Study On The Effect Of Self-stress Of Backfill Concrete Of Anchorage Slot

Prestressed Concrete lining structure is a new type of tunnel liner, and there are manyhydraulic tunnels which are builder with these structure forms of Large-scale waterconservancy engineering. A compressive pre-stress in the entire cross-section isapplied to tunnel liner, except the location of anchorage slot. The reason for this isthat backfilling of anchorage slot must be complete after anchor beam tension anchor.So the locations of anchorage slot become the weakness of the entire cross-section.This paper’s destination is to solve this problem by optimizing mixing ratio of backfillconcrete, to make sure the concrete backfilled to the anchorage slot develop a certaindegree of self-compressive stress.A new type of expansion sources will be incorporated to concrete formulated intoself-stressing concrete which can fulfil demand of backfill concrete. The expansionsources was been used in rock cutting and silent blasting, and there are hardlyresearch about using the expansion properties to make up concrete. Many experimentsare designed to research the expansion properties of self-stressing concrete andmutually verify the correctness of experimental data and conclusion originates fromexperimental. First trial test will be applied to figure out the range of the expansionsources’ amount. Then further test will be carry out to explore the expansionproperties of self-stressing concrete and the stable of expansion of self-stress.The results show that:1. The range of the expansion sources should be controlled in the range of4%~8%，according many engineering. When the content is lower than4%, self-stressproduced in the backfill concrete is too small; when the volume is higher than8%,self-stress is too large, and this can cause severe loss of preload stress.2. The expansion of the free state and self-stress of the constraint condition withthe self-stress concrete increase with content of expansion sources increased3. When the expansion done the expansion properties (swelling deformation andexpansive stress) is relatively stable and will not cause damage again.4. The expansion process of concrete with the SCA is short and there is noinfluence on follow-up processes.5. The range of the SCA incorporated to backfill concrete of anchorage slot usedin prestressed concrete lining structure should be set to4%. The backfill concrete of anchorage slot is in the constraint condition setting and hardening. When the dosageof SCA is8%, pre-stress of2MPa will be produced in the concrete.