Tolerable Settlement Research Articles

Ground Variation, Geotechnical Uncertainties and Reliability of Foundation Design for Sustainable Building Infrastructures with Case Histories

The foundation of any civil engineering structure serves to transfer the superstructure load to the ground without causing any uneven response, excessive settlement and movement. The choice and design of any foundation requires consideration for the load, subsoil type, mineralogy and variation; suitable bearing capacity, groundwater conditions, geological and stress history, tolerable settlement and understanding of the genesis and stratigraphy of the site. Uncertainties are signature characteristic of geotechnical paramterization and design. Application of reliability analysis is recommended for choosing the optimal design and construction materials and method.. Therefore a Geotechnical Consultant designate is required throughout the project life cycle to forestall collapse.

Evaluation of the Static Design Procedure in the Canadian Foundation Engineering Manual for Piles in Cohesionless Soil

Piles provide a convenient solution for heavy structures, where the foundation soil bearing capacity, or the tolerable settlement may be exceeded due to the applied loads. In cohesionless soils, the two frequently used pile installation methods are driving and drilling (or boring). This paper reviews the results of a large database of pile load tests of driven and drilled piles in cohesionless soils at various locations worldwide. The load test results are compared with the static analysis design method for single piles recommended in the Canadian Foundation Engineering Manual (CFEM) and other codes and standards such as the American Association of State Highway and Transportation Officials, Federal Highway Administration, American Petroleum Institute, Eurocode, and the Naval Facilities Engineering Command. An improved pile design procedure is proposed linking the pile design coefficients (β) and (Nt) to the friction angle of the soil, rather than employing the generalized soil type grouping scheme previously used in the CFEM. This improvement included in the new version of the CFEM 2021 produces a more unified value of the pile capacity calculated by different designers, reducing the obtained design capacity discrepancies.

Planning of the foundation a three-story building constructed on potential liquefaction area in Air Tawar Estuary of Padang City

The earthquake has become one of the most lethal problems in Indonesia, especially across the ring of the fire zone. On September 30th, 2009, an earthquake with a magnitude of 7.6 SR occurred, triggering tsunami and liquefaction. The liquefaction potential and tsunami forces need to be mitigated when an earthquake happens to reduce the risk. This study designs the building foundation that can endure the loads from an earthquake, tsunami, and liquefaction in the Air Tawar estuary of Padang City. The soil profile and liquefaction potential can be identified with CPT (Cone Penetration Test) data. After identifying the liquefaction potential, the upper structure was designed to consider the earthquake load and tsunami waves according to FEMA P-464 (2012). Afterward, design the foundation dimensions based on the ultimate load from the upper structure, wherein the amount of the settlement should be smaller than the tolerable soil settlement. The method used in the paper is taking the CPT data in the Air Tawar Estuary. After analyzing the liquefaction potential, making an upper structure design with ETABS 2016, recapitulate the maximum joint reaction to design the foundation that can withstand the ultimate load, and calculate the amount of soil settlement. Thus the design of the upper structure and lower structure take into account liquefaction. The amount of soil settlement obtained in the building design is still within the tolerance range of 9.79 mm, where the maximum limit of reduction is 32m.

Uplift and Settlement Prediction Model of Marine Clay Soil e Integrated with Polyurethane Foam

Abstract Polyurethane (PU) foam is a lightweight material that can be used efficiently as a ground improvement method in solving excessive and differential settlement of soil foundation mainly for infrastructures such as road, highway and parking spaces. The ground improvement method is done by excavation and removal of soft soil at shallow depth and replacement with lightweight PU foam slab. This study is done to simulate the model of marine clay soil integrated with polyurethane foam using finite element method (FEM) PLAXIS 2D for prediction of settlement behavior and uplift effect due to polyurethane foam mitigation method. Model of soft clay foundation stabilized with PU foam slab with variation in thickness and overburden loads were analyzed. Results from FEM exhibited the same trend as the results of the analytical method whereby PU foam has successfully reduced the amount of settlement significantly. With the increase in PU foam thickness, the settlement is reduced, nonetheless the uplift pressure starts to increase beyond the line of effective thickness. PU foam design chart has been produced for practical application in order to adopt the effective thickness of PU foam within tolerable settlement value and uplift pressure with respect to different overburden loads for ground improvement works.

COMPRESSIBLITY OF PEAT SOIL IMPROVED WITH POLYURETHANE

This research investigated the compressibility of natural peat soil and peat soil improved with polyurethane foam. High natural moisture content, high compressibility, low bearing capacity and medium to low permeability is a problem and characteristic of a peat soil. This problem can be solved by reducing the compressibility of the peat soil. The objective of this study is mainly to prove whether the presence of polyurethane foam as a lightweight material on peat soil can reduce the compressibility of peat soil or otherwise. Fifteen samples of peat soil taken from Johan Setia, Klang were tested using Oedometer test with load is doubled at each increment until it reaches the maximum required load which is 10kPa, 20kPa, 40kPa, 80kPa, 160kPa, 320kPa and 640kPa. Polyurethane foam is a lightweight material, therefore reduces the overburden pressure to the underlying soil, hence future settlement can be minimized to a tolerable settlement value. Based on the data obtained from analysis of Oedometer test, the compressibility parameters including void ratio, compression index and swelling index of the peat soil alone are very high which denoted extremely poor condition of the peat soil. The compressibility parameters improved significantly with the PU foam stabilization as PU act as a void filler for peat soil. A slight increase in the compressibility parameters are recorded with higher ratio of isocyanate. However, the maximum pre-consolidation pressure recorded was with PU ratio of 1:1. Therefore, the optimum ratio for PU peat stabilization is in the ratio of 1:1.

COMPRESSIBLITY OF PEAT SOIL IMPROVED WITH POLYURETHANE

This research investigated the compressibility of natural peat soil and peat soil improved with polyurethane foam. High natural moisture content, high compressibility, low bearing capacity and medium to low permeability is a problem and characteristic of a peat soil. This problem can be solved by reducing the compressibility of the peat soil. The objective of this study is mainly to prove whether the presence of polyurethane foam as a lightweight material on peat soil can reduce the compressibility of peat soil or otherwise. Fifteen samples of peat soil taken from Johan Setia, Klang were tested using Oedometer test with load is doubled at each increment until it reaches the maximum required load which is 10kPa, 20kPa, 40kPa, 80kPa, 160kPa, 320kPa and 640kPa. Polyurethane foam is a lightweight material, therefore reduces the overburden pressure to the underlying soil, hence future settlement can be minimized to a tolerable settlement value. Based on the data obtained from analysis of Oedometer test, the compressibility parameters including void ratio, compression index and swelling index of the peat soil alone are very high which denoted extremely poor condition of the peat soil. The compressibility parameters improved significantly with the PU foam stabilization as PU act as a void filler for peat soil. A slight increase in the compressibility parameters are recorded with higher ratio of isocyanate. However, the maximum pre-consolidation pressure recorded was with PU ratio of 1:1. Therefore, the optimum ratio for PU peat stabilization is in the ratio of 1:1.

THE EFFECT OF LATERAL CONFINEMENT ON THE SETTLEMENT CHARACTERISTICS OF SHALLOW FOUNDATIONS ON SAND

Free to read on publisher website Today, most of the high rise buildings consist of basements as part of the substructure. Basement construction is usually supported by embedded type retaining walls such as secant pile walls or diaphragm walls. This provides lateral confinement and the performance of shallow foundations would be affected by this lateral confinement. In this study, the effect of lateral confinement on the settlement characteristics of shallow foundations on sand was studied experimentally and numerically. First, experimental investigation using small-scale laboratory models were carried out and the results were used to validate the finite element (FE), model. Changing the depth of lateral confinement and the distance to the edge of the shallow foundation from the lateral confinement, the stress immediately below the footings corresponding to a settlement of 25 mm was compared. Furthermore, the effect of lateral confinement due to embedded retaining wall on the settlement characteristics of a raft foundation on sand was also studied using the validated finite element model. In scaled physical models of confined foundations, there was an enhancement in allowable bearing capacity at the tolerable settlement with the increase in depth of embedment and the reduction of distance to the confinement. It was observed, for the study variables considered in this study that the bearing capacity can be improved up to 4 times by laterally confining the footing. However, in the analysis of confined raft foundations on sand, there was no significant change in bearing pressure for a 50 mm tolerable settlement with the change of study variables.

Strength-based differential tolerable settlement limits of bridges

Based on realistic modeling of 44 bridges in national bridge inventory using its actual layout and dimensions, a theoretical framework is defined to calculate the tolerable differential settlement limits based on the over-bending moment or over-shear force generated by settlements and the moment or shear capacity of the bridge. First, the derived over-bending moment or over-shear force is validated through literature results. Second, the differential settlement limits of bridges are derived from the bridge strength capacities. Finally, based on the established differential settlement limits, the relationship of bridge differential settlement limits with its span length, number of spans, bridge skew, and the bridge type is discussed and compared with American Association of State Highway and Transportation Officials specification (2010). A statistics-based differential settlement limit criterion is also suggested for steel and pre-stressed concrete bridges and compared with the field survey results. From the research outcomes, it is concluded that extra caution is needed when implementing the 0.4% differential settlement limits of bridge foundations in American Association of State Highway and Transportation Officials.

Reliability analysis for Serviceability Limit State of pile groups foundation

The aim of this paper is to present an approach for the assessment of the Serviceability Limit State (SLS) reliability of pile groups foundation combining the Ultimate Limit State (ULS) reliability method of pile groups. To this end, the linear relationship between the ULS and SLS reliability indices is presented using the formulas for calculating the ULS and SLS reliability indices of single piles. Meanwhile, the influence of system effects, correlation coefficient between pile group efficiency and system effects (ρζ,χ), and limiting tolerable settlement (Slt) on the SLS reliability analysis of pile groups foundation is studied using pile load test data compiled for illustration. The results indicate that both the ULS reliability index (βG-uls) and the SLS reliability index (βG-sls) of pile groups foundation decrease with ρζ,χ, that powerful system effects can enhance the ULS and SLS reliability of pile groups foundation, and that βG-sls increases with Slt. the reliability level estimated by pile load test data is equivalent to that incorporating the SLS requirements with a certain value of Slt between 15 mm and 25 mm. For Slt larger than this value, Reliability-based Design (RBD) of pile groups foundation will depend on the ULS requirements, but, conversely, RBD will depend on the SLS requirements.

The NHS in 1991: Parallels with today

of ministers and NHS leaders. It took quite a while to work out what was happening. The parallel with today is the result of the Five Year Forward View. By stating, virtually for the first time in the history of the NHS, that the structural arrangements no longer have to be the same everywhere, a clutch of different ways of doing things—the new models of care—are being tried and permitted. From apparently total devolution of the health and care budget in Manchester and Cornwall; to GPs and the hospital in Northumbria seeking to turn the latter into an accountable care organisation; to multispeciality community providers in Kent and Birmingham; to other ways of trying to bring the primary and acute systems together elsewhere. In other words, the really interesting stuff, the work that may shape the way the NHS functions in future, is out there on the ground. In 1991, the centre was distinctly nervous about how the new freedoms would be used, and in some cases— notably London—rapidly pulled the new freedoms back for fear of the effect they would have. This time round the various bits of the centre that Lansley’s legislation created, are struggling to work out just how far they can— statutorily or otherwise—let go to let the new models of care emerge. And there, probably, the parallel ends. One huge difference is that in 1991 the reforms were lubricated by cash to make sure the purchaserprovider split did not crash and burn on day one. This time around, providers are projecting big deficits and a mere £200 million has been allocated so far to a transformation fund to help the innovators get there. Huge amounts depend on the outcome of the spending review now underway—how much at what speed does the NHS get? How much does social care? Will the double counting of shifting NHS cash into the Better Care Fund continue? Or, despite the political commitment to eliminating the deficit primarily through spending cuts, will there be sufficient cash to allow a tolerable settlement for each? Do these new models of care signal— if not necessarily the complete end of the purchaser-provider split—a pretty radical reshaping of it, as Sir David Nicholson suggested in his formal lecture for NHS Providers last month? The answer to that lies in the diversity being attempted locally, as well as in the decisions that will be made centrally over the coming months. BJHCM Nick Timmins, senior fellow at the Institute for Government and the King’s Fund, compares the NHS reforms of 1991 to those ongoing today The NHS in 1991: Parallels with today

Target reliability index for serviceability limit state of single piles

The objective is to develop an approach for the determination of the target reliability index for serviceability limit state (SLS) of single piles. This contributes to conducting the SLS reliability-based design (RBD) of piles. Based on a two-parameter, hyperbolic curve-fitting equation describing the load-settlement relation of piles, the SLS model factor is defined. Then, taking into account the uncertainties of load-settlement model, load and bearing capacity of piles, the formula for computing the SLS reliability index (βsls) is obtained using the mean value first order second moment (MVFOSM) method. Meanwhile, the limit state function for conducting the SLS reliability analysis by the Monte Carlo simulation (MCS) method is established. These two methods are finally applied to determine the SLS target reliability index. Herein, the limiting tolerable settlement (slt) is treated as a random variable. For illustration, four load test databases from South Africa are compiled again to conduct reliability analysis and present the recommended target reliability indices. The results indicate that the MVFOSM method overestimates βsls compared to that computed by the MCS method. Besides, both factor of safety (FS) and slt are key factors influencing βsls, so the combination of FS and βsls is welcome to be used for the SLS reliability analysis of piles when slt is determined. For smaller slt, pile types and soils conditions have significant influence on the SLS target reliability indices; for larger slt, slt is the major factor having influence on the SLS target reliability indices. This proves that slt is the most key parameter for the determination of the SLS target reliability index.

Incorporating serviceability limit state requirements into reliability-based analysis and design of piles

This study develops a novel reliability-based approach for the analysis and design of piles by incorporating Serviceability Limit State (SLS) requirements into Load and Resistance Factor Design (LRFD) for Ultimate Limit States (ULS). Three methods for reliability-based analysis and design, namely the Mean Value First Order Second Moment (MVFOSM) method, the Advanced First Order Second Moment (AFOSM) method, and the Monte Carlo Simulation (MCS) method, are employed for comparison. In order to expediently quantify model uncertainties for SLS and incorporate them into the process of reliability-based analysis and design of piles, the SLS model factor (or bias factor) is established based on a two-parameter, hyperbolic curve-fitting equation describing the load-settlement relation. Herein, the limiting tolerable foundation settlement (slt) is treated as a random variable. Four load test databases from South Africa presented by Dithinde et al. (2011) are compiled again to conduct reliability analysis and calculate resistance factors. The case studies illustrate that the AFOSM method has the higher accuracy than the MVFOSM method as verified using the MCS method. This study recommends the AFOSM method to perform reliability analysis and determine resistance factors for Reliability-Based Design (RBD).

Reply to the discussion by Fellenius on “Load tests on full-scale bored pile groups”

Reply to the discussion by Fellenius on “Load tests on full-scale bored pile groups”

Subway tunnel design using a ground surface settlement profile to characterize an acceptable configuration

Tunneling induced settlement is often a controlling factor in the design of a subway or underground facility due to the impact on adjacent or overhead infrastructure. A method is proposed that uses an acceptable ground surface settlement profile to generate a tunnel system configuration that reproduces the acceptable/tolerable settlement profile. A brief discussion of existing methods of tunnel settlement analysis and two (2) case studies illustrating the proposed method are presented. The chosen case studies are urban subgrade rail tunnels (subways) constructed in Istanbul, Turkey and Bangkok, Thailand. Each case study is used to illustrate the use of the bifurcated static back calculation – iterative finite element model prediction/solution method.The initial settlement profiles used for both case histories were measured settlement profiles obtained from the literature (Ercelbi et al., 2005; Suwansawat, 2002). These settlement profiles were assumed to be the tolerable settlement profiles for the subway systems. For each case history, the iterative static back calculation – finite element model ingested the individual literature obtained design settlement profile to identify an optimum tunnel configuration (depth and size) that will reproduce the design settlement profile. Comparisons were made between the as-built tunnel configuration and the tunnel configuration predicted using the proposed method.

Development of Partial Factors for Serviceability Limit State Design of Large-diameter Bored Piles

The serviceability requirement of foundations in terms of total settlement can be expressed using predicted settlement and limiting tolerable settlement with necessary modifications for group effects and system effects. Similar to the limit state design methodology for ultimate limit sates, partial factors can be applied to both limiting tolerable settlement and predicted settlement to attain a specified level of safety. In this paper, partial factors for serviceability design of largediameter bored piles are developed using a first order reliability method, based on the statistics of prediction model performance, as well as statistics of limiting tolerable settlement obtained previously. Five combinations of analysis methods for large-diameter bored piles in soils and six combinations of analysis methods for large-diameter bored pile socketed in rocks are considered.

Reliability Analysis and Updating of Excavation-Induced Ground Settlement for Building Serviceability Assessment

In this paper, the excavation-induced settlement determined by the KJHH model, a recently developed semiempirical model, is used to assess the serviceability reliability of adjacent buildings. The calculated settlement, considered as the load in the context of reliability analyses in this paper, is compared with a tolerable settlement, considered as the resistance herein. The reliability of the adjacent building against “damage” (defined herein as the violation of serviceability requirements such as having intolerable settlement) is first analyzed and the probability of exceedance (i.e., exceeding the tolerable settlement) is calculated. Furthermore, as the excavation proceeds, observed settlement at the current excavation stage is used to update the prediction of settlement at subsequent stages, and the probability of exceedance is updated accordingly.

Differential Settlements and Inelastic Response in Steel Bridge Beams

A proposed method for mitigation of pavement faults at bridge abutments (the “bump at the end of the bridge”) is the use of shallow foundations. Abutments on shallow foundations are expected to settle compatibly with embankments and thus to minimize pavement faults. Allowing bridge abutments to settle may reduce faults, but it creates a demand for tolerance of different settlement in bridge superstructures. Current guidelines for tolerable differential settlement of bridges are empirical only, and the application of elastic analysis of bridge superstructures to determine tolerance of settlement has not produced satisfactory results. Inelastic analysis of steel bridge beams was applied to the computation of tolerable differential settlement. Tests of inelastic rotation capacity of steel beams were reviewed and compared with the results of inelastic analyses. A model of tolerable inelastic rotation capacity in steel beams is proposed.

Closure to “ Tolerable Settlement of Buildings ” by Harvey E. Wahls (November, 1981)

Closure to “ <i>Tolerable Settlement of Buildings</i> ” by Harvey E. Wahls (November, 1981)

Discussion to “ Tolerable Settlement of Buildings ” by Harvey E. Wahls (November, 1981)

Discussion to “ <i>Tolerable Settlement of Buildings</i> ” by Harvey E. Wahls (November, 1981)

Tolerable settlement of buildings : Wahls, H E J Geotech Engng Div ASCE, V107, NGT11, Nov 1981, P1489–1504

Tolerable settlement of buildings : Wahls, H E J Geotech Engng Div ASCE, V107, NGT11, Nov 1981, P1489–1504