Soil Improvement Case Study With Jet Grouting Solution for Soft Soil

SOIL IMPROVEMENT CASE STUDY WITH JET GROUTING SOLUTIONS FOR SOFT SOIL Intan Nurliyana Binti Zainal, Farah Arisha Binti Shahrom, Farah Nur Izuwani Binti Muhamadi Saifulizan, N ur Fatihin Najila Binti Mohd Jaffri, Nuraisha Arissa Binti Mohd Razip Faculty Of Civil And Environmental Engineering, University Tun Hussein Onn Malaysia (UTHM), 86400 Parit Raja, Batu Pahat Johor. Email: [email protected]

ABSTRACT. Jet grouting was used to stabilize the soil and the improvement technique which employs high-speed fluid  jets to erode soils. It is one of the most popular ground improvement technique due to its applicability applicability in almost all soil types. Grout is ejected through a lower nozzle to mix with and displace the soil slurry. The objective of this investigate is to determine the soil stability of soft clayey and sandy soil using Rodin Jet Pile (RJP) method, and determine the upheaval forces in the soft soil using jet grouting method. In this project, the location of the case study is located at 3 places which is  Negeri Sembilan, Sembilan, Jalan Pahang and Shanghai. Shanghai. The content of this paper are based on studies, studies, case histories, and report from researcher and specialist contractor which are experienced in the field. Lastly, from the result from 3 case study that we have made, we can conclude that the Rodin Jet Pile (RP) method can be successfully applied in soft sand and the effectiveness of  jet grouting is depending depending on the selection of correct operating parameters parameters , it is expected more interest as the value of the technique.

1.0 Introduction Jet grouting was used to stabilize the soil around the perimeter and bottom of the excavation. The technique of  jet grouting uses high pressure/velocity jet fluids to erode the existing soil and then to mix the cuttings with cement slurry to form soil Crete. It is a versatile erosion based system used to create in situ engineered geometries of soil-cement generally with limited required access. Jet Grouting creates in-situ columns of grouted soil using very high pressure grout injection. Grouting is performed by pumping high velocity jets of grout (or sometimes grout and air or grout, water and air) through the side of a grout monitor, attached at the end of the drill string. The jets erode and mix the soil as the drill string and the monitor are being rotated and withdrawn. The jet grouting process constructs  jet grout panels, full columns or anything in between (partial columns) with designed strength a nd permeability. Jet Grout column size is dependent on soil type, soil density, injection pressures and flow rates of the various fluids employed, rotation speed, lift rate and type of system used. It is best practice to perform a preconstruction test program to calibrate, adjust and verify jet grout parameters and the design

2.0 Case Study 2.1 Case study: sludge treatment plant using jet grouting on soft soil in Negeri Sembilan, Malaysia. 2.1.1 Introduction A temporary non-strut retaining system by jet grouting constructed to facilitate the construction of sludge treatment plant in Port Dickson, Negeri Sembilan. Jet grouting used to stabilize the soil around the area and the  bottom of the excavated ground. Table 1. Excavation Depth

1. 2. 3. 4.

Structure Sludge digester Raw sludge storage tank Return liquor storage tank Pumping station

Excavation Depth (m) 11.0 7.0 8.0 4.0-8.0

Table 2. Site Condition (Bore Logs) Depth (m) 3.0 –  3.0 – 7.5 7.5

The Standard Penetration test SPTN 0 - 20 blows/ 300 mm

7.5 –  7.5 – 12.0 12.0

5 – 20  – 20 blows / 300 mm

12.0 -16.0

20 –  20  – 40 40 blows / 300 mm

˃ 16.0

˃ 50 –   50 – 40 40 blows /300 mm

Type of soil Very soft sandy silty clay

Stiff clayey sandy silt, containing some sand and gravel Very stiff to hard clayey silt Very hard clayey silt (weathered Schist) & very clayey silty sand, a lot of gravel

Table 3. Design soil parameter for each stratum

2.1.2 Location On a clear plot land with a Shell Oil Refinery on one side and housing residential. Minor contamination of the soil by oil sludge observed on site, however this not considered to pose any serious obstacles for the jet grouting method to works on it.

Fig 1. Photos of the location of the site and the contiminated soil by oil

Fig 2. The contiminated soil by oil

2.1.3 Material Specification Specification of grouted soil to be achieved were made after taking account the soil properties: i. ii. iii.

Undrained shear strength, Cu = 300 kN/m² Young’s Modulus, E = 120000 kN/m² Bulk density, Ƴ = 18 -20 kN/m²

2.1.4 Analysis By using PLAXIS V.7.1, a two-dimensional finite element analysis program. Displacement around the excavation and the strains in both untreated and treated soil element were determined. 3 Stages of analysis i. ii.

The excavation foundation level & lowering of the groundwater groundwater level The application 10 kN/m² surcharge adjacent to excavated trenches. iii. Evaluation of factor of safety (FOS) for excavation trenches

2.1.5 Results The calculation been made, the failure will occur if excavation were proceed in the untreated soil. While for the  jet grouted soil, the FOS calculated after excavation depth reaches final excavation and the lowered lo wered of ground water, the analysis indicate the FOS is above required value is 1.25.

2.1.6 Implementation Table 3. The operating parameters used to form the jet grout column

2.1.7 Project review Overall, pro executed smoothly started April 2002 and completed by August 2002 (4 months period). T his is not APG Geo-system’s Geo-system’s first jet grouting job and its experience suggests that jet-grouting can reliably designed for the construction of retaining walls in Malaysia. The geotechnical engineers involved also indicated that the company would further promote jet grouting retaining wall construction and other geotechnical structure  project.

2.2 Case study: jet grouting for soil stabilization, Shanghai, China. 2.2.1 Introduction This case study was conducted by Z.F. Wang, S.L. Shen, C.E. Ho and Y.H. Kim. It was located at Shanghai, China and South Korea. Jet grouting is a soil treatment technique for stabilizing soft ground by mixing cement slurry with in-situ soil. Jet grouting has been widely used for soft ground modification in various underground  projects to form base seals and buried grout struts for deep excavations, structural support around tunnel eyes at the entrance and departure sites of tunnel boring machine, as well as sealing of leaking joints in diaphragm walls. The jet grouting involves the injection of cement slurry under high pressure from a nozzle fixed on a rotating monitor into the ground. The resulting high speed fluid jet erodes the in-situ soil and simultaneously mixes it with cement slurry to form a soil cement column. Some applications have indicated that the shear strength of the soil-cement column could reach to several mega pascal (MPa). This study focused on demonstrate the performance of Rodin Jet Pile (RJP) method in the soft clayey and sandy soil in Shanghai,

China and Twin-jet method in sandy soils in South Korea. But, for our project we only focused on Rodin Jet Pile (RJP) method for soft clayey soil in S hanghai, China.

2.2.2 Objective 

To determine the soil stability of soft clayey and sand y soil using Rodin Jet Pile (RJP) method.

2.2.3 Methodology And Result 1) Rodin Jet Pile (RJP) Method The construction site in this project was located along the west bank of the Huangpu River in Shanghai. The tunnel was constructed using open cut excavation. The total length of the excavation was about 250 m with a depth of 43 m. A diaphragm wall system served as the retaining wall for the excavation. The diaphragm wall was 1.2 m thick and 65 m deep. The subsurface profile consisted of backfill, clayey silt, soft normal consolidated marine clay, stiff dessicated silt clay, medium sandy silt, and dense silt sand (Figure 1). The ground water level fluctuated between 1 to 2 m below the ground surface. The backfill layer was 7.5 thick with undrained cohesion of 10-20 kPa. The clayey silt layer (CS) varied from lowly to highly compressible, with natural water content approximately equal to the liquid limit and a rather uniform cohesion of about 10 kPa. The marine clay was medium to highly compressible with high water content that were high significantly higher than the liquid limit. The cohesion strength of the marine clay increased with depth ranging from about 15 to 35 kPa. The stiff silty clay layer was of very low compressibility, with natural water contents less than 25% and high cohesion of 40 to 50 kPa. The sandy silt exhibited a rather uniform strength with the cone resistance averaging about 12 MPa. T he  bottom silty to fine sand sa nd layer extended over a thickness of 17 m with CPT resistance greater than 12 MPa and increasing with depth.

Figure 3. Geotechnical profile and soil properties at the RJP test site (after Shen et al. 2009b)

Field trials were conducted to confirm the efficacy of RJP installation in the various soil deposits (Figure 2). Four sets of test columns (labeled as ST, C1, C2, and C3) were installed. Test column ST was installed from the ground surface prior to the excavation. Columns C1, C2 and C3 were installed along the alignment of jet grout wall using standard RJP parameters to confirm the efficacy of RJP in different types of soils. C2 and C3 were used to verify the relationship among diameter, strength, and jetting parameters. The field trials showed that the eroding ability and uniformity of mixing in the various soil layers were significantly different. Within the backfill, clayey silt, and marine clay (from ground surface to a depth of 25 m), the columns were very well formed and the cement was uniformly mixed with the in-situ soil. The column within the stiff clay layer (from the depth of 25 to 29 m), also demonstrated a good quality. However, the diameter of the columns were limited to about 0.8 to 1.2 m due to the poor erosion in this soil layer. For the sandy silt and silty sand (layers below 30 m depth), the eroded distance was much larger than that in the stiff

silty clay. However, the uniformity of mixing in these two layers was observed to be very poor. In general, the diameter of the solidified columns varied between 0.8 m and 3.3 m, and the unconfined compressive strength (UCS) after 28 days was between 0.9 and 8.1 MPa

Figure 4. Layout of test columns using the RJP method (after Shen et al. 2009b)

2.2.4 Conclusion This paper provides an overview about RJP method in Shanghai, China. With the progress of urbanization worldwide, the applications of jet-grouting method have been confronted with more challenging situations than those before. Greater attention was focused on the installation process, resulting in the development of the RJP technology in Shanghai, China. The application of jet grouting technique, as a soil stabilization method was applied. Jet grouted piles have been proven to be a suitable choice for this condition. From the case study before, Rodin Jet Pile (RJP) method in the soft soil deposits of Shanghai, China indicated that large diameter columns with high quality mixing can be achieved in clayey soil. In sandy soil, although column diameters up to 2.0 m were obtained, the uniformity of the resulting soil cement mix with the column was highly variable with unconfined compressive strengths ranging from 0.9 to 8.1 MP a.

2.3 Case study: proposed commercial building using jet grouting at Jalan Pahang, Kuala Lumpur, Malaysia. 2.3.1 Introduction Jet grouting is use at Jalan Pahang , Kuala Lumpur is proposed to prevent upheaval and other undesired soil movements. This will create a firm base in which the micropiling machines may be seated subsequently. The concept for using jet grouting for this project is to resist the upheaval forces in the soft soil. This solution can help to avoid the boundary constraints problem with sheet piling.

2.3.2 Objective 

To determine the upheaval forces in the soft soil usi ng jet grouting method. Table 4.

Layer

Depth (m)

Thickness (m)

Design parameter for various soil strata. Unit wt    ( 3

k N  / m )

Friction angle

 

Cohesion c

u

2

SPT N-value (blows/300m m)

( k N  / m )

1

0.0-7.0

7.0

18

2

7.0-18.0

11.0

18

28-30

 o

Young‘s modulus E 3

( k N  / m )

25

5 - 10

6250

0

4 - 10

3000

3

18.0 18. 0 on

-

22

42

 o

-

-

200000

Fig 5. View of entire site

Fig.6 Jet grouting slope covered with plastic

2.3.3 Methodology And Result The soil at the site consist of deep layer of medium to stiff clayey silt 7m near the surface. Below is deep layer of soil varying from loose sand to slime/very soft clay in 11m . Further down a bedrock layer of karstic limestone , commonly found in Kuala Lumpur area. In jet grouting , a pressurized fluid jet hydraulically cuts into soil before grout is mixed into the ensuing soil slurry. The cutting jet is typically located at the tip of a modified drill bit. As the jet rotates , soil is eroded in a radial pattern at the level of the jet . The drill is lifted from the bottom of the borehole and grout is injected to the cutting lid.The in-situ soil will cut and broken by high pressure jet of slurry and produce homogenously improved zone around the mechanically mixed core. This were carried out by using a series of 1.2 - 1.6 m diameter columns placed in a 1.4 m c/c square grid were grouted using a dual -fluid system. Columns range from 2.6 m to 10 m in length. Approximately 9000 linear meters of columns were grouted in the total for th e project. Table 5. Operating parameters used in jet grouting Jalan Pahang site. Operating parameter

Range /value

 Nozzle diameter diameter

2.8-4.0 mm

Grout injection pressure

200bars

Grout flow rate Air flow rate Rod withdrawal rate

0.05-0.06

m

3

/ min

3

2-3 m / min 12-14 min/

Rod rotation rate

5-10 rpm

Water - cement ratio

0.5

Cement content

600

m

kg / m3

For the project in Jalan Pahang , Kuala Lumpur , there are some problems that is the limestone formation within the local area was either extremely porous or contained fissures or cavities. So , the solution that are made is pre-drilling jet grouting points to minimize heave and spillage. For the final actions for the  projects is removal f the hardened grout to restore the ground profile to its original state.

2.3.4 The system in Jet Grouting.

Fig 7. Jet Grouting System

2.3.5 Conclusion The evolution has come with the passage of time and the accumulation of experience. From the many histories examined , jet grouting has received good reviews of being able to perform better under extremely demanding geotechnical conditions. It is expected that jet grouting will be elevated as the status of a primary design solution offered by many. The effectiveness of jet grouting is depending on the selection of correct operating parameters , it is expected more interest as the value of the technique.The jet grouted blanked work as expected and there were no major problems aside the spillage issue. The only major technical problem is the formation of the sinkholes during the micropiling stage.

3.0 Literature Review 3.1 Jet grouting technology 3.1.1 Conventional Jet Grouting System a. Single Fluid Jet Grouting The single fluid system is the simplest. Grout is pumped through the rod and exits the horizontal nozzle(s) in the monitor at high velocity. This energy breaks down the soil matrix and replaces it with a mixture of grout slurry and in situ soil. Single fluid jet grouting is most effective in cohesionless soils.  b. Double Fluid Jet Grouting The double fluid system is the simultaneously injection of high velocity grout stream within a cone of compressed air. The double fluid system is capable of creating a larger column column than the single fluid system. system. The double fluid system is more effective in cohesive soils than t he single fluid system. c. Triple Fluid Jet Grouting The triple fluid system is the most complicated jet grouting system due to the simultaneous injection of three different fluids, air, water, and grout. Grout emerges at a lower velocity from separate nozzle(s) below the erosion jet(s). This separates the erosion process from the grouting process and tends to yield a higher quality soil-cement mix.

Fig 8. Schematic view of jet grouting technology

3.1.2 Jet Grouting Applications Some key advantages of jet-grouting technology are the easy and safe installation processes without unwanted disruption to other operations. This often results in reduced construction time when compared to alternate and competing systems. When used as a soil improvement technique for building foundations, jet-grouting eliminates ground vibration often associated with other soil improvement technologies. This benefit is of  particular importance in dense urban environments where unwanted vibration during construction may damage the surrounding facilities. Several case histories of jet-grouting are available in construction literature. These uses range from a simple groundwater cut-off wall to more complex applications, such as structural underpinning. A typical list of  jet-grouting applications, illustrated includes:       

excavation support; shoring (temporary and permanent); access shaft; various foundation structures (footings and slabs); single pile with or without steel reinforcement (casing or bars); underpinning of existing structures; and tunnel liners (stabilization).

3.1.3 Radin Jet Pile Technology A variation of the conventional triple-fluid system, called RJP technology, was introduced ny Tsujita (1996). In RJP technology, both water and grout jets are simultaneously injected under high pressures (Shen et al 2009b), such that the soil is subjected to two stages of erosion, initially by the water jet, then followed by secondary erosion by the grout jet. The exposure of the soil twice to the cutting action of the jets enables a larger column o  be formed.

Fig 10. Illustration RJP technology

4.0 Conclusion The jet grouting method has matured to sufficient degree that contractors are comfortable and usually used with prescribing it routinely under certain circumstances. The evolution has come with the passage of time and the accumulation of experience. Projects using jet grouting in various types of soil s and for various purposes have been performed performed and their records form a knowledge knowledge base upon which future studies and works works can draw and build upon. From the many case histories examined, jet grouting has received good reviews of being able to  perform well under extremely demanding demanding geotechnical conditions. Based on the case studies , jet grouting method has been completed. Background theory covering jet grouting operation, the different type of cases that can be solved by using jet grouting method, the design of jet grouting works that suitable for the site use that has been presented. Select case histories presenting jet grouting used in different settings have also been described, with two case studies of jet grouting in the Malaysian environment examined in detail. As good jet grouting design involves an intricate web of practical and theoretical considerations, actual figures from studies and case histories have been presented where possible. The effectiveness of jet grouting is very depend on the selection of correct operating parameters, making it a method in which practical experience is crucial. It is expected more interest will be generated as increasing numbers of geotechnical contractors see the value of investing in the technique. Jet grouting is still in a growth stage, and the future should only see more development as construction community become more familiar and comfortable with the technique.

6.0 References 1.

2. 3.

4. 5. 6. 7. 8. 9.

10. 11. 12.

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