古滑坡滑带土的力学特性与库水位变化对其稳定性影响及加固措施

Influence of mechanical properties of sliding zone and water level changes on ancient landslide stability and its reinforcement measures

与普通滑坡体相比,库岸古滑坡体不仅影响稳定的因素多,且受库水位变化影响明显,极易诱发地质灾害,对人类生命财产安全造成危害。以某水库古滑坡体工程为例,利用现场直剪试验、室内直剪试验及标准贯入试验手段,研究滑带土的力学特性,并对利用得到的参数计算分析水位变化对古滑坡体稳定性影响的规律,得到鹅公带古滑坡体的安全系数随库水位升高成U形的变化规律。采用文献[12]提出的利用应力场判断滑坡体的类型,在高应力水平位置采取加固措施降低应力水平后边坡安全系数就提高的方法,由计算出的应力场判断鹅公带古滑坡具有上部推移下部牵引的特征,属于混合破坏型滑坡,针对其上部和下部坡体进行加固处理。对比分析不同加固方案对滑坡体应力场的改变和比较抗滑桩在不同位置时安全系数与位移场和应力场之间的关系,表明对高应力水平区和位移大的区域进行加固的效果最好,该滑坡体下部也是高应力水平区,由于现场施工条件,考虑经济性,最后采用在滑坡体下部设置反压体加固,加固后3年的实践表明利用边坡应力场的应力水平确定加固位置合理可行。文中的研究方法和思路可为类似工程处理提供一个很好地分析问题和解决问题的思路和同类工程借鉴。

Compared with the ordinary landslide, factors affecting the stability of the reservoir bank ancient landslide are much more. In addition to the regular factors, the stability is influenced by the water level change obviously. Moreover, the reservoir bank ancient landslide would become geological hazard easily, which causes great danger to human life and property. On the basis of an ancient landslide project of a reservoir, mechanical properties of sliding zone are investigated by the in-situ shear test, laboratory shear test and standard penetration test; and the regularity of influence of water level change on the ancient landslide stability is analyzed. The U-shaped changing regularity of safety factor of Egongdai landslide with water level is obtained. Methods presented in reference [12] are that landslide type can be identified by stress field, and then in high stress level sites reinforcement can be used to reduce stress level to increase safety factor. By the above methods, the upper region of Egongdai ancient landslide has thrust load-caused features; while the bottom region has retrogressive features. Therefore, the Egongdai landslide can be defined as combined landslide; and the upper and bottom regions should be reinforced. The influence on stress field of landslide by different reinforcement schemes are compared; and relationship between stress and displacement fields of the landslide and factor of safety of anti-sliding pile is studied. Results show that the optimal reinforcement site is the one of higher stress level and displacement. As for Egongdai landslide, the bottom region is also with high stress level. Considering the construction conditions and economy, an earth berm was finally constructed at the toe of Egongdai landslide 3 years ago. It is proved that determination of reinforcement site by stress level is reasonable. Research results can provide good reference to other similar projects. © 2016, Science Press. All right reserved.