A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering in Civil Engineering. Shamsul Alam at the Department of Civil Engineering, Khulna University of Engineering & Technology, Khulna-9203, Bangladesh. Shamsul Alarn entitled Ozaracterization of K/i u/an Subsoil and Settlement Response of This Soil Improved by Grant fills” has been approved by the Board of Examiners for partial fulfillment of the requirements for the degree of Masters of Science in Civil Engineering , Khulna University of Engineering and technology (KUET).
Head of the Department of Civil Engineering, Khulna University of Engineering & Technology (KUET) for his persistent courage to continue and complete this study. In the eastern side of this zone, the soil contains predominantly silt up to approx. 6m to 7.5m depth. From the experiment, it was seen that the bearing capacity was increased by replacing soft soil with granular materials (sand) at the bottom of the foundation up to 1.95 times than untreated soil.
It was thus shown that for constant depth ((D= 1 Bf) of compacted sand the bearing capacity was significantly increased until the width of the sand fill is equal to twice the width of the foundation. This shows that for constant depth (D1.5Br) of compacted sand, the load-bearing capacity was significantly increased until the width of the sand fill was equal to 2.5 times the width of the foundation.
Mattress Foundation for Boy's Hostel Building
Shallow Foundation Accommodating Large
Method of Determining Bearing Capacity from Test 162 Data
LIST OF TABLES
List of equation of secondary compression index and 142 references (after Bowles, 1997)
Summary of secondary compression index calculated for the 143 North zone
Summary of secondary compression index calculated for the 144 Middle zone
Summary of secondary compression index calculated for the 147 South zone
Natural moisture content and Atterberg limits with 9 respect to depth at Sonadanga (after Hassain and
Buoyancy raft foundation system at Goalkhali for five- 22 store)' hospital building (PWD, 2000)
Chart for calculation of efficiency exponent, 24 (Fleming et al., 1992)
Typical section of the strip-raft foundation system 28 (after Tan et al.,2004)
Relationship between skin friction and shear strength 31 (Fleming et al., 1992)
Variation of & with shear strength of glacial till 32 (Weltman and Healy, i978)
Bearing Capacity Factor (after Design of Pile 33 Foundation, 1994)
Typical borelog at Khulna University campus (after 35 Razzaque and Alamgir, 1999)
Construction of process of rammed aggregate pier( after 41 Fox, 2000)
Boringlogs at coastal plain (after Stamatopoulas and 44 Kotzias, 1985)
Standard penetration resistance versus elevation(after 44 Stamatopoulas and Kotzias, 1985)
Pattern of equidistant drains(after Stamatopoulas and 46 Kotzias, 1985)
Vacuum technique used at Hazawa Station, Japanese 47 national railway (after Lee et al. 1993)
Compactor was placed on a 2ft layer of crushed stone 58 (after Wu and Scheessels 1982)
Variation of Bearing Capacity with Increasing of Depth (D) for Constant B (BBf)
Nomenclatures
- General
- Geology of the Study Area
- Background of the Present Research
- Objectives
- Organization of the Thesis
- General
- Available Geotechnical Data
- Index Properties
Therefore, it is essential to develop a general understanding of the subsoil formation characteristics of this study area. Therefore, we tried to obtain general information about the subsoil of the studied area based on the data received from field and laboratory tests. Thus, the general information about the subsoil of this study area is formulated under this study for better information about the aforementioned subsoil, which can be helpful to planners and other concerned beneficiaries.
Although the KCC area is one of the oldest developed areas of Khulna district, only a few geotechnical field and laboratory data are currently available on the area. These do not correspond to the generalized geotechnical properties of the subsoil in the considered area. In addition, lack of proper understanding of the foundation system can lead to the collapse of the foundations of several buildings in the area.
The moisture content of the organic layer in the area of Chota Boyra (Khulna Medical College) was found to be in the range of 118% to 222%, while the moisture content of the clayey silt layer was found to be in the range of 35% to 40. The soil moisture content was close to the plastic limit, which for the soils varied from 30 to 40 percent and the liquid limit from 50 to 100 percent with the preconsolidation ratio in the order of 5.
LNV!
Consolidation Properties
- Compression Index and Coefficient of Consolidation
- Empirical Relations for Compression Index
- Pre-consolidation Pressure
- Coefficient of Secondary Compression Index (C(,)
Data from compressibility tests of fine-grained soils in the southwestern zone of Bangladesh for estimation of primary consolidation settlement are summarized in Table 2.7 (Serajuddin. 1998). From Table 2.8 it can be seen that the moisture content, wl, initial void ratio, e0 compression index, Cc, compression ratio, R and the coefficient of volume compressibility. The compression index (Cc) of compressible clay and silt has some empirical relationships with the liquid limit (wL), the initial void ratio (e0) and the natural moisture content (wa).
Virgin compression index, Cc can be calculated by different soil parameters such as liquid limit, natural moisture content, initial void ratio and plasticity index. Analysis of comfort parameters, including effective overburden (p' ) and estimated maximum preconsolidation pressure of the past (indicates that the clay and silt soil layers are predominantly normally consolidated in the Khulna area. However, slightly moderated over consolidated clay and silt layer appears to exist. in the southwestern zone of Bangladesh.
Secondary compaction and creep can be a dispersion process in the soil structure that causes particle movement, and they can be associated with electrochemical reactions and location. When soft soil deposits are preloaded or backfilled, subsequent primary settlements are essentially eliminated and significant settlement occurs during the economic life of the structure due to secondary soil compaction (Lee et al., I983). C8 can be directly estimated by 1D-consolidation test or it can be estimated by indirect relationship. The value of Ca R) for a variety of different soil types is shown in Table 2.11.
Ground Water Table
Foundation System for the Study Area
- Theoretical Background of Buoyancy Raft Foundation
- Case Study on Buoyancy Raft Foundation at Goalkahali Area .1 Geotechnical Data
- Foundation System
- Performance
- Theoretical Background of Piled Raft Foundation
- Case Study of Piled Raft Foundation at Klang, Malaysia .1 Geotechnical Data
- Foundation System
- Performance
- Theoretical Background of Deep Pile Foundation
- Case Study of Deep Pile Foundation .1 Geotechnjcal Data
- Foundation System
Due to some relief of the load, the raft settlement will also fall within permissible limits (Varghese, 2005). The ultimate capacity of a block containing the piles and the raft, plus that of the portion of the raft outside the periphery of the piles (Impe, 2001). Both temporary backloading and preloading techniques have been used to control long-term subsidence of the subsoil.
For this reason, the basic capacity of the piles in clay is determined in terms of the undrained shear strength of the clay, c, and a bearing capacity factor, N (Fleming et al., 1992). The point resistance of a pile embedded in soft clay is insignificant; this rarely exceeds 10% of the total capacity (Terzaghi et al., 1996). The skin friction around a pile shaft has been estimated in terms of the undrained shear strength of the soil, using the empirical factor x (Tomlinson, 1957).
The angle of internal friction of normally consolidated clays can be calculated in the case of long-term shear strength. Where, N(1 = Terzaghi bearing capacity factor, Figure 2.16 a = Vertical soil pressure at the top with boundaries AL = pile top surface.
Ground Improvement Techniques for the Study Area
- Case study of Rammed Aggregate Pier (RAP) at Beaverton, USA .1 Geotechnical Data
- Foundation System
- Performance
- Theoretical Background of Preloading without Vertical Drain
- Case study of Preloading without Vertical Drain .1 Geotechnjcal Data
- Foundation System
- Performance
- Case study of Preloading with Vertical Drains
- Cut Replacement Method for foundation in Khulna Universit, Building
- Geotechnical Data
- Performance
- Mattress Foundation for Boy's Hostel Building in Khulna Medical College Area
- Geotechnical Data
- Predicted Performance
- Shallow Foundation Accommodating Large Settlement
- Geotechnical Data
- Foundation System
The settlement of the RAP-supported foundation is estimated assuming that the hard RAP elements and the soft soil settle equally. For the same displacement, stress is concentrated at the top of the RAP element in proportion to the stiffness ratio of the RAP to the unimproved soil. The settlement component of the lower zone is calculated using conventional geotechnical settlement analysis assuming that the vertical stress intensity within the lower zone is the same as that of the bare base without the reinforced upper zone.
The combination of the settlements of these two areas represents the total long-term settlement. Since the sidewall of the cavities is non-uniform, the bond between the RAP and the soil matrix will be more effective. Therefore, the organic layer or organic interlayer may not reduce the capacity of the RAP.
The pier soil reinforcement method significantly increases the bearing capacity of the reinforced matrix zone and significantly reduces foundation settlement. When consolidation of the foundation soil is practically complete (90% of total settlement), the surcharge is removed and the new building is erected. The study shows that the sand piles significantly improved the bearing capacity of the natural soil.
The unconfined compressive strength, natural moisture content, liquid limit and SPT-N value of the upper 14 m thick soft clay layer ranged from 20 to 28 kN/rn2. A geotextile separator and filter layer was placed at the bottom of the excavation of the sofi clay layer. The modulii values of the aggregate layers were determined based on TRL fynetrometer tests and their indirect correlation with modulii.
Foundation bending for foundation cases for wall and column foundations is shown in Figures 2.35 and Figure 2.36. Settlement analysis showed that the final settlement resulting from the fill load itself was approximately equal to 33% of the height of the placed fill. Using pile foundations to avoid massive settlement of the building would cost US$400,000 for the piles alone.
- Performance
- General
- Identification of Sub-Soil Formation
- Identification of Sub-Soil in North Zone
- Identification of Sub-Soil in Middle Zone
- Identification of Sub-Soil in the South Zone
- Grain Size Distribution of Soil in the Study Area
- Organic Matter Content
- Specific Gravity
- Atterberg Limits and Natural Water Content
- Atterberg Limits and Natural Water Content in the Middle Zone
- Atterberg Limits and Natural Water Content in the South Zone
- Shear Strength Characteristics in Cohesive Soil
- Shear Strength Characteristics in Non- cohesive (Sandy) Soil
- Compressibility Characteristics
- Compression Index
- Secondary Compression Index
- General
- Statement of the Problem
- Work Plan
- Physical and Index Properties of the Soil
- Preparation of Artificial Soft Beds
- Techniques for Improvement of Soft Soil Bed
- Loading on Model Foundation for Untreated Soft Soil
- Loading on Model Foundation for Treated Soft Soil
- Load Test on Model Footing
- CC Footing
- Hydraulic Jack
- Dial Gauge
- Experimental Set-up
- Load Settlement Tests
- Method of Determining Bearing Capacity from Test Data
- General
- Load —Settlement Behavior
- Load - Settlement Behavior of Untreated Soil Bed (G-1)
- Degree of Improvement
- Effect of loading on Foundation for Constant Ds (Ds = BO with the Variation of Lateral Dimension of Sand Filling
- Effect of loading on Foundation for D= 1.5 Bf with the Variation of Lateral Dimension of Sand Filling
- Effect of loading on Foundation for D = 2B1 with the Variation of Lateral Dimension of Sand Filling (B)
- Effect of loading on Foundation for B = Bf with the Variation in Depth of Filling (D)
- Conclusions
The load test was performed on the treated base layer G-2, as shown in Figure 4.2a. The test was carried out on the treated base coat G-3 as shown in Figure 4.2b. The test was carried out on the treated base coat G-4 as shown in Figure 4.2c.
The test was conducted on the G-5 treated soil bed as shown in Figure 4.2d. The load test was performed on the G-6 treated soil bed as shown in Figure 4.2e. The test was conducted on the G-7 treated soil bed as shown in Figure 4.2f.
The test was carried out on the treated soil bed G-8 as shown in Figure 4.2g. The test was carried out on the treated soil bed G-9 as shown in the Figure 4.2h. The tests are carried out on the treated soil bed G-10 as shown in Figure 4.2i.
