Mechanical responses of underground carriageway structures due to construction of metro tunnels beneath the existing structure:A case study

To understand the mechanical response pattern of the existing structure and ground due to the construction of metro tunnels underneath,the finite difference method is adopted to study the torsional deformation and stress variation of the existing structure and the effect of underground carriageway structures on the surface subsidence.The curves of the maximum differential subsidence,torsion angle,and distortion of the cross-section of the existing structure show two peaks in succession during traversing of two metro tunnels beneath it.The torsion angle of the existing structure changes when the two tunnels traverse beneath it in opposite directions.The first traversing of the shield tunnel mainly induces the magnitude variation in torsional deformation of the existing structure,but the second traversing of the subsurface tunnel may cause a dynamic change in the magnitude and form of torsional deformation in the existing structure.The shielding effect can reduce the surface subsidence caused by metro tunnel excavation to a certain extent,and the development trend of subsidence becomes slower as the excavation continues.

Lacustrine sedimentary responses to earthquakes—soft-sediment deformation structures since late Pleistocene:A review of current understanding

The traces left by earthquakes in lacustrine sediments are studied to determine the occurrence of ancient earthquakes by identifying seismically induced soft-sediment deformation structures(SSDS).Dating can help reconstruct the relative frequency of earthquakes.Identifying seismically induced seismites,which carry abundant seismic information from numerous SSDS,is both critical and challenging.Studying the deformation mechanism of SSDS and learning about the common criteria of seismically induced SSDS improve the identification of earthquake triggers.With better research into SSDS,seismic events can be effectively captured,and temporal constraints can be carried out by 14C dating and optically stimulated luminescence(OSL)dating to identify and date the occurrence of ancient earthquakes.The present contribution primarily addresses the meaning and mechanism of SSDS and their relationship with earthquake magnitude as well as the common criteria of the SSDS induced by earthquakes.

A Preliminary Study on the Soft–Sediment Deformation Structures in the Late Quaternary Lacustrine Sediments at Tashkorgan, Northeastern Pamir, China

This study identified soft-sediment deformation structures （SSDS） of seismic origin from lacustrine sediments in the late Quaternary paleo-dammed lake at Tashkorgan, northeastern Pamir. The observed deformation structures include sand dykes, liquefied diapir and convolute structures, gravity induced SSDS, and thixotropic pillar and tabular structures. We conducted a preliminary study on the morphology, formation and trigger mechanisms of pillar and tabular structures formed by liquefaction of underlying coarse sand and thixotropy of the upper silty clay. The regional tectonic setting and distribution of lacustrine strata indicate that the most probable trigger for the SSDS in lacustrine sediments was seismic activity, with an approximate earthquake magnitude of M〉6.0; the potential seismogenic fault is the southern part of the Kongur normal fault extensional system. AMS ^4C dating results indicate that the SSDS were formed by seismic events occurring between 26050±100 yrBP and 22710±80 yrBP, implying intense fault activity in this region during the late Pleistocene. This study provides new evidence for understanding tectonic activity and regional geodynamics in western China.

The Seismic Induced Soft Sediment Deformation Structures in the Middle Jurassic of Western Qaidamu Basin

Intervals of soft-sediment deformation structures are well-exposed in Jurassic lacustrine deposits in the western Qaidamu basin. Through field observation, many soft-sediment deformation structures can be identified, such as convoluted bedding, liquefied sand veins, load and flame structures, slump structures and sliding-overlapping structures. Based on their genesis, soft-sediment deformation structures can be classified as three types： seismic induced structures, vertical loading structures, and horizontal shear structures. Based on their geometry and genesis analysis, they are seismic-induced structures. According to the characteristics of convoluted bedding structures and liquefied sand veins, it can be inferred that there were earthquakes greater than magnitude 6 in the study area during the middle Jurassic. Furthermore, the study of the slump structures and sliding- overlapping structures indicates that there was a southeastern slope during the middle Jurassic. Since the distance from the study area to the Altyn Mountain and the Altyn fault is no more than 10km, it can be also inferred that the Altyn Mountain existed then and that the AItyn strike-slip fault was active during the middle Jurassic.

Earthquake-induced Soft-sediment Deformation Structures in the Dengfeng Area,Henan Province,China:Constraints on Qinling Tectonic Evolution during the Early Cambrian

Soft-sediment deformation structures are abundant in the Cambrian Zhushadong and Mantou formations of the Dengfeng area, Henan Province, China. Soft-sediment deformation structures of the Zhushadong Formation consist of fluidized deformation, synsedimentary faults, seismo-folds and plastic deformation; the Mantou Formation is dominated by small-scale horst faults, intruded dikes, fluidized veins, and seismo-cracks. These structures are demonstrated to be earthquake-related by analysis of trigger mechanisms, and may indicate the activity of the Qinling tectonic belt during the early Cambrian. Furthermore, the assemblages of soft-sediment deformation structures altered with time： large-scale, intense deformation in the Zhushadong Formation alters to small-scale, weak deformation in the Mantou Formation. This striking feature may have been caused by changes in hypocentral depth from deep-focus to shallow-focus earthquakes, indicating that the Qinling tectonic belt developed from the subduction of the Shangdan Ocean to the extension of the Erlangping back-arc basin. This study suggests that soft-sediment deformation structures can be used to reveal the activity of a tectonic belt, and, more importantly, changes in deformation assemblages can track the evolution of a tectonic belt.

MPS-FEM Coupled Method for Study of Wave-Structure Interaction

Nowadays,an increasing number of ships and marine structures are manufactured and inevitably operated in rough sea.As a result,some phenomena related to the violent fluid-elastic structure interactions(e.g.,hydrodynamic slamming on marine vessels,tsunami impact on onshore structures,and sloshing in liquid containers)have aroused huge challenges to ocean engineering fields.In this paper,the moving particle semi-implicit(MPS)method and finite element method(FEM)coupled method is proposed for use in numerical investigations of the interaction between a regular wave and a horizontal suspended structure.The fluid domain calculated by the MPS method is dispersed into fluid particles,and the structure domain solved by the FEM method is dispersed into beam elements.The generation of the 2D regular wave is firstly conducted,and convergence verification is performed to determine appropriate particle spacing for the simulation.Next,the regular wave interacting with a rigid structure is initially performed and verified through the comparison with the laboratory experiments.By verification,the MPS-FEM coupled method can be applied to fluid-structure interaction(FSI)problems with waves.On this basis,taking the flexibility of structure into consideration,the elastic dynamic response of the structure subjected to the wave slamming is investigated,including the evolutions of the free surface,the variation of the wave impact pressures,the velocity distribution,and the structural deformation response.By comparison with the rigid case,the effects of the structural flexibility on wave-elastic structure interaction can be obtained.

Tectonically deformed coal types and pore structures in Puhe and Shanchahe coal mines in western Guizhou

To evaluate the effect of tectonic deformation on coal reservoir properties, we provide an analysis of the types of tectonically deformed coal, macroand microscopic deformation and discuss pore structural characteristics and connectivity based on samples from the Puhe and Shanchahe coal mines. Our research shows that the tectonically deformed coal mostly includes cataclastic structural coal, mortar structural coal and schistose structural coal of a brittle deformation series. The major pore structures of different types of tectonically deformed coal are transitional pores and micropores. The pore volumes of macropores and visible fracture pores produced by structural deformations vary over a large range and increase with the intensity of tectonic deformation. Mesopores as connecting passages develop well in schistose structural coal. According to the shapes of intrusive mercury curves, tectonically deformed coal can be divided into parallel, open and occluded types. The parallel type has poor connectivity and is relatively closed; the open type reflects uniformly developed open pores with good connectivity while the occluded type is good for coalbed methane enrichment, but has poor connectivity between pores.

Dynamic Analysis of Deformational Structures of the Xianniishan Fault Zone in the Three Gorges of the Yangtze River

Field investigation and laboratory work reveal that inhomogeneity of the deformation of the Xiannushan fault is mainly characterized by lateral zonation, longitudinal segmentation and downward stratification. Based on these results, a 3-D deformational structure model of the fault was established and its geometrical and kinematic characteristics in two main deformational stages i.e. the main Yanshanian and Himalayan were discussed. The directions of principal and the differential stresses in these two stages were determined by using conjugate joints, striations of fault planes and microstructures of the fault zone. The direction of σI is N-S in direction with differential stresses of 150-250 MPa in the Yanshanian, and N70E with a differential stress ranging from 80-120 MPa in the Himalayan.

Deformation tests and failure process analysis of an anchorage structure

In order to study the failure process of an anchorage structure and the evolution law of the body＇s defor- mation field, anchor push-out tests were carried out based on digital speckle correlation methods （DSCM）. The stress distribution of the anchorage interface was investigated using the particle flow numerical simulation method. The results indicate that there are three stages in the deformation and fail- ure process of an anchorage structure： elastic bonding stage, a de-bonding stage and a failure stage. The stress distribution in the interface controls the stability of the structure. In the elastic bonding stage, the shear stress peak point of the interface is close to the loading end, and the displacement field gradually develops into a ＂V＂ shape, in the de-bonding stage, there is a shear stress plateau in the center of the anchorage section, and shear strain localization begins to form in the deformation field. In the failure stage, the bonding of the interface fails rapidly and the shear stress peak point moves to the anchorage free end. The anchorage structure moves integrally along the macro-cracl~ The de-bonding stage is a research focus in the deformation and failure process of an anchorage structure, and plays an important guiding role in roadway support design and prediction of the stability of the surrounding rock.

Effect of temperature and stress on molecular structure and carbon monoxide generation of lignite from Kailuan mining area

In order to analyze the origin of carbon monoxide(CO) in coal seams, stress–strain experiments under temperature of 50, 150 and 250 °C were conducted using lignite from Kailuan mining area. Fourier transform infrared spectroscopy and elemental analysis were carried out before and after deformation of the samples. The results indicated that CO generated at 150 and 250 °C; the gas component was mostly oxygen(O_2), with small amount of carbon dioxide(CO_2), methane(CH_4) and hydrogen(H_2). At 50 °C, O_2 and a little CO_2 were observed and no CO was found. The carbon content of the coal samples increased slightly after deformation, and the oxygen content, H/C ratio, and O/C ratio decreased. The molecular structure of coal displayed different evolution characteristics at various temperatures. At 50 and 150 °C, the falling off of side chains, broken of ether bond and directional realignment of the aliphatic chains resulting in the formation of long chains were the main performance of coal molecular structure evolution. While at 250 °C, the side chains fell off and short chains formed. Furthermore, at both 150 and 250 °C, condensed degree of aromatic ring increased. Under the action of temperature and pressure, CO forms in two ways.The first is that ether bond breaks, oxygen and carbon atoms combine together and forms CO, or O_2 forming in the broken of ether–oxygen bond leads to the oxidation of free radicals and resulting in the formation of CO. And the second is that CO derives from falling off of C=O group.

ROLE OF UNDERGROUND STRUCTURE DEFORMATION VELOCITY IN THE ANALYSIS OF BLAST-RESISTANT STRUCTURES

The structural deformation velocity plays a significant role in the dynamic calculation of underground blast-resistant structures. The motion differentiating equation of a structure system taking into account the role of deformation velocity of the structure will truthfully describe the actual situation of structural vibration. With the one-dimensional plane wave theory, the expression of load on the structural periphery is developed, and the generalized variation principle for the dynamic analysis of underground arched-bar structures is given. At the same time, the results of the numerical calculation are compared.

Structure and Deformation of Intermetallic Beryllides

Intermetallic beryllides are potential light-weight, high-temperature structural materials. In this paper. the processing techniques, microstructure. deformation, and oxidation properties of intermetallic beryllides are described. In addition to nickel beryllides (NiBe). which is treated as a model system.other high beryllium-containing refractory beryllides, such as Nb2 Be17. VBe12. are also studied.The room temperature deformation and high-temperature creep properties of these beryllides are repor4ed. At room temperature. NiBe exhibits certain tensile ductility (~ 1 .3%). but all other beryllides are essentially brittle. Nonetheless, these beryllides become ductile at temperatures above approximately 1000℃. Their creep properties are presented. The creep properties are compared with those of intermetallic aluminides. Also. a comparison is made between the ductile-to-brittle transition behaviour of intermetallic beryllides and that of aluminides. Although beryllides are generally oxidation resistant at high temperatures, some beryllides, e.g., ZrBe13, suffer the pest reaction during oxidation at intermediate tem peratures. The pest mechanisms are proposed

Deformation and Dislocation Structure in L1_2 Titanium Trialuminide Alloys

The deformation behaviour and the nature of dislocations of the Al3Ti-base L12 alloya modified with Fe and Mn etc, were investigated. The results show that the deformation and fracture character istics are closely related to the alloy compositions. The effect of hot-working process on the room tem perature ductility is remarkable, not only resulting in an appreciable improvement of compressive properties but also showing a 0.28% plastic strain in tensile test. The SISF dissociation of a < 110>dislocations on {111} planes was found at room temperature. The determined dissociation scheme is consistent with the mechanical behaviour of these alloys in the lower temperature region.

Geological structures and potential petroleum exploration areas in the southwestern Sichuan fold-thrust belt, SW China

Based on the latest geological,seismic,drilling and outcrop data,we studied the geological structure,tectonic evolution history and deformation process of the southwestern Sichuan fold-thrust belt to find out the potential hydrocarbon exploration areas in deep layers.During key tectonic periods,the southwestern Sichuan fold-thrust belt developed some characteristic strata and structural deformation features,including the Pre-Sinian multi-row N-S strike rifts,step-shaped platform-margin structures of Sinian Dengying Formation,the western paleo-uplift in the early stage of Late Paleozoic,the Late Paleozoic–Middle Triassic carbonate platform,foreland slope and forebulge during Late Triassic to Cretaceous,and Cenozoic multi-strike rejuvenated fold-thrusting structures.The fold-thrust belt vertically shows a double-layer structural deformation controlled by the salt layer in the Middle Triassic Leikoupo Formation and the base detachment layer at present.The upper deformation layer develops the NE-SW strike thrusts propagating toward basin in long distance,while the deeper deformation layer had near north-south strike basement-involved folds,which deformed the detachment and thrusting structures formed earlier in the upper layer,with the deformation strength high in south part and weak in north part.The southern part of the fold-thrust belt is characterized by basement-involved fold-thrusts formed late,while the central-northern part is dominated by thin-skin thrusts in the shallow layer.The Wuzhongshan anticlinal belt near piedmont is characterized by over-thrust structure above the salt detachment,where the upper over-thrusting nappe consists of a complicated fold core and front limb of a fault-bend fold,while the deep layer has stable subtle in-situ structures.Favorable exploration strata and areas have been identified both in the upper and deeper deformation layers separated by regional salt detachment,wherein multiple anticlinal structures are targets for exploration.Other potential exploration strata and areas in southwestern Sichuan fold-thrust belt include the deep Sinian and Permian in the Wuzhongshan structure,pre-Sinian rifting sequences and related structures,platform-margin belt of Sinian Dengying Formation,and Indosinian paleo-uplift in the east of the Longquanshan structure.

Soft Sediment Deformation Structures in the Maastrichtian Patti Formation, Southern Bida Basin Nigeria: Implications for the Assessment of Endogenic Triggers in the Maastrichtian Sedimentary Record

Detailed fieldwork carried out in the southern part of Bida Basin, Nigeria, allowed the documentation of soft sediment deformation structures (SSDS) in the Maastrichtian Patti Formation. The aim of this study is to examine the sedimentary successions, describe and analyse these deformation features, discuss their deformation mechanisms and potential triggers. The Maastrichtian Patti Formation is composed of lithofacies interpreted to have been deposited in tidal and fluvial sedimentary environments. Soft sediment deformation structures recognised in the tidal sediments were clastic dykes, load cast, isolated sand balls, dish-and-pillar structures, convolute lamination, diapiric structures and recumbent folds. Severely deformed cross beds, ring structures, associated sand balls, normal folds and recumbent folds were identified in the fluvial sediments. SSDS recognised were interpreted to have been caused by effects of liquefaction and fluidization. Field observations, facies analysis and morphology of the SSDS indicate that there are relationship between the depositional environments and SSDS. Endogenic processes are considered as the trigger agents and they are represented by rapid sedimentation and overloading, impact of breaking waves, pressure fluctuations caused by turbulent water flow, cyclic stress and current generated by storm waves and changes in water table. The present study did not identify exogenic processes as trigger agent. The occurrence of SSDS in southern Bida Basin strongly favoured a non-tectonic origin but a clear relationship high energy processes in tidal and fluvial depositional environments.

AN ANALYTICAL METHOD FOR SOLVING INTERNAL FORCES AND DEFORMATIONS OF BAR-SYSTEM STRUCTURE IN SPACE

In this paper, based on the idea of finite element method, the initial parametric method in bending, problem of a beam is extended to analyse the bar-system structure by employing Dirac function and llcavisidc step function.Then a new method for analysing the internal forces and deformations of bar-system structure in space is suggested by improving the mixed method in statically indeterminate structure.The inferred process and obtained answer will be more succinct and accurate when the problem of internal forces and deformations of bar-system structure is analysed by using the new method provided in this paper.

Superplastic extensibility deformation of Al-3%Mn alloy with submicrometer grain size

Submicrometer-grained （SMG） Al-3%Mn （mass fraction） alloy specimens with initial grain size of -0.3 μm were produced by ball milling for 3 h. The Al-3%Mn specimens which were cold rolled with a strain rate of 1×10^-3- 1×10^-2 s-1 at room temperature show high extensibility to failure more than 2500%. Microstructures of pure Al and Al-3%Mn alloy at as-milled and cold-rolled state were examined using X-ray diffraction and transmission electron microscopy （TEM）. Based on the microstructure analysis, it is established that the mechanism of the continued plastic deformation in SMG Al-3%Mn alloy consists of dislocation slip, grain boundary sliding companied by dynamic recovery and recrystallization, and dynamic recrystallization is a main control factor of the large plastic deformation.

Advances in 4D printed shape memory composites and structures:Actuation and application

Shape memory polymer composites(SMPCs)are a type of smart material that can change shapes under the stimulation of the external environment,and they have great potential in aerospace,biomedical,robotics,and electronic devices due to their advantages of high strength and toughness,lightweight,impact resistance,corrosion resistance,and aging resistance.4D printing technology has provided new opportunities for the further development of smart materials.The addition of various fillers enriches the variety of printable materials and provides composites with different properties and functions.The combination of SMPCs and printing technologies realizes the structure-function integration.This paper introduces the emergence and development of 4D printing technologies,the preparation methods and properties of SMPCs for 4D printing;as well as the research progress and potential application of 4D printable SMPCs in recent years in terms of thermal,electrical,magnetic,and optical driving.Finally,the existing problems and future development of 4D printable SMPCs are discussed.

Polyphase Tectonic Events and Cenozoic Basin-Range Coupling in the Tianshan Belt,Northwestern China

Studies show that the Tianshan orogenic belt was built in the late stage of the Paleozoic, as evidenced by the Permian red molasses and foreland basins, which are distributed in parallel with the Tianshan belt, indicating that an intense folding and uplifting event took place. During the Triassic, this orogenic belt was strongly eroded, and basins were further developed. Starting from the Jurassic, a within-plate regional extension occurred, forming a series of Jurassic-Paleogene extensional basins in the peneplaned Tianshan region. Since the Neogene, a collision event between the Indian and the Eurasian plates that took place on the southern side of the Tianshan belt has caused a strong intra-continental orogeny, which is characterized by thrusting and folding. Extremely thick coarse conglomerate and sandy conglomerate of the Xiyu Formation of Neogene System were accumulated unconformably on the Tianshan piedmont. Studies have revealed that the strong compression caused by the Indian-Eurasian collision had a profound influence over the orogenic belt in the hinterland, and MesozoiC-Cenozoic brittle deformed structures superposed on the ductile deformed Paleozoic rocks. The Mesozoic extensional basins were converted into Cenozoic compressional basins. The deformation in the basins is featured by step thrusts and fault-related folds. Statistics of joints show that the principal compressive stress since the Neogene is in a N-S direction. Meanwhile, owing to the underthrusting of the basin toward the orogenic belt, the Paleozoic strata were thrust on the Meso-Cenozoic rocks as tectonic slices, revealing distinct kinematic features in different geologic units. The basin-range coupling zones are characterized by intensive compression, folding and thrusting, accompanied by local sub-E-W-trending strike-slip faults. In the Tianshan region, Cenozoic thrusting is the most common basin-range coupling mode. The folding and faulting of Mesozoic sedimentary rocks, spontaneous combustion of Jurassic coal layers and formation of sintered rocks, the Cenozoic earthquakes and active faulting, and the unique mosaic pattern of basin-range framework of Xinjiang are all products of tectonism since the Neogene.

Advances and Overview of the Study on Paleo-earthquake Events: A Review of Seismites

The distribution and formation mechanisms of typical identified seismites are analyzed based on various factors from plate tectonic positions, types of sedimentary basins and properties of seismogenic faults to focal mechanisms.Especially, structural styles, reserved positions, activity times, formation mechanisms and dynamics of soft-sediment deformation structures triggered by seismic activity are systematically analyzed.According to the genetic types of seismites, we propose 5 categories, including liquefied deformation, thixotropic deformation, hydroplastic deformation, superimposed gravity driving deformation and brittle deformation.Further, based on the main genetic types, composition of sediments and deformation styles, we draw up 35 secondary classifications.To determine paleo-seismic sequences in different times, activities of seismogenic faults, high-resolution tectonic events in one main tectonic movement and paleo-tectonic settings, and to understand the inducing mechanisms of paleo-earthquakes and ecologic environment evolution, researching on seismites are of great significance.Combing multiple approaches to identify the paleoearthquake records, simulating experiments on various soft-sediment deformation structures triggered by different magnitudes of shocking, dating precisely on paleo-seismic events, impacting on paleogeography and biological environment and on energy and resources domain are the frontiers of paleoseismic research.