Creep Settlement Research Articles

Settlement Analysis of Concrete-Walled Buildings Using Soil–Structure Interactions and Finite Element Modeling

This study examines the performance of mat foundations in 13 blocks of eight-story concrete-walled residential buildings. Topographic monitoring bolts were used to monitor the slab’s construction, which was 0.35 m thick and comprised an area of 225 m2. Using the collected data, a retro-analysis of the modulus of elasticity was conducted to obtain the geotechnical parameters for forecasting the settlement using the elasticity theory. A nonlinear approach for construction modeling and soil–structure interactions showed that the earthworks at the start of construction had a significant role in settling. Blocks in landfills settled faster than those in land-cut zones. The partial execution of building levels was found to be critical in terms of angular distortions and stresses in the concrete slab. The partial lifting of the foundation plate was confirmed in blocks with partial building floor execution, demonstrating the importance of assessing the foundation’s behavior at this stage. The modulus of elasticity dropped as construction progressed, with landfill parts being particularly vulnerable. Creep settlements contributed significantly, accounting for about 20% of the total settlements in some blocks. The numerical staged construction model accurately replicated the behaviors observed in the monitoring data, confirming the hypothesis of the partial raising of the foundation during the building process, which resulted in higher angular distortions. Based on the results obtained, the authors strongly recommend that the simultaneous consideration of soil–structure interactions and construction effects be commonly used in foundation designs.

Response of shallow foundations in tire derived aggregate

This study investigates the quasi-static bearing stress-settlement response of shallow foundations in monolithic tire derived aggregate (TDA) layers having a total thickness of 3 m using a large-scale container and loading system. Tests were performed on footings having a range of widths, embedment depths, shapes, and loading inclinations. In tests where tilting was restricted, a clear bearing capacity was not observed for settlements up to 1.2B, where B is the footing width, but in tests where tilting was permitted bearing capacity was observed between settlements of 0.2B to 0.7B. Surface settlements indicate a dragdown response of the TDA adjacent to the footing extending out to more than 3B from the footing center, while settlement plates beneath the footing indicate a zone of influence of induced settlements of 14% at a depth of 4B. While bearing capacity theories for frictional geomaterials provided a reasonable prediction of the bearing capacity of footings in TDA for most tests, the corresponding settlements may be excessive for engineering applications. Accordingly, a correlation was developed between the theoretical bearing capacity and bearing stress at a settlement of 0.1B. A test with sustained loading indicates slight creep settlements with some stress dependency with magnitudes consistent with past studies.

Foundations in Permafrost of Northern Canada: Review of Geotechnical Considerations in Current Practice and Design Examples

In northern Canada where permafrost is prevalent, a persistent shortage of accessible, affordable, and high-quality housing has been ongoing for decades. The design of foundations in permafrost presents unique engineering challenges due to permafrost soil mechanics and the effects of climate change. There is no specific design code for pile or shallow foundations in northern Canada. Consequently, the design process heavily relies on the experience of Arctic engineers. To clearly document the current practice and provide guidance to engineers or professionals, a comprehensive review of the practice in foundation design in the Arctic would be necessary. The main objective of this paper is to provide an overview of the common foundations in permafrost and the geotechnical considerations adopted for building on frozen soils. This study conducted a review of current practices in deep and shallow foundations used in northern Canada. The review summarized the current methods for estimating key factors, including the adfreeze strength, creep settlement, and frost heave, used in foundation design in permafrost. To understand the geotechnical considerations in foundation design, this study carried out interviews with several engineers or professionals experienced in designing foundations in permafrost; the findings and the interviewees’ opinions were summarized. Lastly, in order to demonstrate the design methods obtained from the interviews and review, the paper presents two design examples where screw piles and steel pipe piles were designed to support a residential building in northern Canada, according to the current principles for adfreeze strength, long term creep settlement, and frost heave. The permafrost was assumed to be at −1.5 °C, and the design life span was assumed to be 50 years. The design examples suggested that for an axial load of 75 kN, a 12-m-long steel pipe pile or a 7-m-long screw pile would be needed.

An improved creep correction factor for footings on sand using macro-element simulations

In many settlement prediction methods, the creep settlement of shallow foundations on sand is either disregarded or accounted for using time correction factors that lack a reliable basis. These existing settlement correction factors for creep have mainly been derived from a restricted number of long-term settlement measurements and do not consider the influence of factors such as the load level, rate of load application and properties of the soil below the foundation. In this study, a newly proposed one-dimensional elasto-viscoplastic macro-element was used to investigate the factors influencing the time-dependent behaviour of shallow foundations on sand. The safety factor of the foundation, the creep characteristics of the soils and the duration of load application were found to have important effects on the post-construction settlement development. The simulation results were used to develop an enhanced settlement correction factor for creep, which takes into account the identified factors. The improved settlement correction factor was found to be comparable to existing ones when the safety factor of the foundation is 3. The effectiveness of the proposed settlement correction factor is demonstrated using creep settlement measurements from one field footing test and two case histories.

A simplified algorithm for predicting creep settlement of high fills based on modified power law model

The calculation and prediction of creep settlement is an important basis for judging whether the settlement of high fills is stable and arranging subsequent construction. In this study, a modified power law model is established based on Hypothesis B and Bjerrum's classification of creep deformation. The modified model can uniformly describe the one-dimensional creep deformation of clay, sand and soil-rock mixture, and satisfies the requirement that the one-dimensional creep deformation tends to a constant value over time rather than increasing indefinitely. Then a simplified algorithm for predicting creep settlement is proposed based on the modified model. The simplified algorithm has only three parameters with explicit physical meaning, which are determined by settlement monitoring data. By the settlement monitoring data from high fills at Chengde Airport, Chengchi Expressway and Panzhihua South Railway Station, the fitting and predicted results of the simplified algorithm were compared with other three prediction algorithms commonly used in geotechnical engineering. The results show that the proposed simplified algorithm can predict the creep settlement of high fills more effectively and accurately.

Behaviour of 60-year-old trial embankments on peat

The search for low cost solutions for roads on peatlands inspired the construction of four full scale trial embankments at two sites in Norway in the early 1960's. The embankments are still accessible and this work was motivated by present day needs to develop environmentally sustainable solutions to such problems. The embankments were constructed using locally sourced sand and sawdust and have behaved very well with the sawdust settling beneath the water table as designed and remaining in perfect condition some 60 years later. A detailed characterisation of the distinctly different peat at the two sites is presented and it is shown that the peat properties are as expected from local and international experience. Laboratory work on the sawdust showed that it behaves like a highly compressible fibrous peat. Short-term embankment settlement behaviour was controlled by the level of applied load whereas long-term creep settlements were governed by the peat consolidation properties. Pore water pressures dissipated unexpectedly quickly. Modelling using the Soft Soil Creep model in PLAXIS captured both short- and long-term settlements and the pore pressure dissipation well.

Use of screw pile foundations to reduce temperature of warming permafrost: Lab tests and numerical modeling

Steel screw piles may be a viable pile foundation type in the permafrost region of the Canadian Arctic but the effects of climate change may accelerate the creep settlement rate of the pile. Reducing the temperature around a pile is an effective way of enhancing the long-term performance of a pile. This study proposes a technique that combines the steel screw pile with the artificial ground freezing method, where liquid coolant is circulated through the hollow screw pile shaft to lower the temperature of surrounding permafrost. A series of laboratory experiments of freezing tests was conducted to verify the feasibility of the proposed technique. A finite element model was then developed to evaluate the cooling effect of this technique by analysing the duration of the permafrost freezing and the power of removing the heat from the soil. The numerical model was calibrated against laboratory freezing tests. A series of numerical analyses were performed to investigate the effects of soil properties and screw pile shaft configuration on the ground freezing process in field application. The duration required for freezing the soil at a radial distance of 450 mm to −2 °C was estimated and compared. The results showed that the proposed method was applicable in the field. Numerical results showed that the power of removing the heat from the soil was larger when using the screw segment than the smooth segment. The results are expected to guide the field application of artificial ground freezing around screw piles installed in permafrost.

Development of liquid soil stabilizer (Ca2+) to reduce long-term embankment settlement

Honam High-Speed Railway in South Korea has suffered from long-term embankment settlement. The fines content in embankment material was pointed out as one of the causes. To reduce the settlement, Liquid Soil Stabilizer (LSS) was developed which is mainly composed of calcium chloride (CaCl2) or calcium hydroxide (Ca(OH)2). In this paper, the embankment materials consisting of low-plastic fines, which were represented by kaolinite-sand mixtures (20, 30, and 40% fines content), were treated by Liquid Soil Stabilizer (LSS) and the efficiency of LSS was evaluated by laboratory tests. For the application of LSS, the analysis of the engineering properties, compression behaviour, and creep settlement of embankment material including low-plastic fines was conducted. The LSS reduced the plasticity in all mixtures of soil as fines content increases. Application of the LSS could also provide better compaction efficiency and could reduce the void ratio change in one-dimensional compression. Therefore, to reduce long-term settlement of the embankment, the usage of LSS will be suitable as the on-site soil stabilization method without considering curing time.

Engineering properties of Norwegian peat for calculation of settlements

Despite some 9% of Norway's area being underlain by peat the geotechnical characteristics of the material have not been well documented. As peatlands form an excellent carbon sink there is much pressure on planning authorities to avoid the excavation of peat for infrastructure development. In engineering projects in peat often the resulting settlements both in the short and long term are of greatest concern. Because of the high variability of peat, several, largely empirically based, methods exist for predicting settlement on peat. These were often developed based on specific cases. These techniques have shown to be inadequate to generically predict long term creep settlements and the development of settlement with time. Here the engineering characteristics of peat from several sites in the Trondheim area of mid-Norway are studied using a series of field and laboratory tests including three types of oedometer test. The laboratory and field data, together with empirical correlations found in the literature, were used to provide input into the commercially available constitutive model Soft Soil Creep (SSC) in the computer code PLAXIS. The model was initially calibrated using the laboratory test results and then applied to the back-analysis of two full scale field trials in the Trondheim area, where the peat properties were significantly different. The modelling showed that SSC captured well the vertical settlement versus time behaviour of the peat. Guidance is provided for selecting the critical input parameters for SSC such as stiffness, yield stress and permeability. This work contributes towards efforts being made to bridge the gap between the numerical modelling community and practicing engineers.

Creep settlement analysis of pile foundations using viscoelastic model by incorporating nonlinear soil behaviour

ABSTRACT This study utilizes a nonlinear three-parameter viscoelastic model (a nonlinear spring in series with a Kelvin-Voigt element) to study the time-dependent creep behaviour in a single pile and group of piles. The method is based on modified Mindlin’s approach; and Laplace transforms have been utilized to simplify the viscoelastic problem into an equivalent elastic problem. The soil nonlinearity has been modelled by using a hyperbolic stress-strain relationship. The effects of parameters such as pile spacing, slenderness ratio and pile load factor on shear stress distribution, displacement of pile elements relative to the pile head, effects of enlargement of the pile base and interaction factors have been evaluated. The ratio of interaction factor for immediate and creep settlement is in the range of 0.4−0.9 for various pile groups. Since this study incorporates soil nonlinearity, the interaction factors increase by about 6%−10% when the pile load factor increases from 0.5 to 1.

The Impact of Using Different Types of Soft Soils Treated by Stone Columns on Creep Behavior

The stone column technique is an effective method to increase the strength of soft cohesive soil, which results in a reduction in foundation settlement and an increase in bearing capacity. The topic of restraining creep settlement through the use of stone columns techniques has gained increasing attention and consideration; because stone columns are widely used to treat soft soil deposits, caution should be applied in estimating creep settlement. We discovered a reversible relation between shear parameters and the creep settlement in floating stone columns; while, in case of end-bearing stone columns shows a direct positive relation between shear parameters and the creep settlement, and the creep settlement began at the primary settlement. The shear parameters affected the improvement factor (n) of creep settlement in both floating and end-bearing stone columns. The standard creep coefficient’s n values in floating and end-bearing conditions were more significant than the low creep coefficient’s n values in forwarded geometric conditions. The stress in both floating and end-bearing stone columns was increasing and uniformly distributed along the length of the floating stone column and in the case of end-bearing stone column was limited to the stiffness layer; the maximum vertical stress was in the central point of the embankment. The embankment’s maximum horizontal displacement occurred on the edge.

A one–dimensional elasto-viscoplastic macro-element model for creep analysis of shallow foundations on sand

Footings on sand can exhibit considerable long-term creep settlement. However, most settlement prediction methods account for creep by using either a reduced long-term equivalent sand stiffness or applying an arbitrary time correction factor. In this paper, a novel elasto-viscoplastic macro-element model for shallow foundations on sand under vertical loading is developed that provides a simple and efficient tool for footing settlement prediction explicitly accounting for creep in a realistic manner. By incorporating an isotach relationship postulated for the load-settlement behaviour of shallow foundations on sand, the macro-element is constructed based on the non-stationary flow surface theory and the time effect is incorporated using visco-plasticity. The proposed model, which requires only three input parameters, is shown to be capable of satisfactorily reproducing the load-settlement responses of footings tested in the field and in the geotechnical centrifuge at typical working loads. The proposed model can also reproduce effects seen in practice such as post-creep stiffening and settlements induced by unload-reload cycles.

Large scaled field tests on soft Bangkok clay

In this lecture the interpretations of fully instrumented tests embankments and their role in the development of appropriate ground improvement techniques for highways, motorways and airfields on soft clay deposits is illustrated through well documented case studies in Bangkok, Thailand and Muar Flat Site in Kuala Lumpur. For the Bangkok Plain and with sand backfills the performance of embankments with different schemes of vertical drains was evaluated over a period of 25 years. Aspects such as recharging effects due to the drains, inadequate measures in maintaining vacuum during vacuum applications and possible hydraulic connections with large diameter drains are discussed. For the Muar test embankments, the role of fill strength in residual soil embankment and the field deformation analysis in separating consolidation settlement from immediate settlement and creep settlements is presented. Novel interpretations of settlement from pore pressure dissipations, secondary settlement from field measurements and decay of lateral deformation rate with time were also made.

Analysis of Embankment Supported by Rigid Inclusions Using Plaxis 3D

A rigid inclusion-supported embankment is used to overcome the problems of soft soils. This system is considered complex due to the various interactions between its elements, namely the embankment body, load transfer platform, geogrid layers, piles, and soft soils. The load transfer mechanism is based on the phenomenon of soil arching, the tension in the geogrid layers, support of the soft soils, and friction between piles and soft soil. In this paper, the first part highlights the behaviour of a rigid inclusion-supported embankment validated by field measurements, and the contribution of rigid inclusions technology to the reduction of settlement and creep settlement. In addition, the effect of geogrid in improving the load efficiency and reducing the settlements is presented. In the second part, a comparison is made between many analytical design methods and a three-dimensional finite element analysis method. The results show the inconsistencies between the analytical methods in calculating the load efficiency and the tension in the geogrid.

A new simplified method for calculating short-term and long-term consolidation settlements of multi-layered soils considering creep limit

The long-term consolidation settlement of soft soils under infrastructures is seriously concerned in coastal areas. In practice, soft soil ground is usually composed of multiple layers with different properties, and the effect of soil creep is nonnegligible. However, in conventional consolidation analysis, creep is seldom included during the “primary” consolidation. With conventional creep model, creep strain will reach infinity with time, which is unreasonable in the long-term view. In this study, a new simplified method based on Hypothesis B is presented to calculate both short-term and long-term consolidation settlements of multi-layered soils exhibiting non-linear creep. There are three main characteristics for this new simplified method: (a) the consolidation analysis for multi-layered soil is conducted using spectral method; (b) a nonlinear creep function with creep limit is incorporated to calculate both short-term and long-term creep settlements; (c) the “primary” consolidation and creep are calculated independently and combined with an empirical parameter α together with the consolidation degree U for correcting the creep settlement. Finite element analysis with a self-developed Elastic Visco-Plastic (EVP) constitutive model considering creep limit was also carried out. Verifications by field cases and finite element simulation demonstrate the efficiency and accuracy of the new simplified method in calculating the long-term settlements of soft soil ground under varied engineering conditions. Influences of major parameters selection in the calculation of the new simplified method are also discussed.

Finite element implementation of an isotach elastoplastic constitutive model for soft soils

An isotach elastoplastic constitutive model devised by Yang et al. (2016) and referred to as the Hunter Clay (HC) model attempts to capture a number of key behaviours of soft soils within a critical state framework, namely destructuration, fabric anisotropy and rate dependency, the latter often manifesting in creep settlement. Finite element implementation of the HC model is a useful means by which its application to practical problems can be facilitated. However, there are a number of significant challenges associated with the translation of isotach elastoplastic models into a finite element setting. In this paper, a detailed discussion of these challenges is undertaken and a new finite element implementation of the HC model is subsequently developed. This includes sophisticated numerical integration algorithms which employ automatic time substepping for solution of the governing finite element equations. The ability of the implemented HC model to predict the mechanical behaviour of soft soils under 1D compression is investigated via simulation of laboratory tests carried out on Ballina clay by Pineda et al. (2016) and Parkinson (2018).

Research on creep characteristics of sand with different fine content

The storage yard in port terminal project is generally is formed by backfilling. If the backfill contains high content of fine particle, on the one hand, it will cause difficulty in foundation treatment, on the other hand, excessive settlement will occur during the operation period, which will affecting the normal operation of the project. In this paper, through experimental research on the creep settlement of sandy soils with different fine content, the relevant parameters of sandy soils with different fine-grained contents and different types of finegrained soils are obtained, and through the analysis and fitting of commonly used rheological element models, the settlement calculation parameters of sandy soil with different fine contents are obtained.

Experience in forecasting long-term settlements of energy facilities based on monitoring data analysis

The article discusses the problem of predicting the long-term settlement of reactor compartments of nuclear power plant with a long history of operation and ongoing creep processes. The features of determining the time of the primary consolidation and the application of the parameters of the secondary consolidation are considered. With regard to the existing buildings of the reactor compartments of a nuclear power plant, a forecast of long-term deformations of the base was made, from the present time to 2062, which is the end of the operation period. The analysis and comparison of the obtained results with the data of geotechnical monitoring were also carried out. Analytical forecasting showed a high accuracy in determining the end time of filtration consolidation, however, a comparison of the values of the obtained creep settlements to date and the rate of their development shows significant differences, which makes it necessary to take into account the real picture of deformation for further forecasting in terms of operation time. Possible technological reasons for discrepancies in the results of calculations and geotechnical monitoring are analyzed, as well as theoretical reasons like imperfections of the analytical method used and the possible application of modern numerical methods.

Numerical simulation of creep settlement for high railway foundations based on the UH model considering time effect

Numerical simulation of creep settlement for high railway foundations based on the UH model considering time effect

The initial, primary and secondary consolidation response of soft clay reinforced with a granular column under isolated loading

This paper presents the assessment of consolidation and creep settlements of an isolated circular footing supported on soft clay samples reinforced with a single granular column. Clay samples (300 mm dia., 400 mm high) were formed from reconstituted kaolin and remoulded sleech (exhibiting significant creep). These samples were tested using chambers with various features to capture the settlement under constant foundation loading. In one model, the footing (70 mm dia.) was supported by a 40 mm dia. granular column formed by crushed basalt. The footings, with and without a granular column, were subjected to five vertical loading increments: 60, 120, 180, 240 and 300 kPa in the case of kaolin. In the case of sleech, vertical loading increments were: 60, 120 and 180 kPa. Each test lasted approximately ten months. In the case of kaolin, the settlement reduction factor was marginal, although it was considerably better for sleech. Kaolin exhibited marginal creep settlement under low to moderate bearing pressure, which increased substantially under high bearing pressures. Creep settlement was more prominent in sleech at all levels of bearing pressures. The very interesting finding from the investigation is that the settlement reduction factors due to consolidation and creep are similar in order under low to moderate loadings.