白鹤滩水电站地下厂房层间错动带渗流控制措施研究

Study on seepage control measures for interlayer staggered zone for underground powerhouse of Baihetan Hydropower Station

白鹤滩水电站地下厂房洞室群规模巨大,层间错动带C2贯穿左岸地下厂区整个防渗线路,由于其性状差、透水性强、允许渗透比降小,是左岸厂区主要渗漏通道,因此,提高C2的防渗能力和渗透稳定性,防止形成集中渗漏通道,对左岸厂区防渗体系至关重要。为此,采取截渗洞、系统帷幕灌浆和排水孔幕相组合的防渗排水工程措施,通过三维渗流场有限元计算及帷幕灌浆试验对防渗效果进行分析。结果表明:截渗洞和帷幕灌浆能有效截断渗漏通道,排水孔幕排水降压效果显著,C2渗透系数的变化对地下厂区上游侧渗流场影响不大; C2影响孔段可灌性好,灌后能够满足透水率小于1 Lu的工程防渗要求; C2渗流控制措施总体合理有效,但是排水孔揭穿C2部位渗透比降较大,最大可达7. 0,蓄水初期应重点关注,避免发生渗透变形。

The scale of the underground powerhouse cavern group of Baihetan Hydropower Station is huge,but a interlayer staggered zone C 2 passes through the whole anti-seepage route of the underground power house on the left bank.Due to its poor behavior,strong permeability and small allowable seepage gradient,the interlayer staggered zone is the main seepage passage.Therefore,it is quite important to enhance the anti-seepage capacity and the permeable stability to prevent the formation of a concentrated seepage passage for the anti-seepage system of the powerhouse area on the left bank.Therefore,an engineering measure of anti-seepage and drainage combined with seepage-cutoff tunnel,systematic curtain grouting and drain-hole curtain is adopted.The anti-seepage effect is analyzed through 3-D finite element calculation of seepage field and curtain grouting experiment.The result shows that both the seepage-cutoff tunnel and the curtain grouting can effectively cut the seepage passage therein off,while the drainage and pressure-relief effect of the drain-hole curtain is significant as well.The change of the permeable coefficient of C 2 has less impact on the seepage field at the upstream side of the underground powerhouse area.Meanwhile,the section under the impact of C 2 has a better groutability,thus the engineering anti-seepage requirement of that the permeable rate is less than 1 Lu can be satisfied after grouting.The seepage control measures for C 2 are generally reasonable and effective.However,the permeability gradient at the intersection of C 2 and drain-hole is larger with the maximum up to 7.0,for which great attention must be paid during the early stage of impoundment,so as to avoid occurrence of seepage deformation.