Effects of an impermeable layer on pore pressure response to tsunami-like inundation

Tsunami hazards have been observed to cause soil instability resulting in substantial damage to coastal infrastructure. Studying this problem is difficult owing to tsunamis’ transient, non-uniform and large loading characteristics. To create realistic tsunami conditions in a laboratory environment, we control the body force using a centrifuge facility. With an apparatus specifically designed to mimic tsunami inundation in a scaled-down model, we examine the effects of an embedded impermeable layer on soil instability: the impermeable layer represents a man-made pavement, a building foundation, a clay layer and alike. The results reveal that the effective vertical soil stress is substantially reduced at the underside of the impermeable layer. During the sudden runup flow, this instability is caused by a combination of temporal dislocation of soil grains and an increase in pore pressure under the impermeable layer. The instability during the drawdown phase is caused by the development of excess pore-pressure gradients, and the presence of the impermeable layer substantially enhances the pressure gradients leading to greater soil instability. The laboratory results demonstrate that the presence of an impermeable layer plays an important role in weakening the soil resistance under tsunami-like rapid runup and drawdown processes.

Analysis on Construction Technology and Reinforcement Technology of Building Foundation

In the field of construction engineering, foundation engineering plays a critical role. In actual construction, we must first effectively regulate the foundation construction to ensure the safety and stability of the entire building in order to improve the overall quality of the project. It's also important to look into the technologies that go into building foundations. The construction technology and reinforcing technology of building foundations are examined in this study as a reference.

Roll-over stability as a problem of high-rise buildings’ designing

Roll-over stability of tall buildings under wind loads is considered. The nonlinear nature of the problem is taken into account, including geometric, physical, and structural non-linearity. The problem is solved on the base of a system of linearized incremental equations of structural mechanics that describes the behavior of a system tall building - foundation soil. Several methods are examined for solving nonlinear problems of roll-over stability, specifically: 1) deformation method of systems equilibrium states tracing; 2) method of linearization of nonlinear equations and systems equilibrium states tracing; 3) method of linearization of nonlinear physical relations of a systems with constructive, static, geometric nonlinearity; 4) method of linearization of nonlinear physical relations of a system with constructive nonlinearity based on nonlinear incremental structural mechanics; 5) method of the deformation process tracing for a physically nonlinear soil base, given the increase of discharge zones and constructive nonlinearity. Each of these methods is used to solve a model task. These tasks take into account roll-over stability of high structures under action of wind loads. In general, the problem of roll-over stability of a high object can be represented as repeatedly nonlinear one with various types of non-linearity. In this regard, in the practice of high-rise buildings designing, it is necessary to develop scientifically and methodically substantiated methods of assessing roll-over stability, considering non-linear factors. Taking these factors into account will make it possible to assess the roll-over stability of a high-rise object more accurate.

Effects of Shaft Grouting on the Bearing Behavior of Barrette Piles: A Case Study in Ho Chi Minh City

The shaft-grouted method has been applied on high-rise buildings in Ho Chi Minh City for the purpose of increasing the bearing capacity of barrette piles. The Exim Bank Building foundation, using two kinds of shaft-grouted barrette piles, was 65m (TP1) and 85m (TP2) in depth. To assess the bearing capacity, this project assembly used the O-cell tools installed at 49m depth below the pile head level. Shaft grouting was performed from -25m to the TP1 pile toe level and -65m to the TP2 pile toe level. This work is based on the data from the O-cell experiments at the construction site and the results of finite element simulation in Plaxis software. The effectiveness of shaft grouting was analyzed and the length and position of the ejector were evaluated and compared in order to find the best solution for applying shaft grouting with the aim to ensure safety and mitigate economic problems.

An Experimental Study of Nailed Soil Slope Models: Effects of Building Foundation and Soil Characteristics

A soil nailing system is a proven effective and economic method used to stabilize earth slopes from the external (factors increasing the shear stress) and internal (factors decreasing material strength) failure causes. The laboratory models with scales of 1:10 are used to study the behavior of nailed soil slope with different soil and building foundation parameters. The models consist of Perspex strips as facing and steel bars as a nailing system to increase the stability of the soil slope. The models of sand beds are formed using an automatic sand raining system. Devices and instruments are installed to monitor the behavior of soil-nailed slope during and after construction. The effect of the soil type, soil slope angle, foundation width and position on the force mobilized in the nail, lateral displacement of the slope, settlement of the foundation and the earth pressure at the slope face, under and behind the soil mass at various foundation pressures, has been observed. It is found that the increase of soil density reduces both slopes facing displacement and building foundation settlements. The slope face displacement and footing settlement will increase with an increase in the width of the foundation and foundation position near the crest of the slope.

Time-Series Uncertainty Quantification of Foundation Settlement with Kernel Based Extreme Learning Machine

The dynamic building foundation settlement subsidence are threatening the urban business and residential communities. In the temporal domain, the building foundation settlement often suffers from high level dynamics and needs real-time monitoring. Accurate quantification of the uncertainty of foundation settlement in the near future is essential for the in-advance risk management for buildings. Traditional models for predicting foundation settlement mostly utilizing the point estimates approach which provide a single value that can be close or distant from the actual one. However, such estimation fails to offer the quantification of uncertainties of estimation. The interval prediction, as an alternative, can provide a prediction interval for the ground settlement with high confidence bands. In this paper, a lower upper bound estimation (LUBE) approach integrated with kernel based extreme learning machine (KELM) is proposed to predict the ground settlement levels with prediction intervals in the temporal domain. Comparison with the artificial neural network (ANN) and classical extreme learning machine (ELM) are conducted in this study. Building settlement data collected from Fuxing City, Liaoning Province in China has been used to validate the proposed approach. Comparative results show that the proposed approach can construct higher quality prediction intervals for the future foundation settlement.

Engineering Site Investigation for Foundation Design and Construction in Shale and Sandstone Derived Soils of Okitipupa Area, Southwestern Nigeria

Geotechnical and geo-electrical investigations of Okitipupa has been carried out with the major objectives of establishing the subsoil/geology, evaluate the geotechnical properties and recommend appropriate foundation alternatives for building foundation construction. Seven borings were carried out with hand auger at two cone penetration test locations, and representative samples were collected and analyzed in the laboratory in accordance with relevant geotechnical engineering standards. In addition, six vertical electrical soundings (VES) were also conducted using Schlumberger configuration. The result of VES delineates three major geologic sequence comprising the topsoil/caprock, sand surficial aquifer, and sand intermediate aquifer. The topsoil has resistivity range of 242 – 1503 ohm-m and thickness of 3.4 - 20.9 m composed of clay sand and sand. This layer is capable of supporting shallow foundation such as simple spread, raft of reinforced concrete, with recommended allowable bearing pressure of 100 KN/m2 at depths of 1.0 m and 3.2 m in the northern and southern part of the study area respectively. The estimated settlement are less than 50 mm using foundation width of 0.6 m, but could be reduced by almost 50% if the width is greater than or equal to 2 m. The groundwater level is very deep (>10 m) and may not likely threatens the integrity of the foundation structures. The estimated allowable bearing capacity for strip footing (203 – 980 KN/m2), square footing (608 – 2940 KN/m2) within 1.4 m depth is appropriate. The capacity of driven (deep foundation) circular piles of diameters 400mm, 500mm, and 600mm, the recommended pile capacity varies at depth of 5 m (69 – 124 KN), 10 m (225 – 378 KN), and 15 m (470 – 766 KN), while that of bored circular pile ranges from (36 – 75 KN), 10 m (93 – 180 KN), and 15 m (170 – 317 KN).