Objective: Accurately and quickly determining investment estimation for utility tunnels is crucial for cost optimization and investment decision-making. Owing to the rapid development of artificial intelligence technology and the continuous accumulation of engineering investment databases, research on engineering investment estimation based on machine learning has become a hot topic. However, existing studies on utility tunnel investment estimation suffer from problems such as small data samples, reliance on single methods, lack of performance comparisons among multiple algorithms, low accuracy, and poor generalization performance. These issues result in significant prediction errors in practical applications that fail to meet the needs of engineering practice. Therefore, there is an urgent need to develop a universal investment estimation model for utility tunnels based on machine learning and data-driven approaches. Methods: This study presents a systematic approach to constructing a utility tunnel investment estimation model, covering the data collection, preprocessing, feature engineering, multi-algorithm comparison, hyperparameter optimization, performance evaluation, and model application processes. Six key factors affecting utility tunnel investment estimation were selected as the input variables of the model, including tunnel length, number of chambers, excavation depth, cross-sectional size, construction method, and construction city, while the civil engineering cost of utility tunnels was taken as the output variable. A dataset containing 98 utility tunnel investment samples was created. Three data preprocessing methods were adopted to standardize the input variables of the dataset, including Min-Max normalization, Z-Score standardization, and RobustScaler. Based on Pearson's correlation analysis of the input variables and civil engineering cost, as well as the results of the feature importance analysis, nine groups of feature combinations that play a decisive role in predicting civil engineering cost were screened out. For multi-algorithm comparison, five classic machine learning algorithms were used to construct the utility tunnel investment estimation model: categorical boosting regression, gradient boosting decision tree, decision tree, extreme gradient boosting (XGB), and K-nearest neighbors. The Optuna hyperparameter optimization algorithm was used to optimize the model hyperparameters, and its performance was compared with that of the model without hyperparameter optimization. The performance of the estimation model was evaluated based on the coefficient of determination (R² value) under three scenarios: three different preprocessing methods, nine different feature combinations, and with or without Optuna hyperparameter optimization. Through this evaluation, the optimal data preprocessing method and feature combination were determined, as well as the performance of Optuna hyperparameter optimization. Finally, the optimal estimation model was identified. Based on the optimal estimation model, an empirical prediction analysis of investment estimation was conducted for two utility tunnels in Beijing. Results: The results show that the RobustScaler method is the optimal data preprocessing method for the dataset and the five algorithm models in this paper. Using the F-1 feature combination yields the highest average R² value (0.623) among the five algorithm models, making F-1 the optimal feature combination. Hyperparameter optimization using the Optuna algorithm improves the performance of the five models by up to 40.4%, compared with no optimization. The Optuna-XGB algorithm model performed best after optimization with an R² value of 0.843. The prediction deviation rates for the two utility tunnels in Beijing are 5.63% and 6.50%, respectively, for the Optuna-XGB algorithm model (the best-performing model), which are significantly lower than the 10% deviation requirement. Conclusions: This study presents a data-driven investment estimation model for the civil engineering of utility tunnels, utilizing machine learning. The model's performance is examined in relation to the impact of data preprocessing methods, feature combinations, and the Optuna hyperparameter optimization algorithm. The optimal model proposed in this paper is highly accurate, which is significant for optimizing utility tunnel costs and making investment decisions, as well as ensuring their sustainable development.