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Loading conditions are among the significant determinants of the stability of embankment dams: they need to be carefully investigated during the design phase of the dam construction. Unfortunately, it is almost impossible to investigate the combination of these parameters in-situ. In the current work, the influence of rapid drawdown loading conditions on the stability of the embankment dam was investigated with the help of numerical modeling for a case of the Aktobe dam in Kazakhstan. The seepage analyses were carried out concurrently with slope stability analyses. Mainly, five different drawdown cases were investigated, which are: steady-state, instantaneous drawdown, 5-days drawdown, 10-days drawdown, and 1m per day drawdown rate. In terms of flow type, both steady-state and transient flow conditions were investigated. In general, when the embankment was subjected to the 1 m per day drawdown rate a minimum factor of safety value of 1.486 was retrieved from computations. The factor of safety value is equivalent to a 3.7 % increase from the 10 days drawdown rate, 8.3 % from the 5 days drawdown rate and 48.6 % from the instantaneous drawdown.

Concrete strength gain can be significantly affected by the initial characteristics of the raw materials. Unfortunately, information on the potential influence of the initial water pH on concrete strength gain is still scarce. In this study, the potential effects of the initial water pH on concrete strength gain were investigated using a combination of sensors and a sclerometric test. The impact of initial pH on the strength gain process was investigated using three distinct pH values (4.0, 7.0, and 12). The primary variables examined were pH variations over time, internal temperature, and strength gain. The problem was further examined using a number of statistical techniques, including Single-way Analysis of Variance, Scheffé's approach, and Correlation Matrixes. When the temperature data from 4.0, 7.0, and 12 pH values were put through the Analysis of Variance, a p-value of 2.4 × 10−261 was retrieved. Additionally, when the strength gain data from 4.0, 7.0, and 12 pH values were subjected to the Analysis of Variance, a p-value of 2.9 × 10−168 was retrieved. The results showed that the differences in the list data retrieved from the investigated pH values were statistically significant. Based on the results, we can state that the initial pH level in the mixing water can have noticeably varied consequences in terms of the strength gain of the concrete and should be carefully considered during the preparation process of concrete. The findings retrieved from this study provide a piece of useful information in the construction field, especially with concrete strength management. [ABSTRACT FROM AUTHOR]

In connection with the global trends of increasing requirements for efficiency and environmental friendliness of production, to create the safest possible conditions, innovative technologies are more intensively developed and applied. Today, an urgent issue is the improvement of systems for monitoring the construction of buildings and structures. The study presents an embedded sensor for non-destructive wireless control of reinforced concrete structures by the Maturity method, which allows monitoring data on the current concrete strength gain and internal temperature using special software. The features of the device, consisting of three main components: temperature gauges, a data collection station, and server software are disclosed. Experimental studies on debugging the sensor operation are presented. The test results presented in the work confirm the characteristics and functionality of the sensor. Thus, the strength values of concrete samples obtained by embedded sensors showed a greater convergence (R2 = 0.9357) with fundamental compressive strength values, compared to those obtained by the Shock-pulse method (R2 = 0.8965). Application of the proposed solution may significantly optimize the concrete formwork removal cycles speeding up the pace of construction, saving man-hours and other resources, including finances. [ABSTRACT FROM AUTHOR]

This study investigated the potential influence of operating water levels and loading conditions on the slope stability of an embankment dam. Four different operating reservoir levels (normal, reduced, embankment height, and overflow) were considered in the study. Numerical modeling was used to investigate the problem in the case of the Chardara dam within the Syrdarya catchment in Kazakhstan. Based on the drawdown rates and operating conditions, minimum factor of safety values ranging from 0.56 (total failure) to 2.5 were retrieved. Furthermore, a very high correlation was observed between drawdown days, the minimum factor of safety values, the maximum factor of safety values, and pore-water pressures, with correlation coefficients ranging from 0.561 to 0.997 (strong to very strong correlation). On the other hand, the highest negative correlation of 0.997 was observed between the minimum factor of safety values and pore-water pressures. Additionally, based on the results from the analysis of variance, three reservoir operating levels (normal, embankment height, and overflow) resulted in p-values less than 0.05, indicating that the variations in the factor of safety values from the drawdown rates were statistically significant. The findings of this study demonstrated that, not only may the drawdown rate be detrimental to the embankments, but that different operating levels can also affect slope stability in different ways. [ABSTRACT FROM AUTHOR]

The maturity method is deservedly considered one of the reliable indirect methods for determining the strength at the early stages of concrete curing. The main parameter in the calculation is the internal temperature of concrete that accumulates during the chemical reaction of concrete curing, while external factors such as ambient temperature and relative humidity are fallaciously omitted. In this work, the complex maturity method was developed based on ASTM C1074, accounting for the influence of ambient temperature and relative humidity and coefficients indicating their influence weight. The laboratory testing to measure the concrete strength by compression method and non-destructive sclerometer method were performed on concrete samples according to ASTM C109, GOST 22690, and GOST 10180. According to the calibration dependence of the existing and proposed methods results in comparison with the strength of cubic samples, the highest coefficient of determination R2 = 0.976 was revealed for the complex method of maturity, which indicates its reliability in contrast with sclerometer and traditional maturity methods. The determination of complex maturity allows for an evaluation of the current state of concrete strength, but also reduces the waiting time for concrete curing and increases the economic effect during construction. [ABSTRACT FROM AUTHOR]