Cong Zeng

Study on Influence Factors to Application of Large-Scale HDD to Oil and Gas Pipe Installation

Horizontal directional Drilling (HDD) is widely used to install oil and natural gas pipes that have to cross river or lake areas in China. With low-cost, environment friendly, high-efficiency, HDD is recommended as the first alternative of the West-to-East natural gas transmission project. However, there are still lots of technology obstacles around large-scale HDD crossings, especially in gravel-cobble strata, soft-hard combining strata, and water sensitivity strata. In order to deal with these obstacles and find out the critical factors leading to troubles and failures during HDD crossing, this paper analyzes more than 12 cases of oil and gas pipe that were installed by HDD technology. Six normal troubles and seven potential factors will be involved to analyze the relationship between troubles and potential factors.

Preparation and recycling of drilling mud in large scale Horizontal Directional Drilling projects in Mainland China

The preparation and recycling of slurry is a very complicated and crucial task in large Horizontal Directional Drilling (HDD) river-crossing project. This paper introduced the successful and advanced experiences of the utilization and management of slurry in large HDD projects in China. Different property requirements of slurry in different periods of the project are discussed. Research is focused on the recycling system of slurry, including the filtration of slurry which returned from the drill hole, and how to add bentonite and additives in this filtrated slurry. The recycling of slurry can save a large amount of bentonite and additives. The disposal methods of waste mud in the job site were discussed, and two methods were recommended to be adopted to dispose waste mud. One is mechanical methods, using centrifugal machine; the other is chemical method, using chemical material to solidify waste mud.

Steel Curved Pipe Jacking Construction under Complicated Conditions for a Curved Pipe Roof

The Gongbei Tunnel is currently being constructed in Zhuhai, with a combination of curved pipe jacking roof for ground support and ground freezing waterproof applied, to guarantee the tunnel traverse under the Gongbei Port. This pipe roof is comprised 36 steel curved jacking pipe strings of 1620 mm diameter with 355mm~358mm gap between adjacent strings. The pipe jacking construction has been faced with various challenges due to the site conditions of multiple soft soil and high groundwater pressure. These challenges include risks of excessive soil deformation, possibility of path deviation, excessive jacking force, leaking of pipe joint seals and failure of gasketed launch seal and reception. This paper will provide an overview of this project and summarize the most challenging aspects they faced. The relevant techniques applied during construction, such as selection of pipe jacking machine, controlling trajectory of close curved pipe jacking, sealing test of pipe joint, pipe jacking mud in rich salt multiple formations and pipe jacking reception device under high underground water pressure are introduced in detail last.

Study on the Lining Design Methods for the Trenchless Rehabilitation of Urban Water Mains

With the frequent occurrence of pipe-failure accidents of urban water mains and the increasing application of trenchless rehabilitation technology in municipal pipeline systems, this paper focuses on a crucial matter of the trenchless rehabilitation of urban water mains: lining design. Rational design of linings plays a significant role in a certain trenchless pipe rehabilitation engineering, which is directly related to the final structural strength of the rehabilitated pipe system, the flowing capacity of the rehabilitated pipe and the final cost of the project. As water mains are pressure pipes and complicated pressure waves may occur in the running period, the lining design of water mains is quite different from the pipes which mainly withstand external pressure. However, the existing lining design theory mainly concerns external pressure, seldom concerning internal pressure. So this paper tries to establish a set of new lining design methods for the rehabilitation of water mains, concerning external pressure as well as internal pressure waves. Based on the summary of the existing lining design theories, the lining design methods in this paper are established through mechanical analysis of the conditions of pipe loads and the strength of the rehabilitated water mains resisting inner and outer loads. Through a series of mechanical analysis and references of existing lining design theories and related mechanical models, this paper finally provides a set of relatively effective lining design methods for different trenchless rehabilitation techniques using in water mains. The study in this paper will offer references for the future trenchless rehabilitation of urban water mains.

Study on the Drilling Fluid for Coarse Sand in Large Diameter Horizontal Directional Drilling

This paper speaks to the problem of cuttings suspended difficultly when drilling in coarse sand formations. The authors research the right kind of drilling fluid for the program and the effects of components on properties of the drilling fluid. The test results show that with the content of bentonite, NaOH and CMC increasing, the viscosity of drilling fluid shows a growing trend. NaOH has a greater impact on the ability of suspended cuttings. By orthogonal testing to determine the optimal drilling fluid, it provides a reference for the construction site.

The Design of a Modular Pipeline and Soil Interaction Testing Soil Box System

Pipeline soil box experiment designed to research the response characteristics of interaction between underground pipeline and soil. It simulates pipeline installation, operation and rehabilitation and provides an effective guidance for theoretical study and actual construction. This new modular pipeline testing soil box system is assembled by several modular walls which allow dimensions to be easily changed. It can also undertake a variety of pipeline simulation experiments and can meet the need for multi-diameter pipeline experiments by changing the size and number of the end wall flange holes. In addition, there are several rubber bladders installed that can simulate 100 m water pressure or about 40 m soil pressure. To reduce the effect of box wall interface friction, wall surfaces are covered with lubrication materials. This soil box can be widely used in the study of buried pipelines or pipelines installed by horizontal directional drilling and pipe jacking technology.

The Present Conditions and Sustainability of Underground Infrastructure Asset Management in Mainland China

With an aging underground infrastructure and the influence of other factors such as population growth, tighter health and environmental requirements, inadequate inspection and maintenance, and lack of consistency and uniformity in design, construction and operation practices, the performances of underground infrastructure is in very serious condition. It is reported that 70% of Chinese cities do not have the basic data about the underground infrastructure, which frequently results in damage to existing underground infrastructure on the construction job site. The direct and indirect economic loss is estimated up to 6 billion dollars each year in mainland China. In this paper, the authors discuss the present conditions of underground infrastructure in detail, analyze the main factors affecting the performances of underground infrastructure, and put forth some long term methods or efforts which should be taken to ensure the sustainability of underground infrastructure in mainland China.