Settlement Calculation Method Research Articles

Influence of Cross-Correlation on the Modelled Uncertainty in Stress–Strain Behavior of Soft Clays

Reliability-based design is increasingly being applied to geotechnical problems because it allows the robust consideration of various sources of uncertainty, such as the inherent variability of soil properties. Some soil properties, however, are mutually dependent, and ignoring this cross-correlation may lead to biased estimates of the probability of unsatisfactory performance. Hence, in this study, the Gaussian copula was used to evaluate how the applied cross-correlation or independence between the compressibility properties affects the uncertainty in the stress–strain response of two marine soft clays. Two settlement calculation methods were considered: the compression index and Janbu tangential stiffness methods. The correlation coefficients were defined from the site-specific oedometer data at two extensively studied clay sites, and from a database. The simulated oedometer curves were compared to the observed variability in the site-specific data. The settlements in the clay sublayers were then computed, and different cases were compared by means of boxplots. It is concluded that the Janbu method leads to a significant overestimation of uncertainty in settlement if the cross-correlation between the compressibility parameters is ignored. On contrary, the compression index method seems less sensitive to the assumed correlation structure, and as such, the parameters can be treated as independent in most cases.

Settlement Calculation Method for Peat Soil Foundations

The calculation of the settlement of a peat soil foundation is based mainly on the formula obtained by data fitting or simply modifying the universal calculation formula. The deformation mechanism reflected by these calculation methods is indistinct. Therefore, several model tests were carried out using the embankment structure of the Dali–Lijiang expressway as a prototype, and the settlement was analyzed with the one-way consolidation deformation and in situ settlement of other researchers. First, the S − logt (S is the deformation) curve of peat soil showed no obvious inverse “S” change, which is different from that of soft soil or mucky soil. According to the S − t curve, the deformation process of peat soil can be divided into three stages. Second, the relationship between the compression modulus and load was analyzed and combined with the settlement calculation results. The compressive modulus between 12.5 and 25 kPa [En(0.125–0.25)] was proposed to be used when calculating the settlement of peat soil foundations by the layerwise summation method. Moreover, the compression modulus of the three consolidation stages was proposed to be used to calculate the settlement of peat soil foundations by the layered sum method. At the same time, the influence of confinement on the compression modulus of the third consolidation stage should be considered and corrected. The accuracy of the settlement calculation method proposed in this paper was higher than the accuracy of the standard layerwise summation method, regardless of whether the horizontal limiting conditions of the standard method are modified.

A New Calculation Method for Life Cycle Settlement of Soft Ground with Creep Treated by Columns

A New Calculation Method for Life Cycle Settlement of Soft Ground with Creep Treated by Columns

Three-Stage Analysis Method for Calculating the Settlement of Large-Diameter Extralong Piles

In terms of safety, large-diameter extralong piles require highly accurate settlement prediction because of their high load-bearing capacity. According to the bearing mechanism of the large-diameter extralong pile, in this paper, a novel and scientifically accurate three-stage analysis method is proposed for predicting pile settlement based on Randolph’s study of pile forces in homogeneous soils, in view of the limitation that the accuracy of the conventional settlement calculation method is only applicable to the pile in the end-bearing frictional bearing condition. The three-stage analysis method fully considers the deformation characteristics of the pile in three different bearing states: pure friction bearing stage, end-bearing friction bearing stage, and damage stage. The critical load of TP4-1 in this paper is 9620.89 kN, and the ultimate compressive bearing capacity is 19279.09 kN, as calculated using the three-stage analysis method, and thus the three bearing states are clearly defined. The settlement under all levels of load obtained using this method can be very close to the real-case settlement, and the maximum error of the TP4-1 pile is only 0.52 mm, as observed by numerical simulation, static load test of TP4-1, and experiments on the other three test piles.

Stochastic Medium Model for the Settlement Calculation of Prefabricated Vertical Drains of Soft Soil Foundations in the Coastal Area of South China

The prefabricated vertical drain (PVD) is an essential means to mitigate the settlement of soft soil foundations in coastal areas of South China. The commonly used elastoplastic analytical method cannot directly reflect the interaction of different PVDs and the resulting displacement of soft soil. At the same time, these elastoplastic analysis and numerical simulation methods are greatly influenced by the values adopted for rock and soil material parameters. In this paper, we present a stochastic medium model that can directly reflect the interaction of different PVDs and the resulting displacement of soft soil. It is not affected by the characteristics of rock and soil themselves and can also reflect the actual deformation process of soft soil. According to engineering practice, the settlement curves of soft soil foundations in coastal areas of South China with PVDs exhibited distinct normal distribution characteristics, which was consistent with the description of settlement by the stochastic medium model. Hence, based on the stochastic medium model, this paper analyzed the settlement mechanism of PVDs and established a stochastic medium model for the settlement calculation of PVDs. A function for the soft soil foundation in the coastal area of South China cross-section settlement curve was presented by back analysis of the PVD model. We chose the stochastic medium model based on this methodology to explore the interaction between different PVDs. The above models were then applied to an expressway in South China. Comparing actual settlement monitoring values to calculated values obtained with the PVD model, the error between the two models was less than 15%. This research provides a new settlement calculation method of PVDs in soft soil foundations in the coastal area of South China and a new basis for designing soft soil foundations.

Vertical Fiberglass Micropiles as Soil-Reinforcing Elements.

This article is dedicated to developing a ground improvement technique using vertically oriented reinforcement elements prefabricated utilizing fiberglass pultruded pipe and helical shape wideners at the bottom toe. Structures of the prefabricated helical micropiles varied by the length and cross-section area introduced into the soil massive as reinforcing bearing elements. The effect of the reinforcements geometry variation was investigated through a reinforcement factor (µ), based on which a calculation method for measuring settlement of reinforced soil has been previously developed Full-scale field plate load tests were performed before and after reinforcing the soil to investigate the changes in the soil stiffness after the reinforcement process. Comparative analysis between the reinforced and reference soft sandy soil indicates an average increase in the deformation properties of the fiber reinforced soils by 8%, 30%, 63% at the applied pressures of 100, 300, and 550 kPa, respectively. The influence of the fiber reinforced polymers (FRP) geometrical properties on the final composite settlement was determined. A comparative analysis of the calculated and the actual plate load tests results reveals that the previously proposed settlement calculation method is adequate for further development.

Settlement Characteristics of Split Grouting Pile Composite Foundation in Loess Areas

Loess foundations often affect the stability of superstructures due to their insufficient bearing capacities; thus, reinforcement measures are crucial for mitigating the uneven settlement of foundations. This study aims to investigate the settlement characteristics of composite foundations for loess foundations reinforced by splitting grouting piles. First, split grouting tests were carried out on loess foundations. After the test piles reached the design strength, static load tests and geotechnical tests were carried out to obtain the Q‐s curves of the test piles. The pile‐forming mechanism was analyzed via excavations at an on‐site test pile. Furthermore, the traditional settlement calculation method of composite foundations was used to calculate the settlement of split grouting pile composite foundations, and the results were compared with field test results to explore a suitable settlement calculation method of split grouting pile composite foundations. Finally, the numerical model of split grouting pile composite foundations was established according to the pile forming mechanism, and the settlement deformation characteristics of single pile and pile group composite foundations were analyzed. The relative errors of the composite modulus method and the stress correction method for calculating the settlement of the composite foundations were 6.4% and 32.8%, respectively, and the composite modulus method was closer to the test values. The calculated curves of the numerical model were in good agreement with the measured curves and relevant literature research results, demonstrating the rationality of the modeling method; the findings of this study provide theoretical guidance for designing loess foundation splitting grouting reinforcement and for predicting settlement during later construction periods.

Model Test and Theoretical Analysis of New and Old Embankments Differential Settlement Considering Lateral Deformation

In the embankment widening project, the new embankment will produce large deformation due to the low degree of consolidation, which will affect the stability of the embankment. Obtaining the settlement law of embankment is the premise to ensure the stability of the embankment. In this paper, the deformation law of the new embankment is studied through the embankment model test, and the settlement calculation method of the new embankment is proposed. The model test results show that the new and old embankments have a large settlement difference during the loading process, and the maximum settlement of the new embankment is twice that of the old embankment. The lateral deformation of the new embankment is directly proportional to the vertical deformation, sliding occurs under the ultimate load, and the bearing capacity is lost. Based on the one-dimensional calculation method, the lateral deformation coefficient is introduced, and the two-dimensional embankment settlement formula is obtained. The new embankment is meshed, and the deformation of each node is calculated by the formula, and the difference between the settlement and the model test data is 6.2%, which proves the feasibility and accuracy of the calculation method.

Analytical Solution for Settlement of Homogeneous Structure where the Tunnel Passes Underneath and Its Application

Based on Winkler elastic foundation beam theory, Peck modified formula and Laplace transform are used to solve the approximate differential equation of the deflection curve. The settlement calculation method for important homogeneous structures where the tunnel passes underneath is studied. The analytical solution for the settlement of the homogeneous structure is derived and verified. The field monitoring and numerical analysis results are compared. Laplace transform method requires fewer parameters to solve the approximate differential equation of the deflection curve, and its calculation efficiency is high, and the result is the same as that of the classical literature. The method can be applied to practical engineering, and satisfactory results can be obtained. The analytical process in this paper provides a reference for solving similar problems, and the solution can be used for ground settlement and providing an early warning for settlement when the underground engineering passes through the important homogeneous structure from below.

A Three-Section-Settlement Calculation Method for Composite Foundation Reinforced by Geogrid-Encased Stone Columns

The analysis of the bearing characteristics and deformation mechanism of composite foundation reinforced with geogrid-encased stone columns is presented in order to obtain its settlement calculation method. The settlement of composite foundation is divided into three sections which are the reinforced section, unreinforced section, and underlying stratum. Based on Hooke’s law of space problem and the thoughts of the layer-wise summation method, the relative slip displacement between pile and soil of reinforced section without plastic zone is analyzed. The settlement of reinforced section is calculated by the layered iteration method based on the pile element model. The compatibility of vertical and radial deformations of unreinforced section is analyzed based on the pile-soil element model. The settlement of underlying stratum is still calculated by the layer-wise summation method. Finally, two engineering examples are analyzed and the results show that the settlement calculated by the presented method is close to the measured one. The method overcomes the defect that the calculated results by the other existing methods are more dangerous and it is more feasible and can be applied in engineering practice.

An Improved Nonlinear Settlement Calculation Method for Soft Clay considering Structural Characteristics

The settlement calculation model for soft clay foundation is established based on Hooke’s law and the Duncan-Chang model. By introducing the concept of damage ratio, the method for determining the deformation modulus of soil before and after damage under load is presented, and a nonlinear settlement calculation method which considers the structural characteristics of soft clay is proposed. In the end, a practical engineering example is analyzed with the proposed method and some current methods for soft clay settlement calculation. The results indicated that the proposed method is feasible and applicable in practical engineering.

Load-displacement behaviour of tapered piles: Theoretical modelling and analysis

This paper presents a simplified analytical approach for evaluating the load-displacement response of single tapered pile and pile groups under static axial compressive loads. The response of the tapered pile shaft is considered elastically in the initial stage, whereas the increase in stresses due to slippage along the pile-soil interface is obtained from a developed undrained cylindrical cavity expansion solution based on the K0-based anisotropic modified Cam-clay (K0-AMCC) model. An effective iterative computer program is developed to calculate the load-displacement behaviour of a single tapered pile. Regarding the response analysis of tapered pile groups, a finite-difference method is employed to calculate the interaction between tapered pile shaft, and the linear elastic model to simulate the interaction developed at the pile base. A reduction coefficient is introduced into the analysis of pile shaft interaction to clarify the reinforcing effect between tapered piles. Therefore, the settlement calculation methods of pile groups are proposed for different pile cap stiffness. The calculation methods of single tapered pile and pile groups are validated using two 3D Finite Element (FE) programs, and the comparison results show that reasonable predictions can be made using the method proposed in this paper. Parametric studies are conducted to investigate the effects of taper angle, soil anisotropy, pile spacing, and pile number on the load-displacement behaviour of single tapered pile and tapered pile groups.

Practical Method for Calculating Settlement of underlying stratum in composite ground

In the current settlement calculation methods of composite ground, there are considerable discrepancies between calculating data and measuring data. Based on Mindlin displacement solution, a simple and practical approach is presented for the calculation of settlement of underlying stratum of the reinforced area in composite ground. According to this method, the calculated result agrees well with measured data.

POTENTIAL CONSOLIDATION SETTLEMENT DUE TO LOAD STRESSES OF BUILDING STRUCTURES

Semarang is a capital city of Central Java province in Indonesia, in which mostly dominated by large lowlands at coastal areas that formed by alluvial fan and flood-plain of thick clayey soil as Quaternary deposits. The thick clayey soils deposits encountered in the coastal areas are having a high compressibility behavior and categorized as normally consolidated clays. Presence of building structures for public facilities, heavy industry, residential areas, and the other infrastructures subsequently accelerates consolidation settlement in a large part of the northern Semarang city. This research is intended to reveal rates of potential consolidation settlements due to load stresses impact of building structures by means of one-dimensional settlement calculation method based on the compressible features of the clayey soils. The settlement phenomenon is extensively caused by the presence of voids in the soil structure that contributing to the existence of compression index (Cc), the thickness of the compressible clayey soils, and surcharges load of building structures. By simplifying the surcharge load model of the light structure about 15 kPa, then for medium and heavy structure about 35 and 60 kPa, hence the potential consolidation settlement of light, medium, and heavy structures are about 1.42, 2.90, and 4.38 cm, respectively.

Surface Settlement Induced by Subway Tunnel Construction Based on Modified Peck Formula

A surface subsidence model is established to address the issue of the increase in surface settlement with time. Considering the effects of time factors and depth on surface subsidence, the formula was derived and it was used to calculate the three-dimensional space–time prediction of two-line tunnel settlements in construction processes. Thus, we obtain the calculation method of ground settlement for single- and double-line tunnels. Research relies on Shenzhen Metro Line 7 project. On the basis of the comparison between FLAC 3D calculation software and on-site monitoring, the reliability of the proposed modified Peck formula for the calculation of surface settlement induced by shallow tunnel construction is verified. Research indicates that (1) the proposed calculation method for ground settlement induced by subway tunnel construction is accurate; (2) the modified Peck formula predicts soil settlement at different times and depths; and (3) the revealed surface settlement law is consistent with numerical simulation and measured results, which can effectively reveal the mechanism and law of surface settlement caused by tunnel excavation.

Settlement of Soft Clay Subgrade Under Coupled Effects of Vibration Frequency and Dynamic Stress Ratio Caused by High-Speed Train Loads

Settlement regularity of soft clay subgrade under cyclic principal stress rotation caused by high-speed train loads is investigated. In laboratory tests, it is found that, with increasing vibration frequency at a fixed dynamic stress ratio, the increase of axial plastic cumulative strain in saturated soil is restricted at mid-high frequencies (0.5-2 Hz), and the changes in pore-water pressure are not evident. Combined with the empirical settlement formula and analysis of the dynamic amplification equation of German standard, a simplified settlement calculation method accounting for resonance is obtained.

A Simplified Calculation Method for Liquefaction-Induced Settlement of Shallow Foundation

This work was aimed at developing a practical and simple settlement estimation of shallow foundation on liquefiable deposits. The study conducted a centrifuge test, a series of comprehensive numerical analysis, back analysis, equation calibration, and verification with data from not only centrifuge test but also the literature. It finally proposed a quick calculation method based on Meyerhof’s settlement equation (1965). A two-dimensional numerical analysis, named ALID, (Analysis for Liquefaction-induced Deformation), was employed for obtaining settlement of shallow foundations on liquefiable soils with different relative densities under various seismic conditions. Its performance was first verified through a centrifuge test conducted in this study. Then, the developed method based on Meyerhof’s settlement equation was employed, and a new parameter, NLR, was proposed to present the strength of liquefied soils by replacing N value in the original equation. The NLR was obtained through back analysis of the numerical results and modified accordingly after comparison with the data from the literature. This paper, finally, demonstrated the practical use of the proposed method involving NLR by predicting 199 sets of liquefaction-induced settlement of shallow foundation reported in the past, including a latest most liquefaction-induced settlement of a house in 0206 earthquake on February 6, 2016, in Taiwan.

쇄석말뚝의 침하량 산정방법 적용성에 관한 연구

쇄석말뚝공법은 비교적 강성이 크고 압축성이 작은 쇄석을 연약한 점성토 지반 및 느슨한 사질토 지반에 치환 후 다져 시공함으로써 연약한 지반의 지지력 증가와 침하량 감소, 압밀배수에 의한 지반개량 효과에 더불어 사질토 지반에서는 지진 발생시 액상화 방지에 효과적인 공법이다. 쇄석말뚝공법은 여러 토목분야에서 활용되고 국제적으로 상당히 많은 시공실적을 보이고 있으나, 아직까지 정형화된 침하량 산정방법은 없다. 따라서 본 연구에서는 쇄석말뚝공법의 합리적인 침하량을 예측하기 위하여 기존에 제안되어 사용되고 있는 침하량 이론식들을 비교 분석하여 적용성을 평가하였다. 그 결과 Hook's law 식이 수치해석과 가장 근접하는 것으로 확인되었다. Stone column is the method that replace soft ground such as weak clay and loose sand with gravel or crushed stone which has relatively high stiffness and low compressive. Stone column increases bearing capacity of the soft ground, reduces settlement, produces ground improvement effect by consolidation drain, and is effective to prevent soil liquefaction in sandy ground during an earthquake. Stone column has been used in many civil works, and has recorded quite a lot of construction achievement internationally, but there is no standardized settlement calculation method yet. Therefore, in this study, the applicability of the existing theoretical equations were evaluated through comparison and analysis to predict a reasonable settlement of the Stone column. Consequently, Hook's law formula was verified to be the most close to numerical analysis.

Analysis of consolidation settlement of normally consolidated soil by layering under 3D conditions

This study analyzed the effects of conventional practice of calculating consolidation settlement of soft ground by dividing the ground into one or more layers. Based on a numerical analysis of the accuracy of the calculation and the settlement behavior resulting from layering, this study found that the existing settlement calculation method always underestimates settlement, and that the smaller the number of dividing layers, the smaller the calculated settlement is observed. In addition, when the ground is divided into an infinite number of layers, the settlement is 1.2 to 50 times larger than the case when the ground is considered as a single layer, and the difference grows larger at the lower ratio of an applied pressure to an effective stress (A0), the higher ratio of a layer thickness to a footing width (H/B), and the lower ratio of the length to width of a footing (L/B). The exact settlement can also be obtained under a single-layer condition, even when using the existing settlement calculation method, if the representative depth of calculation of the effective stress is set at a depth of approximately 10-38% from the top of the clay layer.

The behavior of compression and degradation for municipal solid waste and combined settlement calculation method

The total compression of municipal solid waste (MSW) consists of primary, secondary, and decomposition compressions. It is usually difficult to distinguish between the three parts of compressions. In this study, the odeometer test was used to distinguish between the primary and secondary compressions to determine the primary and secondary compression coefficient. In addition, the ending time of the primary compressions were proposed based on municipal solid waste compression tests in a degradation-inhibited condition by adding vinegar. The amount of the secondary compression occurring in the primary compression stage has a relatively high percentage to either the total compression or the total secondary compression. The relationship between the degradation ratio and time was obtained from the tests independently. Furthermore, a combined compression calculation method of municipal solid waste for all three parts of compressions including considering organics degradation is proposed based on a one-dimensional compression method. The relationship between the methane generation potential L0 of LandGEM model and degradation compression index was also discussed in the paper. A special column compression apparatus system, which can be used to simulate the whole compression process of municipal solid waste in China, was designed. According to the results obtained from 197-day column compression test, the new combined calculation method for municipal solid waste compression was analyzed. The degradation compression is the main part of the compression of MSW in the medium test period.