Water cut-off process for concrete structure

A water cut-off process for a concrete wall of an underground structure having water-leaking portions, wherein a void is formed between the concrete wall and the ground, said process comprising the following steps:

• drilling a through-hole extending from the inside into the outside of the concrete wall of said underground structure at each water-leaking portion thereof;
• inserting a pipe into each through-hole, each pipe including a valve;
• temporarily interrupting a large amount of water spouting from a discharge end of each pipe by shutting off said valve;
• grouting cement slurry under low pressure through each pipe into each through-hole and pushing the cement slurry into the void between said concrete wall and the ground using a grouting pump against the pressure of the leaking water, while mixing an accelerating agent into said cement slurry,
• allowing the mixture of said cement slurry and said accelerating agent to stand for approximately one day to form a hardened cement layer on a surface of said concrete wall facing the ground where said void is formed;
• cutting off the end of said pipe projecting from a surface of said concrete wall away from the ground;
• removing unhardened cement from each pipe if water continues to leak therefrom;
• packing a mound of a cement powder composition over each water-leaking pipe under pressure using a cement filling gun;
• compressing said packed cement power in said pipe and said through-hole by exerting;
• a strong impacting stress thereon using an impacting tool to consolidate and compact said cement powder composition in said pipe and said through-hole;
• repeating the processes of packing and compressing said cement powder composition until said through-hole is filled with said cement powder composition;
• and
• leveling off the resulting through-hole with a cement paste.