Ultimate Lateral Capacity of Rigid Pile in c–φ Soil

To date no analytical solution of the pile ultimate lateral capacity for the general c–φ soil has been obtained. In the present study, a new dimensionless embedded ratio was proposed and the analytical solutions of ultimate lateral capacity and rotation center of rigid pile in c–φ soils were obtained. The results showed that both the dimensionless ultimate lateral capacity and dimensionless rotation center were the univariate functions of the embedded ratio. Also,the ultimate lateral capacity in the c–φ soil was the combination of the ultimate lateral capacity（f;） in the clay, and the ultimate lateral capacity（f;） in the sand. Therefore, the Broms chart for clay, solution for clay（φ=0） put forward by Poulos and Davis, solution for sand（c=0） obtained by Petrasovits and Awad, and Kondner’s ultimate bending moment were all proven to be the special cases of the general solution in the present study. A comparison of the field and laboratory tests in 93 cases showed that the average ratios of the theoretical values to the experimental value ranged from 0.85 to 1.15. Also, the theoretical values displayed a good agreement with the test values.

Response of carrying capacity of piles induced by adjacent Metro tunneling

Construction of tunnels in urban areas requires assessment of the impact of tunneling on the stability and integrity of existing pile foundations. We have focused our attention to the analysis of the carrying capacity of pile foundations provided by the impact of construction of urban tunnels on adjacent pile foundations, under the engineering background of the construction of the # 2 Line of the Guangzhou subway. It is carried out using a fast Lagrangian analysis of a continuum in a 3D numerical code, which is an elastoplastic three-dimensional finite difference model, to simulate the response of piles under the entire process of metro tunneling （deactivation of soil element and activation of the lining）. The adjacent stratum around the tunnel is classified into three regions： Zone Ⅰ （upper adjacent stratum of tunnel）, Zone Ⅱ （45°-upper-lateral adjacent stratum of tunnel） and Zone Ⅲ （lateral adjacent stratum of tunnel）. In each region one typical pile is chosen to be calculated and analyzed in detail. Numerical simulations are mainly conducted at three points of each pile shaft： the side-friction force of the pile, the tip resistance of the pile and the axial loading of the pile. A contrasting analysis has been conducted both in the response of typical piles in different regions and from computer calculated values with site monitoring values. The results of numerical simulations show that the impact on carrying capacity of the piles lies mainly in the impact of construction of urban tunnels on the side-friction forces and the tip resistance of piles. The impact differs considerably among the different strata zones where the pile tips are located. The complicated rules of side-friction force and tip resistance of piles has resulted in complicated rules of pile axial loading thus, in the end, it impacts the carrying capacity of pile-foundations. It is necessary to take positive measures, such as stratum grouting stabilization or foundation underpinning, etc, to deal with the carrying capacity and the settlement of pile-foundations. The results are of value to similar engineering projects.

Prediction of bearing capacity of pile foundation using deep learning approaches

The accurate prediction of bearing capacity is crucial in ensuring the structural integrity and safety of pile foundations.This research compares the Deep Neural Networks(DNN),Convolutional Neural Networks(CNN),Recurrent Neural Networks(RNN),Long Short-Term Memory(LSTM),and Bidirectional LSTM(BiLSTM)algorithms utilizing a data set of 257 dynamic pile load tests for the first time.Also,this research illustrates the multicollinearity effect on DNN,CNN,RNN,LSTM,and BiLSTM models’performance and accuracy for the first time.A comprehensive comparative analysis is conducted,employing various statistical performance parameters,rank analysis,and error matrix to evaluate the performance of these models.The performance is further validated using external validation,and visual interpretation is provided using the regression error characteristics(REC)curve and Taylor diagram.Results from the comparative analysis reveal that the DNN(Coefficient of determination(R^(2))_(training(TR))=0.97,root mean squared error(RMSE)_(TR)=0.0413;R^(2)_(testing(TS))=0.9,RMSE_(TS)=0.08)followed by BiLSTM(R^(2)_(TR)=0.91,RMSE_(TR)=0.782;R^(2)_(TS)=0.89,RMSE_(TS)=0.0862)model demonstrates the highest performance accuracy.It is noted that the BiLSTM model is better than LSTM because the BiLSTM model,which increases the amount of information for the network,is a sequence processing model made up of two LSTMs,one of which takes the input in a forward manner,and the other in a backward direction.The prediction of pile-bearing capacity is strongly influenced by ram weight(having a considerable multicollinearity level),and the effect of the considerable multicollinearity level has been determined for the model based on the recurrent neural network approach.In this study,the recurrent neural network model has the least performance and accuracy in predicting the pile-bearing capacity.

A new method of testing pile using dynamic P-S-curve made by amplitude of wave train

A new method of detecting the vertical bearing capacity for single-pile with high strain is discussed in this paper. A heavy hammer or a small type of rocket is used to strike the pile top and the detectors are used to record vibra- tion graphs. An expression of higher degree of strain (deformation force) is introduced. It is testified theoretically that the displacement, velocity and acceleration cannot be obtained by simple integral acceleration and differential velocity when long displacement and high strain exist, namely when the pile phase generates a whole slip relative to the soil body. That is to say that there are non-linear relations between them. It is educed accordingly that the force P and displacement S are calculated from the amplitude of wave train and (dynamic) P-S curve is drew so as to determine the yield points. Further, a method of determining the vertical bearing capacity for single-pile is dis- cussed. A static load test is utilized to check the result of dynamic test and determine the correlative constants of dynamic-static P(Q)-S curve.

Stability Analysis of Piles Subjected to Lateral Load in Static and Seismic Conditions

It is disclosed a method for the stability analysis of foundation piles and piers subjected to lateral loading, both static and seismic conditions. The stability analysis for stratified soil is based upon the models of foundation soil-structure interaction and the Rankine＇s theory of earth passive pressure. In addition, its application is simpler and it can be solved using a spreadsheet. The procedure described in this work can be used in homogeneous soils as in stratified soils, considers the horizontal drag forces exerted by the soil mass against the foundation during an earthquake, can be used easily in the four pile and piers boundary cases, and considers the pore pressure generated in a fine saturated soil during an earthquake or during a rapid application of the horizontal load. The solution of two examples are shown, one in static condition and one in seismic condition, detailing the procedure step by step.

Effect of soil set-up on the capacity of jacked concrete pipe piles in mixed soils

The increase in capacity of displacement piles with time after installation is typically known as soil/pile set-up. A full-scale field test is carried out to observe the set-up effect for open-ended concrete pipe piles jacked into mixed soils. Both the total capacity and the average unit shaft resistance increase approximately linearly with logarithmic time. The average increase rate for unit shaft resistance is 44% per log cycle, while the average increase for total capacity is approximately 21%. A review on case histories for long-term set-up indicates an average set-up rate of approximately 40%. Based on this, the mechanism of pile set-up is discussed in detail and a three-phase model is suggested.

Multifaceted Bioinspiration for Improving the Shaft Resistance of Deep Foundations

This paper describes the bioinspiration process to derive design concepts for new deep foundation systems that have greater axial capacity per unit volume of pile material compared to conventional deep foundations.The study led to bioinspired ideas that provide greater load capacity by increasing the pile shaft resistance.The bioinspiration approach used problem-solving strategies to define the problem and transfer strategies from biology to geotechnical engineering.The bioinspiration considered the load transfer mechanism of hydroskeletons and the anchorage of the earthworm,razor clam,kelp,and lateral roots of plants.The biostrategies that were transferred to the engineering domain included a flexible but incompressible core,passive behaviour against external loading,a longitudinally split shell that allows expansion for anchorage,and lateral root-type or setae-type anchoring elements.The concepts of three bioinspired deep foundation systems were proposed and described.The advantage of this approach was illustrated with two examples of the new laterally expansive pile in drained sand under axial compression.The finite element analysis of these examples showed that the new laterally expansive pile can provide considerably greater load capacity compared to a conventional cylindrical pile due to the increased lateral confining pressure developed along the expanded pile core.