城市基坑富水破碎岩体注浆加固技术研究

Study on Grouting Reinforcement Technology of Water Rich Broken Rock Mass in Urban Foundation Pit

在城市地下基坑开挖过程中,由于地下水和工程地质条件的影响,普通注浆材料对破碎岩体地层的加固效果较差。本次研究利用改性聚氨酯粘合剂对普通快硬性水泥注浆材料进行改良,室内制备了改性聚氨酯/水泥基新型复合注浆材料,并对其展开了综合试验研究。研究表明:(1)掺入改性聚氨酯粘合剂后,注浆材料的扩散半径和抗压强度会逐渐降低,但流动性及承载能力依然在良好的范围内;新型复合注浆材料的初凝时间和终凝时间得到了大幅改善,不同MP材料浓度条件下,新型盾构注浆浆液初凝时间分别为21 min、18 min、12 min、10 min以及8.5 min,终凝时间则分别为117min、91min、66 min、57 min以及42 min;(2)随着MP材料浓度的增大,碎石土注浆结石体试样的渗透性逐渐减小。利用纯水泥注浆材料注浆加固的结石体试样的渗透系数为2.01×10^(-9)cm·s^(-1),随着MP材料浓度的逐渐增大,结石体的渗透系数分别降低到1.79×10^(-9)cm·s^(-1)、1.68×10^(-9)cm·s^(-1)、1.61×10^(-9)cm·s^(-1)以及1.55×10^(-9)cm·s^(-1);(3)当养护时间较短时,新型复合注浆材料对碎石体的加固效果不断增强,结石体的抗压强度和抗折强度也不断提高,而当养护时间足够长时,随着MP材料浓度的不段增大,结石体的抗压强度和抗折强度均呈现出先增大后减小的变化趋势。

During the excavation of urban underground foundation pit,due to the influence of groundwater and engineering geological conditions,the reinforcement effect of ordinary grouting materials on the broken rock stratum is poor.In this study,modified polyurethane adhesive was used to improve the ordinary quick hardening cement grouting material,and a new type of modified polyurethane/cement-based composite grouting material was prepared indoor,and a comprehensive experimental study was carried out on it.The results show that:(1)after adding modified polyurethane adhesive,the diffusion radius and compressive strength of grouting materials will gradually decrease,but the fluidity and bearing capacity are still in a good range;the initial setting time and final setting time of the new composite grouting material have been greatly improved.Under different MP material concentrations,the initial setting time of the new shield grouting slurry is 21 min,18 min,12 min,10 min and 8.5 min respectively,and the final setting time is 117 min,91 min,66 min,57 min and 42 min respectively;(2)with the increase of MP material concentration,the permeability of gravel soil grouting stone sample decreases gradually.The permeability coefficient of the stone sample reinforced by pure cement grouting material is 2.01×10^(-9)cm·s^(-1),with the gradual increase of MP material concentration,the permeability coefficient of stone body decreases to 1.79×10^(-9)cm·s^(-1)、1.68×10^(-9)cm·s^(-1)、1.61×10^(-9)cm·s^(-1)and 1.55×10^(-9)cm·s^(-1);(3)when the curing time is short,the strengthening effect of the new composite grouting material on the gravel body is continuously enhanced,and the compressive strength and flexural strength of the stone body are also continuously improved,when the curing time is long enough,the compressive strength and flexural strength of the stone body will increase first and then decrease with the increase of MP material concentration.