BAUER Soil Improvement

Transcription

1 BAUER Soil Improvement

2 a fast and economic solution 2

3 3 In the 1960s Bauer started performing ground improvement. The first vibrator for vibrocompaction was created in 1962 under the supervision of Dr.-Ing. Karlheinz Bauer. In areas where the subsoil has an insufficient bearing capacity, vibrocompaction or vibroreplacement can be a faster and cost efficient solution in comparison to deep foundations. Soil improvement is often used for land reclamation projects as well as oil and gas or infrastructure projects.

4 More than 45 years experience Some of our highlight projects: 1962 Development and construction of the first Bauer vibrator for vibrocompaction, based on a hydraulic driven engine 1971 Collini-Center, Mannheim, Germany Vibrocompaction up to a depth of 12 m 1975 Las Palmas, Grand Canary Vibrocompaction of 250,000 m³ of the so called Picon material (a volcanic slag) 1978 Thuwal, Kingdom of Saudi Arabia Vibrocompaction with 160,000 lin.m for a new harbor construction working from a ponton 1988 Cardiff, United Kingdom Installation of 24,000 lin.m of stone columns with a length of 9 m to 10 m for the ring road 1990 Singapore Securing of dams against settlement and shear failure by installing 230,000 lin.m of stone columns 1995 Vancouver, Canada Delta Port, vibrocompaction of 1.5 Mio. m³ of fill, working from a ponton to a depth of approximately 31 m 1999 Schleuse Hohenwarte, Germany 28,000 lin.m of vibrocompaction up to a depth of 30 m 2004 Palm Jumeirah, Dubai, UAE Soil improvement of the crown, 500,000 m² vibrocompaction 2005 Peribonka Dam, Canada Vibrocompaction of 700,000 m³ of the fills and partially the river deposits at the main dam base up to a depth of 35 m 2009 Cleveland Clinic, Al Sowah Island, Abu Dhabi, UAE Vibrocompaction of 90,000 m² to a depth of approximately 10 m 2012 Davao City, Philippines Vibrocompaction of 100,000 lin.m up to a depth of 18 m Ocean Reef Island, Panama Vibrocompaction of 100,000 m² up to a depth of 15 m

5 Soil improvement is a special foundation technique to improve the soil characteristics such as the relative density or Young s modulus of elasticity. The technique is required in cases where the bearing capacity of the subsoil is not adequate for the General planned construction. In addition, a mitigation of earthquake induced liquefaction can be obtained. In comparison to piles or barrettes (which describe columnar elements that transfer loads), the subsoil will be considered as an improved soil continuum. Bauer offers two different techniques: Vibrodisplacement to install stone columns and Vibrocompaction also known as vibroflotation 100% Clay Silt Sand Gravel Stone 90% Values of P (%), by Weight 80% 70% 60% 50% 40% 30% Vibrodisplacement Vibrocompaction 20% 10% 0% Particle Size (mm) The table shows which ground conditions suit vibrocompaction and which suit vibrodisplacement (stone columns) Vibrocompaction Applicable in non-cohesive soil with a maximum fine content of 10 % such as sands or gravels. During the movement of the vibrator the solid part of the matrix will be floated and afterwards compacted, with the result that the void ratio of the matrix decreases. Vibro Compaction Matrix (loose material) Flotation Matrix (dense material) Vibroreplacement Applicable in mixed grained or cohesive soils, such as sandy silts to finegrained soils with undrained shear strength values ranging from 20 to 100 kn/m² by assembling compacted coarse grained backfill material (stone aggregates). 5

6 Why Soil Improvement? During the planning stage of a construction project, a soil investigation is usually carried out at the proposed site by a geotechnical specialist who assesses the bearing capacity of the subsoil and recommends possible types of foundation. Normally, the subsoil provides adequate bearing capacity without special foundation measures being required. If the geotechnical specialist comes to the conclusion that the subsoil does not have sufficient bearing capacity, various solutions are available, such as soil improvement or deep foundations. Advantages of Soil Improvement No excavation material, therefore no cost impact resulting from transportation and no dealing with contaminated soils. Simple foundation conditions, similar to natural subsoils with an adequate bearing capacity. The technique is highly adaptable. In general, no groundwater lowering required during installation phase. Therefore no requirements for permits and no risk to adjacent buildings. Environmentally compatible by using only natural materials. By providing high level technical supervision and workmanship throughout the project execution and understanding the interaction between subsoil and structure, it is possible to fulfill the design requirements like increasing the bearing capacity and mitigating liquefaction. In many cases, soil improvement offers an economical and fast method for improving the engineering characteristics of the prevailing subsoil. Pile Subsoil with an adequate bearing capacity Improved subsoil (by vibrocompaction or vibroreplacement) Subsoil with an adequate bearing capacity Different subsoil conditions and possible foundation solutions 6

7 Vibrocompaction Granular or weakly cohesive sediments (fines less than a maximum of 10 %) such as gravel or sand often have very uneven layer densities in their natural state. With vibrocompaction the relative density can be increased up to around 80 %. In the Techniques process, the soil is floated by a water or air flush, the vibrator sinks and a settlement depression is formed at surface level. This is filled with additional material. By extracting the vibrator in stages, a compacted zone 2-4 m diameter is created. The upper meters of subsoil cannot be compacted effectively by the vibrocompaction technique only. These areas must be compacted by surface compaction techniques like rollers or similar. Vibroreplacement Using vibroreplacement technique, the added material is transported directly to the vibrator tip (bottom feed method), compacted by multiple displacement stages and pressed into the surrounding soil. This creates a crushed rock or gravel column which improves the surrounding soil due to the higher rigidity of the additional installed material. The selection of the most suitable technique depends primarily on the ground conditions, the loads to be carried and the boundary conditions. 7

8 Regarding vibrocompaction we investigate the improved soil by field tests such as CPTu or SPT. In case of vibroreplacement we estimate the soil conditions of the Design improved layers by using the theory of Priebe, which is common practice all over the world. The following diagram (Priebe, 1995) gives you an impression of how to assess the so- called improvement factor by a given friction angle of the stone column (φ s ), the area ratio and an assumed Poisson s ratio of the soil (μ B ). 6 Improvement Factor n φ s = 45,0 φ s = 42,5 φ s = 40,0 φ s = 37,5 φ s = 35,0 μ B = 1/ Area Ratio A/A c As an alternative for the assessment of the settlement it might be reasonable to use FE-Applications. The results can give you a better impression of the behaviour of the stone column in different layers. Through FE-Calculations you can also assess the bulking effect in soft layers. 8

9 Testing The execution of the so-called Cone Penetration Tests (CPT) is the most common practice to investigate the success of soil improvement, especially for vibrocompaction. The resulting graphs display for example the cone resistance against depth and friction ratio. Cone Resistance q c [MPa] Depth [m] The graphs of a CPT can be used to evaluate for example the soil type and the Young s modulus. In addition, it is possible to assess the liquefaction mitigation due to soil improvement works. To prove the success of a soil improvement by vibroreplacement, a zone load test can be executed. In this case for example, a concrete plate will be manufactured, set in place to cover a number of stone columns and loaded in stages (dead load test) or as an alternative you can use a kentledge test. The settlement during the different load stages will be recorded, so you receive the load settlement behaviour of the improved soil. Concrete block (kentledge) Beam Load dispatcher (e.g. timber mat) Load cell Hydraulic jack Kentledge support Dial gauge extensometers Reference beam Reinforced concrete test base 9

10 Quality Based on extensive experience Bauer uses methods, equipment and techniques which allow safe execution of soil improvement projects. All process-specific production data are monitored and displayed on the B-Tronic monitor inside the operator cabin for quality purposes. Electronic data acquisition of all relevant production data for documentation purposes is also carried out by the B-Tronic system. By deploying our professional employees on all our projects, Bauer guarantees the quality of the soil improvement works. Documentation and quality management happens in accordance to the rules of DIN EN ISO Equipment TR 75/TR Head piece with 2 flushing connection TR 17 R Follower pipe Ø Joint (Isolator) Ø Poker with wear shield and flush holes Ø [115] 900 The horizontal centrifugal forces of the deep vibrator are generated by a hydraulic motor and an oscillator inside the vibrator section. When deploying deep vibrators in conjunction with customized Bauer base machines, the required hydraulic power can be provided by the base machine itself (BG, BF or MC) or by a separate hydraulic power pack, for example the HD 460. Bauer uses two different vibrator types, the TR 17 and the TR 75/TR 85. The TR 17 can reach a penetration depth of up to 25 m and the TR 75/TR 85 up to 45 m. 10

11 Projects Worldwide Palm Jumeirah, Dubai, UAE For the Palm the Emirate of Dubai builts a 7,000,000 m² artificial island off Jumeirah Beach to house hotels and luxury villas. Most of the area was compacted by 17 Bauer deep vibrators. Port of Balboa, Panama In the port of Balboa on the pacific coast of Panama, Bauer Fundaciones Panama compacted some 15 hectare of newly reclaimed land down to a depth of 22 m. The improved ground is being utilized to extend the second largest container terminal in Latin America and will in future be capable of withstanding all kinds of loads that such use demands. Cleveland Clinic, Abu Dhabi, UAE In Abu Dhabi, on Al Sowah Island, the 90,000 m² Cleveland Clinic is under construction. Bauer deployed as many as ten TR 85 deep vibrators when carrying out vibroflotation densification to provide ground improvement of the 10 m thick alluvial sand layer. Highend I to III, Schindellegi, Switzerland In Schindellegi, Highend I to III, a housing estate at the hillside was constructed. For the necessary ground improvement 12,800 lin.m vibroreplacement (stone columns) were installed, comprising of 1,117 columns with a length of up to 12 m. 11

12 BAUER Spezialtiefbau GmbH BAUER - Strasse Schrobenhausen, Germany Tel.: Fax: BST@bauer.de /2014