- Estimation of static jacking load (P ep ) for the prestressed centrifugal concrete piles on some types of ground structure in Hai Duong city. - 1 DAVICO JSC, Hai Duong City, Vietnam. - Nowadays, the prestressed centrifugal concrete piles (PCCP) are applied in most major construction projects in Hai Duong city. - The pile bearing capacity and static jacking load (P ep ) are very important parameters for optimizing the pile foundation design, and they depend on the types of ground structure. - The paper introduces the estimated method for the pile static jacking load which was applied for two types of ground structure in Hai Duong city (type I and type II). - The results showed that the maximum static jacking load (P epmax ) was 66.6 tons and 76.6 tons at the depth of 32 m for types I and II, respectively. - K = 1.4 for firm sandy clay and K = 1.2 for soft soil.. - Hai Duong ground structure, Pile bearing capacity, Pile foundation, Prestressed centrifugal concrete piles,. - Static jacking load.. - Hai Duong city is located at the Red River delta with a wide distribution of soft soil aged Holocene at the shallow depth (Le Hong Quan, 2009).. - Currently, the demand for urban construction in Hai Duong city is on the rise. - Since the presence of soft soil is at shallow depth, the pile foundations are often used for most construction works. - With the pile foundation, these are two following technical requirements. - Firstly, the pile is not broken during transportation or ground driving. - In which, the static jacking load of the pile (P ep ) is an important factor that helps to estimate the bearing capacity of the pile (P đn ) as well as determine the maximum jacking load (P epmax. - The P đn value is used in pile foundation design, while the P epmax value is used to execute the pile. - manufacturing and the pile driving at the site.. - Normally, the parameter P epmax must be smaller than the bearing capacity of the pile material (P vl. - The estimation of P ep is especially necessary in the case of stratigraphy with intermediate soil layers.. - In some practical cases, P ep in the intermediate soil layers may be larger than the design value, causing the pile to break. - Therefore, it is necessary to estimate P epmax in the actual strata as the basis for P vl design.. - The PCCP is prefabricated with a fixed strength for each type of pile. - However, in the actual construction in Hai Duong, there are many cases that the bearing capacity of the PCCP is much higher than P epmax and P đn . - However, currently, there is no research on the estimation of pile static jacking load, especially for the soil ground structure in Hai Duong city. - Thus, in this study, the estimation of pile static jacking load for PCCP on some typical types of ground structure in Hai Duong city will be conducted.. - Theoretically, the bearing capacity of the pile (P đn ) is the sum of tip resistance (Q c ) and total friction (Q s ) (Prakash Shamsher, D, Sharma Hari, 1999). - The static jacking load P ep must overcome P đn for the pile to be driven into the ground at a certain depth so that P ep = K.P đn . - Q s - total sleeve friction of the soil around the pile.. - In which: A - cross-sectional area of the tip pile;. - U - circumference of the cross-section of the pile. - thickness of the soil layer. - f si - sleeve friction of the soil.. - u - internal friction angle of the soil (degree). - z - effective stress at a depth of pile toe (kN/m 2. - u ) are determined in an undrained condition corresponding to the pile pressing process.. - 2 ) (6) 𝑁 𝑐 = 𝐶𝑜𝑡𝑔𝜑 𝑢 (𝑁 𝑞 − 1) (7) 𝑁 𝛾 = 1,8(𝑁 𝑞 − 1)𝑡𝑔𝜑 𝑢 (8) In equation (1), the coefficient K depends on the soil type and the penetration speed, usually equals 1.5÷2. - It should be noted that when driving the pile through clayey layers, it often leads to the appearance of excess pore water pressure (U), which decreases the soil shear strength. - By contrast, driving the pile in sandy soil will make soil denser and increases the soil shear strength. - Thus, we can use the expression (1) to estimate P ep at different depths of the pile. - It is necessary to estimate P ep in each meter of the pile according to Vietnamese standards (TCVN 9394:. - The characteristics of ground structure in the study area. - Type I is most widely distributed in Hai Duong city area, including Pham Ngu Lao, Tran Hung Dao, Binh Han, Ngoc Chau, Nhi Chau, Cam Thuong, and Quang Trung wards. - arrangement order is soft soil - hard soil - soft soil - hard soil, narrowly distributed in the center of Hai Duong city with a radius of about 1.5 km 2. - On the basis of the ground structure characteristics described above, two research locations are selected to characterize the ground structure of two types: The first study site is in Truong An urban area (VT1), representing type I;. - In which, the shear strength of the soil is determined in undrained conditions for clayey soils and in saturated conditions for sandy soils. - The groundwater levels in both study sites have an average depth of 2 meters.. - Piles used in the two study sites are PCCP with. - Layers Depth of distribution. - (m) Soil type. - Soil type. - sandy clay . - Medium dense, fine sand . - Accordingly, the calculation of P ep is performed for each meter of the depth. - N q , N c determined by the formulas for the soil layer at the considered depth. - The results of P ep estimation in soil layers are summarized in Table 3.. - The estimated results of P ep depend on not only the pile size and soil properties but also the coefficient K. - In general, K is selected according to the soil type as mentioned in Section 2. - However, it is necessary to compare the calculation results with the actual data of pile jacking load at the site.. - Since then, K is selected suitably for each soil type.. - During the pile driving process, the actual jacking loads and speed parameters of the pile are recorded for each meter of depth.. - The estimated results of P ep and the actual data of pile jacking load are shown in Figure 4. - In which, K = 1.8 for fine sand. - When designing the friction pile foundation, the designer usually drives the pile into the bearing soil layer of 5÷10 m, depending on the load. - The estimated value of P epmax at a depth of 37 m (in bearing soil layer of 10 m) is 97.6 tons in VT1 and 90.7 tons in VT2. - However, in fact, it is not recommended to design the 300 pile beyond the depth of 32 m to ensure the requirement of pile limited slenderness. - The value of P epmax at a depth of 32 m is 66.6 tons at VT1 and 76.6 tons at VT2.. - Figure 3b shows that the actual jacking load at the depth of 5÷10 m is 30% higher than the calculated values. - The reason is that the density of loose sand increases significantly while driving the pile in sand.. - Results of P ep estimation.. - The pile driver ZYC180BS - B.. - When performing static driving of PCCP pile (300) to the depth of 32 m in Hai Duong city, P epmax is 66.6 tons in type I (VT1) and 76.6 tons in type II (VT2). - In-ground structure type I, P ep. - increases gradually with the depth of the pile.. - While in type II, P ep reaches 50 tons when driving the pile through the middle fine sand layer (layer 4) at a depth of 6÷10 m.. - The coefficient K is selected suitably for each soil type in the study area as follows: K = 1.8 for fine sand. - Depending on the design depth of the pile, the estimated P ep value can be used to prepare the jacking machines and counterweight. - Research on engineering geological problems occurring in the construction of basements for high buildings in Hai Duong City. - Establishment of ground structure zoning map in Hai Duong city area.. - Pile driving and static jacking work - Construction, check, acceptance
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