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Settlement deformation control of loess high fill is the key and difficult point in engineering construction. In this paper, the deformation characteristics of remolded loess under self-weight stress and water content change are summarized by indoor lateral confined compression test and humidification test. Based on the idea of layered summation method, the Gunary stress-strain model and secant modulus method are introduced to divide the settlement of loess high fill foundation into the settlement during construction caused by loading and the settlement after construction caused by water content change, and the calculation method of settlement deformation of loess high fill foundation is put forward. Combined with the actual engineering background, the settlement deformation of high fill engineering is predicted. The results show that the main source of the settlement of high loess fill is the settlement caused by the loading during the construction period. With the increase of fill height, the proportion of post-construction settlement to total settlement increases gradually. Under the condition of optimum moisture content, the exhaust consolidation of soil can be completed when the compaction degree during the construction period reaches more than 95 %, and the later stage of construction is the drainage consolidation of soil. The control of compactness is crucial to high fill engineering. The higher the compactness, the smaller the total settlement. The research results of this paper enrich the calculation theory of settlement deformation of loess high fill foundation, and provide theoretical basis for the study of post-construction settlement and collapsible settlement of loess high fill; it has certain reference value for the construction and post-construction settlement control of loess high fill engineering. [ABSTRACT FROM AUTHOR]

Melen Dam is located on Big Melen Stream. It is about 25 km away from Düzce. Dam body is designed as a roller compacted concrete (RCC) gravity structure with 944 m crest length. The project is built to supply water to the city of Istanbul. The dam body started cracking when the dam height reached about 98 m from the foundation level in October 2016. It was initially thought that cracks were due to shrinkage resulting from the cooling of dam concrete; therefore, the construction of the dam body was not stopped but displacement measuring devices were placed on certain parts of the dam to measure movements in three directions. DSI's (State Hydraulic Works of Turkey) remedial proposal is to construct rockfill buttressing at the downstream side of the dam to increase sliding factor of safety, to build a cutoff wall near the heel of the dam to control seepage water, and to add an upstream membrane to existing dam to prevent leakage through the dam. It is the aim of this paper to discuss the remedial proposal developed by DSI. Geotechnical parameters at the dam site are evaluated under the light of investigations, tests, and observations. Dam behavior and observed settlements are explained by relating settlements to foundation properties and geology. After studying geological and tectonic setting of the dam area together with the active faults around the region, remedial measures are evaluated by considering observed settlements upon dam body completion, by estimating settlements upon dam buttressing and impounding together with possible changes in the properties of dam foundation because of excessive settlements and saturation, and by comparing similar rockfill buttressing solutions applied to other dams around the world with the proposed one for Melen Dam. [ABSTRACT FROM AUTHOR]

Raft and pile foundations are combined with the twofold aim of increasing the overall bearing capacity and reduce the average/differential settlements. This results in a complex system and gives rise to significant soil–structure interaction mechanisms. In the last years, both bearing capacity and settlements of piled raft have been usually expected on the basis of empirical formulas, analytical relationships, and numerical analyses. The conventional design methods currently used in practice are based upon relatively conservative assumptions of raft–soil–pile interaction; as a result, they are in many cases inaccurate and unlikely to result in optimum design. Thus, resorting to numerical analyses seems to be the most reliable method, mainly because of the multiple interactions and the three-dimensional geometry that must be considered in most cases. In this context, 3D finite difference analyses were performed to investigate the behavior of piled raft foundation system in drained conditions of soft clays. The overall objective of the present paper focuses on the load response and effects of multiple interactions of piled raft subjected to vertical loading. For this purpose, several types of foundations were considered including piled raft, group of piles and unpiled raft. For optimization purposes, the behavior of the piled raft was also investigated by varying some parameters as pile number and piling configuration. The concluded observations from the parametric study provide further insight into the mechanical response of piled raft and aim at helping the engineers in taking a logical path in an iterative design process for a piled raft foundation. [ABSTRACT FROM AUTHOR]

In the recent earthquakes, numerous cases of liquefaction occurred in sands containing both plastic and nonplastic fines that resulted in significant damage. Most previous research efforts have focused on clean sands regardless whether the sand contain fines or not made evident by widespread shallow foundation failures, numerous cases of settlement, and lateral displacement. Still, despite the amount of related research, results seem somewhat contradictory. This study directly demonstrates the beneficial or detrimental effect of uncertainty surcharges on seismic responses. Models were subjected to two destructive realistic events with similar PGA with various frequency contents and duration. In this paper, the dynamic analyses were conducted as fully non-linear elasto-plastic coupled stress-flow analyses with coupled liquefaction triggering which reasonably captured the actual behavior. The silty sand deposits underlying the surcharge are capable of liquefying and developing large shear deformations that can cause serious damage. Therefore, excess pore water pressure ratio cannot be enough by itself to evaluate liquefaction potential, so the deformations should be examined. Numerical results provide an estimate of the seismic performance liquefiable deposits underlying the surcharge; these results can be useful for a realistic practical engineering. [ABSTRACT FROM AUTHOR]

A simplified technique was considered to study the effects of incorporating fully wraparound geogrids on the behavior of fine sand soil under a strip footing. Numerical and experimental work were used to estimate this performance. This study has shown that some parameters affect the behavior of reinforced soil with folded geogrid inclusions. In addition, the parametric study was extended to include a fully folded geogrid layer, the embedment depth of the fully folded geogrid, the thickness of a fully folded geogrid, the distribution of stresses in the soil mass, and the additional lateral constriction effect. The significant effects of introducing one or two fully-folded geogrid layers in denser fine sand have been assessed by conducting a series of strip plate load tests. The failure modes were proposed using the finite element method under plane strain conditions. As a result, a modified expression was recommended to develop an improved soil bearing capacity with a fully folded geogrid inclusion. The predicted expression provides a good agreement with the experimental findings; therefore, the approximate error rate was approximately 7%. The bearing capacity increases more with the inclusion of a fully folded geogrid than with planar reinforcement layers. Although the ratio of the length of the geogrid concerning footing width (L/B) of 5 and 7 has the same effect on the settlement values, the significant effect is associated with fully folded geogrid layers of shorter length. The presence of fully folded geogrid reinforcement at burial depths of (u = 0.4B and d = 0.2B) below the surface of the sand layer plays a major role in reducing the vertical normal settlements and significantly improves the bearing capacity. [ABSTRACT FROM AUTHOR]

A series of laboratory load tests were carried out to investigate the effect of geometrical dimensions of a handmade geocell on the ultimate bearing capacity of geocell-reinforced sand beds. The parameters considered in the study include the geocell placement depth from the base of the footing (u), equivalent diameter of geocell pocket (d), height of geocell reinforcement (h), width of geocell reinforcement (b) and relative density of the sand (Dr). A multiple regression equation was developed by analysing the experimental results for estimating the ultimate bearing capacity of the reinforced sand bed. The equation proposed was verified against empirical equation reported by other researchers. The statistical analysis of the model test data shows that the parameters studied have a significant influence on the performance of the footing in terms of its bearing capacity and settlement. The regression equation developed in this investigation is reasonably good in predicting the bearing capacity of a square footing supported on geocell-reinforced sand beds. [ABSTRACT FROM AUTHOR]

Induced partial saturation using chemical substances is an innovative technique to mitigate liquefaction inflicted damage. Despite being a promising method, there is little research on its application beneath shallow foundations, and its effects on the settlement behavior have yet to be elucidated. In this study, the powder of denture cleanser, containing hydrogen peroxide, was mixed with dry sand in different proportions. Gas bubbles were generated in the pore spaces as the sand-chemical mixtures were saturated with water, producing partially saturated samples at varying degrees of saturation in the range of 79.5 to 98%. A series of 1-g shaking table tests were conducted on nearly and partially saturated sand models with relative densities ranging from 33.5 to 76.3%. Detailed analysis of the experimental data indicated that foundation settlements and excess pore pressures developed in partially saturated sand models were smaller than those in nearly saturated counterparts. The reduction in the settlement was more prominent at lower degrees of saturation, lower relative densities, and higher stress levels. These results highlight that chemically generated gas bubbles may be an effective practical method of reducing the liquefaction-induced settlements that shallow foundations suffer in the event of an earthquake. [ABSTRACT FROM AUTHOR]

To evaluate the quality of the subgrade reinforcement by dynamic compaction (DC), a dynamic finite element model was established based on the soil cap yield hardening model. A subroutine was performed to simulate the parameters (e.g., modulus of soil) changing with drop numbers. The numerical results agreed well with the results of the field test, which validated the reliability of the proposed numerical method. The optimal drop number, the degree of compaction in different zones, and density contour of the silty subgrade under 1500kN·m were analyzed by both numerical simulations and field tests. Results indicate that the multi-point tamping mainly improves the degree of compaction between adjacent impact points, producing a "dumbbell-shaped" soil spatial distribution pattern. The ironing compaction can effectively improve the soil within the depth of 1.2 ~ 1.3 m for the shallow soil layer, which makes the density of soil more uniform. Through field test, the static resilience modulus of silty subgrade reinforced by DC is around 50 MPa. The post-construction settlement of the subgrade constructed by DC is less than that by layered filling, indicating that the quality of subgrade treated by DC is reliable. [ABSTRACT FROM AUTHOR]

Through the field inspection, this study investigated the performance of a deep foundation pit supported by suspended piles in soil and rock strata for a subway station in Qingdao Metro Line 3 in China. A large number of site-measured data are analyzed to investigate the settlement of ground surface and pile top, the horizontal displacement of pile and soil at different depths, and the relations between pile displacement and surface settlement under different construction stages. The deformation mechanism and the various influencing factors are discussed. Results showed that the blasting excavation of rock stratum has a great disturbance on the surface settlement outside the pit. The construction of the upper steel pipe support can effectively reduce the influence of disturbance, and the application of lock bolt support with shotcrete below the soil-rock interface can enable the surface settlement rate to be stable. When the foundation bottom reinforced concrete is completed, the ground surface settlement at different measuring points stabilizes in the range of 7~9mm. At the blasting excavation site, the maximum ground surface settlement accounts for 0.051% of the excavation depth. The ratio of maximum pile final lateral displacement to the final ground surface settlement is 1.43. The maximum ground surface settlement accounts for 0.058% of the excavation depth. The ratio of maximum horizontal displacement of soil to the final ground surface settlement is 0.7. Besides, the excavation of the upper soil layers of the foundation pit will result in the soil unloading and sublayer rebound, thus driving the uplift of the pile. The excavation of the lower rock layer influences the overall stability of the bored pile, and the construction of the steel pipe support and the anchor cable can effectively offset this effect. Although the horizontal displacement value is about 6 mm, it still cannot be ignored when compared with the overall lateral shift. When the bottom concrete slab is built, the maximum lateral displacement of the pile is located near the soil-rock interface. [ABSTRACT FROM AUTHOR]