地热输水隧洞衬砌结构受力特性及稳定性研究

青海贵德盆地存在的地热资源使得拉西瓦灌溉工程3~#隧洞产生高地温现象(实测空气温度34℃),灌区往复通水产生的高温降严重影响衬砌结构的稳定性。为此,采用三维有限差分法,结合现场监测试验数据,对该隧洞施工期和运行期衬砌结构的受力特性及其稳定性进行了研究。结果表明:较大的拉应力值使衬砌结构产生裂缝,不利于衬砌结构的稳定性;施工期衬砌结构产生纵向裂缝,运行期衬砌结构产生环向裂缝,其中有压洞易同时产生纵向裂缝;施工期6 m段衬砌结构在两端位置处产生裂缝,9 m段在中间位置处产生裂缝;运行期3 m、6 m、9 m段衬砌结构在中间位置处产生裂缝,12 m段容易在两端1/3位置处产生裂缝;衬砌分缝长度较短时,衬砌结构总体受力情况较好;工程采用分缝长度为6 m段衬砌结构,加配环向钢筋,取得较好成效。该研究成果可为未来在黄河谷地地热资源丰富地区开展相关工程提供技术支持。

Study on stress characteristics and stability of lining structure of water-conveyance tunnel under high geo-temperature

The geothermal resources in Guide Basin produces a high geo-temperature phenomenon in the No. 3 tunnel of LaxiwaIrrigation Project(the measured air-temperature is about 34 ℃ )，and then the high temperature drop produced from the waterconveyance through the tunnel seriously impacts the stability of its lining structure. Therefore，the stress characteristics and stabilityof the lining structure of the tunnel during both the construction period and the operation period are studied with 3 － D finite difference method in combination with the in situ monitoring data. The result shows that higher tensile stress makes cracks occur in the lining structure，which are unfavorable to the lining stability. Longitudinal cracks produce in the lining structure during the construction period and circumferential cracks occur in the lining structure during the operation period，in which longitudinal cracks are prone to occur in the pressure tunnel section at the same time. During the construction，cracks occur at both the ends of the lining structure section with the length of 6 m and occur at the mid-position of the lining structure section with the length of 9 m，while cracks occur at the mid-positions of the lining structure sections with the lengths of 3 m，6 m and 9 m，meanwhile， cracks are prone to occur at 1 /3 positions of both the ends of the section with the length of 12 m. When the length of partition joint of lining is shorter，the general stress state of the lining is better. The lining section with the partition joint length of 6m is adopted for the project，for which circumferential reinforcement is added as well，thus better effect is obtained in the project. This study result can provide technical support and guidance for carrying out the relevant projects in the regions with rich geothermal resources in the valleys of the Yellow Ｒiver.