3.3　Construction Technology and Technical Requirement for Concrete Cushion

The cushion shall be constructed after the subgrade surface layer acceptance，subgrade settlement assessment and CP Ⅲ network achievement have all passed assessment.

The turnout area cushion shall adopt common C25 concrete，thickness is 12cm，the design plane size shall be determined by turnout slab size，and shall be 370mm wider than turnout slab at both sides.

According to construction drawings，the plane position and height of the cushion shall be set out and surveyed，steel formwork shall be adopted，and concrete shall be directly poured by concrete tank truck，the concrete consumption shall be calculated before pouring，and concrete test pieces shall be made beforehand.The cushion shall be 150mm wider than both sides of the base plate.After concrete has reached certain strength，scuffing treatment shall be made on upper plastic layer surface，scuffing depth is 1.8～2.2mm.2％ drainage slope shall be set at both sides until extending 5cm beneath the concrete base plate，the transversely cut joint shall be made on the cushion，the cut joint spacing shall be controlled within 2～5m and the depth shall be 35％ of the cushion depth.The joint shall be cut after the concrete preliminary solidification and the overlapping with board gap shall be avoided，the cut joint shall be possibly away from the isolating wall，in case penetrating joint would be formed.The surface shall be cleaned up after construction.

According to requirement of design and acceptance standard，the constructed cushion shall be accepted，which includes surface smoothness，height and plane position.Written record shall be completed after acceptance qualification.