Surface Strengthening and Support
KHANDALA TUNNEL - BORGHAT SECTION - MAHARASHTRA - India
Maharashtra State Road Development Corporation Limited(MSDRC)
ROCKFALL MITIGATION – KHANDALA (MUMBAI CORRIDOR), MUMBAI–PUNE EW
Figure 2-Initial Site Condition (stretch near Tunnel portal)
Figure 3-Installation activities in progress (stretch near Tunnel portal)
Figure 4-Installation activities in progress (Rockslide stretch)
Figure 5-Sub surface drainage Pipes
ROCKFALL MITIGATION – KHANDALA (MUMBAI CORRIDOR), MUMBAI–PUNE EW_4
Mumbai-Pune Express way (officially known as Yashwantrao Chavan Expressway (YCEW)) is India’s first six-lane concrete expressway in Maharashtra connecting the financial capital of India with state cultural capital, Pune. Built along the Sahyadri mountain ranges through passes and tunnels, it is recognized as one of the dangerous expressways prone to a series of rockfall and landslides causing a heavy damage to infrastructure, traffic disruptions and causalities specially during monsoon season. Two sub-stretches are identified near Khandala location: Rockslide stretch (at a distance of approx. 130m from Khandala Tunnel Portal on the Pune side) and stretch near tunnel portal.
After conducting thorough investigation and taking into consideration the observations of geological experts and geotechnical engineers, Maccaferri has proposed rockfall mitigation measures with secured drapery/nailing with mesh facia system over the previously applied shotcrete and mesh system installed earlier (which has become ineffective). For Rockslide stretch, deep nailing and flexible mesh facia system (Steelgrid MO and HEA panel) has been implemented. The nails (continuously threaded anchors (CTA)-25/32mm dia.) are varying from 4m to 15m in length spaced at 2mx2m. For the stretch near the tunnel portal where surficial instabilities have been observed, systematic anchoring with raster of nails of 3m to 6m lengths spaced at 2.5×2.5m/3x3m have been installed along with Steelgrid MO and Diagonal wire ropes and /or HEA panels. For areas where larger instability thickness between 1.5m and 2m, HEA panels are provided along with Steelgrid MO. Sub-surface drainage pipes (50mm dia perforated PVC pipes wrapped with non-woven geotextile) are also installed at stipulated locations. Pull-out tests were carried out on the nails installed to ascertain the nail capacity. Secured drapery analysis has been carried out for finalizing the nail configuration and mesh selection using Maccaferri’s ‘MacRO Studio’ software. Nailing design was carried out using RocScience’s RS2 software. The project duration mentioned is for the overall project covering different locations.