摘要
在采动区地面井煤层气抽采工程中,工作面的回采会对上覆岩层产生较大的扰动,进而导致地面井变形破坏,不能有效发挥卸压煤层气地面井的抽采效能。固井技术能够有效延长采动作用下卸压煤层气地面井的寿命,水泥作为影响地面井固井质量的关键因素,其早期强度需满足较高的固井要求,水泥固结后形成水泥石,水泥石的力学性能对维持卸压煤层气地面井的稳定性至关重要。通过添加分散剂提高水泥石的力学性能是改善固井效果的有效途径。针对目前采动作用下木质素磺酸钙改性水泥石变形破坏特性的研究较少,通过开展循环荷载下不同质量分数的木质素磺酸钙改性水泥石单轴压缩试验,探究木质素磺酸钙对卸压煤层气地面井水泥石变形破坏特性的影响及其改性机制。研究结果表明:水泥石纵波波速和峰值应力随木质素磺酸钙质量分数增加呈现出先增加后降低的趋势,而水泥石声发射总振铃计数随木质素磺酸钙质量分数增加呈现出先减小后增大的趋势。随着单轴循环梯级的增加,水泥石的变形模量呈现出强化现象,且初始加卸载循环对变形模量的强化作用最为显著。随着木质素磺酸钙的加入,改性水泥石的破坏模式呈现出拉伸主导→剪切主导→拉伸主导的拉剪组合破坏模式,同时改性水泥石的分形维数呈现出先减小后增大的趋势,表明适量木质素磺酸钙的加入能够有效提高单轴循环加卸载下水泥石的抗破坏能力。随着木质素磺酸钙质量分数的增加,水泥石水化产物之间孔隙呈现出先减少后增多的趋势。适量木质素磺酸钙的加入会促进水泥石中C−S−H凝胶和钙矾石的大量生成,沉淀在水泥颗粒表面相互交织,可显著提高水泥石的峰值应力,对于提高水泥石的力学性能具有积极作用,同时也使得水泥石的孔隙率降低,进而导致水泥石纵波波速增加、循环�
In the coalbed methane extraction of surface wells in the mining area,the mining of coal seam in working face will cause a significant disturbance to overlying rock layer,which in turn will lead to the deformation and damage of sur-face wells.The coalbed methane extraction of surface wells in the mining-disturbed areas cannot be effectively performed.Cementing technology can effectively elongate the life span of mining-disturbed coalbed methane surface wells.As a crit-ical factor of the cementing quality of surface wells,the early strength of the cement needs to meet the high cementing re-quirements.Cement stone is formed after cement consolidation.The mechanical properties of cement stone are of great importance to maintain the stability of mining-disturbed coalbed methane surface wells.It is an effective way to improve the cementing effect by adding dispersants to enhance the mechanical properties of cement stone.There are few re-searches on the deformation and failure characteristics of calcium lignosulfonate modified cement under the influence of mining disturbance.Uniaxial compression tests of calcium lignosulfonate modified cement with different mass fractions under cyclic loading were carried out to investigate the effect of calcium lignosulfonate on the deformation and failure characteristics of cement stone in mining-disturbed coalbed methane surface wells and its modification mechanism.The results show that the P-wave velocity and peak stress of cement stone increase first and then decrease with the increase of calcium lignosulfonate mass fraction,while the total acoustic emission ringing counts of cement decreases first and then increases with the increase of calcium lignosulfonate mass fraction.With the increase of the uniaxial cycle steps,the de-formation modulus of cement stone shows a strengthening phenomenon,and the initial loading and unloading cycle has the most significant strengthening effect on the deformation modulus.With the addition of calcium lignosulfonate,the modified cement stone shows
作者
邹全乐
王鑫
李左媛
刘莹
王伟志
ZOU Quanle;WANG Xin;LI Zuoyuan;LIU Ying;WANG Weizhi(State Key Laboratory of Coal Mine Disaster Dynamics and Control,Chongqing University,Chongqing 400044,China;School of Resources and Safety Engineering,Chongqing University,Chongqing 400044,China)
出处
《煤炭学报》
EI
CAS
CSCD
北大核心
2023年第4期1606-1621,共16页
Journal of China Coal Society
基金
重庆英才计划“包干制”资助项目(cstc2022ycjh-bgzxm0077)
重庆市研究生科研创新资助项目(CYS22039)。
关键词
木质素磺酸钙
水泥石
变形破坏
声发射
改性机制
卸压煤层气
calcium lignosulfonate
cement stone
deformation failure
acoustic emission
modification mechanism
depressurized coalbed methane
