## 2 Construction of Cemented Soft Rock Dams
The maximum principal tensile stress of the dam was 0.3 MPa, which satisfied the requirement that the tensile strength of C8 cemented sand and gravel be less than 0.6 MPa. The stress of the dam above 402.0 m decreased gradually from 0.75 MPa at the bottom to 0.17 MPa at the top, both of which are smaller than the allowable compressive stress of C6 cemented sand and gravel (1.5 MPa); no tensile stress was generated in the dam, meeting the material strength requirements of the dam. The maximum vertical normal stress of the foundation was approximately 0.5 MPa, which can meet the bearing capacity requirements when the foundation surface is placed under the highly weathered sandstone and sandy mudstone. Under normal working conditions, the dam foundation system had the lowest factor of safety for the sliding stability along the weak intercalated layer of the type of mudstone with interbedded rock debris; the factors of safety for shear of the overflow dam section and non-overflow dam section were 1.12 and 1.14, respectively, both of which are greater than the code requirement of 1.05, and the factors of safety for shear failure were 4.55 and 4.51, respectively, both of which are also greater than the code requirement of 3.0. The dam stability factor was greater than 1.3 under various working conditions during operation, thus meeting the code requirements. The main project of the Jinijigou cemented soft rock dam reached the dam crest elevation of 422.00 m in June 2019, as shown in Figure 5. The main on-site safety monitoring equipment in Jinjiigou includes 28 osmometers, 6 crack gauges, 6 rock displacement meters, 3 thermometers, and 7 observation piers. The safety monitoring results show that the 28 osmometers with the dam longitudinal 0 + 036.00, 0 + 045.00, and 0 + 016.00 sections of the dam body have not been abnormal since January 2018, and the seepage pressure of the dam body is stable. Since the installation time, the crack gauge and rock displacement meters have been working normally, and there is no abnormal situation. The dam suffered heavy rainfall on 9 August 2021, with a daily rainfall of 500 mm. The dam retained water to an elevation of 417.50 m (overflow dam crest elevation), and the diversion tunnel was opened to discharge water. No leakage point was found and the overall operation was in good condition. Figure 4: Diagram of the vertical normal stress of the dam: (**a**) overflow dam section (Pa); (**b**) non-overflow dam section (Pa); (**c**) vertical normal stress distribution diagram of the overflow dam axis cross-section; and (**d**) vertical normal stress distribution diagram of the non-overflow dam axis cross-section. Figure 5: Jinigou cemented soft rock dam. The Jinjigou Reservoir dam project adopted the scheme of a cemented soft rock gravel dam, which saved a total of CNY 3.96 million in static investment compared to the roller compacted concrete gravity dam scheme. Adopting the new dam construction method shortened the construction period by 20% and it was completed 5 months ahead of schedule, resulting in early irrigation and water supply benefits of about CNY 27 million. Cemented material dams can save about 20% of the investment compared to concrete dams, can save about half of the material usage compared to earth and stone dams and can be constructed more safely and quickly. One of the main economic benefits of cemented sand and gravel dams is their low cost compared to other types of dams. They require fewer materials, and the construction process is relatively simple and can be completed quickly. This means that the overall cost of the project is lower, making it more accessible to smaller communities or organizations with limited budgets. Additionally, cemented sand and gravel dams require less maintenance than other types of dams, which can also save money in the long run. Since they are made from natural materials, they are more resistant to erosion and can last for several decades without requiring major repairs or replacements.