4.6　Grouting

4.6.1　The laboratory slurry mix test and on-site grouting test shall be conducted before the grouting construction.

4.6.2　The automatic pressure and flow recorders shall be used to record grouting pressure and grout flow rate for grouting construction.

4.6.3　The grouting shall be conducted by means of alternate grouting and from periphery to inside.

4.6.4　The grouting hole diameter should be 70mm-110mm，and the position tolerance of hole shall not be greater than 50mm，and verticality tolerance of drilling hole shall be less than 1/100.The tolerance between drill pipe angle and design angle of grouting hole shall not be greater than 2°.

4.6.5　Ordinary Portland cement shall be used and the water-cement ratio should be taken as 0.5-0.6.The grout shall be mixed uniformly and stirred continuously during grouting，and the mixing time shall be less than initial setting time of grout.The grout shall be filtered with sieve before grouting.

4.6.6　The drawbench should be used to uplift grouting pipe.During grouting with plastic valve pipe，the uplifting height of grouting core pipe for each time shall be 330mm.During grouting with perforated pipe，the uplifting or drilling-down height of perforated pipe for each time should be 300mm-500mm.During compaction grouting of mortar with low slump，the uplifting height for each time should be 400mm-600mm.

4.6.7　The grouting pressure shall be determined according to the property of soil layer and the buried depth.The grouting pressures should be 0.2MPa-0.5MPa and 0.2MPa-0.3MPa for split grouting in granual soils and cohesive soils，respectively.During grouting of cement-water glass quicksetting grout，the grouting pressure shall be less than 1MPa and the grout flow rate should be 10L/min-20L/min.During compaction grouting of cement mortar with slump of 25mm-75mm，the grouting pressure should be 1MPa-7MPa and grout flow rate should be 10L/min-20L/min.

4.6.8　The amount of additives and admixtures added in grout mixing shall be determined through tests or shall be selected according to the following indexes：

1　The mixing amount of pulverized flyash should be 20%-50% of cement content；

2　The molar ratio of water glass shall be 3.0-3.3 and its mixing amount should be 0.5%-3.0% of cement content；

3　The mixing amount of surface active agent（or water reducing agent）should be 0.3%-0.5% of cement content；

4　The mixing amount of bentonite should be 1%-5% of cement content.

4.6.9　During construction in winterwhen the grouting is conducted under the condition that daily average temperature is lower than 5℃or minimum temperature is lower than-3℃，measures shall be taken to prevent grout from freezing.During construction in summer，the temperature of water used shall not be higher than 35℃and sunlight protection measures shall be taken to grout and grouting pipeline.

4.6.10　During grouting，such measures as adjusting grout mix ratio，intermittent grouting，adjusting grout setting time and sealing upper opening may be taken to avoid grout oozing out.

4.6.11　The record and quality control for such items as raw material inspection，grouting strength，plan position and depth of grouting hole，grouting construction sequence，grouting pressure and grouting flow rate shall be done well during grouting construction.