38% radial-shrinkage of the thin-wall pipes made of 18Ni Co-free maraging steel after heat treatment was studied with hardness test,micrographs observation,and X-ray diffraction analysis.

The results showed that the major cause of reducing diameter was more non-metallic inclusion in the steel than standard value,billet segregation and shrinkage void.

The problem of reducing diameter has been taken a favorable turn by decreasing lifting speed of CFA and by setting up dewatering point well.

Because of complex formation structure, hole shrinkage, wellbore collapse and lost circulation are easy to occur, leading serious pipe sticking.

Effective calcium-treated mud was testing prepared for the underground salt-water environment with high sodium ion,and the serious pile hole shrinkage and un-position of steel reinforcement cage were solved.

Hole shrinkage often occurs while bored-grouting pile is constructed in expansive clay,the cause is analyzed with engineering practice,"interval construction" is discussed with the effect presenting,which solved the hole shrinkage problem.

Simulation and application of extrusion-sinking technology for thin-walled tube;

he deformation forces in each area are calculated by the basic areas and deformation characteristics of cylindrical tube sinking.

At present, the research related to positive-negative forming theory of revolving shell is imperfect in some aspects(such as push sinking mechanism of shell), and is deficiency in some aspects(such as forming mechanism of compound bulging).

Based on such analysis,some criteria and methods have been proposed for judging the situation of honeycomb,segregation,reducing,diameter extension,breaking zone and sedimentation on the bed of pile,etc.

The relationship of drilling fluid density and formation dip with borehole undergauge creep deformation encountered in salt beds in Xinjiang Oilfield drilling was studied.

The undergauge problem of top formation always affected the exploration and development of Tahe oilfield.

Many of related references at home and abroad were studied in the paper, Finite Element simulation research method was put forward as the main research method on the mechanism of borehole undergauge induced by formation creep.