Technology of mass detection of cement mixing pile based on pressuremeter tests

The existing conventional methods for quality testing of cement mixing piles face challenges such as missing samples at weak points of the pile, sample distortion due to disturbance, and the high difficulty and cost of drilling and coring operations. To address these issues, first a full-scale model test on a cement mixing pile is conducted to reveal the through-going fracture failure pattern during lateral pressure inside the pile. Based on this fracture failure model and the bounded nature of the pile, a model is then proposed to relate the uniaxial compressive strength of the cement soil to the limit the plastic pressure and the initial pressure under lateral compression conditions. Finally, a field test is carried out, in which the lateral pressure testing and coring are performed on the cement mixing pile, and the predicted compressive strength is compared with the actual measurements. The results show that, under lateral pressure, the pile fails along a single radial through-going tensile fracture plane that is roughly symmetric along the pile diameter. The cement soil fails in a highly brittle manner, and the P-S curve obtained from the lateral pressure tests does not exhibit a plastic stage. The maximum limit plastic pressure is observed in the silt layer at the mid-height of the pile, while the minimum value occurs in the sludge layer. The lateral pressure testing method used in this study, along with the strength conversion formula that accounts for through-going fracture failure, can reliably predict the compressive strength of cement mixing piles.