In order to make the concrete sprayed by the shotcrete machine have a good quality, to ensure that the concrete structure has no original defects when forming, so as to ensure the durability of the concrete, the following reasons are analyzed to affect the injection quality of the sprayer during the operation of the sprayer. We analyze from the following aspects:
1. Impact of rock surface cleanliness Before spraying concrete, it is necessary to keep the rock surface to be sprayed without loose rock and clean and free of oil and dirt. At the same time, it is necessary to use hanging steel mesh and anchor rod in the development section of surrounding rock joint to strengthen the integral branch of sprayed concrete layer and surrounding rock. Protection effect.
2. Determination of the mix ratio of on-site shotcrete According to the test, the mixing ratio is adopted in the water seepage or dripping section. In order to ensure the quality of the rock face with large local water seepage or dripping, change the mix ratio. Only fine aggregate is used without coarse aggregate, add 6% quick-setting agent, first spray 2cm thick and then sprayed according to the normal mix ratio. In a wet or dry section. The injection is performed using a mixing ratio.
3. Groundwater impact For the drip or seepage of the rock surface, the blind pipe can be specially set up for refilling or direct sealing. From the field test situation, it is difficult to achieve the effect of no leakage and leakage. This is mainly because the initial injection groundwater distribution is not concentrated, and it is difficult to find the water outlet point for larger water inrush. Therefore, it is more suitable for groundwater and high waterproofing requirements. A layered spray method is employed.
4. The influence of water cement ratio: For wet shotcrete, the larger the water-cement ratio, the worse the acceleration effect, the larger the rebound and the lower the strength of concrete; the smaller the water-cement ratio, the more difficult the construction shotcrete is, the insufficient hydration of cement, the lower the strength and the greater the rebound.
