A critical review on idealization and modeling for interaction among soil–foundation–structure system

In a general sense, control can be described as a cyclic sequence of observing, planning, and executing new actions. Similar to the human body, robotic devices are being equipped with a wide variety of sensors for the purpose of acquiring the needed information for planning and replanning. Because of the harsh work environment, construction robots, such as autonomous excavators, depend on hardened and reliable sensory systems, thus limiting the choices for selecting sensors. For control purposes, the sensory data need to be evaluated for decision‐making purposes. The intelligence for this endeavor has to be based on a thorough understanding of the meaning of the sensory data and high confidence in the appropriateness of future actions. In addition, a special obstacle‐avoidance concept is needed to prevent collisions and other types of accidents. The present paper discusses methods for both motion control and path planning for backhoe excavation. Experimental laboratory data are used to verify theoretical ...

Motion and Path Control for Robotic Excavation

A verified finite element model will be a cheap and useful tool in the development procedure of subsoilers and other soil loosening devices, and can be used to investigate and analyse the performance of resulting prototypes. This study was undertaken to emphasis that the finite element method (FEM) is a proper technique to model soil cutting processes in non-homogeneous soils. This method was used to investigate and analyse soil loosening processes. The effect of geometry on subsoiler performance was investigated by the FEM and compared to results of soil bin tests for four subsoiler geometry types; S1 – vertical shank with 31° angle inclined chisel, S2 – vertical shank with 23° angle inclined chisel, S3 – vertical shank with 15° angle inclined chisel and S4 – 75° rake angle shank with 15° angle inclined chisel. The research was done at the Department of Agricultural and Environmental Engineering, PANNON Agricultural University from 1995 to 1997. A three-dimensional FEM model was developed for cutting of non-homogeneous sandy loam soil by a subsoiler having a chisel and shank with different angles and effective cutting widths. The numerical analysis was performed with COSMOS/M 1.71 FEM software (Structural Research and Analysis Corporation, CA). The soil material was considered as elastic-perfectly plastic, and the Drucker–Prager elastic-perfectly plastic material model was adopted with the flow rule of associated plasticity. Soil-tool interaction was simulated adopting Coulomb's law of friction. Total draught force calculated from the FEM model for different subsoiler geometrical types ranged from 12.43 to 15.32 kN. For the S2 subsoiler, that had a vertical shank and an inclined chisel of 23° angle, the chisel and shank contributed to the total draught force by nearly 60 and 40%, respectively. The FEM model consistently over-predicted the measured subsoiler draught force at all chisel angles. The over-prediction of draught estimation ranged from 11 to 16.8% for a non-homogeneous model and from 15 to 18.4% for a homogeneous one. The smallest draught force, measured (11.20 kN) and predicted (12.43 kN), was recorded for the S4 subsoiler having a shank of 75° rake angle and a chisel of 15° angle. The minor principal stress field showed positions of soil tensile failure situated beneath the chisel as well as within the upper soil layers. Zones under distortion (shear failure) were generated directly in front of the shank and along the whole cutting edge of the chisel extending along a hard pan layer. The S4 subsoiler would consume the least amount of energy and perform proper soil loosening. The FEM proved a good tool for modelling of non-homogeneous soils and development and analysis of subsoiler performance and soil loosening processes.

Finite element analysis of subsoiler cutting in non-homogeneous sandy loam soil

A general procedure based on polynomial expansion of yield function in terms of invariants of the stress tensor is proposed in the context of associated plasticity for isotropic materials undergoing isotropic hardening. The procedure can be used to evolve one or more models for a material by using appropriate laboratory test results. One of the functions showing invariance at ultimate and a single function to describe continuous yield and ultimate yield behavior is investigated in detail. Based on comprehensive series of bests on cubical specimens for different (geological) materials, a hardening or growth function is defined in terms of the trajectory of plastic strain and the ratio of deviatoric to total plastic strain. The predictions of the proposed model are verified with respect to the observed results from tests with different stress paths. The model provides highly satisfactory predictions for both stress‐strain and volumetric strain responses from various stress paths. The proposed model shows po...

Constitutive Model for (Geological) Materials

A mathematical model for predicting the behavior of narrow tillage tools in soils is based on a limit equilibrium analysis. Pertinent soil, tool and interface parameters influencing the tool performance have been identified and incorporated in the model. A comparison of predicted and experimental results is also included. Mathematical models based on emperical as well as semi-emperical methods have been developed to describe the soil-tillage tool interaction (Payne, 1956; Hettiaratchi and Reece, 1967; Hettiaratchi et al., 1966; Osman, 1964; Godwin and Spoor, 1977; McKyes, 1978; Desai et al., 1981). Even though the soil-tool interaction problem is three dimensional in nature, a majority of the models available are based on two-dimensional consideration (Hettiaratchi et al., 1966; Osman, 1964; Payne, 1956). In recent years some progress has been made toward the development of three dimensional models (Hettiaratchi and Reece, 1967; Godwin and Spoor, 1977; McKyes, 1978). However, most of these models are complex, and a sound mathematical background is essential to utilize them. Thus the need exists for more general and less complex models capable of predicting tillage-tool behavior in soils. Unlike costly experimental procedures, availability of such models would permit designers as well as researchers to develop with minimum effort a clear understanding of soil-tool interaction through parametric studies. Therefore, the overall objective of this study was to develop a generalized mathematical model and to examine its validity for predicting the tillage tool performance in soils..

A soil-tool model based on limit equilibrium analysis

A finite element procedure for the general problem of three-dimensional soil-structure interaction involving nonlinearities caused by material behavior, geometrical changes, and interface behavior is presented. The formulation is based on the updated Lagrangian or approximate Eulerian approach with appropriate provision for constitutive laws. Consideration is given to the mathematical and experimental aspects related to the important topic of development and adoption of a constitutive law for the geologic medium. development and use of an interface element to describe the three-dimensional interface behavior are described. The influence of cracking and tensile stress conditions in the soil and interfaces is allowed for by using the stress transfer approach. The procedure is verified by comparing predictions with observation of a structure (tool) pushed in the soil in a special soil-bin test facility.

H. V. Phan

Papers

Mechanics of Three-Dimensional Soil-Structure Interaction