Grout Mix Design for Seepage Control in Temghar Dam by CWPRS,

86.6m high Temghar dam has been constructed across near of during the period March 1997- May 2010. It is a stone masonry gravity dam with 5 m thick septum of cement sand mortar colgrout masonry on upstream face and 3 m thick at base interface of the dam. Further, colgrout masonry has also been provided in toe region upto EL 667.0 m. Total length of dam is 1075 m and comprises of 72 m long spillway portion in the center and non-overflow portion on either flank. Water Leakages started appearing during construction at RL 645 m at chainage 514 m at Monolith no. 14/14A in June 2000 just after the first filling of the reservoir. Further, heavy water leakages with high exit pressure have been observed at many locations when construction reached RL 685. This continuous heavy seepage through dam body raised apprehensions about the structural safety of the dam. Considering severity of the problem and hazard potential of the dam, as it is located just on the upstream of Khadakwasla dam adjoining Pune city, Maharashtra government formed Temghar Dam Expert Committee in the year 2015 by including senior Scientists from CWPRS, Pune, to suggest remedial measures for controlling seepage through dam body. As per recommendations of expert committee, Project Authority entrusted the study of designing suitable cementitious grout mix for carrying out dam body grouting towards arresting seepage through dam body. Extensive Laboratory studies have been conducted on many combinations of mix design by varying proportions of cement, flyash, silica fume, admixtures and quantity of water to achieve best results. For assessing the suitability of grout system, various tests such as flowability test- Marsh cone time of afflux, pH value, bleeding potential, jellification time etc, have been conducted at CWPRS. To study the effectiveness of grouting in reducing seepage and improvement in strength parameters, trial application of suitable grout mix has been carried out by casting and grouting the distressed stone masonry blocks of one cubic meter and conducting NDT, water loss tests and at pre-grouting and post grouting stages. Also strength properties, improvement in mass density and spread of grout have been studied from extracted cores of grouted sample blocks. Based on performance of grouting in sample masonry blocks, grout mix design has been recommended for carrying out dam body grouting of Temghar dam.

Fig. 1: Measurement of Flow time by Marsh Fig. 2: Grouting of Masonry Blocks

Cone Apparatus

As per the suggestions of CWPRS, grouting have been carried out in two stages on three faces of the dam i.e. downstream, top and upstream face of the dam. Also, grouting has been carried out from inspection gallery to the top of foundation gallery. Several site visits have been carried out during the grouting work of Temghar dam by Scientists from CWPRS, Pune for rendering guidance and suggestions during dam body grouting and checking quality of grout mix. The grouting of dam body has been observed to be very successful resulted in more than 90 % seepage/leakage reduction. Seepage is expected to reduce further after Vertical Porous Drains will become operational and application of Shotcrete treatment on upstream face.