9 Execution supervision and control

9.1 General

9.1.1 The supervision of the grouting process shall be based on the design specifications. The supervision procedure shall provide documentation based on detailed observation of each phase of the operation. The documentation shall form the basis for any modifications to the design specifications.

9.1.2 During construction, the design assumptions shall be verified according to the data acquired and, if necessary, modified.

9.2 Supervision

9.2.1 All grouting work should be supervised by suitably experienced representatives from all concerned parties.

9.2.2 Prior grouting experience shall be required of all key personnel.

9.2.3 The execution of the works shall be supervised continuously and all observations made shall be compared with the design parameters and assumptions. If the observations differ significantly from the design, then the reason for deviation shall be investigated and the design or execution parameters adjusted to these new conditions.

9.2.4 The designers shall participate in the decision when specification adjustments are made.

9.2.5 The supervision of grouting sites should be facilitated by automating the mixing and delivery systems and installing mechanical, analogue or, preferably, computerized recording devices for real time monitoring and control of the grout placement parameters.

9.2.6 Records shall be kept during the entire field operation, showing all data pertaining to each phase of the work.

9.2.7 Comprehensive records covering each phase of the work should be incorporated in a final report.

9.3 Monitoring and control

9.3.1 General

9.3.1.1 Prior to commencing work, a location and condition survey should be conducted on any structures and utilities likely to fall within the grout influence zone. Further surveys should be made as grouting proceeds.

9.3.1.2 The type, extent and accuracy of monitoring requirements on and off-site shall be clearly established in project documents and before work commences on site.

9.3.1.3 Computerized systems should be used to:

• monitor the drilling of boreholes;
• measure, control and interpret the drilling parameters;
• measure and control the grouting parameters of the different grouts injected in each grouting stage.

9.3.1.4 The parameters, which should be monitored, recorded and analysed during the grouting process, vary continually with time. Hence, the grouting process should be monitored and preferably controlled by a datalogger or field computer to follow in real-time the grouting parameters.

9.3.1.5 Computerized information control should provide hard copy print-outs or back up copies which should be stored in a safe place.

9.3.1.6 Monitoring and control measurements should be carried out, according to the project requirements (design).

9.3.1.7 When data loggers or field computers are used on site, the data sampling intervals should be chosen according to the project requirements.

9.3.1.8 To determine the success of grouting, appropriate (specified) control tests should be carried out at the earliest practical time in order to react as soon as possible to anomalies.

9.3.1.9 The relative development of the injection pressures, the quantity injected and the flow rate with time should be recorded for each grouting phase and for ongoing comparison as the work progresses.

9.3.2 Environmental impact

9.3.2.1 Any environmental impact assessment and especially the decision regarding admissible limits should be based on two largely independent investigations:

• the status quo should be assessed prior to starting any work, with particular attention paid to groundwater conditions (chemistry, velocity and direction of groundwater flow, existing and planned use of groundwater and distance between withdrawal points);
• the expected polluting effect of the grout and the duration of pollution (in case of transitory effects less stringent levels are applicable) should be determined, distinguishing between gaseous, liquid and solid state.

9.3.3 Control of objective

9.3.3.1 The control methods chosen shall depend on the aim of the treatment.

9.3.3.2 Tests should be conducted both before and after grouting to provide an indication of the grouting success.

9.3.3.3 Test may include permeability tests, mechanical tests in the field and the laboratory, excavation, etc.

9.3.3.4 The choice of permeability test depends on the ground condition, and degree of sophistication required. Rising head or falling head (Lefranc) tests are often conducted in granular soils. Lugeon tests are performed in rock. Large scale pumping or injection tests can determine the regional permeability for a large body of soil or rock.

9.3.3.5 The data recorded during drilling may be used to check whether the objectives are being met.

9.3.4 Monitoring of displacement

9.3.4.1 Appropriate instrumentation should be installed that will be capable of monitoring ground and/or structural movements with sufficient accuracy to ensure that they will remain within the established tolerance limits.

9.3.4.2 (Where required, instrumentation for movement monitoring shall be installed sufficiently in advance of the grouting work to allow the identification of background influences (temperature variations, groundwater fluctuation, etc.), and thereby to compensate for their effect on future readings.

9.3.5 Drilling

9.3.5.1 During drilling, a number of parameters may be recorded automatically:

• rate of penetration;
• fluid pressure;
• flow rate;
• reflected energy;
• rotational speed;
• torque;
• pull down force;
• borehole length.

The interpretation of recorded parameters provides useful information with regard to geological and geotechnical variations.

9.3.6 Grout

9.3.6.1 The quality and consistency of the grout shall be maintained by conducting control tests which monitor the ongoing compliance with the required characteristics.

9.3.6.2 The granulometry of microfine suspensions should be controlled and monitored, taking flocculation into account.

9.3.6.3 On site, the grouts shall be subjected to at least the routine control tests given in Table 5.

In hardened particulate grouts the compressive strength and/or shear strength shall be tested. For testing, see also Annex A.

9.3.6.4 The batching process shall be continuously monitored and recorded.

9.3.6.5 During grouting the grout components and the quantity prepared shall be monitored.

9.3.6.6 Trace indicators may be used on treated ground in order to assess the presence of grout.