## 1 Introduction and Literature Review
The uncertainty of a project is the key issue and the potential main cause for most problems [20,21]. In response to the bottleneck caused by the uncertainties, project managers often actively increase the buffer time to absorb the delay of activity duration caused by the occurrence of these uncertainties during the process of construction management [6,11]. The constraint theoryaims to solve the bottleneck management problem, and could thus improve the overall operations and achieve maximum benefits [22]. In [PERSON]'s opinion, the most important factor is that itcan make actual progress, not conform to the planning progress, which is also related to the bottleneck of the project. Later on, he developed the \"drum-buffer-rope\" (DBR) schedule planning and control techniques using TOC [23]. Production management uses the DBR principle to rectify the uncertainty of activities and enhance the reliability of schedule. [PERSON] indicated that the uncertainty of bottleneck activities duration can be improved by the element \"drum\", and the originally independent activities can be changed into the correlation mutually by the two elements \"buffer\" and \"rope\". The application of the three elements \"drum\", \"buffer\" and \"rope\" in the project schedule can make a contribution to reduce the uncertainty of the construction plan. Compared with the progress management effects of the traditional industrial manufacturing process, JIT system, [PERSON] indicated that the uncertainty can be significantly reduced after using TOC in progress management [24]. [PERSON] also pointed out that with Ford Motor Company in the United States, the on-schedule delivery time achievement rate rose after applying the TOC [25]. [PERSON] [26], [PERSON], [PERSON] [27] and [PERSON] [28] thought that the application of the element \"rope\" can help to determine the start time of the bottleneck activities, which ensure that predecessor activities can be completed on time through the settings that project resources are totally put into the bottleneck activities and the start time of bottleneck activities are the same as scheduled.Steyn believed that the application of the TOC can harmonize the relationship between risk factors and the project plan organization, and can be more effective in reducing the uncertainty of the project construction schedule [29]. In view of the fact that the buffer mode cannot effectively guarantee the project completed on schedule in some projects, [PERSON] et al., proposed a distributed buffer setting mode, and thought that the buffer mode had good robustness with the premise of completion on time [30]. [PERSON] et al. [31] described the three components: plan, control and concentration of the DBR management scheduling model method in detail, and pointed out that such a management method is suitable for resources scheduling of construction projects. [PERSON] et al., proposed the buffer setting method under uncertain project conditions in using TOC [32] that includes several factors such as resource strain, network planning complexity and risk preference of project managers. It solved the problem that resource strain is difficult to be quantified and unified, and also took into account the using of alternative resources to solve the problem of resource shortage. In consideration of the characteristics that there are gradual gaps in activities and many uses of the element \"drum\" in the project plan, [PERSON] et al., analyzed the weakness of the centralized buffer setting method in coping with some \"drum\" elements of the activities network, and proposed one setting method for dispersed capacity constraints. Additionally, he also obtained the project duration, which can be reduced to a great extent under the setting method for dispersed capacity constraint through experiments in different networks with \"drum\" elements [33]. Apparently, the element \"drum\" of DBR progress management and control technology in TOC can improve the uncertainty of bottleneck operation duration.