Case Study An investigation on dam settlement during and end of construction using instrumentation data and numerical analysis Behrang Beiranvand1 · Mehdi Komasi2 Received: 7 November 2020 / Accepted: 29 January 2021 © The Author(s) 2021 OPEN Abstract In the present study, using instrumentation data regarding vertical and horizontal displacement of the dam have been analyzed. Also, the largest and most critical section of the Marvak earth dam is modeled with the behavioral model of the Mohr–Coulomb by GeoStudio software. Numerical modeling of the dam has been done considering the actual embank- ment conditions and to analyze the changes of the immediate settlement during construction and the consolidation settlement just after construction and initial impounding. The outcomes of instrumentation and numerical analysis at the end of Marvak dam construction showed a settlement between 20 and 500 mm. The results show that the settle- ment will occur during the construction at the upper levels and the end of construction at the middle levels of the dam. By comparing observed and predicted data, multivariate regression and the explanation coefcient criterion (R 2) was found to be R2 = 0.9579, which shows a very good correlation between observed and predicted data, and represents a good match for the settlement points and their location with the initial conditions of the design, and the behavior of the dam in terms of the settlement is found to be stable. Keywords Settlement · Marvak earth dam · Instrumentation · Numerical analysis · End of construction 1 Introduction the analysis shows the actual behavior of the dam and the results can be used to provide information to sections that Earth dams are important and huge structures whose do not have monitoring instruments. In fact, if a behavioral foundation is not only on natural earth and rock materi- model with realistic parameters can be found that is well als, but also their raw materials are natural earth or rock matched with the results of the instrument, this model can materials, so continuous monitoring of earth dams is of be used to predict the future behavior of the dam. special importance. Also, high construction costs, high Clough et al. were the frst researchers who utilized the damages due to dam failure and uncertainty in predicting fnite element method in predicting the behavior of an the behavior of geotechnical structures due to the spe- earth dam in 1967. In the study, they used a linear elastic cifc nature of soil materials, indicate the need for accurate model to analyze stresses and deformations in the dam monitoring of earth dams. Dam behavior is usually per- [1]. Then, Duncan and Chang, along with the develop- formed by the results of instrumentation and numerical ment of computers and powerful software, used complex analysis by various software including geostudio. In situ- and nonlinear models of fnite elements to demonstrate ations where the monitoring results are consistent with and analyze the stress–strain behavior of materials [2]. the results of the numerical analysis, it can be said that Nobari and Duncan used the fnite element method to * Behrang Beiranvand, [email protected]; Mehdi Komasi, [email protected] | 1Water Engineering, and Hydraulic Structures, Department of Civil Engineering, Faculty of Engineering, University of Ayatollah Ozma Borujerdi, Borujerd, Iran. 2Water Engineering and Hydraulic Structure PH.D, Department of Civil Engineering, Faculty of Engineering, University of Ayatollah Ozma Borujerdi, Borujerd, Iran. SN Applied Sciences (2021) 3:306 | https://doi.org/10.1007/s42452-021-04306-z Vol.:(0123456789) Case Study SN Applied Sciences (2021) 3:306 | https://doi.org/10.1007/s42452-021-04306-z simulate humid environments. After that, the fnite ele- (Gikas and Sakellario) [12]. Silvani et al. investigated the ment method was seen as a powerful way to predict the efect of buoyancy force and the decrement in the friction behavior of earth dams [3]. A few years later, Zienkiewicz using the Distinct Element Method (DEM) coefcient in a presented detailed reports on the static analysis of earth rockfll column [13]. dams [4]. Abhilasha and Balan applied a commercial In this study, frst, the results of horizontal and vertical software that was studied by researchers and designers displacement monitoring of the Inclinometer and settle- to model the seepage in earth dams and found that the ment instrument installed in the core of the Marvak are results of modeling with Seep/w have acceptable accuracy investigated. Then, the settlement of the earth dam stud- [5]. Rashidi et al. assessed the pore water pressure and set- ied was investigated through fnite diference numerical tlement of the Gavshan earth dam and the comparison of modeling, Geostudio. Finally, by comparing and verifying instrumentation data and numerical modeling using FLAC the recorded data of settlement piezometers and making (2D) software concluded that dam performance in terms sure that they do not contradict existing theories in geo- of pore water pressure, and fnally stability of the dam is technics, a comparison is made between the results of real positive [6]. In another study, Rashidi et al. by examining instruments and numerical methods. and comparing the instrumentation’s outcomes of the Siah Sang dam and numerical analysis using the Mohr–Cou- lomb model showed that the study dam is safer regarding 2 Materials and methods the hydraulic failure just after the construction and the frst impounding period compared to other rockfll dams 2.1 Case study in the world [7]. Karoui et al. investigated the numerical analysis of the behavior of the Seid El Barak dam and its Marvak Dam was constructed on the river of Tireh 38 km comparison with instrumentation data [8]. far from Dorud City, situated in the province of Lorestan, Luo et al. examined the Chengbehi dam monitoring for Iran. The dam is an earth dam with having clay core. The 18 years using piezometric pressure and settlement results construction aims of the dam are to provide storage (about and found that the maximum settlement in the middle of 120 mcm/y) to Tireh, to supply the water required for agri- the dam was 178 mm, which gradually decreased from the culture in the Silakhor plain (5400 hectares area) located middle to the sides. The maximum settlement in the wings downstream of about 50 mcm, to arrange the water needs was 65.8 mm. Also, due to water pressure in the tank, more of downstream lands and to control food. The dam has a settlements were observed upstream of the cutof wall [9]. height of 68 m from the bedrock, a length of 451 m, and a Sukkarak and Jongpradist in their study of rockfll dam’s width of 10 m, normally reservoir has a 60-mcm volume, settlement found that the geometry of the dam is very an elevation (crest) of 1621 masl, the area of the reservoir important, especially in narrow valleys in terms of the set- is 45.5 km2, and the length of the lake is 4.5 km when the tlement. During impounding and operation, the dam body reservoir level reaches its maximum. The dam has a vol- withstands all internal and external loads [10]. This often ume (embankment) of 3,670,000 m3. Construction of the causes horizontal and vertical displacements, called verti- Marvak Dam began in 2003 and was completed in 2014. cal settlement locations (Ik-Soo) [11]. Although major dis- The situation of the Marvak Dam is illustrated in Fig. 1. In placements occur during the dam construction, the inves- Iran and Lorestan province. Table 1 displays the specifca- tigation of the earth dam’s settlement sometimes leads to tion of the dam materials. efective results. In general, the maximum settlement of The Marvak Dam instrumentation has been designed the dam is in its midpoints and gradually decreases until in seven transverse sections and diferent levels, with 27 it reaches zero in the paws. Because of the settlement, the Inclinometer (in-place) and 8 Inclinometer and settle- structure of the dam gradually stretched and the distance ment meter on diferent levels. The frst instrument of between the tiller’s slopes along the base slightly increases the dam was installed in the year 2008. The instrument Fig. 1 The critical section of the Marvak Earth Dam with the position of the installed instru- ments (Sec. 10) Vol:.(1234567890) SN Applied Sciences (2021) 3:306 | https://doi.org/10.1007/s42452-021-04306-z Case Study Table1 Marvak dam profle, (instrument report, Abfan Consulting 8 27 Engineers [14]) Total Dam type Earth dam having clay 1 core Num Crest length (m) 451 Core volume (m3) 453,000 1575 Level (masl) Reservoir volume (mcm) 120 Section 16 Normal water level (masl) 1617 Crest width (m) 15 2 1 1 2 Num Upstream coferdam height (m) 30 Downstream coferdam height (m) 36 1621.5 1608 1590 1575 Level (masl) Section 15 for measuring and controlling internal deformations of the body and core of the Marvak Dam is the use of the 1 1 2 1 1 2 Inclinometer and settlement instrument at diferent levels. Num With the help of this tool, you can check the horizontal and vertical displacement of the core and the downstream 1565 1550 1621.5 1608 1590 1575 Level (masl) shell at diferent points and, if necessary, control the level Section 13 of the reservoir’s water. Besides, the amount of settlement, shell, and foundation at the time of the dam is obtained. 1 1 1 2 1 1 In this study, section number 10 has been investigated Num considering the installation of the most inclinometers and settlement instrument (Table 2). 1535 1530 1525 1621.5 1608 1590 Level (masl) Section 10 2.2 Construction stage deformations ]) 14 2 2 1 Num When building the body of an earth or rockfll dam, the weight of the material and its gradual increase (with increasing the height of the dam) causes the settlement 1530 1621.5 1608 Level (masl) of the body.