Tian Qingqing, Guo Lei, Zhang Yiqing, Gao Hang, Li Zexuan
North China University of Water Resources and Electric Power, Zhengzhou, 450046, China.
Sci Rep. 2024 Jul 16;14(1):16400. doi: 10.1038/s41598-024-62345-z.
In order to further promote the application of cementitious sand gravel (CSG), the mechanical properties and variation rules of CSG material under triaxial test were studied. Considering the influence of fly ash content, water-binder ratio, sand rate and lateral confining pressure, 81 cylinder specimens were designed and made for conventional triaxial test, and the influence laws of stress-strain curve, failure pattern, elastic modulus, energy dissipation and damage evolution of specimens were analyzed. The results showed that the peak of stress-strain curve increased with the increase of confining pressure, and the peak stress, peak strain and energy dissipation all increased significantly, but the damage variable D decreased with the increase of confining pressure. Under triaxial compression, the specimen was basically sheared failure from the bonding surface, and the aggregate generally did not break. Sand rate had a significant effect on the peak stress of CSG, and decreased with the increase of sand rate. Under the conditions of the same cement content, fly ash content and confining pressure, the optimal water-binder ratio 1.2 existed when the sand rate was 0.2 and 0.3. After analyzing and processing the stress-strain curve of triaxial test, a Cuckoo Search-eXtreme Gradient Boosting (CS-XGBoost) curve prediction model was established, and the model was evaluated by evaluation indexes R, RMSE and MAE. The average R of the XGBoost model based on initial parameters under 18 different output features was 0.8573, and the average R of the CS-XGBoost model was 0.9516, an increase of 10.10%. Moreover, the prediction curve was highly consistent with the test curve, indicating that the CS algorithm had significant advantages. The CS-XGBoost model could accurately predict the triaxial stress-strain curve of CSG.
为进一步推动胶凝砂砾石（CSG）的应用，研究了CSG材料在三轴试验下的力学性能及变化规律。考虑到粉煤灰含量、水胶比、砂率和侧向围压的影响，设计制作了81个圆柱体试件进行常规三轴试验，分析了试件应力-应变曲线、破坏模式、弹性模量、能量耗散及损伤演化的影响规律。结果表明，应力-应变曲线峰值随围压增大而增大，峰值应力、峰值应变及能量耗散均显著增加，但损伤变量D随围压增大而减小。三轴压缩时，试件基本沿粘结面剪切破坏，骨料一般不破碎。砂率对CSG峰值应力影响显著，随砂率增大而减小。在水泥含量、粉煤灰含量和围压相同的条件下，砂率为0.2和0.3时存在最优水胶比1.2。对三轴试验应力-应变曲线进行分析处理后，建立了布谷鸟搜索-极端梯度提升（CS-XGBoost）曲线预测模型，并通过评价指标R、RMSE和MAE对模型进行评估。基于初始参数的XGBoost模型在18种不同输出特征下的平均R为0.8573，CS-XGBoost模型的平均R为0.9516，提高了10.10%。而且，预测曲线与试验曲线高度一致，表明CS算法具有显著优势。CS-XGBoost模型能够准确预测CSG的三轴应力-应变曲线。
