VERTICAL BARRIERS SLURRY TRENCH BARRIERS: excavation equipment. prof. E. Fratalocchi Environmental Geotechnics Waste and polluted sites containment

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Winfred Kelley
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1 VERTICAL BARRIERS SLURRY TRENCH BARRIERS: excavation equipment

2 VERTICAL BARRIERS SLURRY TRENCH BARRIERS: excavation equipment rotary drill hydro-mill backhoe Clamshell + Kelly bar

3 VERTICAL BARRIERS SLURRY TRENCH BARRIERS: Problems due to improper construction A strict Construction Quality Assurance CQA and Construction Quality Control CQC are necessary to avoid problems =>

4 VERTICAL BARRIERS SLURRY WALLS: SOIL-BENTONITE Bentonite % for different soils range = 2-5%

5 VERTICAL BARRIERS SLURRY WALLS: SOIL-BENTONITE Typical construction site B-W slurry + soil: Slump = cm g = g/cm 3

6 VERTICAL BARRIERS SLURRY WALLS: SOIL-BENTONITE Excavation and backfilling Soil-bent mix is placed so that it flows down a shallow slope, not free dropped

7 VERTICAL BARRIERS SLURRY WALLS: SOIL-BENTONITE CQA and CQC Sampling before (and after) placement of the slurry to measure: - unit weight (mud balance): > 1.03 g/cm 3 - viscosity (Marsh funnel): < 40 seconds - filter loss (filter press): < 25 ml in 30 at 100 psi Inspection of trench geometry: - width, depth, key penetration, - verticality, continuity, bottom cleaning Sampling and testing of the backfill to measure: - unit weight, slump, composition, k, Careful handling of contaminated materials (slurry, backfill) preventing exposure of workers and other receptors.

8 VERTICAL BARRIERS SLURRY WALLS: SOIL-BENTONITE CQA and CQC UNIT WEIGHT (mud balance) spirit-level fulcrum movable weight scale

9 VERTICAL BARRIERS SLURRY WALLS: SOIL-BENTONITE CQA and CQC VISCOSITY (Marsh funnel)

10 VERTICAL BARRIERS SLURRY WALLS: SOIL-BENTONITE CQA and CQC FILTER LOSS: amount of fluid passed through a permeable membrane in a given time under a given pressure before after controlled pressure slurry sample cake paper filter filtrate

11 VERTICAL BARRIERS SLURRY WALLS: SOIL-BENTONITE CQA and CQC FILTER PRESS API filter press

12 VERTICAL BARRIERS SLURRY WALLS: SOIL-BENTONITE main issues Risk of non homogeneous treatment k = 10-7 cm/s Need of space on site for soil-bentonite mixing Chemical compatibility

13 VERTICAL BARRIERS SLURRY WALLS: SOIL-BENTONITE chemical compatibility

14 GROUTED BARRIERS They are formed by injection of a GROUT into the soil. They are in general more expensive and more permeable than slurry walls => rarely used, mainly for artificial bottom liner Risk of non-uniform treatment Risk of hydro-fracturing (pressures too high) jet grouting method permeation method vibrating beam method injection from a hole into the pores and fissures of soil or rock The holes are spaced to have overlapping of the injection Injection by a special driven beam into the space created when the beam is removed

15 GROUTED BARRIERS The choice of the GROUT depends on: soil hydraulic conductivity soil grain size soil and groundwater chemistry type of pollutant (chemical compatibility) rate of groundwater flow A detailed site characterization is fundamental Chemical grouts: chemical base + catalyst + solvent (water) low viscosity => fine soils Particulate grouts: cement and/or bentonite + water more viscous => coarse soils A combination of them can be used, too.

16 GROUTED BARRIERS Guide for the choice of the GROUT

17 GROUTED BARRIERS Guide for the choice of the GROUT

18 GROUTED BARRIERS Guide for the choice of the GROUT

GROUTED BARRIERS: PERMEATION GROUTING Point Injection method: a grout casing is driven to full depth injection through the end of casing after withdrawing => a column of

19 GROUTED BARRIERS: PERMEATION GROUTING Point Injection method: a grout casing is driven to full depth injection through the end of casing after withdrawing => a column of injected soil is created primary and secondary injection to have continuity AFTER SETTING OF THE PRIMARY k > 10-6 cm/s Injection pressure = ~ 20 kpa/m of depth ~ m

20 GROUTED BARRIERS: PERMEATION GROUTING Tube-a-manchette method: a sleeve pipe with small holes (1/30 cm) is placed in a grout hole The small holes are covered by manchettes (rubber sleeves = one way valves) that are opened under the pressure of the grout regrouting can be done if k> k required also changing the grout primary and secondary injection to have continuity PERMEATING INJECTIONS: column dimensions and continuity of treatment are difficult to control

GROUTED BARRIERS: VIBRATING BEAM METHOD Driving of a H-beam with a vibratory hammer The beam is modified to allow injection of grout (typically a CB mixture) through nozzles at the base of the beam

21 GROUTED BARRIERS: VIBRATING BEAM METHOD Driving of a H-beam with a vibratory hammer The beam is modified to allow injection of grout (typically a CB mixture) through nozzles at the base of the beam while withdrawn Max thickness: cm Continuity is an issue K > 10-6 cm/s Shallow depths (m) steel beam markers of driving depth grout supply pipe final barrier profile (plan view) injection nozzle

of the soil+grout - part of the soil+grout

22 GROUTED BARRIERS: JET GROUTING drilling beginning of jetting Revolving and drawing up of jetting rod completion with secondary jetting - soil erosion and brake-up - mixing of the soil+grout - part of the soil+grout (spoil) flows up around the drill rod jetting rod monitor

23 GROUTED BARRIERS: JET GROUTING secant columns lamellar jet-grouting Revolving and drawing up of jetting rod Drawing up of jetting rod without revolving

24 GROUTED BARRIERS: JET GROUTING SYSTEMS SINGLE ROD (single fluid) CCP (Chemical Churning Pile): injection of GROUT DOUBLE ROD (double fluid) Jumbo-JSP (Jumbo Jet Special Grout): injection of GROUT + AIR TRIPLE ROD (triple fluid) KAJIMA injection of AIR + WATER to erode and break-up soil injection of GROUT

25 GROUTED BARRIERS: JET GROUTING APPLICATIONS LOW PERMEABILITY BARRIERS IMPROVE BEARING CAPACITY OF SOILS REDUCE SETTLEMENTS SLOPE AND EXCAVATION STABILIZATION

26 GROUTED BARRIERS: JET GROUTING FEASIBILITY any kind of soil, - except compact clays (Cu> 400 kpa), un-necessary! - excellent in gravels maximum depth: m usual depth: 5-30 m

27 GROUTED BARRIERS: JET GROUTING Feasibility of different injection methods Clay Silt Sand Gravel Cobbles Get-grouting Resins Silicates LV Silicates HV Fine cement CB mixtures mortars HV, LV = high, low Viscosity = too expensive Grain size (mm)

28 GROUTED BARRIERS: JET GROUTING MONOFLUID, CCP grout grout spoil injection nozzles grouted soil Column diameter: Inclination : cm (less with groundwater) from the vertical

29 GROUTED BARRIERS: JET GROUTING BIFLUID air spoil grout compressed air grout grout injection + annular injection of air grouted soil Column diameter: cm (groundwater poorly influent) Columns: vertical (max 10 )

30 GROUTED BARRIERS: JET GROUTING TRIFLUID grout water compressed air air water grout grout injection spoil water injection + annular injection of air grouted soil Column diameter: cm (groundwater poorly influent) Columns: vertical (max 10 )

31 GROUTED BARRIERS: JET GROUTING Parameters of the different systems

32 GROUTED BARRIERS: JET GROUTING COLUMN DIAMETER (m) Method Clays/silts Silty sands Gravels/sandy gravels Mono-fluid Bi-fluid Tri-fluid

33 GROUTED BARRIERS: JET GROUTING GROUTS: WATER-CEMENT, WC WATER-CEMENT-BENTONITE, CB WC Composition: System: mono-fluid bi-fluid tri-fluid W/C: Amount of mixture injected (spoil included) System: mono-fluid bi-fluid tri-fluid m³/m of column: ~ 0.2 up to 1 up to 1.5 Cement amount (spoil included) System : mono-fluid tri-fluid kg/m of column : coarse soil coarse soil fine soil fine soil

34 GROUTED BARRIERS: JET GROUTING Drilling distance, I Horizontal barrier: Vertical barrier: I/D = 0.71 I = D 2 S 2 D = column diameter, S = required barrier thickness Thickness of an horizontal (bottom) barrier: - The same of bottom liner of hazardous waste landfills - uplift verification needed

35 GROUTED BARRIERS: JET GROUTING CONSTRUCTION AND CONTROLS PILOT- TEST- (2-10 columns) Previous investigation : Soil stratigraphy Soil permeability After construction: - Check column diameter by excavation - Drilling into and out of columns => sampling for lab measures: - compressive strength - permeability

36 GROUTED BARRIERS: JET GROUTING CONTROLS DURING CONSTRUCTION - Revolving and drawing up velocity - Fluids pressure - Fluids flow rate - Spoil - Grout composition - Verticality of drilling

37 GROUTED BARRIERS: JET GROUTING Versatile technology (soils, depths, equipment) Risk of non-uniform diaphragm Quite large volume of spoil (to be cleaned or disposed) => high costs k = cm/s Useful for: - Site with difficult access or limited height - Artificial bottom barriers

BOTTOM BARRIER by JET GROUTING Jet grouting provides the best bottom barrier as: - Good control of grout column dimensions - good control on continuity of treatment - effective in any kind of soil -

38 BOTTOM BARRIER by JET GROUTING Jet grouting provides the best bottom barrier as: - Good control of grout column dimensions - good control on continuity of treatment - effective in any kind of soil - possibility to use cement grouts which has high chemical resistance (injection of grouts are possible only in coarse soils) The jetting is stopped to form short columns or disks beneath the contaminated soil

MIXED IN PLACE BARRIERS In situ mixing of soil and slurry Slurry = water+ bentonite or CB mixture Special equipment with generally three auger mixing hollow shafts,

39 MIXED IN PLACE BARRIERS In situ mixing of soil and slurry Slurry = water+ bentonite or CB mixture Special equipment with generally three auger mixing hollow shafts, Simultaneous soil injection and mixing Partial overlapping => vertical barrier k dependent on the type of soil Risk of un-homogeneous k values K > 10-7 cm/s Bottom part cannot be inspected

soil or bedrock Max depth = 30 m Issues: - Leakage through the interlocks (possible use of special GM

40 STEEL SHEET PILE BARRIERS Constructed by driving interlocked sheet piles into the ground using single or double acting impact or vibratory pile drivers Thin barrier Suitable in loose soils, not in dense soil or bedrock Max depth = 30 m Issues: - Leakage through the interlocks (possible use of special GM joint) - compatibility with acids and salts - rapid placement => suitable for short term measures (emergency)

Compaction and Jet Grouting

Compaction and Jet Grouting Alan Ringen, PE Senior Vice President Breakthroughs in Tunneling Short Course August 16, 2017 Grouting Principles Geotechnical Grouting: The injection of pumpable fluid materials