Application of ANSYS 3D FEM in Studies of Surface Deformation Caused by Pipe Jacking

By using site observation data and establishing 3D model using ANSYS software, this paper has discussed the strain change of stratum stress during process of jacking-in and the impact of machine head on ground surface under different frontal resistances. Analysis of the two cases shows that soil pressure reaches its maximum point when the soil is right above machine head, and soil stress will gradually decline when machine head passes over it. It also shows that impact brought by pipe-jacking construction on stress change of the surrounding soil is limited. The thesis suggest that road surface should be consolidated and soil condition be improved before construction to prevent loss and disaster caused by road surface deformation, jacking force can be increased so that jacking efficiency can be enhanced when ground stratum is well filled with soil, but the frontal resistance facing machine head should be equal to surrounding soil pressure in order to avoid rise of ground surface.

Application of decision tree to selection of MTBM for adverse geological conditions

So many potential risks can be identifed for application of trenchless technology especially using microtunneling methods.Unexpected changes in ground conditions,such as encountering boulders,tree roots,ground water and man-made structures such as old foundations are the principal geotechnical risks,which affect the selection of an appropriate microtunnel boring machine.On the other hand,the performance of each microtunneling technique will differ while encountering such conditions.Hence,predicting the potential hazards provides a better safety and risk management plan.In this study,a couple of potentially hazardous situation,which are commonly associated with ground conditions,were identifed and investigated.A decision tree aid methodology was proposed based on geotechnical risk assessment for selection of proper microtunneling technique.Based on the approach the most appropriate microtunneling technique has the minimum risk level either before or after hazards mitigation measures.In order to check the effciency of the approach in practice,selection of microtunnel boring machine for Hamadan sewerage pipeline project was evaluated.Accordingly,an earth pressure balance(EPB)MTBM was selected for the project.

Bionic Design to Reduce Jacking Force for Trenchless Installations in Clay Soil

The application of trenchless technology is the trend of underground public facilities'installation,replacement and repairing.As the soil-engaging component during penetrating bore,the working resistance of penetration head has remarkable effect on energy consumption of the whole working process.Some typical soil-digging animals,like pangolin and earthworm,they own special micro structures on their surface.It has been widely proved that some micro geometrical structures can effectively reduce adhesion resistance.Four kinds of bionic penetration heads were designed by imitating micro geometrical structures inspired by the soil animals.In this work,the real time jacking forces of the bionic penetration heads were measured and compared with a smooth penetration head(control group)without micro geometrical structures.The result indicated that the jacking forces of the bionic penetration heads were smaller than that of the smooth penetration head.This proved that the bionic penetration heads have the ability of reducing adhesion resistance.The vertical concave penetration head got the smallest jacking force,of which the average jacking force was 18.7%lower than that of the smooth penetration head.The interaction between soil and bionic surface of penetration head was discussed on the condition of wet friction.The bionic surface reduced the adhesion resistance by disturbing the soil and braking the continuous water film between soil and the surface of the penetration head.

Experimental study of the separated joint of an underground pipeline rehabilitated by cured-in-place pipe

Reinforced concrete pipes(RCPs)were commonly used in older underground pipelines in Taiwan,China.However,their joints are prone to damage,including fracture and separation,from problems such as overloading,poor backfilling,and liquefaction.For the rehabilitation of such aged pipelines,trenchless methods are preferred to minimize the impact on transportation.The cured-in-place-pipe(CIPP)rehabilitation could be one of the most popular trenchless methods suitable for the cases with angular alignment and changing cross-section.However,according to the existing standards,no details are available on the performance of the rehabilitated parts of the damaged pipeline,including the effect of separated joint.This study designed and conducted laboratory testing on the composite pipe joint(the CIPP rehabilitated RCPs with a separated joint)with different scenarios,including radial and longitudinal loading tests.The radial test results indicated that,for a small separation distance,CIPP rehabilitation can restore the original function of a pipeline and improve its hoop strength.The longitudinal test revealed that the damage due to bending was controlled by the tensile strength of the liner material.The ultimate flexural strength decreased as the separation distance increased.However,pipelines may be subjected to additional loads due to flotation or subsidence,for which the longitudinal loading capacity is often the limiting parameter.For such conditions,it is necessary to confirm,by more research,whether the wall thickness is sufficient.