1) The presence of stirrups in the photovoltaic spiral ground pile affects the dehydration and cementation time of water glass, thereby affecting the sand casting and hardening speed. After the moisture exceeds a certain range, the molding sand cannot harden. Usually, the moisture content of the original sand does not exceed 0.5 percent (mass fraction).

2) The dust content in the original sand of photovoltaic spiral ground piles affects the strength of organic ester self hardening sodium silicate sand with certain formulas. Dust severe expansion of the specific surface area of sand, consumption of water glass binder in large enamel, significantly reducing the strength of molding sand. In order to achieve the usable strength of the molding sand, the photovoltaic spiral pile has to add water glass into the pile, which worsens the collapsibility of the molding sand. Therefore, it is requested that the content of the original sand powder be less than 1 percent (quality fraction).

3) The residual modulus of recycled sand in photovoltaic spiral ground piles is strictly affected by the water glass film, which affects the process performance of molding sand. To fully affect the usable time of the cut sand, especially during high temperatures, using recycled sand with high residual modulus of water glass film as the raw sand, and using ordinary water glass to make penetrating sand, the photovoltaic spiral ground pile has no usable time at all, and therefore, the photovoltaic spiral ground pile has to use ultra-low modulus modified water glass and extremely slow organic ester It not only increases the cost of molding sand, but also enhances the residual strength of molding sand.