Denghua Zhong

Real-Time Construction Schedule Analysis of Long-Distance Diversion Tunnels Based on Lithological Predictions Using a Markov Process

AbstractSchedules are major concerns in construction planning and management. The mutual interferences among construction activities of long-distance diversion tunnels (LDDTs) are complicated because of their crisscrossing and intensive layout, which will affect scheduling to some degree. Especially, lithology has a conclusive influence on underground construction. But the lithology determination methods of current construction simulation, such as the trend of extrapolation from observations, do not fully consider lithology’s inherent characteristics and the transition probability between different lithological classifications. In the present study, the authors propose a hierarchical simulation model coupling the critical path method (CPM) and cycle operation network (CYCLONE) to arrange the intricate construction sequence of LDDTs. Additionally, a Markov prediction model is embedded into the CYCLONE model as a specific component to consider lithological uncertainty and estimate construction parameters of...

Prediction of curtain grouting efficiency based on ANFIS

As an important method for improving dam foundations, curtain grouting is designed to create a hydraulic barrier to decrease permeability, enhance strength, and reduce deformability of rock masses. To evaluate the improvement of rock masses, the Lugeon value (LU), rock quality designation (RQD), and fracture filled rate (FFR) after grouting are key evaluation indicators of grouting efficiency. A prediction method based on an adaptive neuro-fuzzy inference system is proposed to predict and evaluate curtain grouting efficiency in this study. Geological factors (fracture intensity, LU, and RQD before grouting), effective grouting operation factors (effective grouting pressure, effective grouting time, effective grout volume, and effective cement take), and tested interval depth are considered to be the critical factors that greatly influence the efficiency of curtain grouting and are selected as input parameters for prediction models. The grouting efficiency evaluation indicators (the LU value, RQD, and FFR after grouting) are selected as output parameters for evaluation of the efficiency. In addition, a formula for estimating the influence radius of grouting boreholes, which is used to determine the sphere of grouting influence, is proposed. To better reflect the influence of the position of grouting boreholes on the effects of grouting, this study suggests that the effective grouting operation factors can be calculated using an improved inverse distance weighting method. As a case study, this approach is used to predict the results of grouting and to evaluate the efficiency of curtain grouting in hydropower project A, located in the southwestern part of China. The approach shows considerable accuracy in predicting the results of grouting and evaluating grouting efficiency.

Probabilistic Risk Analysis of Diversion Tunnel Construction Simulation

Comprehensive and effective risk analysis is significant for studying construction simulation of diversion tunnel. Existing tunnel risk simulation approaches mainly analyze ordinary risk factors, and cannot quantitatively study risk events considering their causes. Additionally, in other tunnel probabilistic risk analysis methods, although some studies have made full probabilistic estimates of tunnel schedule, risk factors are unable to be studied considering cyclic construction characteristics and occurrence probability of risk events cannot be determined quantitatively. To address the issues, a probabilistic risk analysis approach of diversion tunnel construction simulation is proposed. Based on hierarchical simulation model, risk factors can be analyzed at operation level of tunnel construction. Moreover, Bayesian network is embedded into simulation program to quantitatively calculate probability of risk events in each simulation cycle, considering geology, design, construction, and management conditions and their mutual dependence.

Construction Simulation for a Core Rockfill Dam Based on Optimal Construction Stages and Zones: Case Study

AbstractConstruction simulation is an effective means to describe the dam filling process of a core rockfill dam. However, present research studies adopt a simplified method to analyze the placement of a rockfill subsystem because of various uncertain working constraints and diverse flow shop construction processes, which include preparing, discharging, paving, compacting, and checking. In addition, because the time and cost minimization and equilibrium of the filling intensity are important matters in the design of core rockfill dam construction stages and zones, full consideration of these matters is required during the construction process. In this work, a construction simulation model for a rockfill dam based on flow shop construction is presented. The model can provide different reasonable construction schemes of each filling layer. In addition, to obtain an optimal plan for the construction stages and zones, entropy weight method and the improved genetic algorithm (GA) are used to address the time-c...

Prediction of Dredging Productivity Using a Rock and Soil Classification Model

AbstractThe prediction of dredging productivity plays an important role in controlling the costs and optimizing the scheduling of the dredging process. However, it is very difficult to achieve satisfactory forecasting efficiency because there are so many uncertain variables, including the rock, soil, and water properties; the main performance index of the dredger; and environmental restrictions. In this paper, the authors have developed a quantitative classification model for dredging materials under complex conditions, in which the weight of the condition attributes is calculated using rough-set theory and conditional entropy. Then, by considering the effect of the rock and soil conditions, the main performance index of the dredger, and the influence of the underwater environment, a prediction model for dredger production efficiency was developed. This approach is applied to a land reclamation project in Tianjin, China. In the study case, the efficiency of the dredger production is predicted fairly well ...