compression of V2 and V3 by narrow foramina is more likely to be the primary cause of the persistent pain instead of the paroxysmal pain in cases of TN with CCP. TN with CCP may be the combination of trigeminal neuralgia induced by NVC and trigeminal neuropathic pain resulting from constant entrapment of V2 and V3. Therefore, considering that microvascular decompression cannot resolve all causes of TN with CCP, percutaneous ablative procedures and stereotactic radiosurgery may be more appropriate for patients with narrow foramina.

Data-driven analysis of soil consolidation with prefabricated vertical drains considering stratigraphic variation

In coastal cities such as Hong Kong, rapid reclamation using prefabricated vertical drains (PVDs) is preferred as it can accelerate land supply to meet the urgent demand for houses. A robust PVD design relies on the correct identification of permeable soil layers and accurate delineation of their stratigraphic connectivity with surrounding drainage boundaries. The current engineering practice often ignores the physical locations of minor drainage boundaries (e.g., sand lenses) in the subsurface stratigraphy and might lead to a false interpretation of potential drainage and consolidation mechanisms. In this study, a data-driven analysis framework that takes stratigraphic uncertainty into consideration is proposed to investigate the spatiotemporal consolidation of PVD-improved ground using sparse site investigation data often encountered in engineering practice. The method adaptively develops multiple geological cross-sections from limited measurements and prior knowledge that is reflected by a single training image. The resulting multiple geological realizations serve as the input for PVD analysis. The proposed data-driven framework allows for a probabilistic evaluation of soil spatiotemporal behavior in terms of the degree of consolidation and future ground settlement. More importantly, the proposed method accurately predicts the spatial distribution of stratigraphic boundaries with quantified uncertainty, which significantly influences the consolidation mechanism.

Effect of soil consolidation on the fractality of the filtration law

In this paper, the effect of consolidation of the soil structure on the fractality of the fluid flow was evaluated. The equation of fractal law of flow in the porous medium under consolidation of two-phase, fully fluid-saturated soil was determined. Given all the simplifications, as well as the undoubted importance of the nature of the porous medium, which primarily determine the possible processes of both consolidation and fractal flow based on the results of the studies, we can conclude that a homogeneous porous reservoir at given parameters under the effect of groundwater pressure will expand its fractal structure.

Laboratory modeling of thermal and temporal cracking in swelling clays

Crack development in a changing environment is the controlling factor for the stability and strength of expansive soils. Expansive soils exhibit large volumetric changes with changes in their moisture conditions that may occasionally lead to reduced bearing capacity and foundation failures. This study purports to model crack initiation and its spatial progression in relation to the moisture content and drying period, respectively. Volumetric soil shrinkage is determined using high-definition digital camera imaging and Vernier scale methods, while the soil settlement under vertical shrinkage deformation could be captured through a tensile stress model for soils. It was revealed that a small change in suction could trigger crack initiation, which would propagate further under different environmental conditions. Furthermore, it was observed that the crack volume increased rapidly at specific moisture content and could penetrate as deep as 1 m after nearly 1.5 months that is fully consistent with the current model predictions. A comparison between the performance of the model proposed in this study and that of two existing models shows that the former predicts the vertical shrinkage strain values in closer agreement with those observed experimentally and is less conservative than those predicted by both models. Nevertheless, the findings from this study could be used to quantify the detrimental behavior of expansive soil present in pavement subgrades and shallow foundations for lightweight structures.

Fibre-Microbial Curing Tests and Slope Stability Analysis

In response to the deformation resistance deficiency and poor toughness characteristics of soil after microbial curing, a combination of fibre reinforcement technology and microbial curing technology was used to conduct microbial curing tests using basalt fibres and denitrifying bacteria. In this paper, the effects of fibre on the strength and toughness of soil consolidation were analysed by unconfined compressive strength test and direct shear test, and the stability of reinforced slope was analysed by numerical simulation. The results show the following. (1) Basalt fibre can effectively improve the characteristics of brittle damage of microbially consolidated soil while increasing the compressive and shear strength. (2) Fibre dosing and fibre length have important effects on the mechanical properties of microbially consolidated soil. (3) The appropriate amount of basalt fibre can promote the generation of calcium carbonate. (4) The plastic strain area of the slope decreases after microbial reinforcement and the maximum equivalent plastic stress decreases by 65 kPa.

LAND SUBSIDENCE AND GEOTECHNICAL IMPACT OF JAKARTA KOTA AREA

Land subsidence has long occurred around the Special Capital Region of Jakarta. It is important to know and deal with Land subsidence events which also cause various negative impacts. Aim: When large amounts of groundwater are withdrawn from certain types of rocks, such as fine-grained sediments, land subsidence occurs. The rock compacts because the water helps to keep the ground in place. When the water is removed, the rocks collapse in on themselves.The immediate impact is the building collapse around the Kota Tua of DKI Jakarta. Methodology and Results: The research method used is a quantitative descriptive survey method by observing the amount of land subsidence that occurs in the Kota Tua area and its surroundings. The results showed that there has been a vertical land subsidence that varies between 20-60 cm. Based on the results of the resistivity values and coordinates plotted on the Regional Geological Map (Jakarta and Kep Seribu), the research location is classified into Lithology: Clay, Sand Silt, Gravel, and Pebbles (Quartenary deposits). The phenomenon, land subsidence, is caused by a combination of various parameters, including natural consolidation of alluvial soils, excessive groundwater extraction, and also building loads from infrastructure development and tectonic factors. Conclusion, significance, and impact study: Knowing the value of land subsidence and its location is expected to support urban planning, basic infrastructure planning and development, housing, settlement planning, and local financial improvement in efforts to mitigate land subsidence disasters.

Experimental Study on the Soil–Structure Responses Induced by Tunnelling in Limited Space

As the economy develops rapidly, newly built tunnels in congested urban areas are becoming more and more common. Based on similarity theory, this study conducted a laboratory model test to investigate the soil–structure responses induced by the construction of a new tunnel in limited space which was formed by the existing underground infrastructures. The soil movement, convergence of the tunnel and distribution of the soil stress were explored. The test results revealed that the limited space could have a significant shielding effect on the soil movement. The maximum ground subsidence and the range of ground settlement induced by the construction of the tunnel in limited space were 60% and 40%, respectively, smaller than those induced by the construction of a tunnel at a “greenfield” site. The deformation of the tunnel was also restrained distinctly. Moreover, a soil settlement trough appeared below the bottom slab of the underground structure. The findings can shed some light on the surrounding responses induced by tunnelling in limited space in soft clay and can offer the valuable guidance for the similar projects.

The Pontine Marshes: An integrated study of the origin, history, and future of a famous coastal wetland in Central Italy

The Pontine Marshes (Central Italy) are known for their long drainage history starting early in Roman times and culminating in their reclamation ( bonifica integrale) by the Fascist’s regime under Mussolini, mostly in the 1930s of past century. The geology of this coastal wetland and causes for its drainage problems received limited attention till recently. We reviewed results from recent studies, identified still existing knowledge gaps and performed additional research to fill these, to produce a full description of the Holocene history and drainage of these marshes. Massive coring data that served to map the soils and surficial geology, observations in archaeological excavations, analytical data on soil and sediment characteristics, and radiocarbon datings allowed us to distinguish several phases in this history, with a main break in the early Roman Republican period with the first systematic drainage works. Earlier, natural processes brought about by sea level rise largely controlled its drainage. Once artificial drainage started, soil subsidence became an important process, aggravating the drainage problems. The bonifica introduced mechanical drainage, temporarily masking the impacts of subsidence. We quantified the historical subsidence using DTMs and developed scenarios for the impacts of sea level rise and subsidence in 2100 and 2200, assuming that this rise will be mitigated by a coastal defence system and enhanced capacity of the mechanical drainage. Our results demonstrate the important role of soil subsidence throughout the history of this wetland and need to include subsidence in scenarios for the impacts of sea level rise.

Buildings' Biaxial Tilt Assessment Using Inertial Wireless Sensors and a Parallel Training Model.

Applications of MEMS-based sensing technology are beneficial and versatile. If these electronic sensors integrate efficient processing methods, and if supervisory control and data acquisition (SCADA) software is also required, then mass networked real-time monitoring will be limited by cost, revealing a research gap related to the specific processing of signals. Static and dynamic accelerations are very noisy, and small variations of correctly processed static accelerations can be used as measurements and patterns of the biaxial inclination of many structures. This paper presents a biaxial tilt assessment for buildings based on a parallel training model and real-time measurements using inertial sensors, Wi-Fi Xbee, and Internet connectivity. The specific structural inclinations of the four exterior walls and their severity of rectangular buildings in urban areas with differential soil settlements can be supervised simultaneously in a control center. Two algorithms, combined with a new procedure using successive numeric repetitions designed especially for this work, process the gravitational acceleration signals, improving the final result remarkably. Subsequently, the inclination patterns based on biaxial angles are generated computationally, considering differential settlements and seismic events. The two neural models recognize 18 inclination patterns and their severity using an approach in cascade with a parallel training model for the severity classification. Lastly, the algorithms are integrated into monitoring software with 0.1° resolution, and their performance is verified on a small-scale physical model for laboratory tests. The classifiers had a precision, recall, F1-score, and accuracy greater than 95%.

Two-dimensional plane strain consolidation of unsaturated soils considering the depth-dependent stress

In practical engineering, the total vertical stress in the soil layer is not constant due to stress diffusion, and varies with time and depth. Therefore, the purpose of this paper is to investigate the effect of stress diffusion on the two-dimensional (2D) plane strain consolidation properties of unsaturated soils when the stress varies with time and depth. A series of semi-analytical solutions in terms of excess pore air and water pressures and settlement for 2D plane strain consolidation of unsaturated soils can be derived with the joint use of Laplace transform and Fourier sine series expansion. Then, the inverse Laplace transform of the semi-analytical solution is given in the time domain using a self-programmed code based on Crump's method. The reliability of the obtained solutions is proved by the degeneration. Finally, the 2D plots of excess pore pressures and the curves of settlement varying with time, considering different physical parameters of unsaturated soil stratum and depth-dependent stress, are depicted and analyzed to study the 2D plane strain consolidation properties of unsaturated soils subjected to the depth-dependent stress.